Sport Science: Elastic Energy Demonstration on a Desktop

D. Moss, Editor

When teaching students to perform plyometric exercises, whether it's with jumping drills or medicine balls, it's a good idea to explain the reason for performing such exercises. The main reason is to develop the body's ability to use elastic energy, by first stretching then releasing the involved muscles—much like stretching a rubber band, then letting it snap.

Here's a way to demonstrate how elastic energy works, and to show how powerful it can be.

Demonstration
Have your students put one hand, palm-down, on a table or the floor. Instruct them to lift their index finger as high as possible, then consciously drive it down onto the table as hard as they can. This is a good example of a voluntary muscle contraction.

Then, have them use their other hand to lift the same finger, stretching it as high as they can before  releasing it. The finger will snap down with much more force than it did when the finger muscles weren't stretched. 

This graphically illustrates the difference between a voluntary muscle contraction

and one that is pre stretched and enhanced by elastic energy.

Reference: Loren Seagrave, Speed Dynamics Level III Hurdles Seminar, Cleveland, Ohio, November 1995.