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Effects of age and ACL reconstruction on quadriceps gamma loop function
Michael S Richardson1, Joel T Cramer, Debra A Bemben
1University of Oklahoma, Department of Health and Exercise Science, Neuromuscular Research Laboratory, 401 Asp Avenue, Norman, OK 73019, USA. mgbemben@ou.edu
Journal of Geriatric Physical Therapy (2001)
|April 25, 2006
Summary
Aging and ACL reconstruction impair the gamma loop, a neural system crucial for muscle strength. Vibration testing revealed deficits in older and ACL-reconstructed individuals, unlike young healthy controls.
Area of Science:
- Neuromuscular physiology
- Gerontology
- Sports medicine
Background:
- Aging and anterior cruciate ligament (ACL) reconstruction are linked to muscle strength deficits affecting daily activities.
- Potential mechanisms include reduced muscle fiber size/number (aging) or loss of mechanoreceptors (ACL reconstruction).
- The gamma spindle system (gamma loop) may be a common factor linking these conditions.
Purpose of the Study:
- To investigate the impact of aging and ACL reconstruction on gamma loop function.
- To determine if vibration stimulation differentially affects muscle strength and activation in these groups.
Main Methods:
- Maximal isometric strength (MVC) and quadriceps electromyography (EMG) were measured before and after infrapatellar tendon vibration.
- Three groups were studied: young healthy (n=4), young ACL-reconstructed (n=7), and older healthy (n=4).
Main Results:
- Young healthy individuals showed significant declines in MVC and quadriceps EMG post-vibration, confirming intact gamma loop function.
- Older healthy and ACL-reconstructed groups exhibited no significant changes in these measures after vibration.
Conclusions:
- Gamma loop function appears impaired in older adults and individuals post-ACL reconstruction.
- This impairment may stem from reduced muscle spindle sensitivity or loss of mechanoreceptors in these populations.