Journal Title (Medline/Pubmed accepted abbreviation): Int. J. Sport. Nutr.Exerc.Metab.
Page Numbers: 398-409
Background: Muscle repair and hypertrophy (growth) after exercise are affected by hormone responses to exercise and are measured by rate of muscle synthesis. A large amount of recovery-based physiology occurs during sleep.
Hypothesis: Consuming a beverage with carbohydrates + protein vs. a carbohydrate-only beverage will increase the levels of hormones that promote protein synthesis as well as the rate of protein synthesis during sleep in response to daytime exercise.
Subjects: Ten recreationally active males, age 20 ± 2 y.
Experimental design: randomized, double-blind, cross-over design
C: carbohydrate- 50% glucose and 50% maltodextrin
C+P: carbohydrate + protein- C from above + casein protein hydrolysate
Both were vanilla flavored and artificially sweetened to yield similar tastes.
Protocol: Before the testing sessions, participants were evaluated for body composition and the exercise routine. One-repetition maxima were determined for chest press, shoulder press, lateral pull-down, leg press, and leg extension. The participants’ VO2max and workload capacity (Wmax) were determined on a stationary bicycle. On the testing days, they consumed standardized meals during the day and reported to the laboratory in the evening. They underwent a 2 hr exercise routine including both endurance (cycling) and resistance exercises. Participants consumed 1.5 mL/kg body mass of one of the test beverages every 15 min during exercise and 4 mL/kg 30 and 90 min after exercise. Blood samples were acquired at selected time points throughout exercise and recovery (including during sleep). Muscle biopsies were acquired from the vastus lateralis (quadriceps) before and after exercise and in the morning after exercise to assess fractional rate of protein synthesis.
There has been little research on the effects of nutrition on hormone response during sleep and the studies that do exist show conflicting results. This study showed few differences between recovery drinks on hormones and rate of protein synthesis in sleep immediately following evening exercise. Data from this studies and others suggest that athletes’ nutritional practices throughout the entire day can be important, since the next morning they are likely still recovering from the evening exercise.