This is the most critical split-second in the story—the moment your downward movement stops but your upward movement hasn't yet begun.
: Your Golgi Tendon Organs (GTO) are the "safety brakes" of your body. Their job is to shut the muscle down if the force is too high. In a trained athlete, plyometrics "desensitize" these brakes, allowing the body to tolerate higher workloads without hitting the "abort" button. Chapter 3: The Launch (The Concentric Phase)
: 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!" .