The American College of Sports Medicine (ACSM) is regarded as the leading and most reputable trade association for professionals working in the field of exercise. They publish a number of standards and guidelines on many subjects, including reps, weights, and other topics related to strength training.

They name four different strength-training objectives. They are the development of strength, muscle mass, power, and muscular endurance.

What the ACSM advises

The guidelines recommend about 36 repetitions per exercise for strength, 60 repetitions per exercise for muscle mass, 18 repetitions per exercise for power, and 60 repetitions per exercise for muscular endurance.

Regarding the amount of weight to lift, the guidelines give recommendations as a percentage of a one-repetition maximum (1RM) for an exercise. Specifically, the ACSM says that one can develop strength by lifting an average of 80% of 1RM, muscle mass by lifting an average of 85% of 1RM, and power by lifting an average of 50% of 1RM. No quantity is given for muscular endurance, but the ACSM does recommend ‘light loads.’

There are other organizations that give recommendations, guidelines, position stands, and practices regarding strength development. There are sometimes sharp differences between the recommendations given by the different groups. The American Heart Association (AHA) and the American Association for Cardiovascular and Pulmonary Rehabilitation (AACPH), for example, both recommend just 8-15 repetitions per exercise. Relative to the AHA and AACPH, the ACSM recommends a high volume of repetitions.

But reviewing what the ACSM says, we can state the following:

1. For those pursuing strength and mass, the recommended weights are virtually the same, on average.
2. For the same aforementioned group, the recommended number of repetitions varies widely.
3. The most important variable, the one that distinguishes one method from the other, is repetitions.

Important considerations beyond reps

There are other variables beyond weight and repetitions that should also be considered. The speed of the repetitions, the rest between sets, the number of exercises, and the number of workouts per week are variables that influence the results from strength training. It’s best to work with a professional who knows all of the relevant variables and can figure them out for you.