ARE THERE AGE- AND SEX-RELATED DIFFERENCES IN TIBIALIS POSTERIOR ACTIVATION DURING WALKING?

Introduction: Tibialis posterior tendon dysfunction (TPTD) often leads to acquired flat foot deformity [1]. There is also a tendency for arch height to decrease with age [2]. However, it is unknown whether this change is linked to altered tibialis posterior (TP) activation during gait or is associated with healthy ageing. Research question: Are there differences in TP activation during walking between healthy younger and older adults? Method: 30 subjects equally divided between 2 age groups younger (under 35; n=15, 8F, mean age 28.7y SD 4.4) and older (over 55; n=15, 7F, mean age 58.9y SD 3.3) were recruited. Fine-wire electromyography (EMG) electrodes were inserted into TP under ultrasound guidance. Subjects performed 3 maximal voluntary contractions (MVC) of ankle inversion against resistance, with the applied force measured using a transducer. Subjects performed 6 walks at self-selected speed along a 10m walkway. The highest EMG recorded during the MVCs was used to normalise the walking EMG. Differences in EMG between cohorts grouped by age and sex were determined using statistical parametric mapping (SPM). Force data was compared using ANOVA. Results: There were no significant differences in EMG between cohorts based on age or sex. This suggests that TPTD may not be a pathological response to a natural process of age-related changes in activation. Activation may not account for the higher incidence in women. There was some variation between subjects in normalised EMG amplitudes and further longitudinal studies would be required to link different patterns to future changes in foot posture. There were significant differences in MVC maximum force between males and females, but no difference between age cohorts. Conclusion: TP activation during walking does not appear to deteriorate with age or vary between sexes. Further studies will include subjects with TPTD. We have not demonstrated a need for age and sex matched control cohorts in future studies.