Tempo

What It Is

How fast or slow you perform each repetition.

Why It Matters

How long each repetition takes probably has little bearing on the muscle you build. A meta-analysis spanning repetition durations from roughly 0.5 to 8 seconds found equivalent hypertrophy across the range, the later work that separates the lifting phase from the lowering one has found little between them, and the field's current position stand does not name tempo among the variables worth prescribing for strength, size, or power.

One thing does move, and it is on the lifting phase: deliberately slowing the lift probably costs you a little strength, since decelerating the weight caps the force you produce on exactly the phase a one-repetition maximum tests. In practice that means not stretching the lifting phase past about two seconds on purpose. How long you take to lower the weight is a separate question with a different answer, and there a slower lowering looks equal to a quicker one rather than worse. One guardrail is worth mentioning, though the evidence behind it is thinner: intentionally very slow repetitions (above roughly 10 seconds) appear to impair hypertrophy, since they force you to use a weight too light to drive growth.

You don't need to track any of this. Volume, load, progression, and consistency matter far more, and the lever that matters here is intent rather than arithmetic: training to produce force rapidly appears to improve your rate of force development even when the weight itself moves slowly. Control the weight through a full range of motion, don't deliberately crawl, and drive the lift rather than counting seconds on it.

• Schoenfeld, B.J. et al. (2015). Effect of repetition duration during resistance training on muscle hypertrophy: a systematic review and meta-analysis. Sports Medicine. doi.org/10.1007/s40279-015-0304-0
• Davies, T.B. et al. (2017). Effect of Movement Velocity During Resistance Training on Dynamic Muscular Strength: A Systematic Review and Meta-Analysis. Sports Medicine. doi.org/10.1007/s40279-017-0676-4
• Blazevich, A.J. et al. (2020). Effects of Resistance Training Movement Pattern and Velocity on Isometric Muscular Rate of Force Development: A Systematic Review with Meta-analysis and Meta-regression. Sports Medicine. doi.org/10.1007/s40279-019-01239-x
• McLeod, J.C. et al. (2023). The influence of resistance exercise training prescription variables on skeletal muscle mass, strength, and physical function in healthy adults: An umbrella review. Journal of Sport and Health Science. doi.org/10.1016/j.jshs.2023.06.005
• Hermes, M.J., Fry, A.C. (2023). Intentionally slow concentric velocity resistance exercise and strength adaptations: a meta-analysis. Journal of Strength and Conditioning Research. doi.org/10.1519/JSC.0000000000004490
• Amdi, C.H., King, A. (2025). The effect of eccentric phase duration on maximal strength, muscle hypertrophy and countermovement jump height: A systematic review and meta-analysis. Journal of Sports Sciences. doi.org/10.1080/02640414.2025.2535198
• Enes, A. et al. (2025). How slow should you go? A systematic review with meta-analysis of the effect of resistance training repetition tempo on muscle hypertrophy. Journal of Strength and Conditioning Research. doi.org/10.1519/JSC.0000000000005302
• Currier, B.S. et al. (2026). American College of Sports Medicine Position Stand. Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews. Medicine & Science in Sports & Exercise. doi.org/10.1249/MSS.0000000000003897