Monday, September 29, 2014

Endurance Athletes: Don’t Forget About Protein

Refuel, rehydrate, and repair. These three interrelated approaches should be the focus for all competitive athletes engaged in endurance-based training. Your fuel stores, body fluids, and electrolytes can easily become depleted following a long sustained endurance training session. This makes replenishing fuel stores and rehydrating essential for optimizing training performance. 

However, many endurance athletes tend to overlook the importance of dietary protein and only focus on carbohydrates and hydration. It’s time to change that, here is a quick review on the importance of dietary protein for endurance athletes.

Amino acids – specifically leucine, a known regulator of muscle protein synthesis (Norton 2006) – are oxidized during endurance training. The degree to which amino acids are oxidized is based on several factors such as exercise intensity and low muscle glycogen availability to name a few. None the less, these lost amino acids do not contribute to muscle protein synthesis and should be replaced through your dietary intake.

The current population requirement for protein is set at 0.8 g/kg per day or 0.36 g/lb. per day. This recommendation is not sufficient for athletes involved in strenuous endurance or resistance training. The general protein recommendation for endurance athletes is 1.2 to 1.4 g/kg per day or 0.55 to 0.64 g/lb. per day. (Rodriguez 2007) For example, a 150 lb. endurance athlete should consume in the range of 83 to 96 grams of protein per day. But, the majority of endurance athletes are likely meeting or exceeding this range when their daily energy needs are met. (IOC, 2010) 

Meeting the recommendations for protein, however, may not be as important as the type of protein and the timing of intake for maximizing recovery and adaptations. (Tarnopolsky 2004).

The amount of protein consumed is an important nutritional consideration. After resistance training, even small (5 to 10 g) of protein increases muscle protein synthesis (Moore et al. 2009). Muscle protein synthesis is further increased after the ingestion of a larger (20g) dose of protein, but plateaus with a bigger dose. (Witard et al. 2014) Therefore, it seems practical to recommend similar amounts of protein – that is 20 to 25 g – after endurance training to facilitate muscle remodeling processes.

The quality of protein you consume is also an important factor. Dietary proteins differ in amino acid concentrating and the rates at which they are digested and absorbed. As mentioned subsequently, leucine serves as a substrate for muscle protein synthesis. Therefore athletes who wish to enhance muscle protein synthesis during their early recovery phase may benefit more with the ingestion of rapidly, leucine-enriched proteins like whey (Breen et al. 2011). Other high-quality sources of protein include eggs, dairy, lean meats, and soy.

While little attention has focused on the ability of dietary protein to enhance skeletal muscle remodeling and promote adaptations for the endurance athlete, the fact that dietary protein is the building blocks for muscle makes protein an important – and perhaps underappreciated – nutritional component for endurance athletes. 
Always seek advice from a sports dietitian to optimize dietary protein intake as every athlete is different.

Gavin Van De Walle is an ISSA Certified Fitness Trainer, a NANBF Natural Competitive bodybuilder, a nutrition columnist for “The Collegian,” and a dietetic student at South Dakota State University. Once Gavin becomes an RD, he will aim to achieve the distinguished Certified Specialist in Sports Dietetics (CSSD) credential.

Breen, L., Philip, A., Witard, O.C., Jackman, S.R., Selby, A., Smith, K., et al. 2011. The influence of carbohydrate-protein co-ingestion following endurance exercise on myofibrillar and mitochondrial protein synthesis. J. Physiol. 589(16): 4011-4025. doi:10.1113/jphysiol.2011.211888.
International Olympic Committee (IOC) Consensus Statement on Sports Nutrition, 2010.
Moor, D.R., Robinson, M.J., Fry, J.L., Tang, J.E., Glover, E.I., Wilkinson, S.B., et al. 2009. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am. J. Clin. Nutr. 89(1): 161-168. doi:10.3945/ajcn.2008.26401.
Norton LE, Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr 136: 533S–537S, 2006.
Rodriguez NR, Vislocky LM, Gaine PC. Dietary protein, endurance exercise, and human skeletal-muscle protein turnover. Curr Opin Clin Nutr Metab Care. 2007; 10:40-45.
Tarnopolsky, M. 2004. Protein requirements for endurance athletes. Nutrition, 20(7-8): 662-668. doi.10.1016/j.nut.2004.04.008.
Witard, O.C., Jackman, S.R., Breen, L., Smith, K., Selby, A., and Tipton, K.D. 2014. Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise. Am. J. Clin. Nutr. 99(1): 86-95. doe:10.3945/ajcn.112.055517.