Post workout protein intake effectively stimulates muscle protein synthesis; the building of new muscle tissue.
However, what the optimal post workout protein protocol?
A recently published study in the American Journal of Clinical Nutrition brings some new information to the table.
The milk proteins whey and casein have been studied intensively for their ability to stimulate muscle protein synthesis.
Whey is considered a fast protein, as it rapidly digests into amino acids which then enter the blood.
In contrast, casein is considered a slow protein as upon digestion its amino acids appear more slowly in the blood, have a lower peak value and remain elevated longer.
However, another difference between the proteins is their leucine content. Leucine is the key amino acid that triggers muscle protein synthesis.
Previous research has indicated that whey was more effective than casein to stimulate muscle protein synthesis. However, it could not be determined if this could be attributed to its increased digestion speed or leucine content.
The researchers recruited a group of healthy men. The subjects performed eight sets of 8-10 reps with their ten repetition maximum. They were randomly devided to two groups:
- one group ingested 25g of whey protein immediately after the workout (BOLUS)
- the other groups ingested 2,5g of whey protein every 20 minutes, for a total of 25g (PULSE)
The latter protocol reflects the digestion of a slow protein. Thus, this design allowed the researchers to compare the effect of speed of protein, as all other variables where the same.
The figure below shows the concentration of amino acids in the blood during both protocols. As expected, the PULSE protocol resulted in a lower peak value, but the amino acid concentration remained elevated much longer.
Not surprisingly, the BOLUS protocol had a bigger increase in myofibrillar FSR (a marker for muscle growth) in the early period after training (1-3 h).
However, also in the late period after training (3-5 h), muscle growth was still greater in the BOLUS protocol, despite that amino acids levels had returned to basal values and were lower when compared to the PULSE protocol.
The authors speculate that the peak value of amino acids in blood is a more important signal to stimulate muscle growth than a continuous availability.
A fast protein source such as whey appears to be more beneficial than a slow protein such as casein. And make sure to rapidly consume it!