Upper and lower limb muscle power relationships in mobility-limited older adults

Background. Lower limb muscle power impairments are modifiable factors underlying mobility limitations in older adults. This study examined relationships between upper and lower limb muscle power and their role in predicting mobility performance among community-dwelling older adults. Methods. A cross-sectional analysis was conducted. Participants included 37 mobility-limited adults (24 women, 13 men), aged 65 to 93 years. Measures included upper (elbow extension) and lower limb (double leg press) one repetition maximum (IRM), and muscle power at both 40% and 70% one repetition maximum. Physical performance measures included stair climb time, the Short Physical Performance Battery, and 4-meter walk time. Factors commonly mediating the relationship between impairments and physical performance were analyzed as covariates. Results. Participants had a mean age of 76 years, had five chronic medical conditions, and manifested moderate mobility limitations. Although the associations between the upper and lower limbs were strong (p < .001), the magnitude of association was greater for power (r = .88-89) as compared to strength (r = .69). Multivariate regression analyses revealed consistently strong relationships between limb muscle power and mobility performance measures. Substituting upper for lower limb power within these models did not materially weaken the relationships. Conclusion. Muscle power appears to be a more generalized attribute between the upper and lower limbs than is muscle strength, suggesting that mechanisms underlying velocity of movement, as opposed to force production, may be important factors underlying muscle power in elderly persons. Additionally, upper limb muscle power measures may serve as a useful surrogate measure of limb power having implications for clinicians and researchers.