Time-frequency analysis of muscle activation patterns in individuals with chronic ankle instability during walking

Abstract

Background

Individuals with chronic ankle instability (CAI) exhibit altered walking mechanics, including changes in joint movement and muscle activation patterns at the ankle. However, amplitude-based analyses of muscle activation during walking have shown inconsistent results between individuals with CAI and uninjured controls. Time-frequency analyses can capture transient and frequency-specific muscle activation patterns that amplitude-based analyses may overlook, offering deeper insights into muscle function during dynamic activities.

Research question

Do individuals with CAI demonstrate increased low-frequency muscle activation and decreased high-frequency activation in the time-frequency domain compared to uninjured individuals during walking at their self-selected speed?

Methods

Nineteen individuals with CAI and 19 uninjured controls completed a walking trial on a force-measuring treadmill at their self-selected speed while electromyography sensors recorded muscle activity from the shank muscles. We used wavelet transformation to perform time-frequency decomposition of muscle activation data, then applied principal component analysis to extract unique signal features and compared principal component scores between groups.

Results

Individuals with CAI exhibited significantly greater intensity magnitudes in the medial gastrocnemius and soleus muscles at low frequencies and reduced magnitudes at high frequencies compared to controls (p = 0.006). Individuals with CAI exhibited significantly larger intensity magnitudes in the tibialis anterior and lateral gastrocnemius across all frequencies. Those with CAI showed smaller intensity magnitudes in the fibularis longus muscle overall but had higher magnitudes at low frequencies at the onset of the stance phase.

Significance

Our finding suggests that electromyography analysis in the time-frequency domain has the potential to reveal unique muscle function alterations in individuals with CAI during walking, which cannot be observed in traditional amplitude-based analyses.