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

Abstract

This study aimed to determine the relationship between lower limb muscle strength and explosive force with force plate–derived timing measures of reactive stepping. Nineteen young, healthy adults responded to 6 perturbations using an anterior lean-and-release system. Foot-off, swing, and restabilization times were estimated from force plates. Peak isokinetic torque, isometric torque, and explosive force of the knee extensors/flexors and plantar/dorsiflexors were measured using isokinetic dynamometry. Correlations were run based on a priori hypotheses and corrected for the number of comparisons (Bonferroni) for each variable. Knee extensor explosive force was negatively correlated with swing time (r = −.582, P = .009). Knee flexor peak isometric torque also showed a negative association with restabilization time (r = −.459, P = .048); however, this was not statistically significant after correcting for multiple comparisons. There was no significant relationship between foot-off time and knee or plantar flexor explosive force (P > .025). These findings suggest that there may be utility to identifying specific aspects of reactive step timing when studying the relationship between muscle strength and reactive balance control. Exercise training aimed at improving falls risk should consider targeting specific aspects of muscle strength depending on specific deficits in reactive stepping.

Explosive is not a Term Defined in the International System of Units and Should not be Used to Describe Neuromuscular Performance

“…Unfortunately, several studies have made the error of referring to these biomechanical concepts as 'explosive force' (11,37,40,48) or 'explosive strength' (4,9,12,15,30,38,42). The use of these superfluous terms may cause confusion and misunderstanding as readers may believe that these constructs represent different parameters beyond those which were measured.…”