Q: What are the some of the important roles of Resistance Training and Protein Synthesis?
A: Resistance
Training is a highly effective way to increase muscle protein
synthesis, which result in specific metabolic and biological changes
within muscle. The underlying theme of muscle anabolism (muscle
building; i.e. hypertrophy) is when the rate of muscle protein
synthesis exceeds protein degradation (breakdown) for an extensive
period of time (Koopman 2007).Koopman also explains that following
strenuous exercise, protein degradation is accelerated beyond that of
protein synthesis. Consequently if food intake is deficient, total
protein balance remains negative. As a result, clients and athletes
should strive to consume both carbohydrates and protein following
exercise (including resistance training) to achieve a positive protein
balance. The relationship between exercise and nutrition is extremely
important to promote adaptation and muscle anabolism to training.
Resistance Training and Protein Synthesis
The
primary adaptive response to resistance training is the increase in
muscle hypertrophy, which is indicative to the load applied (i.e.
weight). Phillips (2002) emphasizes that increased loading augments
muscle protein synthesis and degradation and this training induced
increase in protein turnover ultimately promotes protein remodeling,
thus further adaptation. Previous research shows that resistance
training clearly enhances muscle protein synthesis and that a single
bout of resistance training elevates protein synthesis rates within 2-4
hours (3,4,5). These research studies also demonstrate additional
protein synthesis rates lasting between 24-48 hours. It should be noted
these increases in protein synthesis (also termed fractional synthetic
rate) are primarily due to increases in myofibrillar (actin and myosin
contractile proteins) rates.
The Role of Carbohydrates on Protein Synthesis
The
role of carbohydrate on muscle metabolism, specifically protein
metabolism has been credited with the rise of insulin concentrations in
bodily tissues. Early research shows the increased plasma insulin level
to enhance net muscle protein anabolism in humans (6,7,8). However,
previous research from Biolo (9) suggests that insulin should not be
viewed as the major influence of muscle protein synthesis, as insulin
yields only a moderate effect on muscle protein synthesis if amino acid
levels are less than optimal.
Protein and Amino Acids
Aside
from providing a foundation for protein synthesis, amino acids also
serve to produce certain hormones (i.e. glucagon, growth hormone, and
IGF-1). In Addition, amino acids can stimulate 'nutritional signaling
molecules' by regulating muscle protein metabolism, although the exact
physiological mechanism(s) for this response are still unknown. More
importantly, amino acids can alter mRNA translation and protein
synthesis within skeletal muscle. Previous reports suggest that intake
of large amounts (30-40g) of amino acids upon cessation of exercise
greatly increase muscle protein synthesis. Furthermore,
smaller quantities of amino acids with and without carbohydrate have
also shown to accelerate post -exercise protein synthesis and promote
net protein balance (difference between muscle protein synthesis and
breakdown). (10,11,12). The importance of post-exercise protein
consumption is incredible valuable to optimize the anabolic response to
training.
References
1). Koopman R, Nutritional interventions to promote post-exercise muscle protein synthesis. Sports Med. 2007;37(10):895-906. Review.
2). Phillips SM, Parise G, Roy BD, Tipton KD, Wolfe RR, Tamopolsky MA. Resistance training-induced adaptations in skeletal muscle protein turnover in the fed state.
Can J Physiol Pharmacol. 2002 Nov;80(11):1045-53.
3). Chesley A, MacDougall JD, Tarnopolsky MA, Atkinson SA, Smith K. Changes in human muscle protein synthesis after resistance exercise. J Appl Physiol. 1992 Oct;73(4):1383-8
4). MacDougall JD, Gibala MJ, Tarnopolsky MA, MacDonald JR, Interisano SA, Yarasheski KE. The time course for elevated muscle protein synthesis following heavy resistance exercise. Can J Appl Physiol. 1995 Dec;20(4):480-6.
5). Phillips SM, Tipton KD, Aarsland A, Wolf SE, Wolfe RR. Mixed muscle protein synthesis and breakdown after resistance exercise in humans. Am J Physiol. 1997 Jul;273(1 Pt 1)
6). Fryburg DA, Jahn LA, Hill SA, Oliveras DM, Barrett EJ. Insulin
and insulin-like growth factor-I enhance human skeletal muscle protein
anabolism during hyperaminoacidemia by different mechanisms. J Clin Invest. 1995 Oct;96(4):1722-9
7). Gelfand RA, Barrett EJ. Effect of physiologic hyperinsulinemia on skeletal muscle protein synthesis and breakdown in man. J Clin Invest. 1987 Jul;80(1):1-6
8). Hillier TA, Fryburg DA, Jahn LA, Barrett EJ. Extreme hyperinsulinemia unmasks insulin's effect to stimulate protein synthesis in the human forearm. Am J Physiol. 1998 Jun;274(6 Pt 1)
9). Biolo G, Declan Fleming RY, Wolfe RR. Physiologic
hyperinsulinemia stimulates protein synthesis and enhances transport of
selected amino acids in human skeletal muscle.J Clin Invest. 1995 Feb;95(2):811-9
10). Børsheim E, Tipton KD, Wolf SE, Wolfe RR. Essential amino acids and muscle protein recovery from resistance exercise. Am J Physiol Endocrinol Metab. 2002 Oct;283(4)
11). Miller SL, Tipton KD, Chinkes DL, Wolf SE, Wolfe RR. Independent and combined effects of amino acids and glucose after resistance exercise. Med Sci Sports Exerc. 2003 Mar;35(3):449-55.
12). Rasmussen BB, Tipton KD, Miller SL, Wolf SE, Wolfe RR. An oral essential amino acid-carbohydrate supplement enhances muscle protein anabolism after resistance exercise. J Appl Physiol. 2000 Feb;88(2):386-92.
Jonathan Mike, MS, CSCS, USAW, NSCA-CPT, Doctoral Student, Assistant Editor
