The Influence of FAI on Proprioception, Balance Control and Lower Extremities Muscle EMG Activity

Abstract

1330 Functional Ankle Instability (FAI) is a clinical syndrome associated with periarticular muscle weakness and repeated episodes of giving way. Freemann described FAI is a feeling of giving way which will impaire proprioception and postural stability. However, recent studies (Bernier, Perrin & Rijke, 1997; Isakov & Mizrahi, 1997) showed FAI did not affect postural sway or balance control. Otherwise, none of any study examined the influence of FAI on proprioception function, body center of pressure sway and EMG activity altogether. PURPOSE: To analyze the influence and relationship of FAI on propriception function, balance control and lower extrenities EMG activity. METHODS: Twenty-three college-aged healthy students recruited as subjects: 10 subjects with FAI and 13 subjects with normal ankle. AMTI force platform, Biodex isokinetic dynameter and Dasylab EMG recorder were used to collect the ankle active/passive reposition sense, the mean radius of Romberg standing body COP sway, and the four lower limbs muscle (rectus femoris, biceps femoris long head, gastrocnemius lateral head, tibialis anterior) iEMG activity. Descriptive statistics and independent t-test were used to analyze the data and the significant level was set at .05. RESULTS: 1. FAI subjects had significantly poor proprioception and balance control ability, especially in eye-closed situation. 2. FAI Poor proprioception would induce larger range of muscle EMG activity, particular in tibialis anterior, but only found significantly difference in right biceps femoris and gastrocnemius lateral under eye-closed situation. CONCLUSION: Proprioception had close relationship with balance control. FAI will truthly inpaired the proprioception and balance control, induced abnormal lower extremities EMG activities. This study also founded the tibialis anterior played an important role on postural control. More research are needed to examine and clarify if EMG activity could be used as an index of balance ability, especially recovery from ankle injury. Supported by NSC-91-2413-H-179-008, Taiwan, R.O.C.