I honestly believe that the key to stimulating growth via lifting exercises is to know how to overload the muscle when it is stretched; the more force you can put on your body in that state (without injuring it of course) the more you’ll grow.
Forget peak contractions, it is the STRETCHED position that is key.
I’m not saying that some movements performed while holding the peak contraction for a few seconds will not help grow muscle, it does… to some extent. I’m merely saying that if you could only do one thing to stimulate growth, it should be overloading the stretch position.
There are several ways of doing that, but they all come down to being able to maximize force production at the turnaround point of an exercise (when you switch from eccentric to concentric OR from static to concentric):
The perfect rep: I already brushed on this one. The perfect rep should always be performed with the fastest turnaround possible; a snappy turnaround insure maximum force production with a given weight.
Reps from a dead start in the semi-stretched position. Starting a movement from pins (or something similar) while the target muscle group is stretched, but not excessively so (to reduce stretch-reflex participation as much as possible) forces the muscles to produce all of the strength required to overcome the inertia of the barbell; this necessitate a very important muscle contraction and is very effective at stimulating growth.
Eccentrics (negative) with a turnaround: Negatives with 90-110% of your max do have a very important growth-enhancing potential. It’s a misunderstood method and because of that, it is misapplied most of the time. People assume that the benefit of the eccentrics occur during the first 3rd of the lowering action, that lowering the weight as slowly as possible will cause more damage.
However this is not the case; the reason why eccentrics can work well is that they allow you to reach the stretch position with a heavier resistance than normal (thus the potential to increase overload in the stretch position). BUT, if the eccentric portion is not followed by a turnaround (shift to concentric or isometric action) then you will lose most of the benefits of the eccentric action.
So what you need to do is, when you complete the eccentric phase you must attempt to lift the weight. There is a very good chance that you can’t do that because you are either using a supramax weight or are doing 3-5 reps with 90-100% which means that by the 2nd rep you will not be able to lift the load. But simply attempting to lift the weight (then having your partner help you) will give you a forceful turnaround which will overload the stretch position.
- Twitch reps: by doing very rapid, short-range movements, in which you try to accelerate both during the concentric and eccentric while having a snappy turnaround will allow you to overload the stretch position via speed. Both phases of the movement are super fast, which leads to a very high force production at the turnaround, despite using a light weight. In fact, twitch reps will be more effective if a lighter weight (10-20%) is used as it will allow for much more speed in both direction.