The best post-workout shake doesn't just contain easily digested proteins like whey and soya protein. Strength athletes will get more out their training session if they drink a protein shake that contains fast and slow proteins, such as casein. Nutritional scientist at the University of Texas at Galveston will publish an article soon on the subject in the Journal of Nutrition.
The researchers got 19 subjects early in their twenties to train their legs on a leg extension machine, doing 8 sets of 10 reps. For the first three sets the subjects used weights at 55, 60 and 65 percent of the weight with which they could just manage 1 rep [the 1RM], for the remaining five sets they used weights at 70 percent of their 1RM.
The researchers took samples of muscle fibre from the subjects' thigh muscles just before the workout and again four hours after they had finished the workout. They measured the fractional synthetic rate [FSR] – the rate at which muscle fibre protein is produced – in the samples. The researchers also measured the concentration of substances including phenylalanine [an amino acid] and the BCAAs in the subjects' blood.
Consuming whey resulted in a fast and pronounced peak in the amino acid level. Consuming the mixture resulted in a less pronounced peak, but the increase in the level of amino acids lasted longer than it did when only whey was consumed.
That's not so surprising. Casein is a 'slow protein', which is digested slowly and its amino acids only appear in the blood gradually and after a considerable amount of time. Whey is a 'fast protein' that is digested quickly and therefore causes a pronounced amino acid peak. Soya protein is also a fast protein, although it's a little slower than whey.
The protein blend resulted in a stronger increase in muscle fibre protein synthesis than the whey-only protein, the figure above shows.
"Our data and that of others further support the use of a blended protein supplement following resistance exercise compared with an isolated protein", the Texans write in their concluding paragraph. "A blended protein supplement containing sufficient essential amino acid content, several digestion rates, and a prolonged aminoacidemia clearly promotes muscle protein synthesis during postexercise recovery."
The study was partly financed by the soya-giant Solae, and partly by the US government.
J Nutr. 2013 Jan 23. [Epub ahead of print].