High speed eccentric loading (like what’s found in reactive lifts, plyometrics, sprints, etc.) carries with it a number of positive adaptations that can be found pretty much nowhere else. Plenty of people know that sprints and plyos are useful, but few know the exact physiological changes they bring about. In order to clear things up, we’re going to try to shed a little light on the topic. Training methods focused on high speed/high force eccentric loading bring with them the following benefits:
Strength Specificity:
Neurologically speaking, strength is largely specific to muscle contraction type. Someone with high levels of concentric strength will tend to have high levels of eccentric and isometric strength, but it is possible to develop one or two kinds of strength out of proportion with the others. Eccentric loading trains eccentric and isometric strength to a higher degree than does concentric training. And since most sporting movements are dependent on reactivity (which is dependent on eccentric and isometric strength), this is most certainly a good thing.
Fast Twitch Fiber Hypertrophy:
Eccentric training, especially high speed eccentric training, has been shown to hypertrophy type IIa and type IIb fibers to a greater degree than concentric training. Similarly, some research shows a decrease in type I fibers from this type of training as well.
Sarcomeres in Series:
Traditional hypertrophy is an increase in the number of sarcomeres (basic contractile units within a muscle fiber) running in parallel with one another. This appears as a greater muscle cross sectional area. In addition to basic hypertrophy, eccentric loading also builds more sarcomeres running in series (end to end). This appear as longer muscle fascicles and allows for greater muscle shortening speeds.
Intramuscular Connective Tissues:
Eccentric loading makes muscles more resistant to damage caused by further loading. It accomplishes this through building stronger intramuscular connective tissues. This also decreases the likelihood of injury due to muscular overload.
All in all, eccentric training is slightly difficult to apply (as the high intensity it involves increases chances of injury is misapplied), but it’s more than worth it. Understanding why it’s useful isn’t really necessary, but it’s neat to know anyways.
