Wednesday, March 19, 2014

Can Carbs Stimulate Further Muscle Growth?

Following a hard weight lifting workout you may choose to drink a protein shake – and for good reasons. Whey protein powders coupled with resistance training are known stimulators for increasing muscle protein synthesis and hypertrophy (muscle growth). Several studies show whey protein powders are superior to other protein powders, such as casein or soy, due to the high leucine – a branched chain amino acid – content when the goal is to maximize anabolic potential. But, can muscle protein synthesis be elevated even further?

Published in the Journal of the International Society of Sports Nutrition by Stark et al., 1 it was stated that fast-digesting carbohydrates, glucose or maltodextrin, should be combined with protein following resistance training to promote muscle hypertrophy for two reasons. First, there is a synergistic effect of insulin and leucine on muscle protein synthesis; and second, the addition of carbohydrate to a protein supplement would increase lean muscle mass more effectively verses a protein supplement consumed alone.
Another study published in the Journal of the International Society of Sports Nutrition by Figueiredo et al., 2 set out to determine if Stark et al., was accurate in suggesting carbohydrates stimulate muscle protein synthesis further than protein supplementation alone following resistance training. Figueiredo et al. first reviewed several other studies to determine if leucine really does require insulin in order to stimulate protein synthesis. It was stated that insulin is needed in order to increase protein synthesis when amino acids delivery are increased. It was also noted that leucine ingestion (from whey protein powder) has the ability to stimulate insulin secretion.

Figueiredo et al. looked at the second statement on whether insulin acts to inhibit protein degradation. One study 3 was looked at by Børsheim et al. who demonstrated carbohydrates supplementation (100 grams) alone following resistance training is capable of improving net muscle protein balance. However, protein ingestion alone can also inhibit protein breakdown following resistance training. 

So, what is the final verdict? Figueiredo et al. came to the conclusion that concerning muscle hypertrophy, based on the available data, there is no further benefit of carbohydrates when a protein supplement that maximally stimulates muscle protein synthesis is consumed. “Further studies are required before conclusions and recommendations can be made,” stated Figueiredo et al.

Remember, this study set out to see if carbohydrates further increase muscle growth verses a protein supplement alone. Carbohydrates are still essential to help drive your workouts!

About the Author: Gavin Van De Walle is an ISSA Certified Fitness Trainer, a NANBF Natural Competitive bodybuilder, and a dietetic student at South Dakota State University. Following graduation, Gavin will pursue his Ph.D. in nutritional sciences while aiming to make a positive impact on the over well-being and nutritional status of the American people along the way.

1.       Stark M, Lukaszuk J, Prawitz A, Salacinski A: Protein timing and its effects on muscular hypertrophy and strength in individuals engaged in weight-training.
                J Int Soc Sports Nutr 2012, 9(1):54.
2.     Vandre Casagrande Figueiredo, David Cameron-Smith: Is carbohydrate needed to further stimulate muscle protein synthesis/hypertrophy following resistance exercise?
J Int Soc Sports Nutr 2013, 10:42.
3.       Børsheim E, Cree MG, Tipton KD, Elliott TA, Aarsland A, Wolfe RR: Effect of carbohydrate intake on net muscle protein synthesis during recovery from resistance exercise.

J Appl Physiol 2004, 96(2):674-678.