Hypertrophy, explained · Lesson 4
Heavy or light weights: which builds more muscle?
Both, if the set goes almost to the end. In 49 trained men, light sets (30 to 50% of max) or heavy sets (75 to 90%), all to failure, built the same amount of muscle over twelve weeks; heavy loads built more bench press strength. Stay above roughly a third of your max: at 20%, even to failure, the muscle grew half as much.
What counts as a heavy or light weight?
Heavy or light is a share of your max, the weight you can lift just once. In studies, heavy means about three quarters of your max or more, so 8 to 12 reps to failure; light means half or less, 20 reps and up (Morton et al., 2016). The number of reps at a given share of your max varies by person and exercise.
Why do light weights build muscle too?
Heavy, your body switches on your big fibers from the start. Light, it switches on the small ones first, then bigger and bigger ones as they tire (Muddle et al., 2018). In 10 men, muscle samples taken after sets to failure, heavy or light, showed that the fast fibers, the biggest ones, had drawn on their energy stores just as much: they had worked in both cases (Morton et al., 2019).
During an isometric thigh effort taken to failure, heavy loads still called on bigger motor units than light ones (Muddle et al., 2018). So, light, you have to take the set almost to the end, where it burns: in 23 people on the leg extension, a light load taken to failure felt harder and more uncomfortable than a heavy one (Dankel et al., 2019).
Heavy or light: which builds more muscle?
Neither builds more. In 49 trained men, over 12 weeks of a whole-body program, some lifted 30 to 50% of their max (20 to 25 reps), the others 75 to 90% (8 to 12), every set to failure: the same gains in lean mass and fiber size. On the bench press, the heavy group gained 14 kg (31 lb), the light group 9 kg (20 lb), the only strength difference between groups (Morton et al., 2016).
Across 28 studies and 747 adults, growth didn’t depend on the load when sets went to failure, and strength rose more with heavy or moderate loads (Lopez et al., 2021). Same finding across 21 studies (Schoenfeld et al., 2017), and in 18 well-trained men, whose squat improved more with heavy loads (Schoenfeld et al., 2015).
Can you go too light?
Yes. In 30 men, one arm and one leg trained at 20% of max, starting with three sets to failure, while the other side trained at 40, 60 or 80% for the same volume. After twelve weeks, the thigh had grown 8.9% at 20% of max versus 19.5% at 80%, and the elbow flexors 11.4% versus 25% (Lasevicius et al., 2018).
At 30% of max, though, sets taken to failure grew the thigh as much as at 80%; stopped far from failure, they barely did (Lasevicius et al., 2022). For one review, muscle can be built across a wide range of loads (Schoenfeld et al., 2021).
Your workout plan, built for your body.
In Tekio, your bench press page estimates your max, and your weight for one to six reps.
Sources
Studies checked in PubMed. Measured muscle activity isn’t growth: each fact keeps its study’s population and limits.
- Morton RW, Oikawa SY, Wavell CG, et al. (2016). Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. J Appl Physiol (1985) 121(1):129-38. PubMed · DOI
- Muddle TWD, Colquhoun RJ, Magrini MA, et al. (2018). Effects of fatiguing, submaximal high- versus low-torque isometric exercise on motor unit recruitment and firing behavior. Physiol Rep 6(8):e13675. PubMed · DOI
- Morton RW, Sonne MW, Farias Zuniga A, et al. (2019). Muscle fibre activation is unaffected by load and repetition duration when resistance exercise is performed to task failure. J Physiol 597(17):4601-4613. PubMed · DOI
- Dankel SJ, Jessee MB, Mattocks KT, et al. (2019). Perceptual and arterial occlusion responses to very low load blood flow restricted exercise performed to volitional failure. Clin Physiol Funct Imaging 39(1):29-34. PubMed · DOI
- Lopez P, Radaelli R, Taaffe DR, et al. (2021). Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis. Med Sci Sports Exerc 53(6):1206-1216. PubMed · DOI
- Schoenfeld BJ, Grgic J, Ogborn D, et al. (2017). Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-analysis. J Strength Cond Res 31(12):3508-3523. PubMed · DOI
- Schoenfeld BJ, Peterson MD, Ogborn D, et al. (2015). Effects of Low- vs. High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men. J Strength Cond Res 29(10):2954-63. PubMed · DOI
- Lasevicius T, Ugrinowitsch C, Schoenfeld BJ, et al. (2018). Effects of different intensities of resistance training with equated volume load on muscle strength and hypertrophy. Eur J Sport Sci 18(6):772-780. PubMed · DOI
- Lasevicius T, Schoenfeld BJ, Silva-Batista C, et al. (2022). Muscle Failure Promotes Greater Muscle Hypertrophy in Low-Load but Not in High-Load Resistance Training. J Strength Cond Res 36(2):346-351. PubMed · DOI
- Schoenfeld BJ, Grgic J, Van Every DW, et al. (2021). Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum. Sports (Basel) 9(2):32. PubMed · DOI
These lessons inform; they don’t replace advice from a health professional.