From Volume 4, Issue 7 of MASS
A Progression Framework for Hypertrophy
by Eric Helms Ph.D. CSCS
Hypertrophy: It’s a listed goal next to strength, power, and muscular endurance in your textbook or professional manual, complete with ranges for each variable of training. What assumptions does this framework require? This article takes a “first principles perspective” on hypertrophy, using it to provide a model for progression.
A Concept Review of Why and When to Progress Training Volume for Hypertrophy
- Whole muscle hypertrophy is the structural outcome of performing resistance training which causes specific adaptations in components of skeletal muscle. However, hypertrophy is not a specific performance adaptation itself. Progression based on the recovery of training which causes hypertrophy will improve your ability to recover, but not necessarily hypertrophy in all cases.
- Set volume has a dose-response, diminishing returns relationship with hypertrophy, following an inverted U. Eventually, as sets are added, hypertrophy rates plateau, and as more sets are added, rates of growth slow, eventually ceasing, then regressing. Hypertrophy increases strength, allowing increases in load or reps, which maintains the effectiveness (rep range and RPE) of each set.
- While an appropriate initial set-volume optimizes hypertrophy, it is not known when and if sets should increase to maintain the fastest rate of muscle growth possible. But, increasing sets too quickly can slow hypertrophy. Thus, it may be better to increase sets when load or reps are no longer going up, if recovery is also occurring.
In this concept review, I’ll approach hypertrophy training progression from a conceptual standpoint. I know, we’ve spent a lot of time discussing progression already in MASS, and Dr. Zourdos and I are proud to say most of this work comes from the video department (seriously, step it up everyone else). For example, Dr. Zourdos has a two-part series (Part 1, Part 2) on load progression strategies, a video on how to progress assistance work, and I have a video on making progress using muscle group specialization cycles. There’s even more on progression in our content on setting up training, autoregulation, and periodization, even when progression itself isn’t the main focus. However, almost all of it is about how to progress; we haven’t done much on conceptualizing why and when to progress different variables (such as sets, reps, load, and RPE) for the goal of hypertrophy.
In this article, I’ll discuss hypertrophy from a “first principles” perspective. Meaning, I’ll start at a point before most articles or textbooks on training theory start, and thus, before some of the assumptions that are often made. It’s not that these assumptions are necessarily wrong, but they can lead to practices that might be suboptimal if we accept them uncritically. I’ll discuss the nature of hypertrophy, what we know about inducing a stimulus to keep muscle growth going, and finally, I’ll lay out a framework for progression that hopefully provides more pros than cons.
Whole Muscle Hypertrophy
Physique competitors want big muscles, regardless of what contributes to that size, to achieve a certain look. For example, when they pump up, that temporary increase in fullness counts just as much as anything else that contributes to muscle size. Strength athletes, on the other hand, want bigger muscles because more contractile tissue means more force output. However, an increase in contractile tissue is just one potential contributor to whole muscle hypertrophy. Further, the vast majority of muscle growth research uses metrics of whole muscle hypertrophy like muscle thickness, cross sectional area, or lean body mass, which can’t distinguish which components of muscle grew in what proportion.
As I alluded to, whole muscle hypertrophy as a gross outcome is actually the result of a collection of adaptations to different components of skeletal muscle. The appearance of increased muscle size in two individuals who train quite differently – or in the same individual following two distinctly different training phases at different times – may appear outwardly similar at the macro level, but may be the result of differing proportional increases to these components at the micro level. As outlined in a recent review by Haun and colleagues (1), hypertrophy can occur in three broad components (Figure 1):
- Myofibrillar hypertrophy, which is the increase in the size and/or possibly the number of myofibrils.
- Connective tissue hypertrophy, which includes increases in the volume of muscles’ extracellular matrix with increases in its mineral or protein content.
- Sarcoplasmic hypertrophy, which is a non-transient increase in the volume of the sarcoplasm, which may include increases in the volume of the mitochondria, sarcoplasmic reticulum, t-tubules, and/or enzyme or substrate content.
Conceptually, unlike strength or muscular endurance, whole muscle hypertrophy is not a specific performance adaptation. Rather, change in whole muscle size is the gross structural consequence of specific structures adapting in response to stimuli. A change in whole muscle size can occur in response to a broad range of training styles, varying widely from low-load high-rep to high-load low-rep training (2), low-to-high total volumes (3), short-to-long rest periods (4), training short of (5) or to failure (6), and with various modalities from free weights to machines (7). Thus, a change in whole muscle size reflects the adaptive demands that could be caused by, but are not limited to: 1) The need for more contractile tissue to produce force; 2) The need for more connective tissue to transmit force or to “house” hypertrophy when it occurs in other parts of skeletal muscle; and/or 3) The need for more cellular organelles, enzymes, or substrates related to energy production for the completion of more work. Therefore, it may be imperfect to conceptualize “hypertrophy” as a training type in the same way we think of strength, power, or muscular endurance. Training paradigms for these performance outcomes are designed to balance the stimulus, recovery, and adaptation of training for a specific performance adaptation; yet, whole muscle hypertrophy is a structural consequence of specific adaptations, not a specific adaptation itself (although again, it can absolutely contribute to force production, and thus strength and power, which I will discuss more later in this article).
While a wide array of variables can be manipulated to cause whole muscle hypertrophy, applied research has narrowed the variables to some degree to get closer to “optimal,” establishing that loads equal to or greater than 30-40% of 1RM (8), when trained at least reasonably close to momentary muscle fatigue for a sufficient number of sets that last sufficiently long (~5-6 reps+) (9), should produce robust hypertrophy, if there is a sufficient supply of energy and protein for its creation (10). Perhaps unsurprisingly, there is also a dose-response relationship between the total number of sets performed (when sets are at a sufficient load and proximity to failure) and the magnitude of whole muscle hypertrophy (11). Also in line with many other physiological adaptations, some work suggests this relationship follows an “inverted U” (12), such that at a certain point, further increases in the number of sets reduces the rate of muscle growth, presumably as the recovery demand of training saps the adaptive resources for hypertrophy (Figure 2). Indeed, in some applied studies, groups doing more volume than a lower volume comparison group have actually not experienced measurable hypertrophy, or even experienced a small loss of lean mass (13, 14).
Is Set Progression the Logical Conclusion?
This dose response relationship between volume and muscle growth has led to the creation of systems of hypertrophy training which prioritize manipulating sets as a means of progressing the specific stimulus (set volume) most related to hypertrophy. Such a system is seemingly built on the following premise:
As your ability to recover from more sets increases, the number of sets you can benefit from increases as well.
At first glance, this is not an unreasonable premise given the dose-response relationship between hypertrophy and set volume. However, there are actually a number of issues with this idea. First, the dose-response relationship is based on comparisons between groups doing different total volumes, not different week-to-week progressions of volume across training cycles. To my knowledge, there aren’t any studies that match for total volume, while comparing a group that increases sets each week against a group that maintains a fixed number of sets. Therefore, while we can say doing enough sets produces more muscle growth than not doing enough sets in a mesocycle, we can’t necessarily conclude sets should be increased in a mesocycle. Simply put, while this premise could be true, we don’t have data to support it.
Secondly, you could argue based on the principle of specificity, that the only thing we can be strictly confident in regarding doing more sets, is that doing more sets gets you better at doing more sets. To truly assess the premise of whether or not increases in set volume will result in more growth if you are recovering from your current set volume, we have to assess the meaning of recovery (and its time course). Depending on who you talk to, recovery is defined differently. Most often, speaking colloquially, recovery is described subjectively. As an aside, “subjective recovery” has merit despite it not being objective. Believe it or not, validated questionnaires which use quantitative scales to rate subjective recovery outperform objective markers for monitoring and mirroring training load (15). More pertinent to the present discussion, in sports science, recovery is most simply defined as returning to one’s baseline performance (16). While using this objective, sports science definition of recovery is more black and white, using it in the context of hypertrophy training comes back to the problem of hypertrophy not being a performance adaptation. The importance and utility of stimulus, recovery, and adaptation are self-evident when applied to specific training for a specific performance adaptation. If you are trying to lift a very heavy load, or do many reps with a moderate load, you train for that task by doing it, and you monitor progress and recovery by your performance. You lift heavy loads, or do many reps with moderate loads, respectively, with added complexity existing only to manage recovery and accomplish the task more efficiently. While both of these tasks can result in hypertrophy, they aren’t perfectly synonymous with hypertrophy. If I was to put this another way, getting better at recovering from the work which stimulates hypertrophy is not necessarily the same thing as being able to stimulate more hypertrophy by doing more work.
Conceptually, your “optimal volume” for hypertrophy is only clearly related to your recovery if said recovery is poor enough to prevent you from performing that amount of volume. Likewise, there’s no reason you couldn’t be adapted to performing and recovering from very high volumes, far in excess of what would be optimal for hypertrophy (think CrossFit). For example, imagine we had perfect knowledge of your optimal volume. Then, imagine you could complete it all across Monday, Friday, and Saturday sessions. If you had a high workload capacity and were adapted to a high exercise frequency, the repeated bout effect would enable you to perform a decent amount of volume at a reasonable level of effort on Wednesday. However, if you were already at what was optimal, this additional training wouldn’t help you grow; just because you can do more volume, doesn’t mean you always should. Truly, for the premise that recovery indicates a need for more stimulus, we’d have to define recovery as “the recovery of all physiological processes related to hypertrophy.” Unfortunately, that isn’t something we can feasibly measure at this point in time.
Volume Load Progression
The conversation about volume and hypertrophy is not new, but it has changed. For years, experts have said volume should progress at some stage if the goal is hypertrophy. I’ve said this, however, at the time most people meant volume load (sets x reps x load). To my knowledge, the 2015 Stronger By Science article “The New Approach to Training Volume” by Nathan Jones was the first to connect the dots and conclude that perhaps instead of volume load (sets x reps x load), we should be counting the number of “hard sets.” He made a good case that hard sets are a simpler, more accurate representation of how stimulative training volume is for hypertrophy. In the peer reviewed literature, Baz-Valle and colleagues argued a similar position in a 2018 systematic review we covered in MASS, concluding “the total number of sets to failure, or near to, seems to be an adequate method to quantify training volume when the repetition range lies between 6 and 20+ if all the other variables are kept constant” (9). I agree with these conclusions, as they’re based on the fact that most studies report greater hypertrophy in groups performing more sets that meet this criteria. Indeed, in the second edition of my books I gave volume recommendations as the number of sets for this reason.
However, conceptualizing volume for hypertrophy as the number of sets has different implications for progression than when conceptualizing it as volume load, which I don’t think most people consider. Specifically, while I’m confident that volume load should steadily progress if your goal is hypertrophy, I’m not confident the same can be said about the number of sets. Why? As discussed earlier, bigger muscles are generally stronger muscles. If you are growing, that should eventually show up on the bar (or cable stack). Even if you keep reps and sets the same, this means volume load will increase (sets x reps x load). Therefore, if you are growing, it leads to strength increases, and volume load must go up.
This ties into how you view progressive overload and the relationship between strength and hypertrophy. Increasing your strength doesn’t make you grow; rather, when strength increases on movements in the same rep range after the novice stage, it is at least in part due to the contribution of bigger muscles to force production (17). From this perspective, “progressive overload” isn’t something you must proactively do by progressing the overload. Rather, your progress occurs because you caused overload. Meaning, increases in volume load from strength gains (doing more reps or lifting more weight) are a confirmation that overload occurred. Therefore, volume load eventually has to increase if you are actually growing, if all else is equal.
While the need to increase volume load is arguably self evident, we can’t say the same for the number of sets. There are no data I’m aware of indicating that set volumes necessarily increase with training age. As stated, there are plenty of studies comparing groups doing different set volumes, establishing the aforementioned dose response relationship, but there aren’t studies tracking individuals through multiple points over their lifting careers to establish optimal set volume. With that said, we do have evidence that quickly increasing sets on a weekly basis can coincide with a slowed rate of hypertrophy. Specifically, Haun and colleagues increased sets by two, every week from 10 to 32 sets, but only observed significant increases in extracellular water-corrected lean body mass from pre- to mid-testing, but not from mid- to post-testing (18). Meaning, muscle growth slowed as sets continued to increase to a very high number (technically, we can’t know the set increases caused this slow down, but they didn’t prevent it).
This shouldn’t be surprising, as out of all the variables influencing volume load, adding sets increases it the most. Going from 10 to 32 sets, if reps and load remains the same, is a 320% increase in the work completed! Such a rapid increase can overwhelm one’s ability to adapt and recover. Consider how much more aggressive adding sets is compared to adding reps or load. Going from 3 sets of 10 with 100kg (3000kg), to 3 sets of 10 with 105kg (3150kg) or to 3 sets of 11 with 100kg (3300kg) is a modest 5 or 10% increase, respectively, compared to a 33% increase going to 4 sets of 10 with 100kg (4000kg). More importantly, since “hard sets” of at least ~5-6 reps are most representative of the hypertrophy stimulus, I’d argue that load and repetition increases serve a different function than increasing sets. As you get stronger, if you don’t increase load or do more reps, your sets get further from failure. Thus, increases in load or reps maintain the relative stimulus of each set. Adding sets on the other hand is, well, adding sets. It could be viewed as a true increase in volume for hypertrophy, rather than ensuring your current volume remains effective.
When Set Progression is Warranted
I’ve argued that set progression is an aggressive move, but that doesn’t mean you should never do it. Further, there is some data we can use to help us make decisions about how to increase sets. Most studies assign a certain number of sets for “high” and “low” volume groups without consideration of how much volume the participants were doing before the study. Greg reviewed a study that found arbitrary assignment to 22 sets/week produced less hypertrophy than increasing habitual volume by 20%, even though at the group level, volume between conditions was similar (19). This indicates if you are to increase sets, it should be a relative increase from where you were. However, just because it’s better to make a relative increase in set volume from what you were doing previously, doesn’t mean it’s always a good idea to increase sets in the first place.
Indeed, there is evidence that decreasing your volume in some cases can increase your rate of hypertrophy. In a recent study assessing hypertrophy, Aube and colleagues compared multiple groups performing different set-volumes and also reported the change in set-volume among the participants compared to what they were doing habitually. Interestingly, among the individuals who grew the most (the top tertile of responders), they increased their number of sets by 6.6 ± 12.4 per week (20). That standard deviation, which is almost twice the mean, indicates a few of the individuals who grew the most in this study likely reduced the number of sets they were previously doing. Strictly speaking, it’s possible that those who decreased their sets in the fastest growing tertile were actually growing even faster before they enrolled in the study. Perhaps they were such genetic specimens they would end up in the top tertile of hypertrophy no matter what, but hypothetically, the point remains given our understanding of the inverted U relationship between volume and hypertrophy. Simply put, if you’re already doing sets in excess of what is optimal for you, decreasing your number of sets could make you grow faster, or start growing again if you were plateaued.
Practically, you want to set a reasonable starting volume which you think will be ideal for hypertrophy, based on your current knowledge. Then, adjust volume over time to ensure you stay as close to that goal as possible. When first starting out, if you don’t have historical data indicating that a certain set volume seems to result in your best growth, it’s not a bad idea to use the existing published data and start at ~8-12 hard sets per muscle group per week (11). With an appropriate initial volume, you should be able to increase load and/or reps over time if other variables are properly in place. These variables include sufficient proximity to failure, rest, your rep range and load falling within specific (but broad) ranges, a reasonable training organization, adequate nutritional support, and sleep. From this point, increases in reps and load indicate overload is occurring and serve to maintain the efficacy of your sets. Then, when load or reps are no longer progressing, it’s worth considering if a “true” volume increase to the number of sets is warranted. Specifically, this is likely appropriate if you are also recovering well in both subjective and objective terms while reps and load are also plateaued (Figure 3).
Another conceptual use of set progression is specialization cycles. Dr. Zourdos discussed the concept in relation to high volume training here in his Interpretation, Next Steps, and Application and Takeaways. As established, sets are an aggressive increase in volume load, so it might make more sense to “free up” the resources to adapt and recover from high volumes by only using high volume training on one or two body parts at a time while sets are reduced on your other muscle groups. This gets around the problem of doing too much too quickly, and allows an advanced trainee to increase the volume on a muscle-group-by-muscle-group basis, without increasing total volume to counterproductive levels. For a more in depth look at how to do this, see my video specifically on this topic.
As we’ve discussed numerous times in MASS, despite volume having a known and important relationship with hypertrophy, you can do too much. You can also increase it too quickly. While I’ve called into question certain assumptions, it doesn’t mean some don’t contain elements of utility or truth. For example, I mentioned we don’t have data to support the idea that set volume must increase with training age. However, absence of evidence is not evidence of absence. In my anecdotal experience, going from post-newbie levels of muscle mass to growing noticeably again often does require a sizable increase in set volume (if you didn’t start too high in the first place). Further, just because recovery isn’t directly related to hypertrophy, doesn’t mean it can’t be useful when assessing the cause of a plateau.
Therefore, the premises which I questioned should not be wholly rejected, but rather updated with added nuance. Many might have simply concluded before reading this article: “Volume is the variable most related to hypertrophy and best quantified as hard sets. Therefore, we should progress sets in our training cycles.” My hope is now you understand that progressing reps or load shouldn’t be compared to increasing sets, as increasing reps or load can serve a different purpose. Further, you physically won’t always be able to increase reps or load, but you can always add another set. Meaning, in addition to ensuring the effectiveness of your existing set volume, increases in reps or load serve diagnostically to help you assess the effectiveness of your training and your objective recovery. Therefore, increases in reps or load is not in contrast with increases in sets. Rather, they can go hand in hand, with plateaus in reps or load helping to inform when sets should increase.
Applications and Takeaways
- Steady improvements in reps or load are a practical gauge of whether growth is likely occurring. While strength gains indicate hypertrophy, the acute recovery of performance is not necessarily tied to hypertrophy. Work capacity and recovery can improve without necessarily changing your current optimal volume for hypertrophy. Of all variables, sets increase total work the most, and too much work over short time frames can impede muscle growth. Thus, rep or load progression can indicate overload occurred, and serves to maintain the relative effectiveness of each set. When reps or load are not progressing, recovery can be assessed to determine if an increase in sets is warranted. This framework may maximize the upsides and minimize the downsides of progressing each of these variables for the goal of hypertrophy.
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