Muscle Torque-Velocity Relationships and Fatigue With Reduced Knee Joint Range of Motion in Young and Older Adults

• Published in: Journal of applied biomechanics Vol. 40; no. 4; p. 261
• Main Authors: Smith, Zoe H, Martin, R Anthony, Casto, Erica, Bigelow, Carol, Busa, Michael A, Kent, Jane A
• Format: Journal Article
• Language: English
• Published: United States 01.08.2024
• Subjects: Adult; Aged; Aging - physiology; Biomechanical Phenomena; Female; Humans; Knee Joint - physiology; Male; Muscle Contraction - physiology; Muscle Fatigue - physiology; Muscle, Skeletal - physiology; Range of Motion, Articular - physiology; Torque; quadriceps; aging; power; recovery
• DOI: 10.1123/jab.2023-0130

The purpose of this study was to evaluate the influence of knee joint range of motion (RoM) on the torque-velocity relationship and fatigue in the knee extensor muscles of 7 young (median = 26 y) and 7 older (68 y) adults. Each leg was assigned a RoM (35° or 75°) over which to perform a torque-velocity protocol (maximal isokinetic contractions, 60-300°·s-1) and a fatigue protocol (120 maximal contractions at 120°·s-1, 0.5 Hz). Six older participants were unable to reach 300°·s-1 over 35°. Therefore, the velocity eliciting 75% of peak torque at 60°·s-1 (V75, °·s-1) was calculated for each RoM from a fit of individual torque-velocity curves (60-240°·s-1), and ΔV75 (35°-75°) was determined. Fatigue (final torque/initial torque) was used to calculate Δfatigue (35°-75°). ΔV75 was not different from 0 in young (-28.3°·s-1 [-158.6 to 55.7], median [range], P = .091) or older (-18.5°·s-1 [-95.0 to 23.9], P = .128), with no difference by age (P = .710). In contrast, fatigue was greater for 75° in young (Δfatigue = 25.9% [17.5-30.3], P = .018) and older (17.2% [11.9-52.9], P = .018), with no effect of age (P = .710). These data indicate that, regardless of age, RoM did not alter the torque-velocity relationship between 60 and 240°·s-1, and fatigue was greater with a larger RoM.