No Difference Between Fast and Slow Proteins on Long Term Muscle Adaptation

24 Apr 2017 --- A new study looking into the effects of protein intake on muscle mass and strength during resistance training has shown that the supplementation with 100% fast protein and 50% of fast protein does not lead to higher long-term adaptations in muscle.

Previous studies have looked at the separate effects of the two classes of proteins found in milk, including whey and casein, on muscle protein synthesis after a single bout of resistance exercise.

However, until now, the combined effects of these two proteins on the muscle responses to resistance training have not yet been investigated.

The new study aimed to examine the effects of protein supplementation varying by the ratio between fast-digested protein, such as milk soluble proteins and slow digested protein, such as casein. Researchers observed the impact of such drinks on the muscle during a 9-week resistance-training program.

In a double-blind protocol, 31 resistance-trained men were assigned to 3 groups receiving a drink containing 20g of protein comprising either 100% of fast protein or 20% of fast protein and 80% of casein at the end of training bouts.

Body composition and maximal strength in dynamic and isometric were analyzed before and after participants underwent resistance training. Blood plasma aminoacidemia kinetic was also measured after resistance exercise.

The results showed a higher leucine bioavailability after ingestion of 100% of fast protein 50% of fast protein drinks, when compared with 20% of fast protein.

However, the resistance training induced changes in lean body mass and isometric muscle strength increased similarly in all experimental groups.

Overall, compared to the 20% of fast protein group, the higher rise in plasma amino acids following the ingestion of 100% of fast protein 50% of fast protein drinks did not lead to a higher rate of long-term adaptations in muscle.