Long-term effects of shoe mileage on knee and ankle joints muscle co-contraction during walking in females with genu varus

Background Shoe mileage may influence the risk of sustaining injuries during walking. Research question What are the effects of shoe mileage on knee and ankle muscle co-contraction during walking in females with genu varus? Methods Fifteen healthy and 15 women diagnosed with genu varus received a new pair of running shoes. They were asked to wear these shoes over 6 months. Pre and post intervention, muscle activities of the dominant limb were recorded during a walking test at preferred gait speed. Two dependent variables were assessed to examine muscle co-contraction: (1) directed co-contraction ratios of agonists and antagonists, and (2) general joint muscle co-contraction. Findings Results demonstrated significant main effects of the “shoe” factor for general ankle co-contraction during the push-off phase (p = 0.013, d = 1.503). Irrespective of experimental group, paired comparisons revealed significantly lower general ankle co-contraction during the push-off phase after the intervention. A significant main effects of “shoe” for general knee co-contraction during loading phase (p = 0.025, d = 0.895) was also observed. In both groups, paired comparison revealed significantly lower general knee co-contraction during the push-off phase in the post condition. We did not find any significant main effect of group nor group-by-shoe interaction for general ankle co-contraction during the stance phase. Likewise, we did not observe any significant main effect of “shoe”, “group” and “group-by-shoe” interaction for mediolateral directed knee co-contraction during stance phase of walking (p > 0.05). Significance Our findings showed that the shoe mileage but not the genu varus condition affects the general and directed co-contraction of the muscles stabilizing the knee and ankle joints. Together with the observed findings on ankle and knee muscle co-contraction, it is essential to change running shoes after a long wearing time in both healthy and genu varus females.