A lot of people get quite confused when knowing what weight, repetitions and sets they should be using when in the gym. There’s no real magic number. Every variable has a different effect on the body.
Below, is a diagram I put to together, giving you an overview on how many repetitions and sets you should be using and the intensity (or weight) you need to lift in order get a therapeutic response from your exercise(s).
Let’s just say in the Squat exercise you can lift 100kg for one repetition. This is your “maximum” also know as your 1-rep-max or (1RM). This is at YOUR 100% intensity.
If, for example, you wanted to develop power in this exercise, using 1-6 reps for 80-100% (in this case it would a 80kg-100kg load), for 6-12 sets, is best.This is because using a repetition range of six or less develops more strength in the nervous system. In short, the bigger your nervous system the more power you have in your muscles.
If you wanted to build more muscle in your legs, you would need to use between 75-85% of your “1RM” (in this case it would a 75kg-85kg load), for 6-15 repetitions, for 4-8 sets. This is because using a repetition range of 6-15 put more stress on the muscular cellular system rather then one the nervous system. In short, placing more stress (also know as tensile loading) on the “muscular” cellular system, elicits more muscle growth.
Working in the lower end range of the 6-15 repetitions, say around 6-9 works the more fast twitch muscle fibers. Doing 10-15 repetitions works the more slow twitch muscle fibers.
If you wanted to have some muscular strength and endurance you would need to use a load 60% (in this case it would a 60kg load) or less for 15-25+ reps, for 3-6 sets.
Not sure how much weight to use?
If you are not sure how much weight to put on the bar or machine, then use the repetitions as a guide. For example, if your goal is to build more muscle. Then using the 8-12 rep range is the most optimal (for most people). If you use a certain weight and you can only get five or six reps out, then it’s too heavy. On the other hand, if you get to your 12th repetition and you feel like you can get more reps out, then you are using a weight that is to light to elicit a muscle building response. Both examples defeat the objective of building muscle. Repetitions are the “king” exercise variable!
Saying that, all these variables depend on how long your have been training, your training goal, genetics, the muscle group being trained and the level of your health. The three examples above are a rough and fairly loose guideline. For a more detailed explanation on this topic check out Charles Poliquin’s book Modern Trends in Strength Training by clicking here.
Best of luck!