Comparison of the ankle, knee, hip, and trunk corrective action shown during single-leg stance on firm, foam, and multiaxial surfaces

Objective: To compare the quantity of ankle, knee, hip, and trunk corrective actions shown during single-leg stance. Design: Counter-balanced crossover design. Single-leg stance under the conditions of eyes open on firm, foam, and multiaxial surfaces and eyes closed on a firm surface were recorded for 12 seconds in 18 participants. Setting: A university neuromuscular research laboratory. Participants: Eighteen healthy and recreationally active college students. Interventions: Not applicable. Main Outcome Measure: Average angular displacement magnitude between successive sampling instances for the ankle, knee, hip, and trunk. Results: A significant condition by joint interaction was revealed. Post hoc comparisons revealed that the ankle dominated as the source of corrective action across each of the testing conditions. As the challenge became greater because of foam surface or eyes closed, more corrective action occurred at proximal joints (hip and/or knee). Conclusions: The ankle is of primary importance during single-leg stance on firm, foam, and multiaxial surfaces, with proximal joints having an increased role under more challenging conditions. These results provide a scientific basis for clinicians' and researchers' decisions about support surface and visual condition during single-leg postural control testing and training.