Mild Quadriceps and Hamstring Strength Deficits Do Not Persist After Sport-Related Concussion

Abstract

Background: Risk for lower extremity musculoskeletal injury increases after sport-related concussion (SRC) and may result from unresolved motor control deficits. Muscle weakness is a deficit that could contribute to musculoskeletal injury risk. Hypothesis: Athletes with SRC will demonstrate quadriceps and hamstring muscle weakness at the time of return to sport and 30 days later compared with controls. Study Design: Prospective matched cohort. Level of Evidence: Level 3. Methods: A total of 31 athletes with SRC (CONCUSSION) were matched by sex, age, and activity level to controls (CONTROL). Testing was conducted at initial assessment and 30 days later; initial assessment in CONCUSSION occurred when cleared for return to play. Isokinetic testing assessed quadriceps and hamstring strength of the dominant and nondominant legs at 60 and 180 deg/s. Peak torque values were normalized to body mass (N-m/kg). Data were analyzed with repeated measures general linear models (group × time), and effect sizes were calculated. Results: Analysis at 60 deg/s included 26 matched pairs (15 male per group) and at 180 deg/s included 30 matched pairs (17 males per group). Time from concussion to initial assessment was 21.3 (7.8) mean (standard deviation) days. No significant interactions or main effects were detected ( P > 0.05). Across muscle groups, legs, and testing speeds, effect sizes at initial assessment were small ( d = 0.117 to 0.353), equating to a strength deficit in CONCUSSION of 0.04 to 0.18 N-m/kg, and effect sizes were further reduced at 30-day follow-up (d = −0.191 to 0.252). Conclusion: In athletes with SRC, quadriceps and hamstring strength were decreased only minimally at return to play compared with controls and the difference lessened over 30 days. Clinical Relevance: Strength deficits may not be a major contributor to increased lower extremity musculoskeletal injury risk after SRC. Strength training could be implemented before return to play after SRC to mitigate any strength deficits.

Does prior concussion lead to biomechanical alterations associated with lateral ankle sprain and anterior cruciate ligament injury? A systematic review and meta-analysis

“…These findings suggest that postconcussion neurophysiological irregularities in brain structures are related to motor control/planning and may alter functional movements. Additionally, a recent study has proposed athletes with acute concussions have a mild decrease in quadriceps muscular strength which could possibly be indicative of motor dysfunction following concussion 87. Particularly, lower quadriceps muscular strength has been associated with lower knee flexion angle during the initial contact of jump-landing tasks 88.…”

“…It has been postulated that insufficient neuromuscular control in the activation of the hamstrings and quadriceps muscles may serve as a potential mechanism, resulting in increased external knee abduction loading 89. Neuromuscular dysfunction has been identified in individuals postconcussion10 11 and athletes suffered from acute concussions may experience a slight decline in quadriceps muscular strength 87. While the magnitude of the impact of quadriceps muscular strength deficits on internal knee adduction moment remains uncertain, it may be a potential manifestation of neuromuscular dysfunction following concussions.…”