Measures of static postural control moderate the association of strength and power with functional dynamic balance

Background and aims Age-related reductions in strength and power are considered to negatively impact balance control, but the existence of a direct association is still an issue of debate. This is possibly due to the fact that balance assessment is complex, reflects different underlying physiologic mechanisms and involves quantitative measurements of postural sway or timing of performance during balance tasks. The present study evaluated the moderator effect of static postural control on the association of power and strength with dynamic balance tasks. Methods Fifty-seven healthy 65-75 year old individuals performed tests of dynamic functional balance (walking speed under different conditions) and of strength, power and static postural control. Results and conclusions Dynamic balance performance (walking speed) was associated with lower limb strength and power, as well as postural control under conditions requiring postural adjustments (narrow surface walking r(2) = 0.31, p<0.001). An interaction effect between strength and static postural control was found with narrow surface walking and talking while walking (change of beta 0.980, p<0.001 in strength for 1 SD improvements in static postural control for narrow walking, and beta -0.730, p<0.01 in talking while walking). These results indicate that good static postural control facilitates the utilisation of lower limb strength to better perform complex, dynamic functional balance tasks. Practical implications for assessment and training are discussed.