The Relationships Between Upper and Lower Extremity Muscle Strength, Rate of Force Development, and Fatigue in Adults

Electronic handgrip dynamometry allows for multiple muscle function aspects to be feasibly measured, yet their relationship with lower extremity muscle function is unknown. We sought to determine the relationships between upper and lower extremity mechanical isometric muscle strength, rate of force development (RFD), and endurance by limb dominance in resistance trained adults. The analytic sample included 30 adults aged 32.1 ± 13.5 years. An electronic handgrip dynamometer ascertained upper extremity strength capacity, RFD, and endurance. Lower extremity strength, RFD, and endurance were collected with the isometric feature on an isokinetic knee dynamometer. Limb dominance was self-reported. Pearson correlations were used for the analyses. Each muscle function attribute on the dominant limb of the upper and lower extremities were correlated: r = 0.76 (p < 0.01) for strength, r = 0.37 (p = 0.04) for RFD, and r = -0.48 (p < 0.01) for endurance. Although strength from the non-dominant limbs were correlated (r = 0.67; p < 0.01), no significant correlations were observed for RFD (r = 0.20; p = 0.29) and endurance (r = -0.21; p = 0.26). For adults aged 18-34 years, only upper and lower extremity strength was correlated on the dominant (r = 0.69; p < 0.01) and non-dominant limbs (r = 0.75; p < 0.01); however, strength (r = 0.88; p < 0.01) and endurance (r = -0.68; p = 0.01) were correlated in adults aged 35-70 years. Upper and lower extremity fatigability was likewise correlated in females (r = -0.56; p = 0.01). Our findings suggest that electronic handgrip dynamometry derived strength, RFD, and endurance could be a whole-body indicator of these muscle function attributes given their relationships with the lower extremities. These findings underscore the promise of handgrip dynamometry in routine muscle function assessments across different age groups.