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Human Vastus Lateralis Skeletal Muscle Biopsy Using the Weil-Blakesley Conchotome
Published on: March 4, 2016
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Age-related neuromuscular changes affecting human vastus lateralis
M Piasecki1, A Ireland1, D Stashuk2
1School of Healthcare Science, Manchester Metropolitan University, Manchester, UK.
The Journal of Physiology
|October 22, 2015
Summary
Older men experience significant loss of motor units (MUs) in thigh muscles, with remaining MUs becoming larger and less stable. These neuromuscular changes precede noticeable declines in muscle function, indicating a prelude to age-related movement issues.
Area of Science:
- Neuromuscular physiology
- Gerontology
- Skeletal muscle biology
Background:
- Skeletal muscle size and strength decrease with age.
- Healthy aging involves neuromuscular remodeling, including motor neuron loss and motor unit (MU) enlargement.
- The vastus lateralis (VL) muscle shows significant changes in aging, but the link between neuromuscular structure and function is not fully understood.
Purpose of the Study:
- To investigate changes in motor unit (MU) number, size, and stability in the vastus lateralis (VL) of older men compared to younger men.
- To correlate these neuromuscular changes with muscle size and explore their implications for age-related muscle weakness.
Main Methods:
- Electromyographic (EMG) signals (intramuscular and surface) were recorded from the VL during submaximal contractions in young and older men.
- Motor unit potential (MUP) size, firing rates, and complexity (phases, turns, near-fiber jiggle) were analyzed.
- Motor unit number estimates (MUNEs) and quadriceps cross-sectional area (via MRI) were determined.
Main Results:
- Older men exhibited significantly fewer motor units (MUs) in the VL, with estimates suggesting a 50-60% reduction compared to young men, even after accounting for smaller muscle size.
- Remaining MUs in older men were larger (+25%) and less stable, showing increased complexity in their electrical potentials.
- Older participants had approximately 70% of the MUNE values observed in younger individuals.
Conclusions:
- A substantial loss of motor units (MUs) occurs in the vastus lateralis of older men.
- The surviving MUs in older adults are enlarged and demonstrate reduced neuromuscular junction stability.
- These neuromuscular alterations precede clinically significant muscle mass and function loss, suggesting they are early indicators of age-related motor decline.
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