To wiggle or not to wiggle

or, a conversation with Dr. Tim Hewett; director of the Sports Medicine Biodynamics Center at Cincinnati Children's Hospiatal. Tim has some cool unpublished research going on involving ACL injuries. It goes like this:

Normal & ACL deficient athletes are placed in front of a biofeedback screen, hands folded across chest, SLB, contralateral leg 90/90. A square on the screen moves in different directions, and they have to move their head with the square. The preliminary results look like this:

The uninjured athletes, at lower speeds, performed the task with little variability which increased as the speeds did. This was just the opposite in the injured athletes. They had a tendency to "lock down" the lower extremity as speeds increased.

My question to Dr. Hewett was why this was in opposition to perturbation training concepts, where "stillness" is desirable. His answer was, " in an unstabilized situation locking down is good. In a normally stable position, locking down is probably bad". My response was, "but your bio feedback screen was causing head movement, which created instability, no? His answer was, "humm, that does give me something to think about". I then asked him if perhaps when the instability is driven bottom up, "locking down" is good, and bad when it is driven top down. He said he wasn't ready to come to that conclusion.

Another statement he made was the time from when the foot hits the ground till the ACL lig tears is from 50-70 mlliseconds. Spinal level reflexes occur at 80-150; too slow to prevent an ACL tear. He feels the benefit of neuromuscular training to be preparatory rather than reactive.