Satellite cell pool expansion is affected by skeletal muscle characteristics

Introduction: We investigated changes in satellite cell (SC) pool size after an acute bout of strenuous exercise and evaluated the influence of baseline SC count and fiber type. Methods: Participants completed a downhill running (DHR) intervention (5 × 8 min, 2‐min rest; 80% VO _2max; ?10% gradient). Muscle biopsies were taken 7 days before VO _2max and 7–9 days after the DHR intervention. Delayed‐onset muscle soreness (DOMS) and creatine kinase activity (CK) were measured on days 1, 2, 7, and 9 post‐DHR. SCs were identified by Pax7 and laminin staining. Relative distribution of MHC isoforms was determined by electrophoresis. Results: DOMS and CK peaked on day 1 post‐DHR (P < 0.01). The SC pool increased (26%) after DHR (P = 0.005). SCs/total myonuclei after recovery correlated with baseline SCs (r = 0.979, P = 0.003) and VO _2max (r = 0.956, P = 0.011), whereas change in SC pool (Pax7⁺ cells/total myonuclei: recovery minus baseline) tended to correlate with percent MHC II (r = 0.848; P = 0.06). Conclusion: Interindividual physiological characteristics affect SC pool expansion after a single bout of DHR and are influenced by VO _2max. Muscle Nerve, 2013