The objective of this study was to investigate the effects of a lateral ankle sprain(s) on balance and jumping performance in varsity athletes. Clinicians often use subjective balance and jumping tasks during the rehabilitation process as criteria for returning an athlete to sport. There is a high recurrence rate of lateral ankle sprains with ongoing reports of mechanical and/or functional ankle instability often leading to chronic ankle instability. Perhaps including objective kinetic and kinematic measurements in the course of rehabilitating an ankle sprain injury may provide further information regarding the recovery process of the athlete.

Participants in this study included varsity athletes with and without a history of ankle sprains. A total of 65 participants (age 19.9 ± 1.43 years) were baseline tested using a balance and jumping task. This study was unique in design as it used a repeated measures model where each participant acted as their own control. Twelve (12) athletes (age 19.7 ± 1.5 years) were asked to repeat the baseline testing at two different time points after sustaining a lateral ankle sprain:​ 1) immediately following injury and 2) at time of return-to-play. Participants were tested using static and dynamic tasks while barefoot for a total of 17 trials. Twelve (12) infrared markers were placed on the participants to estimate centre of mass motion. The static task was a single leg balance task with eyes closed for thirty seconds. The dynamic task was a single leg jump and landing movement with eyes open. Objective measures used to compare baseline results to return-to-play results for the standing task included:​ the root mean square (RMS) of the centre of pressure (COP), centre of pressure velocity (COPv), centre of mass (COM), centre of mass velocity (COMv) in both medial / lateral (M/L) and anterior / posterior (A/P) directions and the COM-COP maximum for both M/L and A/P. Objective measures used for the jump task included:​ force loading rates, force impulses, jump height and time-to-stabilize after landing. Athletes completed two self-reported outcome instruments, The Foot and Ankle Disability Index which evaluates functional activities of daily living and sport-specific tasks prior to injury and at return-to-play.

This study provides evidence that athletes who sustained a lateral ankle sprain did not demonstrate any significant deficits when assessed in the return to play phase for the standing balance task. The jumping and landing task provides support that the impulse created during take-off during baseline (0.230 BW*s) was higher compared to return-to-play (0.223 BW*s). The second impulse measured upon landing was also higher at baseline (0.24 BW*s) and lower after sustaining a lateral ankle sprain at return-to-play (0.22 BW*s). This suggests that the athletes may employ an alternate landing strategy in order to dissipate force away from the ankle when landing. The overall performance of the task as measured by jump height did not change.

The sport scale portion of the questionnaire yielded significant findings. The return-to play scores (84.5 ±17.14) were significantly lower as compared to baseline scores (96.2 ± 9.23), (p=0.0498).

These measurable results show that athletes who have sustained a lateral ankle sprain did not return to their baseline pre-injury state with respect to the chosen standing and jump performance variables. Previous research has found deficits after sustaining an injury however those studies typically compare to a control group as opposed to the same individual. Since ankle sprains are the most common musculoskeletal injury, these are important findings for both the athlete and clinicians. These results suggest that incorporating a more quantifiable and sophisticated evaluation using functional movements post-injury could identify existing deficits and thereby be addressed more comprehensively prior to returning an athlete to competition. Further research investigating biomechanical and functional changes that occur after injury may lead to improved rehabilitation protocols.