In a recent study in the JSCR: Effect of plyometric vs. dynamic weight training on the energy cost of running; researchers demonstrated
that plyometrics had slightly superior effects on reductions in energy
cost of running compared with dynamic weight training, leading them to
render the conclusion that athletic development for the running athlete
should emphasize plyometric activities.
While I definitely agree with the thought process, my next question is, “why?” Why does plyometric training improve performance better? In
looking at the study, the weight training group only performed
explosive concentric strength training, whereas the plyometric group performed depth jumps from a range of heights.
As I noted in a previous post, eccentric training has a litany of uses in the areas of gaining mobility, enhancing resiliency, and
mitigating the speed of pronation, but I’ve really not spent much time
discussing the acute value of eccentric actions from a performance
perspective. These benefits are the same reason why I’m not at all
surprised plyometrics reined supreme over “dynamic” weight training in
the mentioned study.
Eccentric contraction has long been understood to be a very effective method for enhancing strength and power, with many suggesting
that eccentric contractions are superior to concentric training. Again
I ask why? What makes eccentric more powerful than concentric for
enhancing certain athletic qualities?
Eccentric training induces a greater neural adaptation according to Hortobagyi et al (1996), Duclay et al (2008), and Brandenburg (2002).
As less motor units are utilized in eccentric contraction, individual
motor units receive proportionally greater stimulation than in
concentric exercise (Linnamo, 2002). As noted previously eccentric
actions may produce structural adaptations that are favorable for
performance, including sarcomeres in series, meaning that each
sarcomere has to contract a shorter distance to produce a desired
contraction, potentially leading to shorter coupling times. Finally,
drop jumping has been shown to improve the ability to utilize the SSC
(duh?) that is a key player in locomotion. Research in the 1980s
demonstrated that non-drop jump trained athletes were unable to
effectively use eccentric loading in jumping and actually lost
efficiency (Schmidtbleicher, 1987).
The point of all of this ranting being that if we are seeking to develop fast athletes, we need to ensure that we have an eccentric
component. I’m not sold yet that they can only be plyometric
components to training as the study suggests, but believe that we can
probably get athletes to succeed with occasional focus on the eccentric
component in our lifting sessions as well.
We, of course, must be smart about when we’re programming an emphasis on these types of contractions as they tend to create damage
and can make athletes quite sore. I think in the early stages of SPP
would be one of the better times to get these included before you
transition away from maximal strength.