Repetition speed and tempo for muscle growth

Repetition speed and tempo for muscle growth

Many people would like to spend their time in the gym as efficiently as possible. This means that many people would like to gain the most muscle mass possible in the shortest amount of time. In order to achieve this goal, every training should be optimized. Due to this, people would like to know more about the optimal duration per repetition and time under tension. In this article, we will explain more about the best duration per repetition and suggested lifting tempo for optimal muscle growth.

What are repetitions and sets

Repetition and sets are two key components of resistance training. A repetition, or “rep” for short, refers to the completion of a single movement during an exercise. For example, in a bicep curl, one repetition would involve lifting the weight from a starting position to a full contraction of the bicep muscle, and then lowering the weight back down to the starting position. Basically, a repetition (rep) is one completion of an exercise.

A set refers to selected amount of repetitions that are performed in a row before you rest. For example, if someone performs 10 repetitions of bicep curls, takes a short break, and then performs another 10 repetitions, they have completed 2 sets of 10 repetitions.

Phases during repetitions (concentric, isometric, eccentric)

Repetitions usually consist of 3 phases. These are often called: concentric, isometric, and eccentric phase. It is important to know what the 3 phases are, in order to understand the best tempo.

  • Concentric phase: The concentric phase is also known as the “lifting, or “positive” phase. During this phase, muscles produce force in order to overcome resistance placed on them. During this movement, the muscle shortens and contracts. For example, during a bicep curl, the concentric phase happens when the lifter bends their elbow to lift the weight towards their shoulder.
  • Isometric phase: The isometric phase is also known as the “hold” phase. During this phase, the forces produced by the muscles are equal to the resistance placed on them. This means there is no muscle movement at all.
  • Eccentric phase: The eccentric phase is also known as the “negative” phase. During this phase, the muscles are actively resisting the force acting upon it. This results in the lengthening of the muscle fibers. For example, during a bicep curl, the eccentric phase happens when the lifter is lowering the weights.

When we are talking about the suggested tempo, we usually distinguish the 3 phases. This results in a format which includes the recommended seconds per phase. This is often displayed as, for example: “2-1-3”. This means 2 seconds up, 1 second pause, 3 seconds down.

What is time under tension

Before we can continue with the suggested tempo per repetition for muscle growth, we need to quickly explain an important element called time under tension. Time under tension (TUT) is a measure of the total amount of time that muscles are under stress during an exercise set. It refers to the duration of time that muscles are being used through the eccentric, isometric, and concentric phase of a movement. It is important to realize that time under tension and repetition tempo are closely related, and could affect one another.

Optimal duration / seconds per repetition for muscle growth

Many studies and people have focused on the optimal time under tension. However, it is also important to look at the lifting tempo in order to get the best possible results. Unfortunately, not many studies have been done regarding the optimal tempo per repetition. Due to this, there are some debates if you should do slow or fast repetitions if you want to maximize muscle growth.

  • Slow repetitions: Slow repetitions are often associated with a greater time under tension, and usually take up to ~5-8 seconds per repetition. Most studies indicate that these slower repetitions, with a controlled eccentric (lowering) phase, are more effective for muscle growth than fast repetitions [1][2]. However, there are studies which indicate that the consistent use of super slow repetitions of >10 seconds, are not as beneficial are as “normal” slow repetitions or fast repetitions [3].
  • Fast repetitions: Fast repetitions are commonly associated with strength, and usually take ~2 seconds per repetition. It has been confirmed by several studies that fast repetitions are more beneficial than slow repetitions if you want to improve strength [1][4][5][6].

While many studies confirm the popular belief that slow repetitions are better for size, and fast repetitions are better for strength, there are also studies which have shown different outcomes. Some studies indicate that slow repetitions are better for increasing both strength and muscle size [7]. However, there are also studies which indicate that fast repetitions are better for both strength and muscle size. When we look at the results from most studies, it appears that muscle growth is similar when repetitions ranging from 2 to 6 seconds are used [8].

Combining fast and slow reps

Many people use a combination of a fast and slow movement. This is often done by using a fast concentric movement and a slow eccentric movement. Which basically means: slow and controlled down, and a faster explosive motion up. Examples of durations which can be used look like: “2-1-3” or “1-1-4”. Many people favor a slower concentric movement since this may help to prevent injuries and feel the mind muscle connection. Unfortunately, studies have not made it clear if combining different speeds can further enhance muscle growth. However, this seems like a very suitable pace for most people.

Furthermore, some people suggest changing the tempo you use once in a while. Studies have not proven the usefullness. But, this could be used in order to keep workouts interesting. Based on the progressive overload principle, changing your repetition speed from time to time, can perhaps help to achieve better results [9].


There are a limited amount of studies regarding the optimal tempo. Furthermore, most studies have limitations, and the outcomes of these studies can differ. In order to make final conclusions more research is required.


  1. Munn, J., Herbert, R. D., Hancock, M. J., & Gandevia, S. C. (2005). Resistance training for strength: effect of number of sets and contraction speed. Medicine & Science in Sports & Exercise, 37(9), 1622-1626.
  2. Yendrizal, Y. (2018, March). THE EFFECT OF WEIGHT TRAINING USING FAST AND SLOW REPETITION MOVEMENT TOWARDS THIGH MUSCLE HYPERTROPHY. In 3rd International Conference on Sports Science, Health and Recreation.
  3. Schuenke, M. D., Herman, J. R., Gliders, R. M., Hagerman, F. C., Hikida, R. S., Rana, S. R., … & Staron, R. S. (2012). Early-phase muscular adaptations in response to slow-speed versus traditional resistance-training regimens. European journal of applied physiology, 112, 3585-3595.
  4. González-Badillo, J. J., Rodríguez-Rosell, D., Sánchez-Medina, L., Gorostiaga, E. M., & Pareja-Blanco, F. (2014). Maximal intended velocity training induces greater gains in bench press performance than deliberately slower half-velocity training. European journal of sport science, 14(8), 772-781.
  5. Neils, C. M., Udermann, B. E., Brice, G. A., Winchester, J. B., & McGuigan, M. R. (2005). Influence of contraction velocity in untrained individuals over the initial early phase of resistance training. The Journal of Strength & Conditioning Research, 19(4), 883-887.
  6. Kim, E., Dear, A., Ferguson, S. L., Seo, D., & Bemben, M. G. (2011). Effects of 4 weeks of traditional resistance training vs. superslow strength training on early phase adaptations in strength, flexibility, and aerobic capacity in college-aged women. The Journal of Strength & Conditioning Research, 25(11), 3006-3013.
  7. Pereira, P. E. A., Motoyama, Y. L., Esteves, G. J., Quinelato, W. C., Botter, L., Tanaka, K. H., & Azevedo, P. (2016). Resistance training with slow speed of movement is better for hypertrophy and muscle strength gains than fast speed of movement. International journal of applied exercise physiology, 5(2).
  8. Schoenfeld, B. J., Ogborn, D. I., & Krieger, J. W. (2015). Effect of repetition duration during resistance training on muscle hypertrophy: a systematic review and meta-analysis. Sports Medicine, 45, 577-585.
  9. Peterson, M. D., Pistilli, E., Haff, G. G., Hoffman, E. P., & Gordon, P. M. (2011). Progression of volume load and muscular adaptation during resistance exercise. European journal of applied physiology, 111, 1063-1071.


Mario Klasens Author XBR