Does Fatigue Impact Static and Dynamic Balance Variables in Athletes with a Previous Ankle Injury?

Ankle injury, resulting in deficits in static and dynamic balance, can result in significant time loss to sport, affect daily activities and potentially place athletes at greater risk of re-injury. In order to identify athletes at risk of ankle injury accurate and reliable balance assessment tools are required. The purpose of the current study was to quantify reliability of static and dynamic balance variables in currently healthy, previously injured, athletes (n = 19) and assess the impact of an intense intermittent zig-zag running protocol to volitional exhaustion, rated by RPE, on balance variables. A test re-test design assessed short-term reliability and measurement error by computing ICC and 95% limits of agreement (LoA). The Y balance test was deemed a reliable measuring tool for assessing dynamic balance, recording strong reliability (ICC = 0.96, 95% LoA from -95.7 to 105.8%). A HURlabs iBalance force platform assessed the static balance variables sway velocity and C90area; sway velocity (mmˑs^-1) recorded strong reliability (ICC = 0.79). Significant post-fatiguing protocol increases (p < 0.001) were detected in single-leg static balance for both C90area (mm²) and sway velocity (mmˑs^-1) assessed on stable and unstable surfaces (stable: 227 ± 84 vs. 366 ± 146 mm² and 18.6 ± 4.2 vs. 22.9 ± 5.3 mmˑs^-1: unstable; 275 ± 128 vs. 370 ± 140 mm² and 19.3 ± 4.3 vs. 21.5 ± 4.0 mmˑs^-1). Non-significant post-fatiguing protocol differences (p > 0.05) were detected in dynamic balance variables (anterior, posteromedial, posterolateral and composite reach scores) measured at 4-min after completing the protocol. Further research should investigate the effects of fatigue on dynamic YBT variables immediately post-exercise and determine if differences exist when comparing previously injured and un-injured limbs.