The functions of proteins When we hear the word “protein” we often simply think of the protein containing foods that we eat. In reality, however, proteins are much more exciting than that! Rather, we should consider proteins as “little machines with big structures” who each perform unique daily functions. Indeed, our muscles contain hundreds of proteins that all perform a variety of functions that are essential to everyday life and of course, exercise performance. For example, the “contractile” proteins are responsible for making our muscles produce force, the “structural” proteins provide structure to our muscles and the “enzymatic” proteins help provide the action molecules that can break down carbohydrate and fat to produce energy. This energy is then used by the structural proteins to produce movement. As such, all of our muscle proteins work together to accomplish the task in hand i.e. move as fast as possible! Protein and training adaptation Protein is often considered essential for athletes involved in weight training in order to promote muscle growth. In this situation, the combination of lifting heavy weights and protein feeding is used to build new proteins (especially the contractile proteins) and hence, our muscles get bigger. In relation to the endurance athlete, however, protein intake is equally as important. In this situation the stress of endurance exercise creates a metabolic signal to instruct our muscles to make new proteins involved in aerobic metabolism e.g. mitochondrial enzymes. Exercise also causes many of our muscle proteins to actually break down (referred to as protein degradation), a process that can of course be detrimental to training adaptation. Thankfully, in the presence of adequate protein feeding, the combined effects of exercise and protein ingestion results in the formation of new proteins being made (referred to as protein synthesis) such that we can better withstand the physical demands associated with the next training session. It is these repeated changes in protein synthesis in response to every single training session which forms the basis of how our muscles adapt and recondition to the demands of training. In order for such optimal training adaptation to occur, it is therefore essential that protein is ingested in close proximity to the exercise stimulus given that protein rich foods and supplements contain the key amino acids that are used as the building blocks to make new proteins in our muscles. In the context of the endurance athlete, these amino acids are used to make the many hundreds of enzymes that are required in order to provide energy from the breakdown of carbohydrate and fat. The net result is that our muscles now contain more mitochondria (the factories where we produce energy during endurance exercise) and our exercise performance is significantly improved! Protein Requirements for the Endurance Athlete A scientific consensus on the optimal daily requirements for protein ingestion for endurance athletes has not been reached yet though most scientists would agree it is somewhere in the region of 1.4-1.8 grams per kilogram of the athlete’s body mass. As such, a 75 kg athlete would need between 105 – 135 grams per day and may actually need more during training periods designed to reduce body fat but preserve muscle mass. In the latter situation, athletes are often advised to increase daily protein intake to 2-2.5 g/kg, an amount which has shown to maintain muscle mass during targeted times of weight and body fat loss. Perhaps more important than total daily protein intake, however, is the pattern of ingestion of protein intake throughout the day where it is advised that protein is consumed as 20-30 gram boluses every 3-4 hours. In the context of exercise, it is also advised that protein is consumed within 60 minutes prior to exercise and immediately post-exercise (again in 20-30 gram feedings), though emerging evidence is now suggesting that endurance athletes should also consume protein during exercise so as to prevent the protein degradation (and hence promote better training adaptation) that occurs during prolonged exercise of moderate to high-intensity. Finally, an important time to consume protein is prior to sleep where in this instance, amino acids can be delivered to your muscles so as to maintain protein synthesis in the overnight period. Protein sources for endurance athletes In addition to high quality protein foods (e.g. fish/poultry/diary/red meat/eggs/greek yoghurt etc), protein supplements are an extremely useful addition to the endurance athlete’s toolkit. Indeed, protein supplements are high in the essential amino acid leucine (the key trigger to activate the process of protein synthesis) and are often digested quicker than whole foods thereby providing an efficient recovery strategy. The Science in Sport protein range can be used to meet your daily protein requirements by proving protein options that can be consumed as snacks (Protein Bar, WHEY20), before, during and after exercise (Advanced Isolate / Whey / WHEY20 / REGO) as well prior to sleep (Overnight Protein). Written By Professor James Morton A professor of Exercise Metabolism at Liverpool John Moores University (LJMU) and a Registered Sports and Exercise Nutrition Practitioner with the British Dietetic Association’s UK Sport and Exercise Nutrition Register (SENr), James is responsible for research and innovation at Science in Sport, overseeing the Performance Solutions Team.