Lower extremity strength and coordination are independent contributors to maximum vertical jump height

We previously reported that lower extremity muscular strength of older adul ts did not predict success of a balance recovery task. We propose that lowe r extremity coordination may limit performance independently of lower extre mity strength. The present study was conducted to determine the extent to w hich knee extension strength and hip-knee coordination independently contri bute to maximum vertical jump height. Maximum vertical jump height and isom etric and isokinetic knee extension strength and power were determined in 1 3 young adults. Hip-knee coordination during the vertical jump was quantifi ed using relative phase angles. Stepwise nonlinear multiple regression dete rmined the variable set that best modeled the relationship between the depe ndent variable, maximum vertical jump height, and the independent variables of strength, power, and coordination. The quadratic terms of the normalize d knee extension strength at 60 deg(.)s(-1), and the average relative phase during the propulsion phase of the vertical jump, collectively accounted f or more than 80% of the shared variance (p = .001). The standardized regres sion coefficients of the two terms, .59 and .52, respectively (p = .004 and .008). indicated the independence and significance of the contributions of knee extension strength and hip-knee coordination to maximum vertical jump height. Despite the pitfalls of extrapolating these results to older adult s performing a balance recovery task, the results are interpreted as suppor ting the contention that while muscle strength confers a number of function al benefits, the ability to avoid falling as a result of a trip is not nece ssarily ensured. Increased muscle strength per se can occur in the absence of improved kinematic coordination.