When you perform a set of an exercise. Every rep you do is slightly harder than the last rep. Your muscles work hard to lift the weight in the given exercise and eventually tire out.
If you focus on maintaining the correct technique of the exercise without stopping the set, eventually your muscles will become so tired that they will not lift the weight another inch.
This is called training to failure!
The closer you get to failure, the more stimulating each rep becomes.
When one of Our programs indicates you should “Train close to failure”,
What this means is that you must lift a weight heavy enough, and perform enough reps with the correct technique so your body receives a signal that it must get stronger.
Although the most common phrase used is “Training to failure“, I will often say “Training to Stimulus“.
The goal is to lift enough weight for enough reps, with good form up to the point in which your body is forced to respond and get stronger.
The point of stimulus occurs just before all-out failure and is a far better target for completing a successful set.
Complete muscular failure, although very rewarding, can sometimes be quite dangerous. The closer you get to failure, the more likely you are to use the sloppy technique.
Training to a stimulus will allow you to rack up a lot of rewarding reps without also having to complete the more risky reps closer to failure.