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Monday, 11 June 2012

500words on...Eccentric Strength...


500 words...
by Stuart McMillan

The ability to produce large amounts of force in as quick a possible time is paramount to all power-speed sports. With this in mind, strength and conditioning coaches design programs and exercises that they hope will lead to optimal improvements in this quality – indeed, almost all monitoring tools (force platforms, vertical jumps, Olympic lifting maximums, etc) test almost exclusively the ability to produce force.  
What is often over-looked is the body’s ability to resist (yield) large amounts of force – force that is ever-present in all of these power-speed sports (sprinting, for example – a sport that has no external resistance whatsoever - bar gravity and air - exerts forces of up to five times body weight in less than 1/10th second upon ground contact); in fact, before an athlete can apply any force whatsoever, he must first yield to the constant forces that are acting upon him (namely, gravity, inertia, and the specific forces unique to his sport); without developing the abilities required to efficiently endure these forces, the body will not (an cannot) apply the types of forces it is otherwise capable of. 
It is for this reason that we spend a significant amount of time within our strength-training program developing the ability to resist force – the ability to DEcelerate, rather than ACCelerate. This ability has been given many terms in the literature, including coupling time, amortization phase, plyometric ability, and stiffness.  For our purposes, we prefer to define it as ‘eccentric strength’.  Traditional programs will often include exercises that employ slow eccentrics or ‘accentuated negatives’ within their loading schemes; often, though, this is quite haphazard in its application, and there is little understanding of how it is used within the structure of the yearly training plan and how it can best be employed. 
Eccentric-dominant exercises (those that begin with the eccentric movement - thereby requiring specific control of the eccentric phase, in the knowledge that the weight must be returned to its starting position volitionally - i.e. using force; for example, back squat, single-leg squat, bench press, etc.) are the cornerstone to any successful strength program. Within our system, we tend to focus more on abilities that involve controlling the eccentric portion of these exercises earlier in the training year (traditional eccentrics, bar and band eccentrics, accentuated negatives, and various forms of isometrics). As the season progresses, the available time in which we work to control these forces is reduced, and the focus involves less the eccentric control, and more the eccentric speed.  This work nicely mirrors that of our specific training, which involves moving at greater velocities as the season progresses (whether it be through specific programming or just the improvement in speed qualities through training, or both).
Emphasis on eccentric speed requires that the athlete perform exercises that require deceleration from either high velocity or high force (or both) as quickly and efficiently as possible.  Traditional exercises have included depth landings; while within our system, we employ a multitude of weighted variations.

2 comments:

  1. People tend to be a lot about propulsion and much less about amortization. Do you have a sample of progression of exercices that you use throughout the year. I guess the key factors are time under tension and tension, is it in concordance with your pliometric scheme?

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    1. I will expand on this in a separate blog-post...but you see it pretty much the same way I do.

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