Q: How many reps should I do for maximum benefit?

A: High reps, medium reps, low reps each have their pros and cons. In fact, it can be downright confusing which is better. What’s actually true is that they all serve their purpose, depending on your health objective.

High reps (15 or more):
15 or more reps can feel like a lot and if you’ve tried it, you know it can be difficult. If you’re unaccustomed to training in this zone, you’ll find your muscles fatigue quickly, and 40 pounds starts to feel more like 100 by the final rep. High-rep training is an excellent means of increasing muscular endurance, which can be very handy in sports endeavors.

Low reps (5 or less):
Low reps are a foundation of the powerlifting approach, which involves coupling very heavy weights with low reps. However, muscle-fiber stimulation, and thus growth, is correlated closely to the amount of time a muscle is under tension. Short, intense sets of 15 seconds or less will develop strength, but they simply aren’t as effective in prodding a muscle to grow as sets of 30 to 60 seconds.

Moderate reps (8–12):
In this range, the set lasts longer than a few seconds, and the body is forced to rely on the glycolytic-energy system, which leads to the formation of lactic acid. You may think of lactic acid as a bad thing, since it’s mistakenly associated with the muscle ache you feel days after a workout, but that soreness is actually a very fleeting reaction that’s vital to new muscle-tissue production. What happens as a result is new muscle mass – for a stronger, younger you.