| Summary: | 碩士 === 國立陽明大學 === 物理治療暨輔助科技學系 === 97 === Background: Functional ankle instability (FAI) was considered as the main reason of recurrent ankle sprains in athletes. The major hypotheses of causing functional ankle instability are delayed reaction time and decreased muscle activity in lower extremities during threats of ankle sprain. Despite self-reported symptoms, there is no universal standard to identify the case with FAI. Researchers often use the peroneal muscle reaction time during the sudden inversion test, and the peroneal muscle activity in the single leg landing to assess individuals with FAI. However, the findings regarding the peroneal reaction time in the literature were inconsistent, mainly due to the variations in the testing parameters. Furthermore, there was few data available for the peroneal muscle activities and muscle coordination during the single leg landing in previous studies. Purpose: This study was therefore designed to investigate the effects of various testing parameters in the sudden inversion and single leg landing tests; and to compare the differences in the muscle reaction time and muscle activities of the peroneus longus, tibialis anterior, and soleus between subjects with and without FAI. Method: We recruited 14 healthy and 14 FAI subjects for this investigation. Three levels of testing parameters were used: 15, 30, and 45 degrees for the sudden inversion test, and 25, 35, and 45 cm for the landing test. Muscle activities and reaction time of tibialis anterior, soleus and peroneus longus of involved side and sound side in FAI group, and both sides in control group, were recorded by surface electromyography system. Results: There were significant differences in the muscle reaction time and muscle activation under different testing conditions in both control and FAI groups. Compared to the control group, the involved side of FAI group showed faster peroneal reaction time and smaller peroneal muscle activation during testing. Conclusion: The inclination angle of the sudden inversion test and the landing height would significantly influence the result of peroneal muscle performance. The reaction time and muscle activation of the peroneus longus altered in subjects with FAI. Further studies should take into considerations of the effect of testing parameters, and to investigate the mechanisms behind the changes of the muscle performance in subjects with functional ankle instability.
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