Association Between Impact Asymmetry And Running-related Injury

Running-related injuries (RRIs) are predominantly overuse and may be related to asymmetries in impact that are magnified by repetition. Variability in impact may also contribute to the development of an RRI. PURPOSE: To determine if asymmetries in impact acceleration and variability of impact acceleration are associated with subsequent RRI. METHODS: 188 healthy recreational runners ran on a treadmill at 3.0 m/s with an insole-embedded inertial measurement unit (IMU). Participants were followed for 3 months and asked to report any RRI. RRI during the 3-month follow-up period was the main outcome. The injured side was chosen as the study limb and in uninjured participants the study limb was randomized. Predictors were asymmetry in peak resultant, vertical, and anteroposterior acceleration as well as asymmetry in the coefficient of variation (COV) for the three acceleration variables. Predictor variables were divided into tertiles (high negative asymmetry, low positive/negative asymmetry, high positive asymmetry) where a positive asymmetry represented a higher peak acceleration on the study limb side. Logistic regression was completed using the middle tertile as the reference. RESULTS: 111 runners were included in the final analysis after excluding those who did not complete the follow-up surveys or who ran less than 20 k per week during any of the follow-up periods. 28 were diagnosed with an RRI and 83 remained uninjured at 3 months. Participants with a high negative asymmetry in peak resultant acceleration were injured at 3.52 (95% CI: 1.23-11.22; p = 0.024) times the rate of those with a low asymmetry. No other predictor variables were associated with RRI. CONCLUSION: A high negative peak resultant acceleration asymmetry was associated with an increased risk of developing RRI. This may reflect an early favoring of the prospectively injured limb as it reflects a lower impact on that side at baseline testing. Findings from this study suggest that asymmetries in peak resultant acceleration could be used as an early predictor of RRI in recreational runners. Future studies should investigate whether interventions aimed at reducing asymmetries could reduce risk of RRI.