Altered muscle satellite cell activation following 16 wk of resistance training in young men

Abstract

Skeletal muscle satellite cells (SC) play an important role in muscle adaptation. In untrained individuals, SC content and activation status have been observed to increase in response to a single bout of exercise. Muscle fiber characteristics change considerably when resistance exercise is performed chronically, but whether training status affects the activity of SC in response to a single bout of exercise remains unknown. We examined the changes in SC content and activation status following a single bout of resistance exercise, before and following a 16-wk progressive resistance training (RT) program in 14 young (25 ± 3 yr) men. Before and after RT, percutaneous biopsies from the vastus lateralis muscle were taken before a single bout of resistance exercise and after 24 and 72 h of postexercise recovery. Muscle fiber size, capillarization, and SC response were determined by immunohistochemistry. Following RT, there was a greater activation of SC after 24 h in response to a single bout of resistance exercise (Pre, 1.4 ± 0.3; 24 h, 3.1 ± 0.3 Pax7/MyoD cells per 100 fibers) compared with before RT (Pre, 1.4 ± 0.3; 24 h, 2.2 ± 0.3 Pax7/MyoD cells per 100 fibers, P < 0.05); no difference was observed 72 h postexercise. Following 16 wk of RT, MyoD mRNA expression increased from basal to 24 h after the single bout of exercise (P < 0.05); this change was not observed before training. Individual capillary-to-fiber ratio (C/Fi) increased in both type I (1.8 ± 0.3 to 2.0 ± 0.3 C/Fi, P < 0.05) and type II (1.7 ± 0.3 to 2.2 ± 0.3 C/Fi, P < 0.05) fibers in response to RT. After RT, enhanced activation of SC in response to resistance exercise is accompanied by increases in muscle fiber capillarization.

MicroRNAs in Muscle: Characterizing the Powerlifter Phenotype

“…Resistance training induces angiogenesis to support hypertrophy but on its own does not normally increase capillary density (Nederveen et al, 2017). The direct inhibitors of VEGF, miR-15a/16 were however, upregulated in the powerlifters, which may limit angiogenesis in powerlifters.…”

The influence of capillarization on satellite cell pool expansion and activation following exercise‐induced muscle damage in healthy young men

“…; Nederveen et al . ) with appreciable expansion occurring by 24 h and peaking 72 h post‐stimulus (Snijders et al . ).…”

“…; Nederveen et al . , ). Consequently, it has been proposed that SC content (Emslie‐Smith & Engel, ; Christov et al .…”

Low‐load resistance exercise during inactivity is associated with greater fibre area and satellite cell expression in older skeletal muscle

“…However, SC in older muscle are located at a greater distance from capillaries than in young individuals, which may impair their biological function and, ultimately, the plasticity of skeletal muscle with age . Moreover, the age‐related decrease in muscle capillarization may impair nutrient delivery to skeletal muscle, which could be a contributing factor to both an impairment in muscle metabolism and SC function …”