: As your quads and calves lengthen to absorb the impact, specialized sensory receptors called muscle spindles act as tripwires. They sense the rapid stretch and immediately send an urgent signal to your spinal cord: "We're stretching too fast—contract now!" .
The story begins with a drop. As you fall toward the ground, gravity pulls on your mass, and your body prepares to catch it. Plyometric anatomy
: If you linger here for more than about 0.25 seconds, the "story" ends in a flop. The elastic energy stored in your tendons dissipates as heat, and the muscle spindles' urgent signal fades away. : As your quads and calves lengthen to