The sport and hobby of bodybuilding has long been ridiculed for its ‘bro science’ approach. The anecdotal based history of building muscle tissue – a process known as hypertrophy – stems from the lack of research surrounding the topic when the sport was popularised in the 70s.
The ‘try it and see’ methods were born out of necessity over the years and using some basic intuition, with lower rep ranges favoured for strength development and higher rep ranges considered advantageous for develop muscle tissue. But with the research into the topic increasing and valid conclusions slowly formed are we now in a better position to truly determine the amount of volume that is optimal for developing more muscle tissue?
How does a muscle increase in size?
Before diving into the big question it’s useful to understand how and why a muscle grows. For the purposes of this article only a hypertrophic response is discussed. The muscle can also growth through hyperplasia – which refers to a process of increasing the amount of muscle cells, as opposed to the growth of current cells, but we’ll save this for another article!
At the smallest level muscles are made up of two proteins called actin and myosin, which are thin and thick filaments, respectively. When we voluntarily contract a muscle, such as if we were to do a bicep curl, these thick and thin filaments slide over one another to shorten the muscle and therefore form a muscle contraction. This process is referred to as the sliding filament theory.
When the muscle is forced to contract under a load, it places stress on the muscle fibers and causes small micro-tears. This forms the stimulation process of hypertrophy, however in order for the muscle to then repair and develop, the rest is equally important. The rest period post-training allows for the necessary immune and hormonal response enabling the muscle cells to adapt: a increase in muscle cell/myofibril size and over time an apparent increase in musculature.
From a survival standpoint this makes sense, it’s your body’s way of adapting to a prior stress it’s been faced with so it’s better prepared to cope with the challenge should it arise in the future. Always remember that the body doesn’t know your training in a air conditioned gym, it just assumes you’re always battling nature and responds accordingly to help keep you alive!
What is training volume?
Now that the why’s and how’s have been established we move onto the what’s: what is the amount of volume and mechanical stress needed to elicit this response. The example above provided a crude example and 1 bicep curl typically doesn’t tend to yield sufficient stress for hypertrophy, we need more volume to optimise muscle growth, but how much more and can too much volume have an adverse effect on muscle growth? This is where the topic of training volume becomes a key consideration and hot topic within the fitness community.
A quick Google search of ‘Training volume‘ will generate many different definitions but it can be thought of as the amount of weight used multiplied by the reps performed multiplied by the sets performed. For example if you perform a back squat with 100k for 10 reps and 5 sets within a session, twice a week, then the volume for that exercise is 5000kg/week.
However not all reps are created equally and it’s more favourable in terms of training response to view the working reps as part of the volume equation. These reps are typically performed at a slow contraction speed and have a high motor unit recruitment. Another self-assessed way to determine working sets may be use a scale such as the RPE (rate of perceived exertion), which aims to record rate of exertion from 1 (being the lowest), up to a 10, which would be an all out 1 rep max, as an example. Sets that work up to an 8 and above within the RPE scale, for me, are noted as working sets as the necessary amount of motor units is typically being recruited at this exertion.
How much volume per set is optimal for muscle growth?
This question is debated in research and in gyms alike on an ongoing basis, and based on the fairly mixed research outcomes, for good reason!
The research god-father of training protocol for hypertrophy is Brad Schoenfeld, PhD.
In 2016, Schoenfeld conducted a study where subjects were split into 2 groups: 1 group was given a powerlifting training protocol of 7 sets of 3RM (rep maxes – the maximal amount of weight they can lift for just 3 reps) and 3 minutes rest between sets. Whilst the other group were given 3 sets of 10 reps with 90 seconds per rest between sets.
All subjects were classified as experienced lifters, having lifted consistently at least 3 times a week for a year prior to the study.
Subjects performed 3 lifting sessions each week and both groups completed the same exercises (barbell military press, flat barbell press, lat pulldown, seated cable row, barbell back squat, machine leg press, and machine leg extension), with the differing rep/set protocol:
|Group 1||Group 2|
The volume load or the amount of weight lifted in total for each session remained the same (i.e. Reps x training load) despite the higher weight and moderate weight approach from each group.
Both protocols led to an increase in muscle thickness with no significant difference between the 2 groups. This findings suggests that when volume is equalised, hypertrophy is achieved.
Although noteworthy to mention that the powerlifting group suffered from more cases of joint pain and 2 subjects had to withdrawal from the study due to injury. Interviews with subjects also reviewed that the high load group suffered more with fatigued in comparison to the group performing higher volume.
Other analysis – such as the one done by Greg Nuckols – all notes a trend towards favouring moderate rep ranges (8-12) over the heavier (up to 5 rep) sets. Although the literature differed greatly from case-to-case.
With that being said this leads us to believe that although hypertrophy is absolutely possible using higher loads, lower rep set approaches, it may be more conducive to favour a moderate rep approach for your set volume to help safeguard from injury and allow for a more sustained training approach.
Although I do think high load/lower volume sets have their place within a longer-term training program meso-cycle, particularly for compound lifts such as barbell back squats; deadlifts and bench press as the broad muscle group exposure from heavier loads periodically will elicit strength benefits which will aid with progressively overloading the muscle and may assist with breaking through plateaus with training loads.
Beyond the moderate ranges of 8-12 hypertrophy it’s still possible and studies have noted hypertrophic responses from up to 30 rep sets (Goto et al.). Although reassuring in the absence of full gym access, the only thing to add here is that you need to go more towards all out failure within the set, this is essentially because 80/85% of a 30 rep set is purely pre-fatiguing the muscle/motor units and it is that last 15% that provides the necessary stimulus for muscle growth.
How much training volume per week is optimal for muscle hypertrophy?
Although the studies and reviews listed above did lead to muscle hypertrophy, the total weekly was equalised so we cannot deduce from these alone that their set amounts were optimal, this wasn’t the primary focus on the studies.
So how much volume is enough volume for muscle growth per muscle group each week? And is there a tipping point where doing any more than is necessary has an adverse effect on your muscle growth and only compounds fatigue without any benefit?
Unlike the reps per set debate, volume per muscle group per week isn’t quite as clear and finding the sweet spot for ones weekly volume is a tougher question to answer.
This is largely due to genetic variability and recovery capacity, something that’s also transient with training experience, as more advanced lifters tend to handle more training volume than newbie lifters.
To add to the complexity, many lifts engage multiple muscle groups, for example the deadlift works the hamstrings, erector Spinae, glutes, lats, traps etc, so defining which exercises -such as these – contribute to true weekly volume for each muscle groups becomes even more complex.
Researcher Regis Radaelli investigated this hotly debated topic in 2015 (study). Radaelli took 48 subjects and split them into 3 different groups, all 3 performed 3 resistance training sessions each week over a 6 month period.
Each group performed 7 different exercises each session spanning across the whole body, with groups performing either 1, 3 or 5 sets per exercise to failure in the 8-12 rep range. In terms of hypertrophy, the results indicated that the 5 set group made significantly more improvement based on muscle thickness compared to the 3 set and 1 set group, with the 1 set group making insignificant progress over the duration of the study.
The overall tricep volume here was 45 sets a week if you include their more passive engagement for the bench press and shoulder press.
This – along with Schoenfeld’s 2019 study – is the highest amount of weekly volume per muscle group measured in a study. The data here points towards a correlation between higher weekly training volume for each muscle group and a hypertrophic response.
But is the potential here limited and are you running the risk of falling off the wrong end of a U shaped curve by committing yourself to more volume?
I’m not no doubt the answer here is yes and as you continue to layer on more volume, you layer on more fatigue and no longer get the training response necessary to stimulate further hypertrophy.
It’s also worth noting that in both of the studies above the subject were trained individuals and therefore their ability to handle and respond well to this amount of training volume was greater than those who are less trained or even worse, those who had never done resistance training before. Giving a complete training newbie 45 sets per week per muscle group would be a recipe for disaster!
The right amount of weekly volume is really determined by your training experience. Menno Helselman’s meta-analysis indicates similar findings with the correlation between higher volume weeks being stronger in trained athletes Vs untrained.
If you’re completely new to resistance training then starting out with 15/20 sets per muscle group should initially serve as your upper limit. Monitor key variables from here with this volume including post session muscle soreness; performance in terms of your training loads; quality of muscle pump and general energy levels day to day. If the trajectory of these factors in continually positive then look to slowly ramp up the volume over time in accordance with the speed your body adapts.
At this stage it’s also worth reminding ourselves that training is a form of stress, it’s positive stress – if used correctly – but stress nonetheless, so your training volume can be impacted by other holistic lifestyle factors such as stress levels; your energy balance (running a huge calorie deficit will be a limiting factor) and general quality of your sleep and nutrition. This is why total training volume is never static for too long and should be transient in accordance with performance, experience and other lifestyle factors.
Training frequency per muscle group
The final consideration within this article is the weekly training frequency and by this I mean how often do you split all of this volume up within the context of a week? Would you work through all your volume for a muscle group in just one session, similar to the BroSplit protocol or is it more advantageous to split the volume out and if so, why? Back to the research!
Schoenfeld explored this further in his 2016 meta-analysis. Findings from the analysis suggest that when total volume is equalised, training a muscle group over 2 session is more effective for muscle growth Vs putting all volume into just the 1 session.
Muscle protein synthesis is raised for 24-48 hours post-resistance training session and just 4 sets of exercise can elicit such a response it my be favourable to split volume up, rather than pooling it all together.
Furthermore, excessive sets beyond this point continue to accrue fatigue, both muscular and systemic leading to the possibility of sub-maximal loads beyond this point and fatigue issues in sessions to follow.
This was also hypothesised in the Denkel review in 2016. The review itself concluded that more focus should be placed on higher training frequency Vs session set volume and suggests that muscle protein synthesis activation is a key consideration as to why that may be the case:
With that being said, what are the key takeaways from all this volume talk? The points below are formed from my opinion from training experience, both from myself and practical implications with clients as well as the literature reviewed:
• Although it’s possible to increase your muscle tissue by using heavy set loads and also high volume sets, if it can be avoided and gaining muscle tissue is the primary focus I tend to advise against this and instead opt for a 8-12 rep range, particularly for beginners.
• Heavier sets are conducive for hypertrophy and especially strength, mainly using compound lifts, such as back squats, bent over rows, deadlifts and therefore require a high degree of technical application, which comes with more lifting experience and coaching.
• Heavier sets also tend to come with higher injury risk. Given hypertrophy (naturally) is a slow process that requires consistent training and nutrition from a long-term perspective higher rep ranges offer a bit more of a sustainable approach.
• Higher rep sets up to 30 are useful to utilise especially during times of necessity such as if you don’t have full gym access; on holiday and only have bodyweight to work with. However if given the option the bulk of mine and clients rep range for muscle growth is 8-12.
• Overall weekly training volume is so nuanced that providing black and white guidelines across the board isn’t useful. The key takeaway is that as we become more experienced as lifters we begin to adapt more and more to the stimulus/training volume (sets/reps/weight).
• One way to progressively overload the muscle is to include more training volume in the form of sets. The question of when to add more (and remove) volume should be reviewed periodically based on factors including overall state of fatigue; muscle recovery (soreness post-session); quality of muscle pump and performance indicators such as increasing training loads.
• For individuals who are new to resistance training I believe there to be some benefit in starting on the lower end of the volume spectrum Vs higher initial predictions. If the training volume is too much too soon it can easily lead to too much muscle soreness and consequently less training frequency and weekly volume and systemic fatigue which then needs to be unravelled. Therefore 10-15 sets per week per muscle group tends to be a good starting place in this instance.
• Training frequency – in my mind – is less of a nuanced debate and BroSplit training templates of once per week per muscle group doesn’t appear to be the most effective use of ones time. If time permits twice per week appears to be constructive and experienced lifters who are working through high volume periods may even see some benefit from increasing this to 3 times per week, although the research isn’t yet entirely conclusive.
The rationale for this would be to spike muscle protein synthesis on a more frequent basis, which is a key driver for muscle growth. Splitting this volume out would further allow for less compounded fatigue to become a load limiting factor.
For example if you done 12 sets of bench press all within just the 1 session, after around 3 to 4 sets you will likely see a dip off in performance. This could be mitigated by performing 4 sets at 3 different points within the week to allow for recovery inbetween.