Effect of a six week wobble board training program on a sudden inversion in the standing position in patients with functional ankle instability

Background: Despite the fact that wobble board training is recommended for enhancing joint stability in patients with functional ankle instability there is still no evidence that wobble board training significantly shortens peroneal reaction time or motor response time. As connective tissue of the ankle joint gets heavily stressed during ankle sprains, it is important to study the effect of wobble board training on the control of inversion speed in order to prevent possible nociceptive strains of joint capsular tissue. Methods: 36 patients with functional ankle instability were randomized into a training group or a control group (receiving no intervention). Accelerometric and electromyographic analyses of a sudden ankle inversion of 49° in the standing position were used to assess the effect of wobble board training. As a result of drop-out, 25 patients (30 ankles) remained in the study. Results: In trained patients, the sudden inversion was decelerated significantly earlier (25,8 msec. ± 3,7 versus 28,9 msec. ± 4,1; p= .001 for the first decelerating moment and 86 msec. ± 8,8 versus 93 msec. ± 7,3; p= .032 for the second decelerating moment) at significantly smaller inversion angles (15,1° ± 2,4 versus 16,7° ± 2,7; p= .005 for the first decelerating moment and 44,4° ± 2,9 versus 46,1° ± 2,3; p= .028 for the second decelerating moment). Wobble board training did not significantly shorten the peroneal latency time (50,5 msec. ± 11,3; p> .05) or motor response time (75,7 msec. ± 11,9; p> .05) in trained patients. Neither was inversion speed significantly reduced in trained patients (465,4 °/sec ± 60; p> .05).Reliability coefficients (Intraclass correlation) of the first and second decelerating moments ranged from .47 to .82. Discussion: The observed significant effects on the decelerating moments can not be explained by a faster reacting peroneus longus muscle, as in this setting the motor response time of the peroneus longus muscle is not found to be significantly shortened. The significant effects are probably the result of an intra individual variation in time. Conclusion: Because of the reliability of the test results, it remains unclear whether wobble board training significantly affected the ankle joint control during sudden inversions in patients with functional ankle instability. Keywords: ankle instability, training, EMG, accelerometry.