Relationship between postural sway on an unstable platform and ankle plantar flexor force steadiness in community-dwelling older women.

Abstract Background Force steadiness is evaluated as force variability during constant force exertion around a target level. Ankle plantar flexor force steadiness is reported to be related to postural sway on an unstable platform in healthy young adults; however, this relationship in older adults is unclear. Research question This study aimed to investigate whether ankle plantar flexor force steadiness was related to postural sway on stable and unstable platforms in older adults. Methods Twenty-six community-dwelling older women participated in this study (72 ± 6 years). Maximal isometric strength and force steadiness at 5%, 20 %, and 50 % of the maximal strength of ankle plantar flexion were assessed. Postural sway in the anteroposterior direction during bipedal standing was measured on stable and unstable platforms. Results The results showed that force steadiness at any intensity level and maximal isometric strength were not related to postural sway on the stable platform. Force steadiness at 20 % of maximal strength alone was significantly correlated with postural sway on the unstable platform (ρ = 0.441, p Significance These results indicate that the ability to control muscle force could be important for postural stability on an unstable platform in older adults.