Cold water immersion (a.k.a., “ice baths”) has become a popular method amongst exercise enthusiasts and athletes to enhance recovery after an intense training bout. The strategy involves exposing either the trained limb or the whole body to very cold liquid temperatures. According to p...
Brad Schoenfeld, Ph.D, C.S.C.S., is an internationally renowned fitness expert and widely regarded as one of the leading authorities on body composition training (muscle development and fat loss). He is a lifetime drug-free bodybuilder, and has won numerous natural bodybuilding titles.
Progressive overload is a well-established principle for achieving continued progress in resistance training programs. In general terms, progressive overload can be defined as consistently challenging the neuromuscular system beyond its present capacity. It’s commonly accepted that this requires an increase the amount of weight on the bar as one gets stronger to maintain the intensity of effort in a targeted loading zone (i.e., repetition range). However, little attention has been given to other methods of progressive overload, such as increasing the number of repetitions over time. Surprisingly, no study to date had endeavored to investigate the topic in a controlled fashion.
This study actually was the brainchild of my colleague, Jared Feather. Jared was planning to carry out this study as part of his doctoral work several years ago. He contacted me in 2019 about the possibility of conducting the study under my supervision at Lehman (he had intended to pursue his doctorate at AUT in New Zealand but collect data in the USA). Ultimately, Jared decided to forego his doctorate for the time being to work for Renaissance Periodization. That said, we discussed the importance of filling a gaping gap in the literature and concluded that the topic needed to be investigated regardless. Thus, I agreed to take on the project and carry out data collection in my lab.
In Spring 2020, we set out to conduct the study. We were about halfway finished with data collection when Covid-19 hit; by mid-March, we had to cease all research-related activities. Our research team had devoted over 500 hours of time to the study, but sadly it was all for naught; none of the data could be used.
Despite this setback, we were determined to complete the study.
Fast forward to Fall, 2021. My master’s degree student, Daniel Plotkin, expressed his interest in taking on the study for his thesis, with support from our terrific team of research assistants at Lehman. (Side note: Daniel has since graduated our program and is now pursuing his PhD under the mentorship of Dr. Mike Roberts at the University of Auburn). Fortunately, there were no issues with Covid this time around, We finalized data collection and statistical analysis in Spring 2022, and received official word of acceptance of our manuscript from PeerJ in September 2022.
If you want to delve into the technical aspects of the methods and findings, give the paper a read; it’s open access. For those who’d prefer a consumer-friendly synopsis, here’s the scoop…
What We Did
We randomized a cohort of young men and women with at least 1 year of consistent resistance training experience to perform a lower body training program where they either aimed to increase load while keeping repetitions constant or to increase repetitions while keeping load constant. The training protocol itself was otherwise identical between groups, consisting of 4 sets of the back squat, leg extension, straight-leg calf raise and seated calf raise performed twice per week. Training lasted 8 weeks, with testing performed pre- and post-study. To evaluate muscular adaptations, we carried out a battery of assessments including changes in muscle thickness of the quads and calves via B-mode ultrasound, total and regional body composition via multi-frequency bioelectrical impedance analysis, and 1RM in the Smith machine squat.
What We Found
Overall, results for most measures were quite similar between groups. Rectus femoris growth modestly favored the group that progressed by adding reps; hypertrophy of the other muscles did not show appreciable differences between conditions (see image below). Although strength increases slightly favored the group that progressed by increasing load, the range of effects spanned from relatively modest negative effects to appreciable positive effects and thus are of questionable practical meaningfulness. Other tests of local muscular endurance and power showed no benefit to one progression model compared to the other.
What are the Practical Implications of Findings
The results of our study challenge the generally accepted theory that progression must be carried out through increases in load. In fact, increasing repetitions at the same load showed similar gains in hypertrophy in most of the muscles we assessed, and there was even a modest benefit for hypertrophy of the rectus femoris. While strength increases slightly favored the group that increased load, the results showed a wide spread of variance that calls into question their practical significance. When considering the findings as a whole, both progression models were effective in enhancing muscular adaptations in a cohort of trained lifters and can be considered viable programming options.
Now before jumping to absolute conclusions, it’s important to note that the study only lasted 8 weeks. Although this is typical of training mesocycles, particularly for those of more advanced lifters, we cannot necessarily extrapolate results over longer time periods. Thus, our findings do not necessarily mean that a lifter can continue to simply increase reps forever without adding load to the bar at some point. Evidence suggests that training with very high rep ranges (>40 or so per set) tends to impair increases in hypertrophy. This would seem to be most relevant to those with less resistance training experience, as the ability to increase reps to such an extent is diminished in well-trained lifters. Hence, it’s conceivable that more advanced lifters can continue progress by adding repetitions for longer periods of time; this hypothesis warrants further study.
I’d also note that our protocol targeted a moderate repetition range for the initial training loads (10RM). It is well-documented that maximal strength gains are achieved with the use of heavy loads (at or near 1RM). Thus, these results are not necessarily applicable to strength athletes (e.g., powerlifters) or those who are most concerned about optimizing dynamic strength. In these cases, some type of load progression seemingly would be necessary to maintain training close to maximal loads.
Take-Home Conclusions
Overall, our study suggests that, from a hypertrophy standpoint, progressive overload can be made by altering load, repetitions, or conceivably a combination of the two, at least over the course of typical mesocycles (i.e., 8-week training block). Given that rectus femoris growth favored the repetitions groups, it is conceivable that progressing reps may be favorable in some contexts over others.
On a more general level, the mode of progression does not have to be an either/or choice. It may be best to employ a variety of progression strategies over time to ultimately elicit optimal improvements in muscular adaptations. In this regard, variety may be the spice of gainz.
Our recent meta-analysis helps to lend perspective on the topic, providing some practical insights as well as highlighting gaps in the literature that preclude our ability to draw strong conclusions. In this post I’ll delve into our meta-analytic findings and offer some key takeaways for program design.
We then carried out a robust variance meta-analysis model to determine potential hypertrophic differences between single- and multi-joint exercises. We also subanalyzed studies based on whether they equated the number of sets per exercise per muscle group to assess if training volume had confounding effects on muscle growth.
What We Found We identified 7 studies that met inclusion criteria. Our basic meta-analysis found similar gains in hypertrophy for both single- and multi-joint exercises. The relatively trivial confidence intervals of the effect size (-0.07 to 0.25) indicate that any differences would be of little practical relevance. Subanalysis failed to reveal that training volume had any effects on outcomes.
What are the Practical Implications of Findings Looking purely at the meta-analytic findings, it would seem there’s no difference between performing single- vs. multi-joint exercises from a hypertrophy standpoint. If true, this would mean that you could simply rely on compound movements to get huge and hence save a good amount of time in the gym since multi-joint exercises are more time-efficient choices.
But hold on…
As often is the case in research, there are important gaps in the literature that must be taken into account from a practical standpoint. First and foremost, 6 of the 7 studies looked at biceps or triceps hypertrophy; the other study looked at the quads. Thus, no research has been done into the effects of multi-joint exercise on muscles such as the delts, glutes, hamstrings, and calves, among others.
Why is this an issue?
Well, evidence indicates preferential hypertrophy of the rectus femoris in the leg extension (a single-joint exercise) compared to the squat. This suggests that combining single- and multi-joint lower body exercises may have a synergistic effect on quad development. Moreover, research shows negligible growth of the hamstrings during the squat, suggesting that direct hamstrings exercises (e.g., leg curls, stiff-leg deadlifts, etc) are necessary for complete development of this muscle; logic would dictate this would also be the case for the calf muscles, which receive relatively little stimulation during compound lower body movements. Although studies on deltoid hypertrophy are lacking, both applied anatomy and EMG research indicate that shoulder presses focus primarily on the anterior head of the muscle; to work the middle and posterior delts would thus require targeted single-joint work (i.e., lateral raises and rear delt flys).
In addition, rarely do studies investigate the different heads of the upper arm muscles. One study did in fact show that the bench press (a multi-joint exercise) promoted greater hypertrophy in the lateral triceps head than the overhead triceps extension (a single joint exercise) whereas the overhead extension elicited greater hypertrophy in the long head of the tri’s compared to the bench press. It’s not clear whether the short and long heads of the biceps brachii would see similarly differential responses with the performance of single- versus multi-joint exercise (i.e., curls vs rows), but the possibility can’t be ruled out.
Finally and importantly, no research on the topic to date has assessed growth at multiple sites across a given muscle. Numerous studies have shown that muscles can hypertrophy in a non-uniform fashion, with varying degrees of proximal, mid, and distal growth observed depending on a given training protocol. Although speculative, this raises the possibility that variations in length-tension changes between single- and multi-joint could promote hypertrophy at different aspects along the length of a muscle; we simply don’t know at this point because the topic has yet to be objectively studied.
Take-Home Conclusions:
From a practical standpoint, it’s relatively clear that multi-joint movements promote substantial hypertrophic benefits even in muscles that many people customarily believe require “direct” training (e.g., biceps and triceps). Accordingly, for those who are time-pressed and do not aspire to bodybuilding-type goals, this implies you can construct a routine based solely on multi-joint exercises and derive substantial benefits from a hypertrophy standpoint.
On the other hand, if the goal is to optimize your muscular potential, it appears necessary to include single-joint exercises as part of a comprehensive training program. This will help to ensure that all the body’s major muscles, as well specific subdivisions of a given muscle, are maximally stimulated for development. Program design should focus on integrating applied anatomical theory that takes into account each muscle’s unique composition and function.
Few topics in the field of exercise are as controversial as training to failure. Views on the topic tend to be polarizing, with some fitness pros strongly advocating the need to go all-out for optimal muscle adaptations, and others claiming failure training not only isn’t necessary, but in fact may be detrimental to gains.
Who’s right?
Our recent systematic review and meta-analysis provides some answers on the topic, while at the same time raising many more questions. The paper is open access and thus free for all to read, but I think it’s essential to delve beyond the numbers to fully appreciate its practical implications. Here’s the scoop…
What We Did
We searched the current literature to locate all randomized control trial studies that directly compared measures of strength and hypertrophy when carried out to muscle failure versus not to failure. Only human studies with healthy subjects that had a minimum duration of six weeks were considered for inclusion; we excluded studies that used blood flow restriction resistance training or concurrent training interventions (e.g., combined resistance and aerobic training). We then carried out a random effects meta-analysis that pooled results of all included studies to quantify the effects of failure training on muscular adaptations. A subgroup analysis of training status, body-region, exercise selection and training volume was performed to determine their potential influence on results.
What We Found
A total of 15 studies were identified that met inclusion criteria. A basic meta-analysis of pooled results found no statistical differences between training to failure versus stopping short of failure for both strength and hypertrophy outcomes; the trivial to small observed effect size differences between conditions in both outcomes (-0.09 and 0.22, respectively), suggest that any effects were of little practical meaningfulness.
Subgroup analysis showed a moderating effect of training volume on strength gains, whereby studies that did not equate volume favored non-failure training; the effect size differential was of a moderate magnitude (ES: –0.32). Alternatively, subgroup analysis found a moderating effect of training status on muscle growth, whereby trained individuals achieved a small hypertrophic benefit (ES = 0.15) from failure training.
What are the Practical Implications of Findings
On a general level, our meta-analysis indicates that training to failure isn’t necessary for maximizing muscular strength or hypertrophy. That said, numerous gaps in the literature preclude our ability to draw strong conclusions on the topic. The following points need to be considered when attempting to translate the research into individual program design:
• The choice doesn’t have to be binary: All failure-training studies to date have employed designs where one group trains to failure in every set while the other group does not train to failure in every set. This doesn’t necessarily reflect real-world programming. Fact is, you don’t have to take all sets to (or not to) failure. Training to failure on each set ultimately tends to compromise volume load, which in turn may impair hypertrophic adaptations. Moreover, there is some evidence that continually training to failure across multiple sets brings about markers of overtraining, which in turn may negatively impact muscle-building capacity. There are numerous strategies to employ failure training in a program. For example, you can perhaps limit its use to the last set or two of an exercise…perhaps use it selectively on certain exercises (see below)…perhaps reserve its use for higher rep sets (see below)…perhaps periodize its implementation across workouts or training cycles (see below)…the possibilities are almost endless. Thing is, no study has yet endeavored to study these possibilities, so all we have to go on at this point is anecdote and logical rationale.
• If not failure, then what is the appropriate set end point? : Assuming we take the results of the meta-analysis at face value and accept that training to failure isn’t obligatory for optimizing muscular adaptations, the ensuing question would be: “How close to failure do you need to train?” Unfortunately, there isn’t enough evidence to answer the question. Given that a muscle has to be sufficiently challenged to promote adaptation, we can logically make the case that at least some sets would need to be taken relatively close to failure. However, what value would that equate to in the repetitions in reserve (RIR) scale? An RIR of 1? An RIR of 2? An RIR of 3…or more? And consistent with what was mentioned in the above bullet point, how does this play out across multiple sets of an exercise? At this point, there is considerable room for debate on the topic.
• Does training frequency enter into the equation? : Although controlled evidence is lacking, it logically follows that training to failure increases recovery time between sessions. Assuming so, it makes sense that those training with higher session frequencies (>3 or 4 sessions per week) may not be able to tolerate as much (or any?) failure training. A case can be made that failure training not only has recovery implications for the targeted muscle groups, but on the neuromuscular system as a whole. At this point no research has endeavored to investigate the need to manage the level of effort based on how often you train.
• Is the need to train to failure load-dependent? : It has been speculated that you must train (closer) to failure when using higher rep schemes, both to recruit and simulate fast twitch fibers. Despite this speculation, there is a paucity of controlled research on the topic. The evidence we currently do have appears to support that higher rep training requires a higher level of effort, but whether all-out failure is obligatory remains somewhat equivocal. It is also important to note that failure in low repetition training is brought about by neuromuscular factors whereas failure in high-rep training is brought about by peripheral factors; are these factors associated with mechanisms that may elicit different hypertrophic responses and, if so, would failure be a modifying variable in the response? And given that higher rep sets involve a higher perception of discomfort, is true “failure” actually reached by most lifters when training with lighter loads before they simply give up due to the displeasure sensation? These questions require further investigation.
• What about training experience? : Our meta-regression showed that failure training was more beneficial in those with resistance training experience compared to novice trainees. However, there are a couple of caveats to this finding. For one, the overall magnitude of effect of was relatively small (ES = 0.15), calling into question the practical meaningfulness of the finding. Moreover, as noted in the exclusion criteria, we excluded a study by Carroll et al. (that employed trained lifters), due to the fact that it had an aerobic training component as part of the design (research indicates that aerobic training can interfere with muscular adaptations, and the degree of interference may be more pronounced in trained lifters). However, whether the aerobic training component actually influenced results remains unclear. Had this study been included, the result favoring failure training for trained lifters would have been nullified. I’d also note that a recently published study was just published showing no benefit to failure training in trained men; the study came out after publication of our paper and thus was not included for analysis, but certainly would have further reduced the observed effect. With all this said, no study to date has investigated failure training in highly trained lifters. It is conceivable that when lifters get increasingly closer to their genetic ceiling, a greater intensity of effort is required to achieve muscular gains. On the other hand, highly trained lifters also tend to be able to use heavier loads and are able to “dig deeper” to push the limits of failure training. Perhaps this means elite lifters should take fewer sets to failure because of the resultant neuromuscular stress on the body?
• Is age a consideration? : It is fairly well-established that recovery ability tends to decline as people age; all other things being equal, older lifters require more time to recuperate after a resistance training session compared to younger trainees. Given that failure training negatively impacts recovery, perhaps it should be employed more sparingly in this population? Unfortunately, there is scant research to date on the effects of failure training in older individuals, limiting our ability to draw strong conclusions on the topic.
• Does the type of exercise matter? : All exercises are not necessarily created equal when it comes to failure training. For example, taking sets of deadlifts or bent rows to failure can be highly taxing to the neuromuscular system. Alternatively, I’ve never heard anyone say they were crushed from going all-out on cable lateral raises. Single vs multi-joint…free weight vs machine…upper vs lower body…each of these variables concerning exercise selection requires consideration when deciding on the level of effort to expend. Unfortunately, the literature to date has not endeavored to investigate the complexities of this topic.
Take-Home Conclusions:
So where does this leave us from a practical standpoint? As with most applied exercise-related topics, research can only provide general guidelines into application for program design. Hence, here is my evidence-based take on the topic that synthesizes the current research in combination with insights from personal experience.
First, muscular adaptation requires a stimulus that challenges the body beyond its present capacity. In novice lifters, this can be achieved stopping quite a ways away from failure; even cardio is sufficient to cause appreciable muscle growth in this population! As you gain training experience, the need to train closer to failure becomes increasingly more important. Although it’s difficult to provide specifics, I’d say that at least some sets need to be within a rep or so of volitional failure. I’d also speculate that for highly trained lifters (e.g. competitive bodybuilders), there is a need to take some sets to failure to optimize muscle-building. Along these lines, as you get older, failure training should be employed more sparingly to allow for adequate recovery.
Second, when failure training is warranted, it should be applied somewhat conservatively, erring on the side of caution. A good rule-of-thumb is to limit its use to the last set of a given exercise; other sets should employ an RIR of 1 to 3. Moreover, you may need to further limit failure training with higher frequency routines. Periodizing failure training is a viable option, whereby more sets are carried out to failure prior to a peaking phase, potentially followed by a tapering phase. I’d note that numerous research studies show robust strength and hypertrophic gains when multiple sets are carried out to failure over short-term interventions (~8 to 10 weeks); however, continuing to train in this fashion likely will bring about negative consequences (i.e. overtraining). Thus, alternating periods using very high levels of effort with reduced levels of effort potentially may promote supercompensation of gains without devolving into an overtrained state.
Third, failure training should be prioritized in single-joint movements. These exercises induce less stress on the neuromuscular system, and thus don’t tax your recuperative abilities as much as multi-joint movements. Alternatively, limit the use of failure training on compound movements, particularly structural exercises using free weights (e.g. squats, bent rows, etc.). Machine-based exercises, in addition to being somewhat less taxing from a neuromuscular standpoint, provide a degree of safety when training to failure if you don’t have a spotter.
Finally and importantly, how all these considerations play out in practice will be specific to individual needs and abilities. Both genetic and lifestyle factors have a major role in program design. Ultimately, continued experimentation is required to optimize individual response over time.
However, there is a well-established phenomenon called the repeated bout effect, whereby continual performance of the same routine markedly attenuates damage-related symptoms compared to the initial bout. In fact, there is evidence that just one additional bout of the same exercise protocol reduces the swelling response to only one-third of the initial bout. Consistent training with the same routine further diminishes these effects, as eloquently shown in a study by Damas et al who tracked indices of muscle damage across 10 weeks of regimented resistance training carried out to volitional muscular failure. As shown in the graph above, damage was substantial after the initial training session. By the fifth workout, damage was substantially reduced and by the 19th workout, damage was practically inconsequential as measured 48 hours post-exercise. Post-testing for our study was done 48 to 72 hours after the last bout of a routine that was performed 24 times over an 8-week period. Thus, while I can’t completely rule out the possibility that there was swelling in the muscles, it would seem highly unlikely that this would have confounded our findings. This is particularly true given that our subjects were resistance-trained men with 4+ years training experience, who were already acclimated to the stresses of regular lifting.
On a separate note, in the discussion section of our paper we briefly discussed the results of another study on the topic carried out by Ostrowski et al. We noted that, similar to our study, the results of Ostrowski et al supported the hypothesis that volume is a primary driver of hypertrophy. Some have asked why we did not discuss the dose-response implications between their study and ours. This was a matter of economy. Comparing and contrasting findings would have required fairly extensive discussion to properly cover nuances of the topic. Moreover, for thoroughness we then would have had to delve into the other dose-response paper by Radaelli et al, further increasing word count. Our discussion section was already quite lengthy, and we felt it was better to err on the side of brevity. However, it’s certainly a fair point and I will aim to address those studies now.
Ostrowski et al carried a study in resistance-trained men, who were randomized to perform either 1, 2 or 4 sets per exercise. For triceps, our results were somewhat inconsistent with theirs. Whereas we showed that muscle thickness increased by 1.1%, 3% and 5.5% for the low, middle and high volume groups, respectively, they showed increases of 2.3%, 4.7% and 4.8%, respectively. The primary difference between findings is that Ostrowski showed similar growth between middle and high volume groups while ours showed a graded increase from low to middle to high. The overall differences were modest on this outcome. Possible reasons for the discrepancy could be due to differences in methods. Ostrowski et al used a typical bodybuilding-type routine that involved a four day split. Subjects trained legs on Day 1; chest and shoulders on Day 2; back and calves on Day 3; and arms on Day 4. On the other hand, our study employed a total body routine where all muscles were trained in the same session, three times per week. Ostrowski et al also had subjects perform single joint exercises for the triceps in addition to their contribution in pushing movements, whereas subjects in our study just performed pushing movements. As discussed in the limitations of our paper, there is evidence that multijoint movements produce similar hypertrophy to single joint movements, but we cannot rule out that inclusion of targeted training for the triceps influenced differences in results. I’d note that the triceps data from our study was the least compelling of the four muscles measured for showing an effect of volume on hypertrophy. Thus, given the fairly low response across conditions, the discrepancy also could be due to the effects of random chance.
With respect to lower body hypertrophy, our results are somewhat in concert with those of Ostrowski et al. Ostrowski et al found quadriceps thickness increased of 6.8%, 5%, and 13.1% for low, middle and high volume groups, respectively. These findings are fairly consistent with ours, which found an increase in mid-thigh hypertrophy of 3.4%, 5.4, and 12.5%, and lateral thigh hypertrophy of 5.0%, 7.9, and 13.7% in the low, middle and high volume conditions, respectively. The fact that their low and middle volume conditions did not show differences may be related to the low volumes performed in both of these conditions (3 and 6 sets per muscle per week, respectively) whereas the high volume condition performed 12 sets per muscle per week. It’s also interesting that much greater levels of volume were required to achieve similar hypertrophic responses in the quadriceps between our study and that of Ostrowski; the reasons for this are not clear.
Our findings are consistent with those of Radaelli et al, who randomized young men to perform either 1, 3 or 5 sets per exercise per week. The subjects were military personnel who regularly performed calisthenic-type exercise but were not involved with resistance training at the time of the study. They reported increases in biceps thickness of 1.1%, 7.8% and 17% whereas our study found post-study increases in biceps thickness of 1.6%, 4.7% and 6.9% for the low, middle and high volume groups, respectively. For the triceps, Radaelli et al found pre- to post-study increases of 0%, 1.7%, and 20.8% for the low, middle and high volume groups, respectively. As noted above, we found 1.1%, 3% and 5.5% for the same conditions. Thus, both studies showed a dose-response relationship between volume and hypertrophy, albeit Radaelli et al reported much greater increases for the highest volume condition. Radaelli et al did not report results for lower body hypertrophy, so we cannot contrast findings in this regard. The reasons for similarities between findings potentially can be attributed to the fact that our designs were similar. Both studies employed graded doses of 1, 3 and 5 sets per exercise per session and both had subjects perform a total body routine, three days per week. A difference between studies is that subjects in Radaelli performed single joint exercises for the biceps and triceps whereas our study only performed multijoint movements for these muscles. Moreover, their study lasted 6 months whereas ours lasted 2 months.
Since acceptance of our paper, two additional studies have been published on the topic. I’ll discuss the ultrasound results, as they are specific to our findings. Heaselgrave et al randomized resistance-trained men to perform either 9, 18 or 27 sets of biceps training each week. Subjects performed a combination of multi and single joint exercises for the muscle. Although results did not rise to a level of statistical significance, scrutinization of the individual data appears to show a fairly clear hormetic response (i.e. inverted U), with results peaking in the middle volume condition as shown in the graph above. This study had a couple of notable limitations. For one, subjects were allowed to train on their own outside of the study but were advised not to perform any direct biceps exercise. Although subjects did not report significant confounding from outside training, it is known that self-report can lack accuracy and it therefore remains questionable whether additional training was in fact carried out. Moreover, the subjects in the higher volume conditions trained two days per week while the lowest volume condition trained one day per week. Thus, this study in actuality had two treatment variables, confounding the ability to draw causality on volume alone.
Finally, Haun et al recently carried out a study in resistance-trained men. The study employed a somewhat unusual design, whereby volume was ramped up each week over the course of 6 weeks, beginning with 10 sets per muscle per week and progressing to 32 sets per muscle in week 6. Only 4 exercises were employed: back squat, bench press, stiff legged deadlift, and lat pulldown. A strong point of this study was that they employed midpoint testing after the 3rd week, thereby providing insights into how changes occurred over time. Muscle thickness for the biceps brachii increased from baseline to the midpoint, but then attenuated by the end of the study. This suggests results peaked at 20 sets per muscle per week. Alternatively, results for the vastus lateralis showed no significant changes from mid to post testing, but significantly increased from midpoint (20 sets/muscle/week) to the end of the study (32 sets/muscle/week). Interestingly, the authors also carried out biopsy testing and found that CSA of the vastus lateralis significantly decreased from baseline to mid but then significantly increased from mid to post. It should be noted that the overall magnitude of the increases in this study were quite modest. That may be due to the design, whereby subjects performed 10 reps at 60% of 1RM each set. This is a relatively light load for trained subjects, and it can be speculated they weren’t sufficiently challenged. Another factor to consider is that volume was progressively increased each week, so subjects only trained at a given volume for 1 week. It is therefore difficult to extrapolate the effects of training at a prescribed volume over multiple weeks.
In summing up the literature to date, the one thing that appears clear is that volume plays a fairly prominent role in maximizing growth, but nevertheless significant hypertrophy can be obtained at fairly low volumes. It’s difficult to reconcile discrepancies between studies given differences in methodology. And as as is almost always the case in an applied science such as exercise, prescription will be specific to the individual as there are large interindividual variances associated with response to volume. The astute fitness pro will take the current research into account and then use his/her expertise to customize program prescription, taking into account the potential benefit balanced against the time commitment involved.
For as long as I can recall, bodybuilders have been preaching the importance of a mind-muscle connection for maximizing muscle development. In case you’re not aware, a mind-muscle connection (a variation of the concept in the field of motor learning known as an “internal focus of attention”) is the process of actively thinking about the target muscle during training and then feeling it work through the full range of motion. According to theory, this strategy maximizes stimulation of the muscles you’re trying to target in a given exercise while reducing the involvement of “secondary” movers. This combination hypothetically should result in greater growth.
Hypothetically….
Numerous studies have confirmed that a mind-muscle connection does in fact increase activation of the target muscle as measured by a technique called electromyography. However, higher activation of a muscle doesn’t necessarily mean it will hypertrophy to a greater extent over the course of a long-term training program. To my amazement, no one had endeavored to investigate whether adopting a mind-muscle connection during training actually had a beneficial effect on muscle growth in a controlled, long-term study.
So the curious science nerd that I am, I took it upon myself to find out. Here’s the scoop on our recently published paper on the topic.
What We Did
30 college-aged men agreed to participate in the study and were randomly assigned to either train with an internal focus (mind-muscle connection) or an external focus. All participants performed 4 sets of arm curls and leg extensions for 8 to 12 RM on 3 non-consecutive days per week, with sets carried out to muscular failure. Every rep of every set was supervised by one of my research assistants. The mind-muscle group was instructed to “squeeze the muscle” on each rep while the external focus group was instructed to “get the weight up.” The exercise portion of the program lasted 8 weeks with a week taken for testing immediately before and immediately following the training period.
As those of you who follow my work undoubtedly know, the vast majority of my studies are carried out in subjects with resistance training experience. However, in this case I decided to use untrained subjects.
Why?
Well, trained individuals tend to get hardened into a given attentional focus (called a “deep basin” in motor learning). It’s therefore difficult to get these individuals to change their focus during training. This would be especially problematic in a study such as this since there is no way to be sure what the lifter is actually thinking when training. An untrained lifter is a blank slate and thus we could be more confident that he would follow the prescribed attentional focus strategy.
I also chose to use only single joint exercises for the study. The reasoning here is that it’s easier to focus on a given muscle during a single joint lift. Squats, rows and presses involve multiple primary muscle movers that makes it difficult for a lifter – particularly one with no training experience – to focus on a given single muscle. What’s more, multijoint exercises require more of a learning curve to coordinate movement patterns in the early stages of training, which would further impair the ability to develop a mind-muscle connection as well as delaying the onset of hypertrophy in favor of neural adaptations.
What We Found
After 8 weeks of consistent training, subjects who used a mind-muscle condition had almost double the muscle growth in the biceps brachii compared to those using an external focus (12.4% vs 6.9%, respectively). Alternatively, muscle growth for the quadriceps was similar between conditions. From a maximal strength standpoint, isometric strength of the elbow flexors increased substantially more for the internal focus group while knee extensor strength was markedly greater for the external focus group.
What We Learned
The novel finding of the study was that superior gains in biceps hypertrophy were made by employing an internal focus of attention. Based on these findings, it appears the bros were right; employing a mind-muscle connection enhances muscle growth.
But wait a sec; if that’s the case, then how come attentional focus did not seem to matter for thigh hypertrophy…?
Although it’s impossible to say for sure since we didn’t attempt to investigate mechanisms, a possible reason is that subjects simply found it easier to focus on the biceps as opposed to the quads. This is logical given that the upper extremities are used for fine motor skills (i.e. picking things up, writing, etc) while the lower extremities are involved in gross motor skills (i.e. walking, kicking, etc). Thus, people tend to be more conscious of their arm muscles and less so of the leg musculature. The fact that the subjects were untrained would seemingly contribute to this discrepancy. I’d hypothesize that well-trained lifters would be better able to focus on the quads when training and thus achieve better hypertrophy. This needs further study.
Here’s the take home: It appears beneficial to adopt a mind-muscle connection if your goal is to maximize muscle growth. Instead of worrying about a specific tempo, simply focus on the muscle being trained and visualize it working throughout the full range of motion. Now this comes with the caveat that findings are specific to a moderate rep range; using heavy loads (i.e. 3-5 reps) may preclude the ability to take advantage of this strategy as your focus would conceivably have to shift to just getting up the weight as efficiently as possible. Importantly, this is just one study and shouldn’t be taken as the be-all-end-all on the topic. Hopefully more longitudinal studies will be conducted on the topic to draw more definitive conclusions. Future research should look to compare internal versus external focus strategies using multi-joint exercises in trained lifters to better understand how a mind-muscle connection impacts growth.
For further insights, check out the video I did for Omar Isuf’s YouTube channel below. I discuss the nuances of the topic and their relevance to practical application in a lifting program.
Below is an excerpt from my book, Strong & Sculpted that discusses my current approach to warming up prior to resistance training. I neglected to include a chapter on the topic in my book, M.A.X. Muscle Plan so for those following this program, the same info applies.
Warm-Up
To prepare your body for the demands of intense exercise, you should warm up prior to your lifting session. The warm-up contains two basic components: a general warm-up and a specific warm-up. Here’s what you need to know about each component for a safe, effective workout.
General Warm-Up
The general warm-up is a brief bout of low-intensity, large muscle–group, aerobic-type exercise. The objective is to elevate your core temperature and increase blood flow, which in turn enhances the speed of nerve impulses, increases nutrient delivery to working muscles and the removal of waste by-products, and facilitates oxygen release from hemoglobin and myoglobin.
A direct correlation exists between muscle temperature and exercise performance: when a muscle is warm, it can achieve a better contraction. As a rule, the higher a muscle’s temperature is (within a safe physiological range), the better its contractility. And because better contractility translates into greater force production, you’ll ultimately achieve better muscular development.
What’s more, an elevated core temperature diminishes a joint’s resistance to flow (viscosity). This is accomplished via the uptake of synovial fluid, which is secreted from the synovial membrane to lubricate the joint. The net effect is an increase in range of motion and improved joint-related resiliency. Better yet, these factors combine to reduce the risk of a training-related injury.
Suffice it to say that the general warm-up is an important part of a workout.
Virtually any cardiorespiratory activity can be used for the general warm-up. Exercises on equipment such as stationary bikes, stair climbers, and treadmills are fine choices, as are most calisthenic-type exercises (e.g., jumping jacks, burpees). Choose whatever activity you desire as long as the basic objective is met.
The intensity for the general warm-up should be low. To estimate intensity of training, I like to use a rating of perceived exertion (RPE) scale. My preference is the category-ratio RPE scale, which grades perceived effort on a scale from 0 to 10 (0 is lying on your couch, and 10 is an all-out sprint). Aim for an RPE of around 5, which for most people is a moderate walk or slow jog. You can use the talk test as an intensity gauge. With this method, you base intensity on your ability to carry on a conversation; if you have to pause to take a breath while speaking a sentence, you’re working too hard.
Five to ten minutes is all you need for the general warm-up—just enough to break a light sweat. Your resources should not be taxed, nor should you feel tired or out of breath either during or after performance. If so, cut back on the intensity. Remember, the goal here is merely to warm your body tissues and accelerate blood flow—not to achieve cardiorespiratory benefits or reduce body fat.
Specific Warm-Up
The specific warm-up can be considered an extension of the general warm-up. By using exercises that are similar to the activities in the workout, the specific warm-up enhances neuromuscular efficiency for the exercise you are about to perform. In essence, your body gets to rehearse the movements before you perform them at a high level of intensity, translating into better performance during your working sets.
To optimize transfer of training, the exercises in the specific warm-up should mimic the movements in the workout as closely as possible. For example, if you are going to perform a bench press, the specific warm-up would ideally include light sets of bench presses. A viable alternative would be to perform push-ups because the movement pattern is similar to that of a bench press, although the specificity, and thus transfer, would not be as great as with light sets of the given movement. Always stop specific warm-up sets well short of fatigue. The object is not to fatigue your muscles, but rather to get a feel for the exercise so that you’re physically and mentally prepared for intense training.
The specific warm-up is particularly important when training in low-repetition ranges (~ five reps or fewer). I recommend at least a couple of specific warm-up sets per exercise during low-rep training. As a general rule, the first set should be performed at ~40 to 50 percent of 1RM; and the second set, at ~60 to 70 percent of 1RM. Six to eight reps is all you need in these sets—any more is superfluous and potentially counterproductive. Following the specific warm-up, you should be ready and able to plow into your working sets.
The need for specific warm-up sets in medium- to high-rep-range training remains questionable. I recently collaborated on a study that investigated the effects of a warm-up on the ability to carry out repetitions to failure at 80 percent of 1RM (a weight that allows performance of about eight reps) in the squat, bench press, and arm curl (Ribeiro et al., 2014). The verdict: Warming up showed no beneficial effects on the number of repetitions performed in medium- to high-rep-range training nor in a measure called the fatigue index, which is a formula that assesses the decline in the number of repetitions across the first and last sets of each exercise.
At face value these results suggest that warming up is pretty much useless prior to submaximal resistance training. Despite the currently held belief that a specific warm-up enhances exercise performance, no benefits were seen when compared to no warm-up at all. Intuitively, this seems to make sense given that the initial repetitions of a submaximal lifts are in effect their own specific warm-up, and increasing core temperature might be superfluous from a performance standpoint when multiple reps are performed.
It should be noted, however, that we found a slight advantage to performing a specific warm-up prior to the squat (although results did not rise to statistical significance); the specific warm-up prior to the biceps curl seemed to be somewhat detrimental. Thus, more complex movement patterns seem to benefit from the practice effect of a specific warm-up, although this would be of no value prior to simple exercises.
Taking the evidence into account, here’s my recommendation: When performing medium-rep-range work (8 to 12 reps per set), perform a specific warm-up prior to multijoint free weight exercises. One set at about 50 percent of 1RM is all you need to obtain any potential benefits.
Specific warm-up sets are not necessary when training with high reps (15+ reps per set). In this instance, because you’re already using light weights, the initial repetitions of each working set serve as rehearsal reps. What’s more, performance of warm-up sets is counterproductive to the goal of maximizing training density to bring about desired metabolic adaptations.
What About Stretching?
Static stretching is commonly included as part of a prelifting warm-up. This method of flexibility training involves moving a joint through its range of motion to the point where you feel slight discomfort, and then holding the position for a period of time (generally about 30 seconds). Most protocols involve performing several sets of static holds and then moving on to stretches for other muscles. It’s commonly believed that the addition of stretches to a warm-up further reduces injury risk while enhancing physical performance.
In recent years, however, the benefits of preexercise static stretching have come under scrutiny. A large body of research shows that the practice does not decrease injury risk (Thacker et al., 2004). Yes, improving flexibility can conceivably help in injury prevention. Tight muscles have been implicated as a cause of training-related injury, and improving flexibility can reduce this possibility. Because a stretching exercise improves range of motion, including it in an exercise program can enhance overall workout safety. However, the benefits are not specific to stretching prior to training. All that matters is achieving adequate range of motion to properly carry out exercise performance.
The most important consideration here is to make sure your muscles are warm before performing static stretches. This reduces joint viscosity, ensuring that muscles and connective tissue are sufficiently prepped to endure passive or active lengthening.
So you might be thinking, Why not include some basic stretches after the general warm-up? After all, your core temperature is elevated and joint viscosity is reduced. What’s the harm, right?
Interestingly, evidence shows that static stretching performed before a workout can have a detrimental impact on exercise performance. This is most applicable to activities requiring high force output, such as heavy resistance training. The primary theory proposed to account for these performance decrements is a decrease in musculotendinous stiffness. The musculotendinous unit (the muscle and its associated tendons) is responsible for generating force to carry out movement. Like an overstretched rubber band, the musculotendinous unit with increased laxity following stretching impairs force transmission. The upshot is a reduced capacity to lift a given load.
However, caution needs to be used when applying this research to a lifting session. First, most of the studies in question used excessive stretching protocols, in some cases upwards of 30 minutes stretching a single joint! Most preworkout stretching routines involve only a few minutes per joint, and it’s highly questionable whether such brief stretching bouts have any performance-related detriments. Moreover, the vast majority of research on the topic is specific to high- strength and high-power activities. Whether negative effects are associated when training with medium- to high-rep schemes remains speculative.
Given the uncertainty of evidence, you’re best off performing static stretches immediately after your workout. Your body is already warm from engaging in intense exercise, and it generally feels good to cool down by elongating muscles that have been repeatedly contracted. Some research even shows that postworkout stretching may alleviate delayed-onset muscle soreness (see the sidebar What Causes Muscle Soreness After a Workout?), although the extent of the reduction probably isn’t all that meaningful (Henschke & Lin, 2011).
If you want to include some flexibility work prior to lifting, consider dynamic stretches: slow, controlled movements taken through their full range of motion. Examples are arm swings, shoulder circles, high steps, and hip twists. Choose dynamic stretches that are specific to the joint actions being trained in your workout. Perform several sets for each dynamic stretch, attempting to move the body segment farther and farther in a comfortable range with each set.
Contrary to popular belief, you don’t necessarily have to include a stretching component in your regular routine for general health and wellness. Increased flexibility results in decreased joint stability. Being too flexible, therefore, actually increases injury risk. Thus, stretch only those joints that are tight, and avoid any additional flexibility exercise for those that already have adequate range of motion to carry out your required activities of daily living.
Moreover, it’s important to note that resistance training in itself actually improves flexibility. Provided that you train through a complete range of motion, multiset lifting protocols produce similar increases in flexibility to those seen with static stretching routines (Morton et al., 2011). In essence, resistance training is an active form of flexibility training whereby a muscle is contracted and then immediately lengthened. When performed on a regular basis, it can keep you mobile and limber. We can therefore put to rest the myth that lifting slows you down and binds you up!
We are glad that more and more people are demanding and applying evidence in the exercise and nutrition field. That been said, there remains a lot of misunderstanding and misconceptions about an evidence-based Practice (EBP). In this article, we will address some of the common misconceptions and criticisms of EBP. Here we go:
Why do we need EBP? Why can’t we just use anecdotal evidence or expert opinion?
In fact, we’ve used anecdote or expert opinion as ‘evidence’ to treat people throughout the history of medicine. But this approach clearly didn’t work well as shown by hundreds of examples of medical mistakes we made in the past. For example, smoking was ‘good’ for heath until studies showed otherwise; bloodletting was the standard medical treatment for almost 2000 years by the foremost doctors of the West, and so forth. In short, EBP evolved because anecdotal evidence or expert opinion were not producing ‘results’.
The definition of EBM (Evidence Based Medicine) by David Sackett reads: “EBM is a systematic approach to clinical problem-solving that allows integration of the best available research evidence with clinical expertise and patient values”. This principle can be applied across many scientific disciplines, including exercise and nutrition, to optimize results.
What is the evidence?
Many people wrongly assume that the term “best available evidence” in EBM/EBP is limited to research-based evidence. In fact, evidence can be obtained from a well conducted randomized controlled trial, an unsystematic clinical observation, or even expert opinion. For example, the evidence could come from a controlled trial, your favorite fitness guru, or a physiological mechanism. However, the critical point is that the importance or trust we place on the evidence differs based on the type of evidence. We will talk more about this as we talk about the evidence hierarchy.
What about values and preferences?
Every patient or client assigns his/her own values, preferences, and expectations on outcomes and decisions.
For example, some might place a high value on muscle growth, whereas others would value their general health as most important. Some would value building their upper body muscles more than their lower body muscles. Others may value the social aspect of working out at a gym more than the muscle and strength gains.
And rightly so, these personal decisions have no wrong or right and should be listened to and respected. The job of a fitness professional is to help clients achieve whatever goals they desire; we cannot impose our own values no matter how contrasting beliefs and opinions maybe.
What about clinical expertise? And what is the ‘art’ of EBP that people always talk about?
Clinical expertise is what many refer to as the art of EBP. So, does the art of EBP mean applying what has worked for your clients? Clearly not.
Clinical expertise involves basic scientific knowledge, practical expertise, and intuition to:
• diagnose the problem (for example, why can’t this person squat deep, how to correct exercise technique, why he/she is not gaining strength or losing weight.),
• search for the relevant research evidence (how many sets to gain muscle for an advanced trainee, or which exercise targets specific muscles) and critically analyze the research evidence for methodological issues (was the study in beginners, was the outcome measured relevant)
• understand both the benefits, the risks involved, and other alternative approaches to the goal (a Crossfit type workout might be motivating and improve general cardiovascular endurance, but has a high risk of injuries)
• alter the program based on the client feedback and results (reducing the number of sets or modifying the exercise (angles, ROM and do forth) for an older person or someone with pre-existing shoulder injuries.)
• Listen and understand clients value and preferences, clearly communicate the risk, cost, benefits in a simple manner, and use a shared decision approach to come to a decision
And this is called the art of evidence-based approach. As you can see, it forms an integral part of EBP and no amount of research can replace it. Likewise, no amount of clinical expertise can replace research evidence.
What is the evidence hierarchy? And why are RCT’s (Randomized Clinical Trial) at the top of the pyramid?
An evidence hierarchy is one of the foundational concepts of EBP. And there are three important points to keep in mind:
• First, as shown, the different types of evidence are arranged in an orderly fashion. As we go up the hierarchy, the trust or the confidence we place in the study results go up too. RCT’s are the most valid research design, as they allow the ability to infer causality. And expert evidence is the least trustworthy and occupies the bottom position. Meta-analyses- a collection or a group of RCT’s-are generally considered the highest form of evidence, as they synthesize the entire body of literature on a given topic and quantify the results based on a statistical measure of practical meaningfulness. Meta-analyses can be particularly important in exercise- and nutrition-related topics, as the sample sizes are often small and thus pooling the data across studies provides greater statistical power for inference.
• Second, it is important to note that depending on the quality of the study, an RCT can be downgraded, too. A poorly designed study will never provide a high level of evidence, and in fact can impair the ability to draw proper evidence-based conclusions. The hierarchy therefore is not set in stone.
• Third, there is always evidence. So the best available evidence is what is available and need not come from an RCT (Randomized Controlled Trial). But based on the type of evidence, our confidence in the results and our recommendations will differ accordingly.
What if there are no RCT’s? How do I evaluate a program or diet?
First, as mentioned before, there is always evidence. If there are no RCT’s, you simply move down the evidence hierarchy. But as you go lower in the hierarchy, uncertainty about the validity of the evidence goes up as well. Second, you also must compare the benefits, risks, cost, scientific plausibility, and other alternative programs before making recommendations. Below are a few examples where the absence of an RCT does not preclude recommendations.
Example 1: If a client comes with a new program that uses 5 lb weights to increase strength, we know from basic science that without load progression, muscle and strength gains will be nil. Such a program would go against the most fundamental theory of muscle growth. So you can make a strong recommendation against the program, even without an RCT.
Example 2: Recently, the Ebola virus vaccine was used before conducting an RCT. How is that possible? Here is a classic example of weighing the benefits, risks, alternative approaches, and making a strong recommendation with weak evidence. In this case the risk is death, the benefit is obvious, and there are no alternative approaches. Thus, the risk/reward strongly favored giving the vaccine. And 99% of the informed patients would agree with the recommendation.
Example 3: If a client wants to try the Xfit program, you can convey the lack of studies (weak evidence), the risks involved, the time required for learning the right technique, and give other programs which are in line with her/his goals. If he/she still wants to do it, he/she shouldn’t be critiqued for their decision.
Example 4: An observational study shows that eating meat raises cancer. Considering observational studies are lower in the hierarchy no matter how well the study is conducted, recommendations cannot be more than just suggestions.
What if there are no studies and my client wants to try a new program?
As previously noted, if a person understands the uncertainty due to the lack of studies or weak evidence, availability of alternative programs that fit his/her goal, the cost, and risks, he/she can make an informed personal choice. Keep in mind that majority of the questions in exercise and nutrition are of weak evidence. In fact, it is the same for the medical field too. But what is important is to clearly know and convey what your recommendations are based on.
There are a lot of factors like genetics, diet, motivation that can influence your results. A study hence…
Many people are unaware that in a randomized controlled trial, the randomization serves a crucial purpose: The randomization ensures, at least theoretically, that both the known variables and unknown variables that can affect muscle growth or strength are equally distributed into both groups. That is, if there are unknown genetical factors that can drive muscle growth, it is highly likely these genetically gifted individuals will be distributed evenly. This is the reason why RCT are considered to be the gold standard to study cause and effect. Hence, the results of the study can be pinned to the intervention or treatment
There are numerous problems with scientific study. So you cannot use the results of a study to train your clients?
Yes. But one of the basic steps in EBP is to critically analyze the study: If the study has methodological issues or has a different population than your client, you downgrade the evidence accordingly and lower your strength of recommendations.
Most of the studies in bodybuilding/strength training are on untrained individuals.
Yes. And rightly so, caution should be used when extrapolating recommandations to trained individuals. Exercise science is a relatively new field and studies in trained individuals are small in number, but accumulating. Generalizability (i.e. the ability to apply findings from a study to a given population) must always be taken into account when using research to guide decision-making.
I don’t care about “why” it works or the science behind. All I care about are results.
As previously mentioned, EBP evolved to get better results. It didn’t evolve to explain how or why a treatment works. There are 1000’s of life saving treatments and drugs where the underlying mechanism(s) are just unknown.
Studies are looking at an average of the sample. There is a lot of individual differences.
Yes. In fact, n=1 studies occupy the top of the evidence hierarchy because it applies to the specific individual in question. But these are hard and almost impossible for certain outcomes like muscle growth or disease prevention. There are two concerns with so-called trial and error method that is often talked about.
• First, even if you gain benefits with a certain program, in many cases, it is extremely hard to figure out what was the variable that made the difference. Was it the specific exercise, the change in diet, the placebo effects, genetics, or some unknown variable?
• Second, it may not be clear if you are indeed making an improvement depending on the outcome. For example, gains in muscle come very slowly for trained individuals (like years for a several pounds). Hence, you will have to run a program for a few years to see if it works or not. However, controlled research often uses measures that are highly sensitive to subtle changes in muscle mass, and thus can detect improvements in a matter of weeks.
The program worked for me!
What was the outcome measure? Strength, muscle growth, weight loss? What are you comparing against? Against your previous results? What was the magnitude of the benefit? Without knowing answers to these questions, the meaning of the word ‘worked’ is unclear.
Further, if it indeed worked, we still don’t know what made it work, or if it will work for someone else. So your personal anecdotes are often fraught with problems and unfortunately mean very little. And importantly, just because something “worked” doesn’t mean that another approach might not work better.
This X supplement was shown to increase muscle growth in an animal study. Should I use it?
Research in animal models is almost at the bottom of the evidence hierarchy. It is very weak and hence the uncertainty is high, and deserves no greater than a weak recommendation. Although animal models can serve an important purpose in preliminary research, evidence based practice should rely primarily on human studies when developing applied guidelines.
A lot of the research is sponsored by nutritional and exercise machine companies. Hence not trustworthy.
Yes. If there is a conflict of interest, the study is downgraded.
I saw a supplement study which showed a statistically significant weight loss. Can I use that supplement for my client?
No, you also have to look at how much weight the subjects lost. The term “significance” is a function of the probability of results occurring by random chance; it is not necessarily related to the magnitude of the effect. Provided a large enough sample size, results of a study can be statistically significant even with just a 1 lb weight loss over a 1 year period. This is known as ‘clinical significance’.
Would you take a supplement to lose 1 lb in a year? Depending on the cost, the burden of taking a pill every day, and how much you value weight loss, you may or may not.
EBP does not consider a science-based approach.
EBP does consider a science-based approach. A science-based approach provides strong evidence when the program or treatment violates fundamental principles or universal laws. For example, homeopathy.
However, EBP does not support evidence just based on biological plausibility or mechanistic evidence. For example, if a new diet tells you to eat as much as you want to lose weight, it goes against fundamental laws of thermodynamics. You do not need an RCT to make strong recommendations against this diet
“This house believes that in the absence of research evidence, an intervention should not be used” This was the motion of a debate which took place at the end of the recent PhysioUK2015 Conference in Liverpool.
As you know by now, EBP does not exclusively rely on RCT’s. To quote the famous saying in EBP: “There is always evidence”. It is an unfortunate misrepresentation of EBP/EBM to assume that without RCT’s, a treatment cannot be recommended. For example, smoking has perhaps the greatest detrimental effect on health of any social habit, and health-based organizations universally recommended against its use. But we do not even have even a single RCT on smoking!
Effects of smoking are from observational studies. But since the magnitude of harm is very high, it upgraded in the evidence pyramid. Once again, this shows why the hierarchy is not set in stone.
‘Parachute use to prevent death and major trauma related to gravitational challenge’. This is the title of the paper published in BMJ. The paper satirically argues that parachute use has not been subjected to rigorous evaluation by using RCTs’ and therefore has not been shown to save lives. Critics of EBP have used this as a criticism of EBP and the reliance of RCT’s.
EBP has always maintained that RCT’s are not required when the magnitude of benefits is very high.
For example, insulin injection for diabetes, Heimlich maneuver, and anesthesia are all examples of treatments where the magnitude of benefit is very high, and hence RCT’s are not required nor asked for.
I do not have enough knowledge to critically analyze studies.
In closing, we hope the article has helped you better appreciate and understand this simple framework called evidence based practice or evidence based medicine. EBP is currently the best approach we have to make decisions related to health, fitness or strength and conditioning. A good EBP practitioner should have a strong understanding of both the practical and the scientific aspects of exercise and nutrition; and more importantly, an untiring commitment and empathy to your clients and their values and preferences.
A popular theory among fitness professionals is that taking short rest periods between sets maximizes muscular growth. The theory is primarily based on the hormone hypothesis, whereby limiting inter-set rest promotes greater elevations in post-exercise growth hormone, IFG-1 and testosterone, and thus enhances the anabolic response to resistance training. One little problem: Emerging evidence indicates that acute increases in anabolic hormones have little if any effect on muscular adaptations, as detailed in my comprehensive review of the topic
In an effort to directly test the theory, our group published a study last year titled, Longer inter-set rest periods enhance muscle strength and hypertrophy in resistance-trained men. In brief, the study not only refuted the claim of a hypertrophic benefit to short rest periods, but in fact showed that resting 3 minutes between sets actually produced superior growth compared to resting 1 minute. Importantly, the study was carried out using a moderate rep range (8-12 reps/set) with all sets performed to muscular failure. The question therefore arises whether results would be applicable when training with lighter weights. No study had ever investigated the topic.
What We Did
Subjects were 21 young collegiate athletes who had not performed resistance training for at least 2 years prior to the study. The subjects were randomly divided into two groups: A short rest group (SHORT) that rested 30 seconds between sets and a long rest group (LONG) that rested 2.5 minutes between groups. The load was set at 40% of the subjects’ 1RM in the back squat and bench press using a tempo of 1-0-2 (1 second on the concentric, 2 seconds on the eccentric). Four sets were performed for each exercise, with all sets taken to muscular failure. Training was carried out twice a week for 8 weeks.
What We Tested
Measures of muscle hypertrophy and strength were assessed pre- and post-study. Muscle cross sectional area (CSA) of the triceps and thigh was measured by MRI. A 1RM bench press and squat was employed to measure changes in maximal strength.
What We Found
With respect to hypertrophy, the SHORT group increased muscle CSA by 9.8% while LONG showed an increase of 10.6%. Thigh CSA increased by 5.7% in SHORT versus 8.3% in LONG. No statistically significant differences were noted between any measure of muscle growth.
From a strength standpoint, 1RM in the bench press increased by 9.9% in SHORT and 6.5% in LONG while increases in the squat were virtually identical between groups (5.2% versus 5.4) As with the hypertrophy results, no statistically significant between-group differences were observed in the strength measures.
How Can You Apply These Findings
There are a number of interesting takeaways from the study. First and foremost, this is yet another study showing that training with light weights can promote marked gains in muscle mass in a relatively short time period. There is now a large body of supporting research on the topic using varied methodologies across a variety of populations. The evidence is too compelling for even the most ardent critic to dismiss.
Intriguingly, we found that rest interval length had no statistically significant effects on muscular adaptations. On the surface, these results conflict with our previous research showing that 3 minutes rest produced superior increases in strength and hypertrophy compared to resting 1 minute when training in a moderate rep range (~10RM). Our findings here seem to indicate that rest interval length isn’t an important consideration when training with lighter loads.
A closer look at the data, however, suggests a more nuanced take-home message.
It’s important to realize that the term “statistical significance” refers to the probability of an event happening by chance. Our study had a fairly small sample size, which reduces the ability to detect significance. Hence, we have to look beyond whether results were “significant” and consider other statistical measures. To that end, while hypertrophy of the arms was fairly equal between conditions, gains in thigh muscle CSA clearly favored resting longer between sets. A statistic called the effect size, which is a gauge of the meaningfulness of the results, bears out these differences were indeed consequential. The effect size for the LONG group was 0.93 (considered a large effect) while that of the SHORT group was just 0.58 (considered a moderate effect). The chart above illustrates the absolute differences between thigh growth and rest intervals.
When attempting to reconcile the differences between upper and lower body hypertrophy, it may well come down to total training volume. Short rest blunted increases in training volume in both upper and lower training, but the disparity was much more pronounced in the squat than in the bench. This is logical as the leg/glute muscles have much greater muscle mass than those of the upper trunk/arms, and thus the associated fatigue during high-rep training is greater in multi-joint lower body training, particularly a demanding exercise like the squat. Given the known dose-response relationship between hypertrophy and volume (as clearly displayed in our recent meta-analysis on the topic), the substantial decrease in number of reps performed with short rest periods could conceivably explain the lesser muscle growth seen in the thighs.
In addition to the long-term effects, we also measured hormonal elevations from each condition post-exercise. Both SHORT and LONG showed significant acute spikes in growth hormone and IGF-1, but the increases were similar between groups. Since hormonal increases are related to levels of metabolic stress, it can be inferred that metabolic stress was similar between conditions as well. Although short rest periods have generally been shown to enhance metabolic stress, these findings are specific to moderate rep training. Training with very high reps elicits large increases in lactic acid regardless of how long you rest between sets. Thus, rest interval length seemingly has less relevance in promoting metabolite buildup. Whether metabolic stress influenced results in this study is undetermined as we didn’t seek to assess mechanisms of adaptations. That’s an intriguing topic for future research.
The Bottom Line
* Training with light weights can pack on some serious muscle.
* Short rest between sets has a detrimental effect on lower body hypertrophy when squatting while there does not seem to be much if any negative impact on growth from the bench press when training with light weights. Thus, shorter rest periods for light-load upper body work are a viable option to cut down on training time without sacrificing gains.
* Since single joint exercise does not elicit comparable fatigue to multi-joint movements, it is conceivable that short rest would be similarly viable for single-joint lower body exercises such as the leg extension. This remains speculative, however, as the topic wasn’t directly investigated in our study.
Dating back to my early years as a personal trainer in the mid-90’s, I began to become intrigued by the concept of “loading zones” whereby different rep ranges purportedly could bring about differential effects on muscular adaptations. Prevailing wisdom at the time was that heavy loads (1-5 RM) promote maximal strength gains, moderate loads (6-12 RM) elicit maximal increases in muscle mass, and light loads (15+ RM) produce the greatest improvements in local muscular endurance. This concept, discussed extensively in exercise science texts, was termed the “strength-endurance continuum” (see the image below) although direct research on the topic was limited.
The topic of rep ranges was so intriguing to me that I ultimately made it a focus of my doctoral work. Several years ago I published the data collected in accordance with my dissertation study. In brief, the study looked at muscular adaptations in a “bodybuilding-type” routine versus a “powerlifting-type” routine in resistance-trained men when the routines were equated for volume load. Consistent with the “strength-endurance continuum” concept, the study found that the powerlifting-type routine produced the greatest strength increases. Contrary to prevailing wisdom, however, both routines produced similar increases in hypertrophy of the biceps brachii. You can read my write-up of the routine in this blog post.
Importantly, the findings of that study are specific to the respective routines being equated for volume load. While this provides interesting insights on the topic, it is impractical to carry out long-term training with very heavy loads at the volumes used in that study (in fact, the majority of subjects in the powerlifting-type group displayed clear signs of overtraining by study’s end). So the question arises as to whether results would differ if an equal number of sets were performed between heavy and moderate loads?
What We Did
Nineteen college-aged men were recruited to participate in the study. All subjects had at least one year of resistance training experience lifting at least three times per week. Subjects were randomized to either a group that trained in a heavy loading range of 2-4 repetitions per set (HEAVY) or a group that trained in a moderate loading range of 8-12 repetitions per set (MODERATE). All other aspects of the subjects’ program were kept constant between groups. The training protocol consisted of seven exercises that worked all the major muscles of the body each session, with three sets performed per exercise. Training was carried out on three non-consecutive days per week for eight weeks. Subjects were instructed to maintain their normal daily nutritional intake and no differences in either calories or macronutrient consumption was found between groups over the course of the study.
What We Measured
We tested hypertrophy of the elbow flexors, elbow extensors, and quads using b-mode ultrasound. Maximal strength was assessed in the squat and bench press via 1 repetition maximum (RM) testing. Upper body local muscular endurance was determined by assessing the subject’s initial 1RM in the bench press for as many repetitions as possible to muscular failure.
What We Found
The infographic to the left (courtesy of Thomas Coughlin) illustrates the results of the study. In general, overall muscle growth was greater for MODERATE compared to HEAVY. Increases in thickness of the elbow flexors (i.e. biceps brachii and brachialis) modestly favored the use of moderate reps (~5% vs ~3% for MODERATE vs HEAVY, respectively) while gains in the quads substantially favored the moderate rep group (10% vs 4% for MODERATE vs HEAVY, respectively). Interestingly, growth of the triceps was similar between groups.
On the other hand, strength gains were decidedly greater when training with heavy loads. This was seen for improvements in both the 1RM squat (29% versus 16%) and bench press (14% vs 10%), which favored HEAVY compared to MODERATE. Muscle endurance increases were similar between rep ranges.
What are the Practical Implications
The study provides evidence that training with heavy loads helps to maximize muscle strength and training with moderate loads promotes greater increases in muscle mass. Importantly, these findings are specific to routines where the number of sets are equated. At face value, this is consistent with the “strength-endurance continuum” and supports what gym bro’s have been preaching for years in regards to rep ranges.
However, when the results are taken into account with my previous study on the topic that equated volume load, an interesting hypothesis emerges. Since strength gains were greater with heavy loads in both studies, it can be concluded that low-rep training is best for maximizing strength regardless of volume load. On the other hand, since the previous study showed no differences in hypertrophy between conditions when volume load was equated, it can be inferred that volume load is a greater driver of muscle growth irrespective of the rep range. In other words, strength is maximized even with lower training volumes provided heavy loads are used, but higher volumes are needed to maximize gains in size whether you train with moderate or heavy weights.
The study had several limitations including a relatively small sample size, the use of a single-site measurement for muscle growth on each of the respective muscles, and possible confounding from the “novelty factor” (i.e. virtually all the subjects trained with moderate loads, so it is possible that the novel stimulus for those in the heavy load group might have impacted results). These issues must be taken into account when attempting to draw evidence-based conclusions. Most importantly, one study is never the be-all-end-all when it comes to answering questions on an applied science topic. Rather, each study should be considered a piece in a puzzle that lends support to a given theory. The practical implications of programming loading zones will become increasingly clear as we continue to build on this line of research. For now, though, the evidence suggests to train heavy if your goal is maximal strength, and to focus on accumulating volume for maximal gains in muscle mass.
Wanted to keep you updated on all that is going on at the moment. So much to share!
In case you haven’t heard, my newest consumer book called Strong and Sculpted, was released a few weeks ago. Happy to report it’s been the top-selling new book in Amazon.com’s “weight training” category and has gotten stellar reviews from consumers and pros alike. It’s a scientifically-based handbook for optimizing muscle development, providing step-by-step guidelines for program design. Check it out! In addition, my upcoming textbook called, Science and Development of Muscle Hypertrophy, is scheduled to be released at the end of the month. It will be the first text to provide an evidence-based perspective on muscle growth, covering all the research and its practical implications. If you’d like to be amongst the first to receive the book, it’s now available for pre-order on Amazon.com at a 20% discount.
A recent study published in the Journal of the International Society of Sports Nutrition reported that branched chain amino acid (BCAA) supplementation helped accelerate fat loss while preserving lean mass in trained individuals performing resistance training when dieting. On the surface, this would seem to provide compelling evidence of a benefit to supplementation. However, after scrutinizing the study’s methods, my colleagues Alan Aragon, Brad Dieter, and I found some glaring issues with the statistical procedures and reporting of data. We thus wrote a letter to the edtior detailing these errors and inconsistencies. Give it a read, as it points out the importance of perusing the entire study – not just the abstract – when drawing practical applications from research.
Here’s a vid of my favorite way to perform upright rows. The rope takes stress off the wrists, facilitating movement. Make sure your upper arms don’t go beyond parallel to the ground and your elbows stay above the level of your wrists.
Big shout out to my buddy and partner-in-science Bret Contreras for officially publishing the first long-term study on performance outcomes in the hip thrust versus the squat. Bret has devoted his career to developing a better understanding of how strength and hypertrophy of the hip extensors can be optimized through resistance training, and this study provides an important addition to the literature. I know Bret’s working on a number of follow-ups to further this line of research. Stay tuned.
I have a number of speaking engagements schedule for this summer. First up is Bropocalypse 2016 taking place on June 11th and 12th in Sydney, Australia. I’ll be speaking with uber-colleagues Alan Aragon, Bret Contreras, and James Krieger on what will be a terrific weekend of evidence-based learning. Next up is the NSCA National Conference in New Orleans this July, where I’ll speak on loading strategies for maximizing muscular gains. Then comes the CanFitPro World Expo in Toronto, Canada where I’ll be speaking on a number of fitness- and nutrition-related topics, as well as doing a book sign at the expo. Finally, at the end of August I’ll be in Oslo, Norway at the AFPT Fitness Convention along with some of the best and brightest minds in fitness. Last year’s event was a sell-out so if you’re planning to attend book early!
I recently appeared again on Superhuman Radio to discuss some of my recent research as well as my new book. The host, Carl Lanore, always asks pointed questions that make for a compelling listen.
Last but not least, I’ve uploaded a majority of my recent publications to my ResearchGate page. Included is our recent meta-analysis on training frequency, an original study comparing a daily undulating periodized routine to a traditional hypertrophy protocol, and a study on the effects of conjugated linoleic acid (CLA) on fat loss, amongst others. The PDFs are free to download and soak up the knowledge!
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