Reliability of a Lower-Extremity Shear Force Control Task in Young, Uninjured Adults

A novel shear force control task has previously been shown to elucidate different neuromuscular control strategies among individuals after anterior cruciate ligament injury, individuals following anterior cruciate ligament reconstruction, uninjured collegiate athletes, and uninjured recreational athletes. However, the reliability of the methodology has not been evaluated. The purpose of this study was to determine the reliability of this methodology in a population with no lower-extremity injury. Thirteen individuals (7 men, 24.7 [4.8] y, body mass index: 23.9 [3.6] kg/m2) completed a standing force control task in the medial/lateral and anterior/posterior directions for each leg on 2 separate occasions (1 wk apart). Intraclass correlation coefficient with 95% confidence intervals, standard error of measurement, and minimum detectable change were calculated to assess the reliability of largest Lyapunov exponent values. Intraclass correlation coefficient values across all measures were good to excellent (r = .78-.92). Reliability was highest in the medial/lateral direction at the right lower extremity (r = .92; 95% confidence interval, .75-.98, P = .025). The shear force control task exhibited good to excellent reliability across measures, suggesting that it can reliably measure force control variability. This methodology may provide insight into neuromuscular control strategies following injury.