This is a popular question asked by all new members of a gym. The question is directly related to ‘how much weight can you lift’ and ‘how many sets are you doing’.
To begin with, it is important to define exactly what a set and rep is. These definitions may seem obvious, but there are many misconceptions about these terms. One rep is the completion of one full range of motion for whatever exercise you are doing. For instance, if you are doing bicep curls, one rep begins with your arms hanging at your side, about shoulder width apart. You then contract your biceps, bringing the weights up until your forearms are touching your biceps in a slow and controlled motion. You then bring the weights back down to the starting position. In general, the motion that requires exertion (in this case a contraction) should be performed faster than the movement bringing the weights back to the resting position.
One set consists of the number of reps necessary to deplete your strength entirely. This is otherwise known as training until failure. In every set, you should keep doing reps until you cannot perform another one – no matter how hard you try. At the end of such a set, you will feel what is known as the ‘burn’. This is the secretion of lactic acid in the targeted muscle, which is what prevents further reps from being performed.
Although it is important to train until failure, some care must be taken in interpreting the lactic acid limit. Some people will try to go beyond this limit, and will begin to perform reps with imperfect form, in an effort to keep going. With the example of the bicep curls, this may involve switching from a slow and control contraction, to a swinging motion of the dumbbells. This is not at all beneficial, as you are using the momentum of the weights to complete the reps, rather than your muscle strength. The thing to look out for near the end of your set, is when you start to break form. This could arise in a variety of ways. One common indication is that your back begins to curve, and your shoulders slump forward with upper body exercises. Another indication of failure is the onset of quick and jerking motions in your exercises. No matter what muscle you are training, your movements should always be executed with perfect control. Anything short of this is detrimental. So train until failure, but do not break form.
The next factor in this equation is how much weight to use. You should choose the resistance such that you reach failure within 8-15 reps on each set. Once you get to know your body’s limitations better, you will be able to estimate how this sort of weight should feel on your first two reps, and you will then be able to adjust accordingly. Do not make the mistake of assuming that more weight equals better results. If you use too much weight your form will suffer, and you will not reach the same results.
Some recent studies have claimed that if you wish to gain size, you should aim toward the low end of this range – i.e. 8 reps, and if you wish to aim for definition, you should aim for the high end – 15 reps. However, there seems to be conflicting information in these studies, so this is not entirely established. The most important thing is to push yourself to your limit, and you will achieve results. This means that you must train reach failure in every single set – not just the last. It also means that you cannot stop at 15 reps just because you reach that number. You must choose the weight so that you reach failure within the 8-15 range – otherwise you are just performing an arbitrary number of reps.