Purpose: This retrospective study compared the influence of perceived sports involvement on lower extremity neuromuscular adaptations during single-leg countermovement jumping (CMJ), perceived knee function and internal health locus of control (HLOC) scores at a minimum 2-year post-anterior cruciate ligament reconstruction. The hypothesis was that subjects with higher-level sports involvement would display significant differences compared to subjects with lower-level sports involvement.
Methods: Uninvolved and involved lower extremity EMG amplitude (1,000 Hz), vertical ground reaction force (VGRF) (500 Hz) and kinematic (60 Hz) displacement differences were determined during single-leg CMJ. These data and International Knee Documentation Committee subjective knee survey scores, Multidimensional Health Locus of Control Survey internal HLOC subscale scores and sports activity characteristics were compared by sports involvement level.
Results: Subjects that regarded themselves as only sporting sometimes (Group 3, n = 26) had lower IKDC survey and internal HLOC scores, were more likely to decrease sports activities by two intensity levels than highly competitive (Group 1, n = 20) and well-trained/frequently sporting (Group 2, n = 24) subjects, and had greater peak landing VGRF differences suggesting decreased involved lower extremity loading compared to Group 2. During propulsion, Group 1 had greater gluteus maximus (GM) and gastrocnemius (G) EMG differences than Groups 2 and 3. Groups 1 and 2 had decreased vastus medialis (VM) EMG differences during propulsion than Group 3. During landing, Group 1 had greater GM and G EMG differences than Group 3.
Conclusion: Subjects with higher-level sports involvement up-regulated involved lower extremity GM and G activation and down-regulated VM activation. This adaptation may enable continued higher-level sports participation while minimizing knee joint forces. Perceived higher-level sports involvement was related to neuromuscular adaptations, better subjective knee function, a more internal HLOC and higher sports activity intensity.
Level of evidence: Therapeutic case series, level IV.