Myofibre Hypertrophy in the Absence of Changes to Satellite Cell Content Following Concurrent Exercise Training in Young Healthy Men

Abstract

Concurrent exercise training has been suggested to create an ‘interference effect,’ attenuating resistance training-based skeletal muscle adaptations, including myofibre hypertrophy. Satellite cells support myofibre hypertrophy and are influenced by exercise mode. To determine whether satellite cells contribute to the ‘interference effect’ changes in satellite cell and myonuclear content were assessed following a period of training in 32 recreationally active males (age: 25 ± 5 year; body mass index: 24 ± 3 kg⋅m–2; mean ± SD) who undertook 12-week of either isolated (3 d⋅w–1) resistance (RES; n = 10), endurance (END; n = 10), or alternate day (6 d⋅w–1) concurrent (CET, n = 12) training. Skeletal muscle biopsies were obtained pre-intervention and after 2, 8, and 12 weeks of training to determine fibre type-specific cross-sectional area (CSA), satellite cell content (Pax7+DAPI+), and myonuclei (DAPI+) using immunofluorescence microscopy. After 12 weeks, myofibre CSA increased in all training conditions in type II (P = 0.0149) and mixed fibres (P = 0.0102), with no difference between conditions. Satellite cell content remained unchanged after training in both type I and type II fibres. Significant correlations were observed between increases in fibre type-specific myonuclear content and CSA of Type I (r = 0.63, P < 0.0001), Type II (r = 0.69, P < 0.0001), and mixed fibres (r = 0.72, P < 0.0001). Resistance, endurance, and concurrent training induce similar myofibre hypertrophy in the absence of satellite cell and myonuclear pool expansion. These findings suggest that myonuclear accretion via satellite cell fusion is positively correlated with hypertrophy after 12 weeks of concurrent training, and that individuals with more myonuclear content displayed greater myofibre hypertrophy.

Application of diffusion microstructure imaging in musculoskeletal radiology — translation from head to shoulders

“…Comparable to neuronal axons, the myofiber is a complex, but highly organized structure that is composed of myofibrils. Myofiber hypertrophy is a well-known adaptation of skeletal muscle to repetitive exercise to increase muscle strength and performance [44][45][46]. In line with this, we here report that higher V-intra and lower V-ISOwhich corresponds to a larger proportion of myofibrils per voxelwere associated with higher mean and maximum muscle strength.…”

Efectos de una Intervención Nutricional Asociada a Entrenamiento Concurrente en la Composición Corporal de Hombres Físicamente Activos

“…La literatura señala la importancia de las diferentes estrategias nutricionales para complementar un programa de entrenamiento concurrente con el fin de maximizar las adaptaciones en la composición corporal. Es sabido que se necesita una cantidad suficiente de energía y proteínas para optimizar la estimulación de mTORC1 y aumentar o mantener la masa muscular durante la aplicación de programas de entrenamiento (Stokes et al, 2018), al analizar lo ocurrido en nuestra investigación, se considera que el ajuste nutricional puede optimizar los resultados del entrenamiento concurrente ya que las recomendaciones internacionales de macronutrientes permiten favorecer las adaptaciones, en comparación cuando se aplica el entrenamiento concurrente sin una intervención nutricional de por medio, la principal causa de esta mejora se basa en el ajuste nutricional que equilibra aporte de proteínas y carbohidratos para cada participante (2 grs/kg peso y 8 grs/ kg peso, respectivamente). Además, nuestro estudio presenta una combinación de diferentes fuentes de proteínas para permitir una nutrición completa y equilibrada.…”

“…terizado como una mezcla de ejercicios de fuerza y resistencia (Wilson et al, 2012). Este método ha sido estudiado debido a los múltiples beneficios para la salud (Da Silva et al, 2020), rendimiento físico (Petré et al, 2018), y mejora en la composición corporal (Shamim et al, 2021). La evidencia muestra que esta modalidad genera una adaptación superior en las diferentes variables de función corporal relacionadas con la salud (Methenitis, 2018) en comparación con otros métodos, pero también, debido a la interferencia entre las rutas moleculares del entrenamiento de fuerza y resistencia, se han visto resultados mixtos con este tipo de entrenamiento (Gäbler et al, 2018).…”

“…El factor común de todas estas dietas es un consumo alto de proteínas. Esta estrategia podría preservar el tejido muscular en un déficit calórico (Carbone & Pasiakos, 2019) o contribuir al aumento de la masa muscular acompañado de un entrenamiento de fuerza estructurado (Stokes et al, 2018). Es necesario un consumo adecuado de proteínas en un plan de comidas personalizado para lograr adaptaciones al entrenamiento y una carga física tolerada de manera eficiente en un programa de entrenamiento de fuerza-resistencia (Jäger et al, 2017).…”

Fusion and beyond: Satellite cell contributions to loading‐induced skeletal muscle adaptation

“… 212 , 213 , 214 , 215 , 216 , 217 Collectively, the amount and source of myonuclear turnover in adult skeletal muscle, and whether this is affected by exercise, are open questions that deserve further exploration. While muscle can adapt to an extent without satellite cells, it is currently unclear whether having augmented satellite cell number or function could enhance exercise adaptation through development and/or in adulthood; human resistance training studies point to this possibility in some instances, 35 , 182 , 218 , 219 , 220 , 221 but correlation does not mean causation. How satellite cells contribute to neuromuscular junction stability, as well as the myotendinous junction, are also provocative areas of inquiry, 50 , 222 , 223 , 224 , 225 especially in the context of exercise adaptation during aging.…”