Exploring the role of ankle torque fluctuations and intramuscular coherence in gait function among older adults

Objective

This study aimed to investigate the relationship between ankle joint function and walking performance in older adults by assessing qualitative ankle functions through torque fluctuation analysis and tibialis anterior (TA) intramuscular coherence during isometric dorsiflexion.

Methods

Thirty-eight community-dwelling older adults participated in this study. Ankle torque fluctuations and intramuscular coherence were evaluated during a dorsiflexion task at 30% of maximum voluntary torque (MVT). Walking performance was assessed using the 5-meter walk test and the Timed Up and Go (TUG) test. Torque fluctuation indicators, including the coefficient of variation (CV), frequency components, and the primary component calculated by an autoregressive (AR) model, were derived from time-series data. Intramuscular coherence was analyzed in the δ (0–5 Hz) and β (16–35 Hz) frequency bands. Multiple regression analyses adjusted for age were conducted to explore associations between walking performance, torque indicators, and intramuscular coherence.

Results

The TUG test demonstrated a significant relationship with the AR principal component of torque fluctuations, independent of age (p = 0.031), suggesting that temporal variability in ankle torque contributes to dynamic balance. While no significant relationship was observed between gait function and intramuscular coherence, δ-band coherence showed significant correlations with torque variability (CV, r = 0.598, p < 0.001) and spectral power in both the 0.5–5 Hz (r = 0.62, p < 0.001) and 5–10 Hz (r = 0.544, p = 0.001) bands.

Discussion

The AR principal component appears to capture kinematic features to motor control and dynamic balance, as evidenced by its association with TUG performance. Furthermore, the relationship between δ-band coherence and torque fluctuations highlights its potential as a maker of neuromuscular function. Although torque fluctuation characteristics and δ-band coherence did not directly correlate with walking speed, they offer valuable insights into the neurophysiological mechanisms underpinning motor control.

Conclusion

This study demonstrated that temporal variability in ankle torque, as quantified by the AR principal component, contributes to walking ability and dynamic balance in older adults.