Functional fitness tests and their association with upper-limb isokinetic strength in older adults

This study investigated the association between commonly used functional fitness tests (i.e., Up-and-Go Test [UGT], 30-Second Chair Stand Test [30CS], 30-Second Arm Curl Test [30AC], and 6-Minute Walk Test [6MWT]) and upper-limb isokinetc strength (elbow and shoulder flexion-extension isokinetic absolute and relative strength at 60º/s and 180º/s) in older adults. It was hypothesized that upper-limb-specific tests would show stronger associations, that elbow strength would be better explained than shoulder strength, and that higher angular velocities would demonstrate stronger associations.

Three hundred and twenty-seven apparently healthy older adults (247 women and 80 men; age: 69.27 ± 5.62) enrolled in this cross-sectional study. Isokinetic concentric strength was assessed before functional fitness tests.

Small to moderate correlations were observed between functional fitness tests and shoulder and elbow isokinetic strength. Better performance in the UGT, 30AC, and 6MWT was associated with greater strength (r = 0.11-0.46); whereas the 30CS showed inconsistent correlations (r = -0.13-0.30). Regression models including functional fitness tests, age, and sex explained a substantial proportion of the variance, with higher values for elbow (R² = 0.34-0.55) than shoulder strength (R² = 0.12-0.42). No consistent pattern of stronger associations at higher angular velocities was identified.

Upper-limb isokinetic strength is associated with functional fitness in older adults, although associations were generally small to moderate. Functional fitness, together with age and sex, explained up to 55% of the variance. These findings suggest that functional fitness tests may provide indirect and complementary information related to upper-limb strength in settings where isokinetic dynamometry is not available, but they should not be considered surrogate measures of muscle strength.