Slow or fast repetitions? - Are you training for muscle growth or endurance

Slow or fast repetitions? - Are you training for muscle growth or endurance

Is it better to lift weights at a slower pace than a faster one, or is it perhaps better to lift at a moderate pace?

In this blog, we provide an answer to this relevant question based on various studies, investigations, and experiments.

Before starting:

It's crucial to note that all the information presented here is derived from studies and experiments. Nevertheless, it doesn't imply the necessity to overhaul your entire workout program. If you prefer training with slow or fast repetitions, feel free to stick with your preference. However, it's worth acknowledging that there is a distinction between the two approaches. If you desire different results, adjusting the speed of your repetitions might be necessary. Beginners, in particular, may find it essential to start with slow repetitions and lower weights, allowing their muscles to build memory for the exercises.

The difference

When you perform exercises with slow repetitions, there is an increased "time under tension," meaning your muscles experience prolonged stress. This occurs because the muscles are under tension for a more extended period compared to quicker repetitions. In contrast, fast repetitions result in a lower "time under tension." However, with faster repetitions, it is possible to achieve more reps, and the muscles still endure the same amount of stress, provided the same weight is used. The distinction lies in the duration of stress due to the time under tension, which varies between slow and fast repetition speeds.

A study indicates that in traditional strength training with fast/moderate lifts, there was a more significant improvement in both strength and muscle size compared to training with slower lifts. Classic strength training primarily resulted in an increase in fast muscle fibers (type 2), in contrast to slow repetitions, where there was an enhancement in slow muscle fibers (type 1). It's worth noting that slow repetitions were found to be more effective for isolation exercises (single-joint movements) rather than compound exercises (multi-joint movements)

The chart shows the difference between the muscle fibers

Differences Type 1 Type 2A Type 2B
Speed Slow Fast Very quick
Endurance High Medium Low
Strength Low High Very high


"Also read: How many sets are best for your training?"

Why time under tension does not increase muscle growth

One reason why more strength and muscle growth are not achieved solely through increased time under tension is the proven association between training volume and muscle growth in various studiesFaster repetitions, as mentioned earlier, allow for more repetitions with the same weight. For example, if two individuals each perform 8 reps for 3 sets, the person using faster reps can handle 50kg, while the one using slower reps might need to reduce the weight to 40kg for 8 repetitions. The total volume for the faster repetitions is calculated as V = 8*3*50 = 1200 and the slow ones V = 8*3*40 = 960 .

Indeed, there is a notable 20% difference in total volume between the two scenarios, emphasizing the connection between volume and muscle growth. Faster repetitions can contribute to greater muscle growth due to the ability to achieve more repetitions with the same weight. However, it's essential to note that fast repetitions should be executed without relying on momentum. Maintaining proper muscle stress is crucial, as performing repetitions with excessive momentum may diminish the effectiveness of the exercise.

Are slow lifts irrelevant for muscle growth?

As mentioned, volume increases with faster reps, but there is still a reason to perform exercises at a slow speed. Particularly in the eccentric phase, also known as the negative part, doing it slowly can be advantageous. If done quickly, gravity can take over, leading to a loss of tension in your muscles. By performing the eccentric phase slowly, you can increase the volume, preventing excessive reliance on gravity and torque during the upward movement.

Additionally, slow lifts can be employed to reach a state of absolute muscle fatigue or "muscle failure." This can be accomplished by performing the exercises until you are no longer able to lift them, and then exclusively executing the negative part of the exercise at a slow speed, inducing maximal muscle fatigue.

Person sitting on a bench press machine


In summary, there is a notable difference between lifting quickly and slowly. Volume plays a crucial role in achieving muscle growth and strength, and the lower volume associated with slow lifts means that they may not contribute to these aspects to the same extent as fast lifts. However, slow lifts can enhance slow muscle fibers, leading to a greater increase in muscle endurance.

Do you engage in training with fast, moderate, or slow lifts, and if so, what are the reasons for your training?


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