Background: Ground reaction force parameters in a sit-to-stand (STS) movement can be used to evaluate lower extremity function. Few reports, however, are available on whether the ground reaction force parameters in an STS movement reflect dynamic knee and ankle strength or power. The aims of this study were to examine associations among ground reaction force parameters in an STS movement and isokinetic knee and ankle strength and power in healthy older adults, and to compare associations with the five-times STS test. Methods: The following five ground reaction force parameters were measured in 19 men and 28 women: peak reaction force, two rate of force development (RFD) parameters and two time-related parameters. Results: RFD (Δ90 ms)/body weight correlated significantly with average isokinetic knee extension/flexion power in both sexes (partial-r = 0.39–0.54) and average ankle plantar flexion and dorsiflexion power (partial-r = 0.50 and partial-r = 0.49, respectively), in women. No isokinetic parameters were significantly related to the five-times STS test. Conclusion: Ground reaction force parameters in an STS movement can accurately reflect the dynamic strength and power in the lower limbs, which is approximately equal to or better than the strength and power reflected by the five-times STS test.
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