Background: Concussion is one of the most common sports-related injuries, with little understood about the modifiable and non-modifiable risk factors. Researchers have yet to evaluate the association between modifiable sensorimotor function variables and concussive injury. Purpose: Investigate the association between dynamic balance performance, a discrete measure of sensorimotor function, and concussive injuries. Study Design: Prospective Cohort Study Methods: One-hundred and nine elite male Rugby Union players were baseline tested in dynamic balance performance while wearing an inertial sensor, and prospectively followed during the 2016/2017 Rugby Union season. The sample entropy of the inertial sensor gyroscope magnitude signal was derived to provide a discrete measure of dynamic balance performance. Logistic regression modelling was then used to investigate the association between the novel digital biomarker of balance performance, known risk factors of concussion (concussion history, age and playing position) and subsequent concussive injury. Results: Participant demographic data (mean ± SD) was as follows: age: 22.6±3.6 years; height: 185±6.5 cm; weight: 98.9±12.5 Kg; BMI: 28.9±2.9 kg/m 2 ; leg length: 98.8±5.5 cm. Of the 109 players, 44 (40.3%) had a previous history of concussion, while 21 (19.3%) sustained a concussion during the follow-up period. The receiver operatic curve analysis for the anterior sample entropy demonstrated a statistically significant area under the curve (0.64; 95%CI = 0.52 to 0.76; p < 0.05), with the cutoff score of anterior sample entropy ≥ 1.2, that maximized the sensitivity (76.2%) and specificity (53.4%) for identifying individuals who subsequently sustained a concussion. Players with sub-optimal balance performance at baseline were at a 2.81 greater odds (95% CI = 1.02-7.74) of sustaining a concussion during the Rugby Union season than those with optimal balance performance, even when controlling for concussion history. Conclusion: Rugby Union players who possess poorer dynamic balance performance as measured by a wearable inertial sensor during the Y Balance Test have a three-times higher relative risk of sustaining 3 a sports-related concussion, even when controlling for previous history of concussion. These findings have important implications for future research and clinical practice, as it identifies a potential modifiable risk-factor. Further research is required to investigate this association in a large cohort, consisting of males and females, across a range of sports. Clinical Relevance: This study has identified a modifiable risk-factor for concussion in Rugby Union players, suggesting movement control and balance training interventions may help reduce the incidence of concussion in this population.