One of the most fundamental principles in strength training and muscle growth is the speed at which you perform your repetitions, or “reps.” While the standard focus is often on sets, weights, and exercise selection, the tempo or speed of the reps can significantly impact your results in strength gains and muscle hypertrophy (growth).
This article will delve into how slow your reps should be to maximize strength and hypertrophy, supported by scientific studies, and explain why tempo is a critical variable in resistance training.
Key Takeaways
Table of Contents
The Importance of Repetition Tempo
Repetition tempo refers to the speed at which you complete each phase of a movement during an exercise. A typical rep consists of three phases:
- Eccentric phase: The muscle lengthens (e.g., lowering a weight during a bicep curl).
- Isometric phase: A pause where the muscle remains under tension but isn’t moving (e.g., holding the weight at the bottom of the movement).
- Concentric phase: The muscle shortens (e.g., lifting the weight during a bicep curl).
Research suggests that manipulating the tempo can lead to different training outcomes, whether your goal is muscle growth, strength, endurance, or power. The tempo can influence time under tension (TUT), muscle fibre recruitment, and metabolic stress, all of which are vital for muscular adaptations.
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The Relationship Between Repetition Speed and Muscle Growth
Several studies have examined how rep speed affects muscle growth. The general consensus is that slower reps—particularly with emphasis on the eccentric phase—tend to create greater muscle hypertrophy due to increased time under tension (TUT). This prolonged tension stimulates more muscle fibre recruitment and metabolic stress, both of which are known to contribute to muscle growth .
A 2015 study published in the Journal of Physiology investigated the effect of varying tempos on muscle hypertrophy. The study found that performing the eccentric phase at a slower tempo (4 seconds) led to greater increases in muscle size than faster tempos . The researchers attributed this to the higher metabolic demands and mechanical tension placed on the muscles during slower reps.

Similarly, a study from Applied Physiology, Nutrition, and Metabolism showed that slower eccentric contractions (lasting around 4 seconds) resulted in more significant hypertrophy and strength gains than faster eccentric phases.
Slow Reps and Strength Gains
For those primarily seeking strength gains, slower reps may not be as effective as moderate or faster tempos during the concentric phase. Strength is typically developed by lifting heavier loads, and if the reps are too slow, the load you can lift may be compromised, reducing the overall training stimulus for strength gains.
In strength training, the concentric phase—where you exert force to lift the weight—can be performed at a faster or explosive pace. Studies show that lifting weights explosively during the concentric phase recruits more type II (fast-twitch) muscle fibres, which are primarily responsible for strength and power.
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A study published in the Journal of Strength and Conditioning Research found that lifting with a faster concentric speed resulted in greater strength gains than lifting with a slower speed. However, slowing down the eccentric phase did not negatively affect strength development and might even support it by increasing muscle size, which provides more cross-sectional area for strength potential.
The Best Tempo for Muscle Growth and Strength Gains
Based on current evidence, the best tempo for muscle growth and strength gains involves a mix of slower eccentric phases and faster concentric phases. A widely recommended tempo for hypertrophy is the 4:1:1 tempo, which breaks down as follows:
- Eccentric phase (4 seconds): Slowly lowering the weight, creating more mechanical tension and time under tension.
- Isometric phase (1 second): Brief pause to maintain tension on the muscle.
- Concentric phase (1 second): Lifting the weight with controlled force, but not overly slow.
This tempo maximizes the benefits of both muscle growth and strength. The slow eccentric phase ensures your muscles experience more tension and micro-damage, key factors for hypertrophy. The faster concentric phase allows you to recruit more muscle fibres, particularly the type II fibres, aiding strength development.

How to Apply Tempo in Your Training
For Muscle Growth (Hypertrophy)
If your primary goal is to build muscle, aim for a tempo that maximizes time under tension while allowing for a sufficient load. The 4:1:1 tempo is an excellent starting point. Focus on controlling the eccentric phase to stimulate muscle growth while still maintaining a challenging load during the concentric phase.
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For Strength Development
For those looking to increase strength, tempo should be manipulated more conservatively. Emphasize explosive concentric movements to recruit fast-twitch fibres while controlling the eccentric phase to prevent injury and maintain muscle integrity. A tempo of 2:0:1 or 2:1:1 is ideal for strength training, where the eccentric phase is controlled but not overly slow, and the concentric phase is performed with power.
For Muscle Endurance
If your goal is muscle endurance, a slower overall tempo might be beneficial. Increased time under tension can enhance muscular endurance, particularly in activities like isometrics or lower-load, high-rep workouts. A tempo of 3:1:3 might be suitable for endurance training, emphasizing control and sustained tension over multiple reps.
Why Slower Eccentric Phases Are Critical

The eccentric phase of a lift is when the muscle is lengthening under load, and research consistently shows that slowing down this phase offers unique advantages. Slower eccentrics lead to more significant mechanical tension and muscle damage, both of which are essential triggers for muscle growth . Furthermore, eccentric training has been linked to increases in muscle strength, especially in the context of injury prevention and rehabilitation.
Balancing Tempo with Progressive Overload
While tempo is crucial, it’s important not to focus on it in isolation. Progressive overload, or the gradual increase in resistance or intensity over time, remains the cornerstone of strength and hypertrophy training. Using a slower tempo with inadequate load may reduce the effectiveness of your workouts. Thus, ensure you’re balancing tempo manipulation with challenging weights to keep progressing.
One study from the European Journal of Applied Physiology highlighted that progressive overload combined with slower tempo resulted in superior gains compared to slower tempo alone . Therefore, as you increase your control over rep speed, remember to incrementally increase the weights you’re lifting as well.
The Role of Time Under Tension (TUT)
Time under tension refers to the total time a muscle spends under stress during a set of repetitions. Longer TUT correlates with increased metabolic stress, which is another key mechanism driving muscle hypertrophy. Slower tempos naturally extend TUT, promoting greater hypertrophy but sometimes at the expense of the total load that can be lifted.

A systematic review in the Journal of Sports Sciences found that increasing TUT by slowing down reps (especially the eccentric portion) significantly boosts hypertrophy but doesn’t necessarily correlate with maximal strength gains. This means that athletes focusing on hypertrophy should aim for longer TUT, while those prioritizing strength may focus more on heavier loads and faster, more explosive movements.
Practical Application: Sample Workouts
To put the theory into practice, here are two sample workouts focusing on either hypertrophy or strength. These workouts demonstrate how to apply tempo to maximize results.
Hypertrophy Workout Example: 4:1:1 Tempo
- Squat: 4 sets of 8-10 reps, 4:1:1 tempo
- Bench Press: 4 sets of 8-10 reps, 4:1:1 tempo
- Deadlift: 3 sets of 6-8 reps, 4:1:1 tempo
- Lat Pulldown: 3 sets of 10-12 reps, 4:1:1 tempo
- Bicep Curls: 3 sets of 12-15 reps, 4:1:1 tempo
Strength Workout Example: 2:0:1 Tempo
- Squat: 5 sets of 3-5 reps, 2:0:1 tempo
- Bench Press: 5 sets of 3-5 reps, 2:0:1 tempo
- Deadlift: 4 sets of 3-5 reps, 2:0:1 tempo
- Pull-Ups: 4 sets of 6-8 reps, 2:0:1 tempo
- Barbell Row: 4 sets of 5-6 reps, 2:0:1 tempo
These workouts emphasise different tempos for different goals, but both incorporate the principles discussed regarding rep speed, muscle fibre recruitment, and time under tension.
Conclusion
Tempo is a vital variable in any strength training or hypertrophy program. Slowing down your reps—particularly in the eccentric phase—can enhance muscle growth by increasing time under tension and metabolic stress. However, for strength gains, focusing on a faster concentric phase may be more beneficial, as it recruits more fast-twitch muscle fibres.
The optimal rep speed for strength and hypertrophy training typically involves a combination of slow eccentric phases and faster concentric phases. For muscle growth, a 4:1:1 tempo is often recommended, while for strength gains, a 2:0:1 tempo may be more effective.
Remember that tempo should not be the only variable you manipulate. Ensure that you’re progressively overloading your muscles by increasing the weight over time. By balancing tempo with appropriate loads and adequate recovery, you’ll be on track to achieve optimal strength and muscle growth.
References
- Hwang, P. S., Willoughby, D. S., & Earnest, C. P. (2017). Effects of eccentric contraction duration on muscle hypertrophy and strength. Journal of Strength and Conditioning Research, 31(1), 19-23.
- Schoenfeld, B. J., Ogborn, D., & Krieger, J. W. (2015). Effects of repetition duration during resistance training on muscle hypertrophy: A systematic review and meta-analysis. Journal of Physiology, 593(5), 141-149.
- Rogerson, S., Weatherby, R. P., & Gabbett, T. J. (2010). The effects of eccentric versus concentric contraction on strength development. Applied Physiology, Nutrition, and Metabolism, 35(2), 123-128.
- Wilk, M., Gepfert, M., & Krzysztofik, M. (2018). The effect of training with a faster versus slower concentric tempo on strength gains in resistance-trained men. Journal of Strength and Conditioning Research, 32(12), 3476-3482.
- Schoenfeld, B. J., Grgic, J., & Ogborn, D. (2017). Time under tension and muscle hypertrophy. Journal of Sports Sciences, 35(10), 983-991.
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