Journal Title (Medline/Pubmed accepted abbreviation): J. Strength Cond. Res.
doi (if applicable):
Background: Maximizing the rate of recovery will maximize performance in subsequent events, either 10 min or 2 days later. The combination of protein and carbohydrates (specifically, readily available chocolate milk) has been shown to induce net protein synthesis after exercise.
Hypothesis: After endurance exercise, chocolate milk will aid in the replenishment of post-exercise glycogen, activate the mTOR pathway which signals enzymes involved in protein synthesis, reduce signals involved in protein breakdown, and attenuate muscle damage compared to an isocaloric carbohydrate beverage and a calorie-free placebo.
Subjects:Male (n = 5) and female (n = 5) healthy cyclists trained for distance cycling, age 31.8 ± 1.6 yrs
Experimental design: randomized, double-blind, placebo-controlled, crossover design.
Treatments:1) Chocolate milk, 2) an isocaloric beverage made with water, dextrose, and canola oil, and 3) a placebo (sugar-free Kool Aid). Depending on their body weight, subjects consumed 1.0 to 1.4 L total during the recovery period, equaling 1581-2213.4 kcal (divided into 2 doses). The chocolate milk supplement totaled 36.7-51.4 g protein total.
Protocol: Before the trial, the participants were evaluated for VO2max on a stationary bicycle. For each trial, the participants reported to the laboratory after an overnight fast. In order to deplete their glycogen stores, they cycled at 70% VO2max for 90 min on the stationary bicycle, followed by 5 × 1 min intervals alternating between 45% and 90% VO2max. Water was provided every 15 min. During the trials, work and power output as well as respired gases were monitored. After the exercise bout, subjects rested for 4 hrs. One of the 3 supplements was consumed at the start of the rest period and 2 hrs into the rest period. Muscle biopsies were acquired at time = 0, 45 min, and 4 hrs during the rest period to assess glycogen content and signaling markers. After the rest period subjects completed a time trial during which they cycled 40 km with varying intensities as fast as possible. Their performance during this time trial was one of the major determinants for muscle recovery. Blood was collected at defined time points throughout the protocol. Respiratory exchange ratio (RER) was also calculated at given time points.
Chocolate milk improved times in a time trial after glycogen-depleting exercise compared to an isocaloric carbohydrate beverage and a calorie-free beverage. It is likely that the combination of protein availability and sugar allowed the body to recover faster; the sugar aided in the replenishment of glycogen and the protein aided in protein synthesis.
The authors suggest that chocolate milk may aid in recovery just as well as commercially designed recovery beverages, but the authors did not compare chocolate milk to commercial recovery beverages. Depending on the manufacturer, recovery formulations often include branched chain amino acids, structured lipids, and other nutrients that additionally aid in recovery. The comparator beverage in this study just contained carbohydrate and a small amount of lipid and this type of beverage would be more suited to consumption during, rather than after, exercise.