Measures of functional performance and their association with hip and thigh strength.

CONTEXT Insufficient hip and thigh strength may increase an athlete's susceptibility to injury. However, screening for strength deficits using isometric and isokinetic instrumentation may not be practical in all clinical scenarios. OBJECTIVE To determine if functional performance tests are valid indicators of hip and thigh strength. DESIGN Descriptive laboratory study. SETTING Research laboratory. PATIENTS OR OTHER PARTICIPANTS Sixty-two recreationally athletic men (n = 30, age = 21.07 years, height = 173.84 cm, mass = 81.47 kg) and women (n = 32, age = 21.03 years, height = 168.77 cm, mass = 68.22 kg) participants were recruited. INTERVENTION(S) During session 1, we measured isometric peak force and rate of force development for 8 lower extremity muscle groups, followed by an isometric endurance test. During session 2, participants performed functional performance tests. MAIN OUTCOME MEASURE(S) Peak force, rate of force development, fatigue index, hop distance (or height), work (joules), and number of hops performed during the 30-second lateral-hop test were assessed. The r values were squared to calculate r (2). We used Pearson correlations to evaluate the associations between functional performance and strength. RESULTS In men, the strongest relationship was observed between triple-hop work and hip-adductor peak force (r(2) = 50, P ≤ .001). Triple-hop work also was related to hip-adductor (r(2) = 38, P ≤ .01) and hip-flexor (r(2) = 37, P ≤ .01) rate of force development. For women, the strongest relationships were between single-legged vertical-jump work and knee-flexor peak force (r(2) = 0.44, P ≤ .01) and single-legged vertical-jump height and knee-flexor peak force (r(2) = 0.42, P ≤ .01). Single-legged vertical-jump height also was related to knee-flexor rate of force development (r(2) = 0.49, P ≤ .001). The 30-second lateral-hop test did not account for a significant portion of the variance in strength endurance. CONCLUSIONS Hop tests alone did not provide clinicians with enough information to make evidence-based decisions about lower extremity strength in isolated muscle groups.