Resistance Training Volume Is the Key to Muscle Size
The overall volume of resistance exercise is more important than the individual variables of sets, reps and load.
Resistance training volume (RTV) is the total amount of work performed during a session of lifting; in other words, RTV = reps x sets x load (the product of repetitions times number of sets times intensity of load) (Figueiredo, de Salles & Trajano 2018). Any one of these variables can be adjusted to increase volume in a resistance training (RT) program. For example, you can increase RTV by performing extra sets of an exercise, adding more repetitions or increasing the weight being lifted.
Exercisers commonly cite “lack of time” as a high barrier to exercise, which explains why low-volume training has gained popularity. However, Figueiredo, de Salles & Trajano submit that recent publications consistently report that high RTV produces superior muscular adaptations in muscle size (i.e., hypertrophy). Is one of the variables more effective than others at increasing volume for hypertrophy? Research sheds light on this question.
Study reviewed: Schoenfeld, B.J., et al. 2019. Resistance training volume enhances muscle hypertrophy but not strength in trained men. Medicine & Science in Sports & Exercise, 51 (1), 94–103.
Participants: Thirty-four healthy, resistance-trained men (average age 24) were randomly divided into three groups: low volume (1 set per exercise), moderate volume (3 sets per exercise) and high volume (5 sets per exercise).
Intervention: The men did RT 3 days per week for 8 weeks. The program consisted of seven total-body exercises with 8–12 reps per set and 90–120 seconds of rest between sets. Researchers used muscle thickness to measure hypertrophy, which was determined via ultrasound at four body sites (biceps, triceps, mid-thigh and lateral thigh).
Results: Low-, moderate- and high-volume RT programs were all effective for muscle size adaptations. However, the high-volume training proved to be the strongest stimulus for hypertrophy development. While there were significant pre- to postintervention increases in strength and endurance in all groups, no statistically significant differences emerged between the groups.
Study reviewed: Amirthal-ingam, T., et al. 2017. Effects of a modified German volume training program on muscular hypertrophy and strength. Journal of Strength and Conditioning Research, 31 (11), 3109–19.
Participants: In this study, 19 healthy men (aged 19–24 years) with at least 1 year of RT experience were randomly assigned to German volume training (GVT) (10 sets x 10 reps) or modified GVT (5 sets x 10 reps).
Intervention: The study lasted 6 weeks; lifting occurred 3 days per week in a split-routine fashion. For example, session 1 targeted the upper back and chest (flat bench press, incline bench press, latissimus pulldown and seated row), session 2 targeted the legs (leg extension, leg flexion, leg press, lunge and heel raise), and session 3 targeted the arms and shoulders (upright row, shoulder press, biceps curl and triceps pushdown). Dual-energy x-ray absorptiometry (DXA) scans measured lean mass, and ultrasound identified muscular hypertrophy adaptations at four sites: biceps, triceps, hamstrings and quadriceps.
Results: The DXA scans revealed that both groups similarly increased their total-body lean mass (+3.1% for the modified-GVT group and +1.9% for the GVT group), However, the modified-GVT group had superior lean-mass increases in the trunk (+4.2% vs. +1.1%) and arms (+7.8% vs. +3.5%).
The ultrasound scans showed conflicting results: The GVT group had superior increases in triceps thickness (+10.7% vs. +5.6%), while the modified-GVT group had superior increases in biceps thickness (+7.3% vs. +0.9%). Both programs proved to be beneficial for hypertrophy.
Recommendation: The researchers observed that excessive volume may impede muscular adaptations. Amirthalingam and colleagues recommend a training volume of 4–6 sets per exercise to maximize hypertrophic training effects. It seems that gains plateau beyond this set range and may even regress owing to overtraining. Fitness pros should modify their client training programs accordingly.
Mechanisms of Multiple-Set Training
Why does multiple-set training evoke greater hypertrophy than single-set training? Muscle hypertrophy is a multifaceted process that research has not completely explained. However, mechanical load—the weight lifted—is perhaps the most important mechanism activating muscle hypertrophy (Wackerhage et al. 2019). A high RTV exercise stimulus produces sustained mechanical tension on the muscles, which potentially increases the postexercise activity of intracellular molecules responsible for boosting muscle protein synthesis.
Mitchell et al. (2012) report that a possible mechanism is the protein p70S6K. Their research suggests that RT, particularly when sets are taken to fatigue, activates p70S6K, which leads to metabolic changes that increase muscle protein synthesis. Additionally, higher RT volumes likely trigger more metabolic stress on muscle. Metabolic stress causes changes in muscle; effects include reduced concentration of phosphocreatine, increased lactate concentration and a lower ph (i.e., a more acidic environment). These changes have been shown to promote muscle hypertrophy (Wackerhage et al. 2019). It is probable that metabolic changes are greater during multiple-set RT programs as compared with single-set training programs. Wackerhage et al. add that microscopic structural changes to muscle from exercise-induced muscle damage also contribute to the muscle growth response in muscle.
See also: Metabolism and Strength Training
Practical Recommendations and Conclusions
Hypertrophy occurs along a spectrum of volumes, so trainers are encouraged to alternate low-, moderate- and high-volume programs to increase adherence and prevent overtraining with their clients. For instance, 3- to 5-set training can be used for overload and/or overreaching blocks, and 1- to 2-set training can be used for a recovery block. Research strongly suggests that RTV is the primary driver for hypertrophy, and higher-volume programs generally result in greater muscle growth. However, the relationship between RTV and hypertrophy may be described as having an inverted U-shape, meaning that adaptations diminish when too few or too many sets are performed.
Enthusiastic lifters may best optimize muscular hypertrophy adaptations by performing 4–6 sets per exercise (in a training session). Wackerhage et al. (2019) add that for optimal hypertrophy, clients should train at 40%–80% of their 1-repetition maximum, using loads greater than 60% if strength is also a target goal. Wackerhage and colleagues also summarize research indicating the value of resting more than 2 minutes between sets and consuming a diet that contains at least 1.6 grams of protein per kilogram of body weight.
And remember: With every rep, we all get stronger.
See also: Skeletal Muscle Hypertrophy
Figueiredo, V.C., de Salles, B.F., & Trajano, G.S. 2018. Volume for muscle hypertrophy and health outcomes: The most effective variable in resistance training. Sports Medicine, 48 (3), 499–505.
Mitchell, C.J., et al. 2012. Resistance exercise load does not determine training-mediated hypertrophic gains in young men. Journal of Applied Physiology, 113 (1), 71–77.
Wackerhage, H., et al. 2019. Stimuli and sensors that initiate skeletal muscle hypertrophy following resistance exercise. Journal of Applied Physiology, 126 (1), 30–43.