A standard vertical jump test of lower-body power and readiness.
The countermovement jump is a vertical jump test in which the athlete performs a rapid downward dip immediately before jumping, using the resulting stretch-shortening cycle to drive upward propulsion. It's typically performed on a force plate or contact/jump mat, which allows quantification of jump height alongside underlying force-time characteristics rather than height alone.
CMJ output gives clinicians an objective, repeatable marker of lower-limb power production and readiness to load, which is useful when deciding whether an athlete is fit to progress rehab, return to sport, or needs a training/load adjustment. Tracked longitudinally, drops in jump height or changes in asymmetry can flag accumulating neuromuscular fatigue or incomplete recovery before it shows up as pain or reduced performance elsewhere.
The test is usually administered with the athlete standing on a force plate or mat, hands often fixed on the hips to isolate lower-limb contribution, performing a self-selected countermovement dip followed by a maximal vertical jump, typically averaged or best-of across two to three trials. Force plate systems can additionally report peak power, rate of force development, flight time, and inter-limb asymmetry, whereas jump mats derived from flight time alone give jump height only.
Jump height and derived metrics are sensitive to technique, motivation, footwear, and countermovement depth, so poor standardisation across sessions can produce noise that's mistaken for genuine physiological change. Asymmetry and force-time metrics are also more variable and less validated than jump height itself, and a single low score should prompt look at trend and context rather than an isolated pass/fail decision.