Reduced rate of knee extensor torque development in older adults with knee osteoarthritis is associated with intrinsic muscle contractile deficits.
We examined the effect of knee osteoarthritis on the rate of torque development (RTD) of the knee extensors in older adults with advanced-stage knee osteoarthritis (OA; n=15) and recreationally-active controls (n=15) of similar age, sex and health status, as well as the relationship between RTD and the size and contractility of single muscle fibers. OA participants had lower RTD when expressed in absolute terms (Nm/ms). There were sex differences in peak RTD (P<0.05), with greater RTD in men, but no group by sex interaction effects for any variables. The lower RTD in OA versus controls was not explained by variation between groups in the fiber type admixture of the muscle, and was mitigated when RTD was normalized to peak torque (PT). In knee OA volunteers, we found strong correlations between the RTD expressed relative to PT and the velocity of contraction of single myosin heavy chain (MHC) I and IIA/X muscle fibers (r=0.652 and 0.862; both P<0.05) and power output of MHC I fibers (r=0.642; P<0.05). In controls, RTD relative to PT was related to fiber cross-sectional area of MHC IIA/X fibers (r=0.707; P<0.05), but not measures of single fiber contractile performance. To our knowledge, these results represent the first demonstration that variation in whole muscle contractile kinetics in patients with advanced-stage knee osteoarthritis and healthy older adults is related, in part, to the size and function of single muscle fibers.
Department of Medicine, University of Vermont, College of Medicine, Burlington, VT, United States.
Damien M
DM
Callahan
Department of Orthopaedics and Rehabilitation, University of Vermont, College of Medicine, Burlington, VT, United States.
Timothy W
TW
Tourville
Department of Orthopaedics and Rehabilitation, University of Vermont, College of Medicine, Burlington, VT, United States.
James R
JR
Slauterbeck
Department of Medicine, University of Vermont, College of Medicine, Burlington, VT, United States.
Philip A
PA
Ades
Department of Physical Medicine and Rehabilitation, University of Colorado, Denver, CO, United States.
Jennifer
J
Stevens-Lapsley
Department of Orthopaedics and Rehabilitation, University of Vermont, College of Medicine, Burlington, VT, United States.
Bruce D
BD
Beynnon
Department of Medicine, University of Vermont, College of Medicine, Burlington, VT, United States; Department of Orthopaedics and Rehabilitation, University of Vermont, College of Medicine, Burlington, VT, United States; Department of Molecular Physiology and Biophysics, University of Vermont, College of Medicine, Burlington, VT, United States. Electronic address: michael.toth@uvm.edu.
Michael J
MJ
Toth
D000368:Aged; D001706:Biopsy; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000473:pathology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D019415:Torque
D018995:Myosin Heavy Chains
Single muscle fiber; Skinned fiber; Velocity