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In vivo Measurement of Knee Extensor Muscle Function in Mice
Published on: March 4, 2021
Quadriceps neuromuscular function and self-reported functional ability in knee osteoarthritis
M J Berger1, C A McKenzie, D G Chess
1Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada. mberger2010@meds.uwo.ca
Journal of Applied Physiology (Bethesda, Md. : 1985)
|May 19, 2012
Summary
Muscle power at lower loads, not maximal strength, best predicts function in knee osteoarthritis (OA) patients. Muscle size, not nerve activation, explains strength differences in these individuals.
Area of Science:
- Orthopedics
- Rehabilitation Science
- Biomedical Engineering
Background:
- Knee osteoarthritis (OA) significantly impacts patient function and quality of life.
- Understanding the relationship between muscle function and self-reported limitations is crucial for effective rehabilitation strategies.
- Maximal muscle strength and power are often assessed, but their specific associations with functional capacity in knee OA require further elucidation.
Purpose of the Study:
- To investigate the relationship between self-reported function in knee OA patients and their maximal isometric torque and isotonic power across various loads.
- To determine the extent to which muscle volume (MV) and voluntary activation (VA) correlate with torque and power measurements in this population.
Main Methods:
- Forty participants with knee OA underwent assessments of isometric maximal voluntary contraction (MVC) torque and isotonic power at loads ranging from 0% to 50% MVC.
- Functional ability was quantified using the Western Ontario and McMaster Osteoarthritis Index (WOMAC) function subscale.
- Muscle volume (MV) was measured via MRI, and voluntary activation (VA) was assessed using the interpolated twitch technique.
Main Results:
- Isotonic power at lower loads (0-30% MVC) demonstrated a stronger association with self-reported function (r² = 0.21-0.28) compared to MVC torque (r² = 0.18).
- Power at "Zero Load" exhibited the strongest predictive relationship with function (r² = 0.28).
- Muscle volume (MV) was the primary determinant of MVC torque and power (r² = 0.42-0.72), while voluntary activation (VA) explained minimal variance (6% for MVC torque) and was not significantly linked to power output.
Conclusions:
- While both quadriceps MVC torque and power are related to self-reported function in knee OA, muscle power at lower exertion levels is a more sensitive indicator of functional capacity.
- Differences in muscle torque and power among knee OA patients are predominantly attributable to variations in muscle size (MV), rather than deficits in neural activation (VA).
