Joint-specificity dictates contribution of eccentric phase biomechanics and amortization time toward countermovement jump performance in children

Research Objectives: To investigate if the relationship between lower extremity peak eccentric moment, peak eccentric power and a) jump height (JHt), and b) amortization time during countermovement jump is joint-specific in children.

Design: Cross-sectional design

Setting: University Research Laboratory

Participants: Typically developing children (N = 21; age = 8 to 14 years)

Interventions: Not applicable

Main Outcome Measures: In order to gather jump data for countermovement jump (jump preceded by a quick countermovement) we used a rigid body model, using 36 reflective markers and floor-embedded force plates. Following familiarization, participants tried countermovement jump three times successfully. The greater trochanter marker values were used to compute JHt. The time between the final data point of eccentric (countermovement phase) velocity and the first data point of concentric (propulsive phase) velocity of each joint (hip, knee, and ankle) was used to compute the amortization time uniquely for the respective joints. Eccentric moments and powers for the hip, knee, and ankle were normalized for body weight.

Results: Countermovement JHt was positively related with the i) peak eccentric ankle moment (r = 0.465 p = 0.045) and peak eccentric hip power (r = -0.653 p = 0.002) only. Countermovement JHt was negatively related to amortization time at the ankle only (r = -0.540 p = 0.017). No other significant relationships were noted.

Conclusions: Our results show that a quick transition from eccentric to propulsive phase at the ankle during countermovement jump is critical for greater jump height in children. Ankle and hip are the critical joints utilizing eccentric phase during countermovement jump for a greater jump height in children. Our results provide insight into understanding countermovement joint biomechanics in children.

Author(s) Disclosures: None