How many reps you need to do depends on your goals. As a guideline try and
stay within 2 to 6 reps for strength and power, 8 to 12 reps for muscle size
and 15 to 20 reps for endurance. If your goal is to build muscle then your
reps range should be around 8 to 12 reps i.e. the weight should be heavy
enough to allow only 8 reps, actually you should only be able to get 6 reps
with great difficulty on the 6th, but you need to continue on to fight for those
last 2 reps, it should be an absolute struggle to get those last two reps. That's
where the muscle growth is. You always need someone there to watch over
you when you are performing reps like these. On your next visit you should
aim for 9 reps, then 10, 11 and 12, these reps should also be a struggle.
When the time comes that you can force out 12 reps with great difficulty, it's
time to up the weight.
