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Stiffness and muscle function with age and reduced muscle use
M Brown1, J S Fisher, G Salsich
1Program in Physical Therapy, Washington University School of Medicine, St. Louis, Missouri 63108, USA. brownm@medicine.wustl.edu
Summary
Muscle stiffness did not change with age or disuse, but passive tension became a larger part of total muscle tension. Reduced muscle range of motion was observed in aging and unweighted rats.
Area of Science:
- Physiology
- Gerontology
- Muscle Biology
Background:
- Aging and disuse are known to affect muscle function.
- Understanding changes in passive muscle properties is crucial for maintaining mobility.
Purpose of the Study:
- To investigate the effects of aging and hindlimb unweighting on passive muscle stiffness and range of motion.
- To analyze age- and disuse-related alterations in muscle length-tension relationships.
Main Methods:
- Assessed passive muscle stiffness and tension in four hindlimb muscles of young, old, and hindlimb-unweighted old rats.
- Generated length-tension curves to evaluate muscle range of motion and passive tension.
- Measured muscle mass and peak contractile tension.
Main Results:
- Passive muscle stiffness remained unchanged with aging and hindlimb unweighting.
- Passive tension constituted a greater proportion of total tension in older and unweighted rats.
- Hindlimb unweighting significantly reduced the range of motion for all four hindlimb muscles studied.
- Aging caused a loss in range of motion in the plantaris muscle.
- Muscle mass and peak contractile tension declined with both aging and hindlimb unweighting.
Conclusions:
- While passive muscle stiffness is preserved, aging and disuse alter the contribution of passive tension and significantly restrict muscle range of motion.
- These findings highlight the profound impact of reduced muscle use and aging on muscle mechanics, potentially impacting locomotion and overall function.