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This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Award

Summer 2011

Document Type


Degree Name

Master of Science (MS)


Department of Kinesiology


Purpose: Concurrent training attenuates hypertrophy compared to resistance training alone, and does so in a fiber-type specific manner. The mechanism responsible for this ‘interference’ is unclear, and satellite cell physiology, an important hypertrophic factor, has not been examined within this context. Therefore, the purpose of this investigation was to assess the fiber-type specific satellite cell response to acute resistance, aerobic and concurrent exercise. Methods: Eight recreationally active college-aged males (23±1 yrs, 83.4±3.6 kg, 181±2 cm, and 48.5±1.6 ml/kg/min) performed 3 sets of 10 repetitions with a fourth set ≥ 10 repetitions at 75% of 1RM for both unilateral leg extensions and unilateral leg press for acute RE. Ten days later subjects performed the same resistance exercise with the opposite leg followed by 90 minutes of cycling at 60% VO2max to represent acute concurrent and aerobic exercise. Muscle biopsies were obtained immediately before and 4 days after each exercise session. Muscle samples were cross sectioned and stained with for NCAM, Ki-67, DAPI and MHC I via immunohistochemistry to assess satellite cells, activated satellite cells and fiber-type, respectively. Results: Total satellite cell number per fiber increased only in response to acute resistance exercise (+38±10%, p < 0.05), with no change following acute aerobic or concurrent exercise. Changes in total satellite cell number per fiber between resistance, aerobic and concurrent exercise differed only in MHC I fibers (p < 0.05), with no satellite cell number per fiber time by mode interaction observed in non-MHC I muscle fibers. No changes in activated satellite cells were observed under any condition. Conclusion: Acute concurrent exercise blunts the satellite cell response of resistance exercise alone, and does so in a fiber-type specific manner by negating the satellite cell response in MHC I, but not non-MHC I fibers. These results suggest that the interference effect of concurrent resistance training on MHC I hypertrophy may be regulated at the satellite cell level.

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