There are many suggested training regimens that vary the load weight, the number of repetitions, and the rest intervals between sets. While each has its proponents, the end results may depend more on your dedication to your workouts.
The weights workout for muscle hypertrophy should be vigorous, with the number of repetitions kept at the low to medium end of the scale between 8 and 12 repetitions. (The RM is the repetition maximum, which means the most weight you can lift for this number of reps before fatigue.) If you go higher than this, say 15 to 20 repetitions to a set, or more, you are getting into the range where you would probably be better off doing cardio because the return on effort – the energy burn, is better spent jogging, cycling, stepping or rowing. At that number of repetitions, you won’t build much muscle either, so very high-repetition training with small weights has minimum value.
For the sake of simplicity, we apply some basic rules that will allow for safe and effective results.
Reps & load
Choose a load that allows you to perform the maximum reps recommended for that exercise on your first set. On your second, third and fourth set you are likely to perform less reps, which is perfectly fine. Each week you will feel stronger than the week before and perform more reps per set. Once you can successfully perform the maximum reps and sets with that load, it is time to pick up a bigger load the following week.
The importance of training with a stop watch to monitor your rest periods cannot be emphasized enough. The reason why it is so important is to allow you to accurately increase load as and when needed. The longer you rest the more recovery time you give your muscles between sets. This will make it impossible for you to determine your strength gains accurately and increase your load accordingly.