Ground Reaction Force in Sit-to-stand Reflects Lower-extremity Function Better than Timed Test in Older Adults

Abstract

In a clinical setting of nursing-care prevention for older adults, timed tests such as five-time sit-to-stand (STS) have often been used as an assessment of lower-extremity function. However, these tests do not reflect leg muscle function because they involve other factors such as movement skills. Ground reaction force (GRF) parameters in the STS movement are considered applicable to evaluate lower-extremity function because force output can be directly measured with the force platform. Limited information is known, however, about the relationships between the isokinetic test scores for the knee extensors, and flexor strength and power. PURPOSE: The purpose of this study was to: 1) examine associations among the GRF parameters in STS movement and isokinetic knee strength and power in older adults, and 2) compare associations with five-time STS test results. METHODS: Nineteen healthy older men (69.6 ± 2.9 yrs) and 28 older women (68.6 ± 2.9 yrs) were recruited. Each participant was asked to stand up three times quickly from a seated position. Three parameters were measured: 1) peak reaction force per body weight (F/w, kgf·kg-1), which reflected the maximal downward push to raise the body upward, 2) maximal rate of force development per body weight (RFD/w, kgf/s·kg-1), which estimated the capacity for rapid muscle force production, and 3) a movement time (T, ms). Five-time STS test scores were also measured. Four isokinetic parameters: peak torque and average power during isokinetic knee extension and flexion at 60 deg/s were measured using an isokinetic dynamometer (Biodex System 3; Biodex medical systems). RESULTS: The F/w, RFD/w, T and five-time STS test were 1.43 ± 0.10 kgf·kg-1, 11.14 ± 1.48 kgf/s·kg-1, 782 ± 92 ms, 7.37 ± 1.43 s, respectively. After adjusting for age and sex, significant partial correlations were found among all four isokinetic parameters and F/w (partial r =.31∼.34, p <.05), and RFD/w (partial r =.32∼.47, p <.05). No isokinetic parameters were significantly related to T (partial r = -.11∼-.25, ns) or five-time STS test scores (partial r = -.07∼-.27, ns). CONCLUSIONS: These data suggest that the GRF parameters in STS movement can reflect isokinetic knee strength and power better than the five-time STS test.