Jump height is a commonly reported metric used to assess and monitor gross countermovement jump (CMJ) performance of an athlete. A recent study suggested that the countermovement be deconstructed into unloading, eccentric yielding, and eccentric braking phases to better reflect the center of mass (COM) movement effects while also including the predominant muscle actions driving changes in COM movement where appropriate. However, phase-specific variables explaining jump height and are not well understood in trained populations. Purpose: To determine whether good jumpers, defined by jump height, display superior performance in CMJ phase specific-(a) temporal, (b) yank (i.e., rate of force development), and (c) force variables. Methods: Twenty-two collegiate male basketball players (height: 1.99 ± 0.06 m; mass: 93.8 ± 7.5 kg; age: 20 ± 2 years) performed 3 CMJ while ground reaction force (GRF) data (1,000 Hz) were obtained. The CMJ was deconstructed into the following phases previously described in the literature: unloading, eccentric yielding, eccentric braking, and concentric. Phase-specific RFD and force variables were normalized to body mass and calculated as the average RFD and force over the duration of the CMJ phase. Independent samples t-tests (a = 0.05) and Cohen's d effect sizes (large =0.8) were used to compare performance between the poor and good jump height groups. Results: Jump height (p = < 0.001, d = 2.83) RSImod (p = < 0.001, d = 1.77) and concentric power (p = < 0.001, d = 1.68) were significantly different between jump height groups (Table 1). Conclusions: RSImod and concentric power differentiated poor and good jumpers when defined by jump height performance. Phase-specific characteristics were not significantly different between groups. Practical Application: Individuals targeting enhanced CMJ jump height performance might consider exploring strategies or interventions to enhance their concentric power production such as post-action potentiation (PAP), weighted jumps, or targeting loads which induce maximal power outputs with lower extremity exercises rather than focusing on phase-specific qualities.
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