Altered ankle-muscle activation during jump landing in participants with functional instability of the ankle joint

Context: Identification of motor control deficit associated with Functional Instability (FI) of the ankle joint. Objective: To compare patterns of ankle muscle activation during jump landing in participants with FI and a control group. Design: Cross-sectional comparison. Setting: Research laboratory. Participants: Twelve participants with FI (6 m, 6 f; age, 26.4 +/- 4.6 years) and 10 control subjects (5 m, 5 f; age 24.9 +/- 2.5 years). Main Outcome Measures: Integrated electromyographic (IEMG) activity of ankle musculature in the 150-millisecond period immediately prior to and post impact during 2 different jump landing activities. Results: Participants with FI demonstrated a significant reduction in pre-impact peroneus longus IEMG activity during both jumping activities compared to controls (P < .05). There were no significant differences between the groups' soleus or tibialis anterior IEMG activity during the pre- or post-impact periods. Conclusions: These results help to further our understanding of changes in control of ankle movement during dynamic activity in participants with Fl.