Fast or Slow Reps?


American College of Sports Medicine recommendations

George Cho, MFSc, CEP, CSCS


It is common to see individuals performing repetitions at different speeds. Some will go slow on the exertion phase while others go slow on the “resting” “eccentric” phase. For example, for a bench press, some will go 10 seconds on the way up and 10 seconds on the way down. But what does the science and reputed authorities recommend regarding how fast repetitions should be performed during resistance training?


The American College of Sports Medicine (ACSM)’s position paper on progression models states the following: 

It appears that the intent to maximally accelerate the weight during training is critical in maximizing strength gains. Although loading may be moderate to heavy, the intent to lift the weight as fast as possible has been shown to be critical for maximizing strength increases

(Ratamess N et al. Progression Models in Resistance Training for Healthy Adults. Med Sci Sports exerc. (2009). Mar; 41(3). p 693)


Often the heaviness of the load or fatigue during the final few repetitions will not permit moving the weight quickly. This is normal. However, the intention should be to move the weight as fast as possible, not to purposely go slow.

One major issue with intentionally going very slow is that less weight is used since heavy weights are difficult to control. One study showed that a 30% reduction in the training load was necessary in order to do slow repetitions. This is perhaps why the ACSM paper notes thatt purposely using very slow velocities (for example: 10 seconds) results in less peak force, power and even the number of repetitions is decreased compared to fast ones. Slow velocities however may be preferable if one is learning new techniques and getting the "feel" for the exercise. It may help with developing muscular endurance as well.



Untrained: slow to moderate  (~1 - 5 secs concentric, 1 - 5 secs eccentric)

Intermediate: moderate (1 – 2 secs)

Trained: mostly fast velocities (<1 secs) (As fast as possible).


Some examples of concentric actions and velocities to target:

Bicep curl for untrained individuals: 5 seconds on the way up.

Barbell back squats for intermediate individuals: 2 seconds on the way up.

Tricep push-downs on a machine for advanced lifters: pushing the levers down as fast as possible (< 1 second)


Note: remember by concentric, we are referring to shortening the main targeted muscle. Eccentric is the lengthening or loosely put, the “rest” phase of an exercise. Also, "untrained" refers to beginners. "Intermediate" is referring to those with at least about 6 months of training. "Trained" individuals are those with over a year of experience.



During scientific studies, it is very important to tightly control variables. Researchers are very interested in parsing out the little differences between various circumstances. Thus in this case, scientists are going to be very particular about counting the velocities of exercises. But this does not mean that it is necessary for us to do the same. The science informs us on basic guidelines, not on all the exact details of how we should exercise. The take-away is NOT that we should be meticulously timing our movements, but rather that fast is generally better than going really slow when trying to get stronger.  To give an example: moving at 2 seconds is superior to performing at 10 seconds. So instead of painstakingly timing our movements, it is sufficient that we are trying to move the weight as quickly as possible, granted, that we are comfortable with the exercise and the weight.



Slow repetitions of for instance 5 - 10 seconds or more  will not make one weaker, but it is likely inferior. These can still be incorporated into a resistance training program, but most repetitions should be performed with the intention to move the weight as quickly as possible


N Ratamess et al. American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2009 Mar;41(3):687-70

George Cho