Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training

G. E. McCall, W. C. Byrnes, A. Dickinson, Pradip Pattany, S. J. Fleck

Research output: Contribution to journalArticle

223 Citations (Scopus)

Abstract

Twelve male subjects with recreational resistance training backgrounds completed 12 wk of intensified resistance training (3 sessions/wk; 8 exercises/session; 3 sets/exercise; 10 repetitions maximum/set). All major muscle groups were trained, with four exercises emphasizing the forearm flexors. After training, strength (1-repetition maximum preacher curl) increased by 25% (P < 0.05). Magnetic resonance imaging scans revealed an increase in the biceps brachii muscle cross-sectional area (CSA) (from 11.8 ± 2.7 to 13.3 ± 2.6 cm2; n = 8; P < 0.05). Muscle biopsies of the biceps brachii revealed increases (P < 0.05) in fiber areas for type I (from 4,196 ± 859 to 4,617 ± 1,116 μm2; n = 11) and II fibers (from 6,378 ± 1,552 to 7,474 ± 2,017 μm2; n = 11). Fiber number estimated from the above measurements did not change after training (293.2 ± 61.5 x 103 pretraining; 297.5 ± 69.5 x 103 posttraining; n = 8). However, the magnitude of muscle fiber hypertrophy may influence this response because those subjects with less relative muscle fiber hypertrophy, but similar increases in muscle CSA, showed evidence of an increase in fiber number. Capillaries per fiber increased significantly (P < 0.05) for both type I (from 4.9 ± 0.6 to 5.5 ± 0.7; n = 10) and II fibers (from 5.1 ± 0.8 to 6.2 ± 0.7; n = 10). No changes occurred in capillaries per fiber area or muscle area. In conclusion, resistance training resulted in hypertrophy of the total muscle CSA and fiber areas with no change in estimated fiber number, whereas capillary changes were proportional to muscle fiber growth.

Original languageEnglish
Pages (from-to)2004-2012
Number of pages9
JournalJournal of Applied Physiology
Volume81
Issue number5
StatePublished - Nov 1 1996
Externally publishedYes

Fingerprint

Resistance Training
Hypertrophy
Hyperplasia
Muscles
Exercise
Forearm
Magnetic Resonance Imaging
Biopsy

Keywords

  • fiber number
  • fiber type
  • muscle adaptation
  • muscle cross- sectional area
  • weight training

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training. / McCall, G. E.; Byrnes, W. C.; Dickinson, A.; Pattany, Pradip; Fleck, S. J.

In: Journal of Applied Physiology, Vol. 81, No. 5, 01.11.1996, p. 2004-2012.

Research output: Contribution to journalArticle

McCall, G. E. ; Byrnes, W. C. ; Dickinson, A. ; Pattany, Pradip ; Fleck, S. J. / Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training. In: Journal of Applied Physiology. 1996 ; Vol. 81, No. 5. pp. 2004-2012.
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