Previous studies have reported differences in the rate of absorption of the two classes of proteins found in milk (i.e. soluble proteins, including whey, and casein) (Tang et al., 2009). Furthermore, it has been suggested that whey and casein could have different metabolic fates and uses that could have complementary effects on muscle protein synthesis, muscle protein breakdown, and protein deposition (Fabre et al., 2017). The recently published double-blind randomized controlled trial of Fabre et al (2017) compared the effectiveness of three different post workout carbohydrate-protein drinks, differentiated by their fast (soluble milk protein) to slow (casein) protein ratio, to maximise resistance training outcomes. Thirty-one recreationally trained male were randomly allocated into the following 3 groups (1) 100% of pure fast proteins (n=10), (2) 50% of each fast and slow protein (n=11) and (3) 20% of fast mixing with 80% of slow protein (n=10). All participants performed a 9-week resistance training periodised programme involving 4 sessions per week aimed to gain muscle mass and strength. Supplements (20 g of protein + 20 g of carbohydrate mixing with 205 ml of water) were consumed within 15 min after workouts. No food (only water) was allowed to the participants during workouts and for the following 3 hr after having consumed the supplement. After the 9-week intervention, all participants regardless of the group demonstrated significant improvement in lean mass and strength. Even though the drinks providing 100% and 50% of fast protein produced a higher circulating amount of leucine and BCAA over the 2hr after ingestion, no measurable differences on the long-term adaptations (increase lean tissue and strength performance) were observed between groups. Authors concluded that carbohydrate-protein recovery drinks comprising different proportions of fast and slow proteins do not result in differentiated responses of lean tissue and strength to resistance training. In the lines of others studies (Naclerio et al., 2017, Naclerio et al 2017b) the work of Fabre supports the positive effects of post-workout carbohydrate recovery drinks to maximise resistance-training autosomes. As occurred in the study of Naclerio et al (2017b), even though the amount of protein were within the 90% confidence interval (0.18 to 0.30 g·kg-1) to promote muscle protein synthesis after exercise, and beyond which no further increase would be expected at rest (Morton et al., 2015), the administered protein dose was below the maximum recommended optimal amount of ~0.4 g·kg-1 for maximising muscle protein synthesis after training (Macnaughton et al., 2016). Additionally, the lack of a pure (100%) slow protein group should have been considered in the final conclusion and recommendations.
FABRE, M., HAUSSWIRTH, C., TIOLLIER, E., MOLLE, O., LOUIS, J., DURGUERIAN, A., NEUVEUX, N. & BIGARD, X. 2017. Effects of Post-Exercise Protein Intake on Muscle Mass and Strength During Resistance Training: is There an Optimal Ratio Between Fast and Slow Proteins? Int J Sport Nutr Exerc Metab, 1-23.
MACNAUGHTON, L. S., WARDLE, S. L., WITARD, O. C., MCGLORY, C., HAMILTON, D. L., JEROMSON, S., LAWRENCE, C. E., WALLIS, G. A. & TIPTON, K. D. 2016. The response of muscle protein synthesis following whole-body resistance exercise is greater following 40 g than 20 g of ingested whey protein. Physiol Rep, 4.
MORTON, R. W., MCGLORY, C. & PHILLIPS, S. M. 2015. Nutritional interventions to augment resistance training-induced skeletal muscle hypertrophy. Front Physiol, 6, 245.
NACLERIO, F., LARUMBE-ZABALA, E., ASHRAFI, N., SEIJO, M., NIELSEN, B., ALLGROVE, J. & EARNEST, C. P. 2017. Effects of protein-carbohydrate supplementation on immunity and resistance training outcomes: a double-blind, randomized, controlled clinical trial. Eur J Appl Physiol, 117, 267-277.
NACLERIO, F., SEIJO, M., LARUMBE-ZABALA, E., & EARNEST, C. P. 2017b. Carbohydrates Alone or Mixing With Beef or Whey Protein Promote Similar Training Outcomes in Resistance Training Males: A Double Blind, Randomized Controlled Clinical Trial. Int J Sport Nutr Exerc Metab, in press.
TANG, J. E., MOORE, D. R., KUJBIDA, G. W., TARNOPOLSKY, M. A. & PHILLIPS, S. M. 2009. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol (1985), 107, 987-92.