Single-legged hop and single-legged squat balance performance in recreational athletes with a history of concussion

Context: Researchers have suggested that balance deficiencies may linger during functional activities after concussion recovery. Objective: To determine whether participants with a history of concussion demonstrated dynamic balance deficits as compared with control participants during single-legged hops and single-legged squats. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: A total of 15 previously concussed participants (6 men, 9 women; age = 19.7 6 0.9 years, height=169.2 6 9.4 cm, mass=66.0 6 12.8 kg, median time since concussion = 126 days [range = 28-432 days]) were matched with 15 control participants (6 men, 9 women; age = 19.7 6 1.6 years, height = 172.3 6 10.8 cm, mass = 71.0 6 10.4 kg). Intervention(s): During single-legged hops, participants jumped off a 30-cm box placed at 50% of their height behind a force plate, landed on a single limb, and attempted to achieve a stable position as quickly as possible. Participants performed single-legged squats while standing on a force plate. Main Outcome Measure(s): Time to stabilization (TTS; time for the normalized ground reaction force to stabilize after landing) was calculated during the single-legged hop, and center-of-pressure path and speed were calculated during single-legged squats. Groups were compared using analysis of covariance, controlling for average days since concussion. Results: The concussion group demonstrated a longer TTS than the control group during the single-legged hop on the nondominant leg (mean difference = 0.35 seconds [95% confidence interval = 0.04, 0.64]; F2,27 = 5.69, P = .02). No TTS differences were observed for the dominant leg (F2,27 = 0.64, P=.43). No group differences were present for the singlelegged squat on either leg (P ≥ .11). Conclusions: Dynamic balance-control deficits after concussion may contribute to an increased musculoskeletal injury risk. Given our findings, we suggest that neuromuscular deficits currently not assessed after concussion may linger. Time to stabilization is a clinically applicable measure that has been used to distinguish patients with various pathologic conditions, such as chronic ankle instability and anterior cruciate ligament reconstruction, from healthy control participants. Whereas the single-legged squat may not sufficiently challenge balance control, future study of the more dynamic single-legged hop is needed to determine its potential diagnostic and prognostic value after concussion.