The body must be in balance. It works the best if all opposing muscles are balanced in strength. The body uses a principle called
reciprocal inhibition. This means if one muscle is weak or under developed compared to its counterpart, then the body is only as strong as it's weakest muscle in that joint.
The weak muscle may shut down the strong muscle so the body will not harm itself. The body is also
more prone to have a weak muscle spasm in order to compensate for it not being strong enough compared to its counterpart. In the case of sprinting, the hip flexor muscles are not as strong as the buttock muscles or hip extension muscles.
This means that the body can run only as fast as the strength of the weakest muscle. In sprinting, the action of the leg pushing
off or propelling the body is labeled the thrusting leg. The action of bringing the leg forward into position to thrust again is labeled the recoiling leg.
The inventor of the Speed Trainer has mathematically proven that you can only run as fast as you can put your leg out in
front of you. With Speed Trainers, you can use your legs faster than you thought possible. Speed Trainers concentrate on and adds resistance to the recoiling leg.
