The functions of proteins
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.
Promoting training adaptations
The stress of endurance exercise causes many of our muscles to breakdown, a process that can, of course, be detrimental to performance. However, in the presence of adequate protein feeding, the combined effects of exercise and protein ingestion results in the formation of new proteins referred to as protein synthesis. It is this repeated process of protein breakdown and rebuild, in response to every single training session, that forms the basis of how our muscles adapt and recondition to the demands of exercise.
Exercise also creates a metabolic signal to instruct our muscles to make new proteins involved in aerobic metabolism e.g. mitochondria. The mitochondria can be considered the powerhouse of the cell and provide the site of energy production, where carbohydrate and fat are broken down for fuel. In order for such optimal training adaptations to occur, it is therefore essential that protein is ingested in close proximity to the exercise stimulus.
Endurance athletes now use protein to promote recovery and optimal body composition. At times, individuals may programme training blocks with the goal of weight loss in mind. In these situations, calorie and carbohydrate restriction can place additional stress on the body and individuals are advised to increase daily protein intake to 2-2.5 grams per kilo body weight per day, an amount which has shown to maintain muscle mass during targeted times of weight and body fat loss.
Protein requirements and sources
A consensus on the daily protein requirements for the endurance athlete has not yet been reached, though most would agree it is somewhere in the region of 1.4-1.8 grams per kilogram body weight per day. As such, a 75 kg individual would need between 105 and 135 grams of protein per day. Even if you train just 2-3 times per week, your protein intake needed is likely to increase towards the upper end of this range.
Perhaps more important than total daily protein, however, is the pattern of ingestion throughout the day, where it is advised that protein is consumed as 20-40 g feedings every 3-4 hours. In addition to high-quality whole foods, protein supplements and snacks such as Protein20 are an extremely useful addition to the endurance athlete’s toolkit.
Author: Ben Samuels
Performance nutritionist at Science in Sport