HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 104/6/1736    most recent 01215.2007v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Petrella, J. K. Articles by Bamman, M. M. PubMed PubMed Citation Articles by Petrella, J. K. Articles by Bamman, M. M.

Potent myofiber hypertrophy during resistance training in humans is associated with satellite cell-mediated myonuclear addition: a cluster analysis

Departments of ¹Physiology and Biophysics and ³Surgery, The University of Alabama at Birmingham, Birmingham; and ²Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Birmingham, Alabama

Submitted 14 November 2007 ; accepted in final form 18 April 2008

A present debate in muscle biology is whether myonuclear addition is required during skeletal muscle hypertrophy. We utilized K-means cluster analysis to classify 66 humans after 16 wk of knee extensor resistance training as extreme (Xtr, n = 17), modest (Mod, n = 32), or nonresponders (Non, n = 17) based on myofiber hypertrophy, which averaged 58, 28, and 0%, respectively (Bamman MM, Petrella JK, Kim JS, Mayhew DL, Cross JM. J Appl Physiol 102: 2232–2239, 2007). We hypothesized that robust hypertrophy seen in Xtr was driven by superior satellite cell (SC) activation and myonuclear addition. Vastus lateralis biopsies were obtained at baseline and week 16. SCs were identified immunohistochemically by surface expression of neural cell adhesion molecule. At baseline, myofiber size did not differ among clusters; however, the SC population was greater in Xtr (P < 0.01) than both Mod and Non, suggesting superior basal myogenic potential. SC number increased robustly during training in Xtr only (117%; P < 0.001). Myonuclear addition occurred in Mod (9%; P < 0.05) and was most effectively accomplished in Xtr (26%; P < 0.001). After training, Xtr had more myonuclei per fiber than Non (23%; P < 0.05) and tended to have more than Mod (19%; P = 0.056). Both Xtr and Mod expanded the myonuclear domain to meet (Mod) or exceed (Xtr) 2,000 µm² per nucleus, possibly driving demand for myonuclear addition to support myofiber expansion. These findings strongly suggest myonuclear addition via SC recruitment may be required to achieve substantial myofiber hypertrophy in humans. Individuals with a greater basal presence of SCs demonstrated, with training, a remarkable ability to expand the SC pool, incorporate new nuclei, and achieve robust growth.

strength training; skeletal muscle; neural cell adhesion molecule; myonucleus; myogenesis