J.T. Nadeau, J.T. Droessler, M.C. Eastwood, C.L. Whitlock, V.R. Gieser, & B.K. Higginson

Gonzaga University, Spokane, WA

Gait modification can be beneficial in reducing pain or compensating for muscle weakness at the ankle or hip. Two strategies proposed for clinical gait modification are the ankle strategy and hip strategy. The ankle strategy is characterized by increased plantar flexion, which provides a forward push to the leg that can either propel the whole body in late stance or initiate recovery during swing phase. This strategy is commonly utilized among elderly individuals with anterior hip impairments. For the hip strategy, hip flexor muscles pull the leg forward during swing phase to reduce peak plantar pressures or compensate for impaired ankle power generation in the elderly. PURPOSE: To verify gait adaptation efficacy by analysis of plantar flexor EMG coupled with lower limb kinematics. METHODS: Thirteen healthy female undergraduate students walked on a treadmill at a self-selected speed using three gait strategies: natural ankle push-off (NP), increased ankle push-off (IP), and decreased ankle push-off (DP). IP was intended to simulate the ankle strategy, while DP was to simulate the hip strategy. Average muscle activation for the right lateral gastrocnemius (LG), medial gastrocnemius (MG) and soleus (S) were quantified and normalized with respect to NP over five subsequent strides. Lower extremity joint and segment angles were measured at both heel strike and toe off. All measures were averaged over five strides and compared using within-subject repeated measures ANOVA (α = 0.05). RESULTS: Relative to the NP strategy, average muscle activation was significantly higher in IP for the LG (54.7%, p = 0.002), MG (26.1%, p = 0.034) and S (40.6%, p = 0.008), while no significant changes in activation were found for DP (LG: 11.0%, p = 0.256; MG: 1.2%, p = 1.000; S: 8.5%, p = 0.258). Leg and thigh segment angles for the IP strategy at heel strike were significantly smaller than in NP (1.9%, p = 0.010 and 1.4%, p = 0.009, respectively). No significant kinematic differences were found between DP and NP strategies. CONCLUSION: Based solely on muscle activation, young healthy females were able to adapt to the ankle strategy, but may have had difficulty adapting to the hip strategy. Lower leg kinematics did not appear to be effective indicators of gait strategy adaptation.

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