| dc.description.abstract | Appraising anterior cruciate ligament (ACL) injury risk is of great interest to the orthopedic and sports medicine professional. Due to the high prevalence of non-contact ACL injuries, professionals have sought to identify intrinsic and modifiable neuromuscular and biomechanical risk factors to aid in the design of injury risk screens that have the discriminatory capacity to stratify ACL injury risk and the efficiency to be implemented at-scale. Prospective studies have revealed that poor dynamic postural stability (DPS), quantified as time to stabilization (TTS), following a backwards single-legged jump-landing (BSLJL) and poor hip external rotation and abduction strength relative to body weight, quantified using a handheld dynamometer, are two risk factors for ACL injury. The purposes of this study were to assess the effects of repeated BSLJL on within-session motor learning as quantified by DPS, evaluate the reliability of DPS, and determine the relation between DPS, hip strength, and fatigue. Twenty-seven recreationally active college-aged adults (24.0 ± 2.8 y, 1.73 ± 0.08 m, 75. ± 14.0 kg) were enrolled in this semi-randomized, cross-over study. During visit one, subjects completed 10 BSLJL trials per leg without familiarization and had their hip external rotation and abduction strength measured. During visits two through four, subjects complete two fatigue sessions and one control session in a randomized order. During these sessions, subjects completed two sets of three BSLJL trials per leg separate by either a seated rest in a chair (control) or a short-term functional fatigue protocol (fatigue). DPS was quantified as TTS and the dynamic postural stability index (DPSI). To appropriately familiarize a subject to the BSLJL, results suggest that a minimum of six familiarization trials per leg are required to sufficiently reduce the motor learning effect. Results also indicate that TTS reliability is poor after 10 trials per leg whereas DPSI reliability is good after just two trials per leg and excellent after just six trials per leg. Finally, results indicate that following completion of a fatigue protocol, there are decrements in TTS, but not in DPSI. Further, greater hip abduction strength is associated with better DPSI when rested and fatigued, but not TTS. | en_US |
