A number of recent studies involving sophisticated techniques for measuring changes in muscle size have suggested that high protein diets combined with heavy resistance training can enhance muscle strength and size.
For example, in one study [1] male athletes who consumed an extra 23g of protein per day during 12 weeks of strength training achieved significantly greater size gains than those who did not take extra protein. However, strength gains were similar in both groups.
In a study carried out at McMaster University [2], strength athletes were given either low protein (0.86g/kg), medium protein (1.4g/kg or high protein (2.4g/kg) diet for 13 days. The low protein diet, which is similar to the recommended diet for sedentary people, caused the athletes to lose body protein (muscle mass). However, both the medium and high protein diets resulted in an increased body protein content, i.e. their muscle mass increased. No further gains were made by increasing their intake from 1.4g to 2.4g/kg.
Thus, muscle mass gains do not increase in a linear fashion with increasing protein intake. Once an optimal intake has been reached, surplus protein is not converted into muscle.
In conclusion, the studies on strength athletes indicate that strength training increases protein requirements to approximately 1.4-1.7g/kg/day.
- [1] W.R. Frontera et al, Canadian Journal of Sports Sciences
- [2] M. A. Tarnopolsky et al, Journal of Applied Physiology
