Rep count for muscle building

Rep count is more than a matter of preference: the same weight and the same exercise on the same day can produce quite different responses. Here is a practical way to find a suitable rep range for an exercise—and why you should not treat the result as set in stone.

Why does rep count matter?

When it comes to muscle building, a common question is whether it is better to do 6–8, 8–10 or 10–12 reps. The answer depends on the exercise, the muscle group you are training, your technique and your actual strength on that particular day.

The old-school method goes like this: choose one basic exercise and test how many reps you can perform with a weight that is 80% of your 1 RM. For your chest, this could be the bench press. For your lats, pull-ups; for your quadriceps, squats; for your biceps, standing barbell curls; and for your biceps femoris, lying leg curls.

The simple truth is that this offers a useful indication, but not a definitive answer. This is especially true when you test a compound exercise that works several muscles at once.

Rep count and the 1 RM test in practice

Start with a light warm-up. Then rest for 3 minutes and establish your 1 RM, or one-rep max. Make sure you do this with a spotter. If your first or second attempt fails, rest for 4–5 minutes after each attempt.

Once you know your 1 RM, rest for 10 minutes. During this time, calculate your 1 RM minus 20%. After the 10 minutes are up, perform as many reps as you can with good technique using a weight of 1 RM − 20%. Take about 4 seconds to lower the weight. Lift forcefully and with control, but do not deliberately slow the lifting phase.

Record your rep count. If you managed 7 reps, this suggests that a moderate rep range suits you for this exercise. If you managed fewer than 7 reps, the result points more toward explosive strength. If you managed more than 7 reps, you tolerate longer sets better in this movement.

Here is the next step. Calculate 15% of the rep count you achieved. Subtract this from your rep count to get the lower limit. Add the same 15% to get the upper limit. If you performed 7 reps with 80% of your maximum weight, your muscle building rep range for the bench press could be 6–8 reps.

The calculation looks like this:

1. 15% of 7 = 1
2. 7 − 1 = 6
3. 7 + 1 = 8

So, in this example, the ideal rep range would be 6–8 reps.

Rep count tells you about more than one muscle

We need to be honest here. The bench press does not just test your chest muscles. Your shoulder muscles, triceps and a number of stabilizing muscles also work to keep your body and the barbell in position. So we are really talking about the rep range for a pressing movement, rather than just the muscle fiber composition of your chest.

The same applies to other compound exercises. A squat does not tell you only about your quadriceps. A pull-up does not tell you only about your lats. The more an exercise isolates a muscle, the more closely you can link the result to that muscle, but complete isolation is rare in the gym.

Your 1 RM also fluctuates quite a lot. Some days you are stronger in the afternoon; on others, you have slept poorly, your eating is off or your mind is on other things. Changes can happen even within a few hours. This means that all the percentages you use in this calculation fluctuate too.

Rep count in your training program

Your test result is a useful starting point, not a lifelong rule. If your result points to a range of 6–8, that does not mean you should always train exclusively within that range. Your body needs different stimuli.

1. Use your main range, such as 6–8 reps, when you want to put a clear emphasis on strength in the exercise.
2. Include moderate-rep sets in your training cycle, such as 8–10 and 10–12 reps, to keep your training load from becoming too repetitive.
3. Shorter sets may suit muscles with faster-twitch fibers, such as the biceps femoris or the long head of the triceps.
4. Muscles with slower-twitch characteristics or a mix of fiber types often tolerate a broader range.

For example, in some training cycles you could use ranges of 6–8, 4–6 and 3–5 for the biceps femoris. For the quadriceps, 15–20, 10–12 and 6–8 may also work. This shows just how broad the range that supports progress can be: 3–8 for the biceps femoris and as wide as 6–20 for the quadriceps.

So what is actually happening? You are not looking for a magic number. You are looking for a range where your technique holds up, the training load is sufficient and your muscle can do more work over time.

FAQ

Is a 1 RM test suitable for beginners?

Generally, not for a complete beginner. If your technique is not reliable, a 1 RM test is too risky. Start with moderate weights instead and learn to perform the exercise properly.

Does the same rep range suit every muscle?

No. Some muscles and exercises respond better to shorter sets, others to longer ones. That is why it is worth changing your rep ranges from one training cycle to the next.

Does the formula reveal the exact distribution of muscle fiber types?

No. It offers a practical indication of a suitable rep range for the exercise. A compound exercise works several muscles at once, so you cannot attribute the result to just one muscle.

Translated by: Janar Rückenberg

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