Effects of Inversion Perturbation After Drop Landing on the Latency of the Ankle Musculature

Abstract

Ankle sprains are a common injury affecting a large number of athletes and workers every year. Of specific concern is the latency of the peroneus longus and peroneus brevis which provide a dynamic defense mechanism against a lateral ankle sprain when the ankle is forced into excessive inversion. Previous research has used a tilt platform or trap door mechanism to measure the latency of these two muscles with and without ankle support; however these studies lacked the dynamic nature usually encountered when a person lands on an obstacle that forces the foot into inversion. For the present study an outersole with fulcrum was developed to more accurately replicate the mechanism of a lateral ankle sprain when participants land from a jump. A startle response, indicated by co-contraction of antagonist muscles has been noted for movements associated with whiplash injuries to the neck, however, the startle response has not previously been applied to the ankle. If present, this finding would have large implications for the future prevention of lateral ankle sprains. Therefore, the purpose of this study was to measure latencies of the peroneus longus, peroneus brevis, and tibialis anterior muscles during the performance of a single leg drop landing with the ankle forced into 25° of inversion by a fulcrum and outersole attached to the bottom of the participant’s shoe. The latencies were measured across participants with no history of an ankle sprain, a history of a lateral ankle sprain, and a history of a high ankle sprain. Moreover, the influence of ankle taping on this response was also measured, as well as the ratio of evertor/invertor activity to determine if the startle response was present. The results revealed that the latency of the peroneus longus and peroneus brevis was shorter using the outersole mechanism than those measured using a tilt platform/trap door, but there was no difference in the latency across the different injury groups. There was a significant interaction between the startle event and injury group, and the trend for an increasing ratio of evertor/invertor activity was present. In addition, there was a significant reduction in the latency of the peroneus longus when using ankle taping. Future research should continue to use the outersole methodology to examine the latency of the ankle musculature. Participants with more recent ankle injuries should be examined; the startle response should be investigated further for the development of training protocols; and the affects of physical activity on the latency of the ankle musculature with ankle taping should also be examined.