The effect of perturbation magnitude on lower limb muscle activity during reactive stepping using functional data analysis

Abstract

This study aimed to determine the effect of perturbation magnitude on stance and stepping limb muscle activation during reactive stepping using functional data analysis. Nineteen healthy, young adults responded to 6 small and 6 large perturbations using an anterior lean-and-release system, evoking a single reactive step. Muscle activity from surface electromyography was compared between the two conditions for medial gastrocnemius, biceps femoris, tibialis anterior, and vastus lateralis of the stance and stepping limb using functional data analysis. Stance limb medial gastrocnemius and biceps femoris activation increased in the large compared to small perturbation condition immediately prior to foot-off and at foot contact. In the stepping limb, significant increases in medial gastrocnemius, biceps femoris, and tibialis anterior activity occurred immediately prior to foot-off during the large perturbations. Similar to the stance limb, medial gastrocnemius and biceps femoris activity significantly increased during and following foot contact in the large, compared to small, perturbation condition. Lastly, vastus lateralis activity significantly increased for large, compared to small, perturbations during foot-off and immediately following foot contact. These findings highlight lower limb muscle activity modulation associated with perturbation magnitude throughout reactive stepping and the additional benefit of implementing functional data analysis to study reactive balance control.

Associations Between Lower Limb Isometric Torque, Isokinetic Torque, and Explosive Force With Phases of Reactive Stepping in Young, Healthy Adults

“…Lastly, while there were moderate correlations between time to restabilization and plantar flexor and knee flexor peak isometric torque, these relationships were not statistically significant. Peak isometric torque was selected for correlation analysis as peak isometric plantar flexor torque (Karamanidis et al, 2008) has been found to be associated with margin of stability following a perturbation, and both plantar flexors and knee flexors have increased muscle activation at foot contact with larger perturbation magnitudes (Saumur et al, 2020). As there is minimal change in knee and ankle joint velocity shortly after foot contact (Madigan & Lloyd, 2005), and stepping limb muscle activity following foot contact is not as steep as those observed at foot-off (Thelen et al, 2000), peak isometric torque was assessed.…”