Lunn, W. R., Pasiakos, S. M., Colletto, M. R., Karfonta, K. E., Carbone, J. W., Anderson, J. M., & Rodriguez, N. R. (2012). Chocolate milk and endurance exercise recovery: protein balance, glycogen, and performance. Medicine & Science in Sports & Exercise, 44, 682-691.

This study examined effects of fat-free chocolate milk consumption on kinetic and cellular markers of protein turnover, muscle glycogen, and performance during recovery from endurance exercise. Male runners (N = 6) participated in two trials separated by one week and consumed either fat-free chocolate milk or a nonnitrogenous isocaloric carbohydrate control beverage after a 45-minute run at 65% of VO2peak. Postexercise muscle protein fractional synthetic rate and whole-body protein turnover were determined during three hours of recovery using muscle biopsies and primed constant infusions of L-[ring-2H5]phenylalanine and L-[1-13C]leucine, respectively. Phosphorylation of translational signaling proteins and activity of proteolytic molecules were determined using Western blotting and enzymatic activity assays. Muscle glycogen was quantified, and treadmill time-to-exhaustion was determined after the recovery period.

Consuming fat-free chocolate milk after exercise resulted in higher mixed muscle protein fractional synthetic rate with lower whole-body proteolysis and synthesis compared to the control condition. Phosphorylation was higher for fat-free chocolate milk, whereas Akt phosphorylation was lower during recovery regardless of dietary treatment. Muscle glycogen was not affected by either dietary treatment; however, time-to-exhaustion was greater for fat-free chocolate milk than for the control experience.

Implication. The consumption of fat-free chocolate milk after endurance exercise on muscle protein fractional synthetic rate, signaling molecules of skeletal muscle protein turnover, leucine kinetics, and performance measures suggest unique benefits of milk compared to a CHO-only beverage.

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