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Am J Physiol Regul Integr Comp Physiol. 2015 Nov 1;309(9):R1101-11. doi: 10.1152/ajpregu.00249.2015. Epub 2015 Sep 2.

Satellite cell activity, without expansion, after nonhypertrophic stimuli.

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Departments of Kinesiology, McMaster University, Hamilton, Ontario, Canada;
School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada;
Department of Pediatrics and Medicine, McMaster University, Hamilton, Ontario, Canada; and.
Departments of Kinesiology, McMaster University, Hamilton, Ontario, Canada; Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada


The purpose of the present studies was to determine the effect of various nonhypertrophic exercise stimuli on satellite cell (SC) pool activity in human skeletal muscle. Previously untrained men and women (men: 29 ± 9 yr and women: 29 ± 2 yr, n = 7 each) completed 6 wk of very low-volume high-intensity sprint interval training. In a separate study, recreationally active men (n = 16) and women (n = 3) completed 6 wk of either traditional moderate-intensity continuous exercise (n = 9, 21 ± 4 yr) or low-volume sprint interval training (n = 10, 21 ± 2 yr). Muscle biopsies were obtained from the vastus lateralis before and after training. The fiber type-specific SC response to training was determined, as was the activity of the SC pool using immunofluorescent microscopy of muscle cross sections. Training did not induce hypertrophy, as assessed by muscle cross-sectional area, nor did the SC pool expand in any group. However, there was an increase in the number of active SCs after each intervention. Specifically, the number of activated (Pax7(+)/MyoD(+), P ≤ 0.05) and differentiating (Pax7(-)/MyoD(+), P ≤ 0.05) SCs increased after each training intervention. Here, we report evidence of activated and cycling SCs that may or may not contribute to exercise-induced adaptations while the SC pool remains constant after three nonhypertrophic exercise training protocols.


MyoD; Pax7; endurance training; muscle stem cells; sprint interval training

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