Here’s a question for you…what’s more important for building muscle: intensity or volume? Or to put it another way; is it better to lift heavy weights with lower reps or lighter weights with higher reps? If you have spent any significant amount of time in the gym you would have undoubtedly discussed this question among fellow trainers. Or perhaps you have seen those individuals in the gym doing what might seem like a crazy amount reps with a light weight and those straining every blood vessel as they try to pump out 5 or 6 reps of a heavy weight.
Load vs Volume
In research circles; more and more, exercise physiologists and scientists are starting to question some of the conventional mindsets on weight training. A lot of these questions centre on the volume (reps) versus load (i.e. weight) balance in weight training and whether it really is necessary to lift heavy all the time for maximum muscle gain. As discussed in part 1 of this series, there are a sound series of studies showing that training with an occlusion (blood-flow restriction) device at 20-30% 1-RM can produce similar strength and mass gains to higher intensity training at 70-80% 1-RM1-4. This series of studies together with others (to be discussed in part 3 of this series) were a stimulus for scientists to investigate more closely how variables such as load and intensity interact to affect muscle hypertrophy.
Study on Load vs Volume
In 2010 a group of Canadian exercise physiologists designed a study which they hoped would unravel the separate influences of load (intensity) and volume on specific anabolic variables after acute resistance exercise. The study compared the effects of unilateral leg extension exercises at 90% of repetition maximum until volitional failure (90RMF) versus 30% of repetition maximum until volitional failure (30RMF)5. In the 90RMF, the average weight lifted for the unilateral leg extensions was 82kg while the average reps were 5. In the 30RMF group, the average weight was 28kg while the average reps were 24. Each group performed 4 sets with a rest of 2-minutes between each. When translating these reps and weights into volume load (i.e. weight x reps), the 90RMF had a total average load of 710kg, whereas the 30RMF lifted an average volume of 1073kg5.
Volume and Muscle Protein Synthesis
Overall, in the 24-hour period following resistance exercise 30RMF (low-load high volume) was more effective at increasing muscle protein synthesis (MPS) than 90RMF (high-load low volume)5. However, during the 24-hour period, the researchers took measurements at 4-hours post-exercise and 24-hours post-exercise. The difference in readings at these two time points between the groups is what was most fascinating. After 4-hours, 90RMF and 30RMF resulted in similar MPS response. However, after 24-hours the increase in MPS was only sustained for 30RMF5. The study’s authors concluded that in contrast to conventional recommendations stipulating heavy loads (i.e. high intensity) are necessary to optimally stimulate muscle protein synthesis; the extent of MPS after resistance exercise is not entirely load dependent, but also volume dependant5.
Intensity Important for Muscle Protein Synthesis
A further addition to this study was the inclusion of a resistance exercise group designed to match the ‘work’ performed by 90RMF by only using a weight equivalent to 30% 1-RM. On average, this resulted in 14 reps at 30% 1-RM to achieve the same volume load as 90RMF. This was compared to an average of 24 reps in 30RMF. When comparing the effect on MPS between 90RMF and the work-matched 30% 1-RM group (30RM-WM), MPS was greater after 4-hours in 90RMF compared with 30RM-WM. From these findings the researchers concluded that the early amplitude of MPS is dependent on contraction intensity, whereas the volume of exercise affects the duration of the MPS response. It is thought that up to a point, increases in the volume of resistance exercise equate to a higher degree of muscle fibre activation. So another way of putting it is: muscle fibre activation affects the duration of the MPS response.
Summary of Load vs Volume Debate
So to summarise the study in layman terms: intensity is important in initiating the initial MPS response, whereas volume is important in sustaining the duration of the MPS response. Performing resistance exercise with lower intensity contractions allows for higher total work by the time fatigue is achieved. Additionally, exercise performed to fatigue results in eventual maximal fibre recruitment. Hence, the stimulus for MPS, in its basic physiological nature, appears to be a matter of muscle fibre recruitment.
Muscle Gain vs Strength Gain
It’s important to note that the conclusion of this study relates to muscle hypertrophy as opposed to muscle strength gains. It is not possible at this stage to say that low-load high volume models of resistance exercise are beneficial for strength gains. If you haven’t already, why not try a week or so of low-load high volume training using a weight that will result in volitional fatigue after approximately 25 reps. You never know, it may just give you that gain in muscle mass you have been looking for.
1. Fujita S, Abe T, Drummond MJ, et al. Blood flow restriction during low-intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis. J Appl Physiol. 2007;103:903–910.
2. Abe T, Kearns CF, Sato Y. Muscle size and strength are increased following walk training with restricted venous blood flow from the leg muscle, Kaatsu-walk training. J Appl Physiol. 2006;100:1460–1466.
3. Moore DR, Burgomaster KA, Schofield LM, et al. Neuromuscular adaptations in human muscle following low intensity resistance training with vascular occlusion. Eur J Appl Physiol. 2004;92:399–406.
4. Takarada Y, Sato Y, Ishii N. Effects of resistance exercise combined with vascular occlusion on muscle function in athletes. Eur J Appl Physiol. 2002;86:308–314.
5. Burd NA, et al. Low-load high volume resistance exercise stimulates muscle protein synthesis more than high-load low volume resistance exercise in young men. PLoS ONE. 2010;5(8):e12033.