King Grub
2016-10-04, 11:36
Protein supplementation during resistance exercise training augments hypertrophic gains. Protein ingestion and the resultant hyperaminoacidemia provides the building blocks (indispensable amino acids – IAA) for, and also triggers an increase in, muscle protein synthesis (MPS), suppression of muscle protein breakdown (MPB), and net positive protein balance (i.e., MPS > MPB). The key amino acid triggering the rise in MPS is leucine, which stimulates the mechanistic target of rapamycin complex-1, a key signalling protein, and triggers a rise in MPS. As such, ingested proteins with a high leucine content would be advantageous in triggering a rise in MPS. Thus, protein quality (reflected in IAA content and protein digestibility) has an impact on changes in MPS and could ultimately affect skeletal muscle mass. Protein quality has been measured by the protein digestibility-corrected amino acid score (PDCAAS); however, the digestible indispensable amino acid score (DIAAS) has been recommended as a better method for protein quality scoring. Under DIAAS there is the recognition that amino acids are individual nutrients and that protein quality is contingent on IAA content and ileal (as opposed to fecal) digestibility. Differences in protein quality may have important ramifications for exercise-induced changes in muscle mass gains made with resistance exercise as well as muscle remodelling. Thus, the purpose of this review is a critical appraisal of studies examining the effects of protein quality in supplementation on changes in muscle mass and strength as well as body composition during resistance training.
Protein quality appears to play a role in determining resistance exercise-induced muscle hypertrophy; however, the effect is more difficult to detect compared to a comparison between the protein and an isoenergetic source of carbohydrate. The leucine content of a protein is the strongest determinant of the capacity of a protein to affect MPS and likely hypertrophy. While the prior performance of exercise will lower the threshold for protein/leucine required to stimulate MPS the importance of leucine content for MPS and likely subsequent hypertrophy needs to be appreciated in the context of not only its content in a protein source but also its digestibility. While there are few studies that have actually derived the DIAAS of proteins this variable is something that needs to be considered moving forward. When comparing proteins of differing quality, larger adequately powered rigorous trials need to be run to assess the impact of protein quality in determining resistance exercise-induced hypertrophy. Future studies in this area may wish to consider the recommendations outlined here in terms of trying to improve overall study quality and, importantly, to allow for easier comparisons between trials.
The impact of protein quality on the promotion of resistance exercise-induced changes in muscle mass. Nutrition & Metabolism September 2016, 13:64.
http://nutritionandmetabolism.biomedcentral.com/articles/10.1186/s12986-016-0124-8
Protein quality appears to play a role in determining resistance exercise-induced muscle hypertrophy; however, the effect is more difficult to detect compared to a comparison between the protein and an isoenergetic source of carbohydrate. The leucine content of a protein is the strongest determinant of the capacity of a protein to affect MPS and likely hypertrophy. While the prior performance of exercise will lower the threshold for protein/leucine required to stimulate MPS the importance of leucine content for MPS and likely subsequent hypertrophy needs to be appreciated in the context of not only its content in a protein source but also its digestibility. While there are few studies that have actually derived the DIAAS of proteins this variable is something that needs to be considered moving forward. When comparing proteins of differing quality, larger adequately powered rigorous trials need to be run to assess the impact of protein quality in determining resistance exercise-induced hypertrophy. Future studies in this area may wish to consider the recommendations outlined here in terms of trying to improve overall study quality and, importantly, to allow for easier comparisons between trials.
The impact of protein quality on the promotion of resistance exercise-induced changes in muscle mass. Nutrition & Metabolism September 2016, 13:64.
http://nutritionandmetabolism.biomedcentral.com/articles/10.1186/s12986-016-0124-8