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Updated: Jul 10, 2026

Fiber Type Identification of Human Skeletal Muscle
Published on: September 22, 2023
Mechanical muscle function, morphology, and fiber type in lifelong trained elderly
Per Aagaard1, Peter S Magnusson, Benny Larsson
1Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark. paagaard@health.sdu.dk
Lifelong strength training preserves muscle mass and function in older adults. Chronic strength training enhances muscle strength, size, and performance, aiding independence in old age.
Area of Science:
- Gerontology
- Exercise Physiology
- Muscle Biology
Background:
- Aging naturally leads to reduced muscle mass and strength.
- Long-term exercise interventions can potentially mitigate age-related muscle decline.
Purpose of the Study:
- To investigate the effects of chronic endurance (E) and strength (S) training on muscle function and morphology in elderly individuals.
- To compare muscle characteristics of trained elderly individuals with an untrained (U) elderly group.
Main Methods:
- Assessed maximal isometric quadriceps strength (MVC), rate of force development (RFD), and muscle fiber composition and size (CSA).
- Studied elderly individuals (68-78 yr) with over 50 years of consistent E or S training, alongside an age-matched untrained group.
Main Results:
- Both E and S groups exhibited greater MVC than the U group.
- Strength training (S) significantly increased contractile RFD and type II fiber CSA compared to U and E groups.
- Endurance training (E) resulted in a higher proportion of type I muscle fibers compared to U and S groups.
Conclusions:
- Lifelong strength training preserves muscle fiber size and mechanical performance, notably RFD, in aging individuals.
- This preservation of muscle morphology and function offers a significant physical reserve, helping maintain muscle mass and function for independent living in old age.
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