There's a trick which can help sprinters to improve their times and strength athletes to get more reps out of the sets. After maximal exertion for example after 1 rep of a bench press at maximal weight your muscles can generate more power. If you rest for at least seven minutes after the maximal exertion, say Brazilian sports scientists.
It's your goal to manage more than 6 reps with over 120 kg on the bench press. But you can't. You can't manage it. It's impossible. How ever much you do your best, after 6 reps it's finished.
If you are not susceptible to injury, you can break through the plateau by making use of the post-activation potentiation phenomenon. To do this you need to warm up first, make one rep with the weight at which you can just manage that one rep and then rest. After that you do the set of which you couldn't manage more than six reps. And probably now you will manage more than six reps. The theory is that after maximal exertion your nervous system sends better messages to your muscles.
The clincher is the amount of rest you take after maximal exertion: according to Charles Poliquin rest periods of 8-12 minutes give the best results. [charlespoliquin.com 09.02.2012]
Sports scientists at the University of Sao Paulo got 11 men in their twenties, with at least one year of training experience, to do a maximal set after warming up. After that they got the men to do one set with half their maximal weight during four different workouts. During the 50%-1RM sets the researchers measured the amount of power the subjects were capable of generating. The more power they generated, the more reps they were probably able to complete.
On one occasion the researchers got the subjects to rest for 1 minute after the 1RM set, on the other occasions they rested for 3, 5 and 7 minutes. The longer the subjects rested, the more power they generated. After a rest period of 7 minutes, the power the subjects generated during the concentric movement was significantly higher than after resting for just 1 minute. See the figure immediately below.
During the eccentric movement, there was also an increase in power generated, but this was not statistically significant.
"Such a strategy could be applied as an interesting alternative to enhance the performance during competition or for tasks aimed at increasing upper-body power in training conditions", the Brazilians conclude. "However, it will be important to study the same effect after longer intervals, with the aim of observing if performance can be further improved."
J Strength Cond Res. 2012 Mar;26(3):739-44.