You may have seen the debate online about which is ‘optimal’: High weight but few repetitions, or low weight with lots of repetitions? One takes grit to power through each rep. The other takes determination to make it ‘through the burn’ to the end of each set. But is one better than the other?
Multiple meta-analyses have been conducted comparing volume-matched (equal weight x set x rep) between different loading schemes. These studies comparing dozens of experiments show both forms have equal effects on hypertrophy (muscle growth) but training at high-weight leads to greater strength gains than high-repetition.
High-weight training has more strength gains1, delays the plateau in performance improvements2, and still induces hypertrophy3,4. To clarify, exercising at high repetitions also improves strength, but high-weight has a greater increase. High-rep induces equal muscle growth, but it requires reaching muscular failure for optimal adaptations, which can be difficult to reach with such low weights1,4.
Muscular endurance, or the ability to repeat an action multiple times, is a little more complicated. It’s natural to think training with high-reps would accustom the muscles to repetitive behaviours while high-load wouldn’t provide any endurance benefit, but that isn’t necessarily true. Physiologically, your body can do a certain number of reps at each relative weight. At 100%, you can do one rep (by definition), but at 50%, you can do many more (say, 20-30). If strength improves, any absolute weight will be lighter relative to your maximum, meaning you can do more reps. However, training with high-reps helps develop neural connections, allowing more efficient movement, particularly at submaximal intensities. Training with high and low-loads results in maximal strength gains and neural connections, causing better endurance adaptations than either high- or low- alone5.
Then there is caloric expenditure. When resistance training, work performed can be calculated by the distance traveled by the weight against resistance in a certain amount of time. There are 4184 joules/calorie, and our muscles waste lots of energy, only converting ~25% of food energy into work during exercise. Therefore, the calculation of work per repetition (in calories) is:
4 x distance x weight
time2 x 4184
Seen here, the higher the weight, the greater the calories. However, the greater the time per rep (an effect of increasing weight), the lower the calories. Lowering the weight will reduce the calories burned per rep, but more reps able to be performed, and the quicker time to complete each rep, implies a potential greater number of calories burned, to a point. Everyone, according to their strengths, will have a different optimum weight x rep balance point that will burn the greatest number of calories.
Therefore, ‘optimal’ is dependent on the question. If, like many people, you’re hoping to gain more strength, then high-weight resistance training seems to be the most effective form. If you’re hoping to build muscular endurance for a certain movement or muscle, mixing in some high-rep work is an excellent idea. If you’re in it to burn more calories, then maximizing the volume (weight x rep x set) is a good goal to have. Yet the research remains clear that any resistance training is better for all measures than none at all1–3, so get working!
Written by: Andres Moran-MacDonald
References
- Lacio, M. et al. Effects of Resistance Training Performed with Different Loads in Untrained and Trained Male Adult Individuals on Maximal Strength and Muscle Hypertrophy: A Systematic Review. Int. J. Environ. Res. Public. Health 18, 11237 (2021).
- Lasevicius, T. et al. Effects of different intensities of resistance training with equated volume load on muscle strength and hypertrophy. Eur. J. Sport Sci. 18, 772–780 (2018).
- Carvalho, L. et al. Muscle hypertrophy and strength gains after resistance training with different volume-matched loads: a systematic review and meta-analysis. Appl. Physiol. Nutr. Metab. 47, 357–368 (2022).
- LOPEZ, P. et al. Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis. Med. Sci. Sports Exerc. 53, 1206–1216 (2021).
- Olmos, A. A. et al. The influence of high-load and combined high- and low-load resistance training on electromyographic behavior during an absolute muscular endurance task. Eur. J. Appl. Physiol. 125, 3599–3617 (2025).