The influence of athletic status on the passive properties of the muscle-tendon unit and traditional performance measures in division I female soccer players and nonathlete controls.

The purpose of this study was to determine if passive muscle-tendon properties of the posterior muscles of the hip and thigh and lower-body muscle power could discriminate between athletic status in division I female soccer athletes and nonathlete controls. Ten athletes (mean ± SE, age = 18.70 ± 0.34 years; mass = 64.61 ± 2.16 kg; height = 165.99 ± 1.46 cm; thigh muscle cross-sectional area = 94.08 ± 2.58 cm) and 11 nonathletes (mean ± SE, age = 19.64 ± 0.51 years; mass = 62.81 ± 2.60 kg; height = 162.44 ± 2.20 cm; thigh muscle cross-sectional area = 86.33 ± 2.81 cm) performed 2 instrumented straight-leg raise (iSLR) assessments using an isokinetic dynamometer programmed in passive mode to move the foot toward the head at 5°·s. During each iSLR, passive stiffness was calculated from the slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curve, and maximum range of motion (ROM) was determined as the point of discomfort but not pain, as indicated by the participant. Lower-body power characteristics were assessed through a countermovement vertical jump (CMJ) test. The results indicated that phase 1 and 2 slopes, CMJ height, and peak power (Pmax) were significantly higher (p = 0.004-0.036) for the athletes compared with the nonathletes; however, maximum ROM was not different (p = 0.601) between groups. Significant relationships were also observed between phase 1 and 2 slopes, and CMJ height and Pmax (r = 0.483-0.827; p ≤ 0.001-0.027). These findings suggest that in addition to traditional power characteristics, passive stiffness may also be a sensitive and effective measure for discriminating athletes from nonathletes. Coaches and practitioners may use these findings when designing training programs aimed at increasing musculotendinous stiffness of the posterior hip and thigh muscles and to help identify athletes with high overall athletic potential.