A Brief Review of Critical Processes in Exercise-Induced Muscular Hypertrophy

Abstract

With regular practice, resistance exercise can lead to gains in skeletal muscle mass by means of hypertrophy. The process of skeletal muscle fiber hypertrophy comes about as a result of the confluence of positive muscle protein balance and satellite cell addition to muscle fibers. Positive muscle protein balance is achieved when the rate of new muscle protein synthesis (MPS) exceeds that of muscle protein breakdown (MPB). While resistance exercise and postprandial hyperaminoacidemia both stimulate MPS, it is through the synergistic effects of these two stimuli that a net gain in muscle proteins occurs and muscle fiber hypertrophy takes place. Current evidence favors the post-exercise period as a time when rapid hyperaminoacidemia promotes a marked rise in the rate of MPS. Dietary proteins with a full complement of essential amino acids and high leucine contents that are rapidly digested are more likely to be efficacious in this regard. Various other compounds have been added to complete proteins, including carbohydrate, arginine and glutamine, in an attempt to augment the effectiveness of the protein in stimulating MPS (or suppressing MPB), but none has proved particularly effective. Evidence points to a higher protein intake in combination with resistance exercise as being efficacious in allowing preservation, and on occasion increases, in skeletal muscle mass with dietary energy restriction aimed at the promotion of weight loss. The goal of this review is to examine practices of protein ingestion in combination with resistance exercise that have some evidence for efficacy and to highlight future areas for investigation.

Daily Distribution of Carbohydrate, Protein and Fat Intake in Elite Youth Academy Soccer Players Over a 7-Day Training Period

“…When youth players are promoted to full-time U18 315 squad status, muscle hypertrophy is a key training goal (Milsom et al, 2015), which 316 may result in players being encouraged to increase protein consumption to support 317 resistance-training hypertrophy programmes (Phillips et al, 2014). 318…”

Effect of resistance exercise training on expression of Hsp70 and inflammatory cytokines in skeletal muscle and adipose tissue of STZ-induced diabetic rats

“…Resistance exercise training increases the rate of protein synthesis in skeletal muscle (Phillips 2014). Hypertrophy of skeletal muscle and the resulting concomitant gain in power are of great interest for people with disease-induced atrophy such as type 1 diabetes.…”

Ribosome biogenesis adaptation in resistance training-induced human skeletal muscle hypertrophy

“…Increased intramuscular protein synthesis in the hours following each resistance exercise (RE) bout appears to be a major mechanism regulating the adaptive mass gain (1). This increased rate of protein synthesis results from a coordinated series of cellular events dictated acutely by an increased translational efficiency (protein synthesized per ribosome) (1,28). The initiation of ribosomal activity, i.e., mRNA translation, is dependent on the activation of the mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) pathways (8,39).…”

“…The initiation of ribosomal activity, i.e., mRNA translation, is dependent on the activation of the mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) pathways (8,39). There are considerable data on the impact of exercise intensity, duration, prior training, and nutritional status on these signaling pathways of translation initiation (1,6,28). However, a further, and less well understood, aspect of RT-induced muscle hypertrophy is the potential for greater translational capacity (quantity of ribosome) (19).…”