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The decline in skeletal muscle mass with aging is mainly attributed to a reduction in type II muscle fiber size.
Exp Gerontol. 2013 May; 48(5):492-8.EG

Abstract

BACKGROUND

The loss of skeletal muscle mass with aging has been attributed to a decline in muscle fiber number and muscle fiber size.

OBJECTIVE

To define to what extent differences in leg muscle cross-sectional area (CSA) between young and elderly men are attributed to differences in muscle fiber size.

METHODS

Quadriceps muscle CSA and type I and type II muscle fiber size were measured in healthy young (n=25; 23 ± 1 y) and older (n=26; 71 ± 1 y) men. Subsequently, the older subjects performed 6 months of resistance type exercise training, after which measurements were repeated. Differences in quadriceps muscle CSA were compared with differences in type I and type II muscle fiber size.

RESULTS

Quadriceps CSA was substantially smaller in older versus young men (68 ± 2 vs 80 ± 2 cm(2), respectively; P<0.001). Type II muscle fiber size was substantially smaller in the elderly vs the young (29%; P<0.001), with a tendency of smaller type I muscle fibers (P=0.052). Differences in type II muscle fiber size fully explained differences in quadriceps CSA between groups. Prolonged resistance type exercise training in the elderly increased type II muscle fiber size by 24 ± 8% (P<0.01), explaining 100 ± 3% of the increase in quadriceps muscle CSA (from 68 ± 2 to 74 ± 2 cm(2)).

CONCLUSION

Reduced muscle mass with aging is mainly attributed to smaller type II muscle fiber size and, as such, is unlikely accompanied by substantial muscle fiber loss. In line, the increase in muscle mass following prolonged resistance type exercise training can be attributed entirely to specific type II muscle fiber hypertrophy.

Authors+Show Affiliations

Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

23425621

Citation

Nilwik, Rachel, et al. "The Decline in Skeletal Muscle Mass With Aging Is Mainly Attributed to a Reduction in Type II Muscle Fiber Size." Experimental Gerontology, vol. 48, no. 5, 2013, pp. 492-8.
Nilwik R, Snijders T, Leenders M, et al. The decline in skeletal muscle mass with aging is mainly attributed to a reduction in type II muscle fiber size. Exp Gerontol. 2013;48(5):492-8.
Nilwik, R., Snijders, T., Leenders, M., Groen, B. B., van Kranenburg, J., Verdijk, L. B., & van Loon, L. J. (2013). The decline in skeletal muscle mass with aging is mainly attributed to a reduction in type II muscle fiber size. Experimental Gerontology, 48(5), 492-8. https://doi.org/10.1016/j.exger.2013.02.012
Nilwik R, et al. The Decline in Skeletal Muscle Mass With Aging Is Mainly Attributed to a Reduction in Type II Muscle Fiber Size. Exp Gerontol. 2013;48(5):492-8. PubMed PMID: 23425621.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The decline in skeletal muscle mass with aging is mainly attributed to a reduction in type II muscle fiber size. AU - Nilwik,Rachel, AU - Snijders,Tim, AU - Leenders,Marika, AU - Groen,Bart B L, AU - van Kranenburg,Janneau, AU - Verdijk,Lex B, AU - van Loon,Luc J C, Y1 - 2013/02/17/ PY - 2012/10/31/received PY - 2013/02/07/revised PY - 2013/02/11/accepted PY - 2013/2/22/entrez PY - 2013/2/22/pubmed PY - 2013/10/1/medline SP - 492 EP - 8 JF - Experimental gerontology JO - Exp Gerontol VL - 48 IS - 5 N2 - BACKGROUND: The loss of skeletal muscle mass with aging has been attributed to a decline in muscle fiber number and muscle fiber size. OBJECTIVE: To define to what extent differences in leg muscle cross-sectional area (CSA) between young and elderly men are attributed to differences in muscle fiber size. METHODS: Quadriceps muscle CSA and type I and type II muscle fiber size were measured in healthy young (n=25; 23 ± 1 y) and older (n=26; 71 ± 1 y) men. Subsequently, the older subjects performed 6 months of resistance type exercise training, after which measurements were repeated. Differences in quadriceps muscle CSA were compared with differences in type I and type II muscle fiber size. RESULTS: Quadriceps CSA was substantially smaller in older versus young men (68 ± 2 vs 80 ± 2 cm(2), respectively; P<0.001). Type II muscle fiber size was substantially smaller in the elderly vs the young (29%; P<0.001), with a tendency of smaller type I muscle fibers (P=0.052). Differences in type II muscle fiber size fully explained differences in quadriceps CSA between groups. Prolonged resistance type exercise training in the elderly increased type II muscle fiber size by 24 ± 8% (P<0.01), explaining 100 ± 3% of the increase in quadriceps muscle CSA (from 68 ± 2 to 74 ± 2 cm(2)). CONCLUSION: Reduced muscle mass with aging is mainly attributed to smaller type II muscle fiber size and, as such, is unlikely accompanied by substantial muscle fiber loss. In line, the increase in muscle mass following prolonged resistance type exercise training can be attributed entirely to specific type II muscle fiber hypertrophy. SN - 1873-6815 UR - https://www.unboundmedicine.com/medline/citation/23425621/The_decline_in_skeletal_muscle_mass_with_aging_is_mainly_attributed_to_a_reduction_in_type_II_muscle_fiber_size_ DB - PRIME DP - Unbound Medicine ER -