Chocolate Milk May Improve Recovery After Exercise News Author: Laurie Barclay, MD
CME Author: Désirée Lie, MD, MSEd
Feb. 27, 2006 — Chocolate milk is an effective postexercise drink that improves recovery, according to the results of a small, randomized trial reported in the February issue of the International Journal of Sport Nutrition and Exercise Metabolism.
"Our study indicates that chocolate milk is a strong alternative to other commercial sports drinks in helping athletes recover from strenuous, energy-depleting exercise," coauthor Joel M. Stager, PhD, from Indiana University in Bloomington, said in a news release. "Chocolate milk contains an optimal carbohydrate to protein ratio, which is critical for helping refuel tired muscles after strenuous exercise and can enable athletes to exercise at a high intensity during subsequent workouts."
On 3 separate days, 9 male, endurance-trained cyclists performed an interval workout followed by 4 hours of recovery, and a subsequent endurance trial to exhaustion at 70% maximum oxygen consumption (VO2max). In a single-blind, randomized design, the men drank equivalent volumes of chocolate milk, fluid replacement drink (FR), or carbohydrate replacement drink (CR) immediately after the first exercise bout and 2 hours of recovery. The chocolate milk and CR had equivalent carbohydrate content. Primary endpoints were time to exhaustion, average heart rate, rating of perceived exertion, and total work for the endurance exercise.
Time to exhaustion and total work were significantly greater for chocolate milk and for FR trials than for CR trials, suggesting that chocolate milk is an effective recovery aid between 2 exhausting exercise bouts.
Study limitations include the possibility that the 4-hour recovery period limited the complete digestion of the complex carbohydrates contained in CR.
"The results of this study suggest that chocolate milk, with its high carbohydrate and protein content, may be considered an effective alternative to commercial FR and CR for recovery from exhausting, glycogen-depleting exercise," the authors write.
The Dairy and Nutrition Council, Inc, supported this study in part.
Int J Sport Nutr Exerc Metab. 2006;16:78-91
Clinical Context
According to the authors, the amount of stored glycogen in skeletal muscles influences exercise performance, and delaying carbohydrate ingestion for 2 hours after a workout can reduce the rate of glycogen resynthesis by half. Studies noted by the authors have suggested that 50 to 75 g of carbohydrate be ingested within 30 to 45 minutes after exercise, with ingestion of 1.2 to 1.5 g carbohydrate per kilogram of body weight per hour for the next few hours. Protein ingestion also has been shown to hasten the rate of glycogen synthesis. CR and FR, which replenish fluid and electrolytes lost during exercise but contain less carbohydrates, are 2 types of postexercise drinks that have been formulated to address glycogen synthesis and carbohydrate replacement.
The current trial is a single-blind, randomized, crossover experimental study using endurance athletes as their own controls to compare the effect of 3 types of drinks: chocolate milk, FR, and CR with the equivalent carbohydrate content of chocolate milk, on performance as measured by time to exhaustion, average heart rate, rating of perceived exertion, and total work performed.
Study Highlights
* 9 healthy, nonsmoking male endurance-trained cyclists aged 19 to 22 years with weight range of 68 to 82 kg from one university were recruited for the study.
* Each subject participated in 4 testing sessions with each session separated by 1 week.
* All subjects kept a dietary record for 3 days prior to the sessions and refrained from heavy exercise within 24 hours.
* The first session consisted of an incremental exercise test on a cycle ergometer to determine VO2max and maximum power output at VO2max.
* The remaining 3 sessions were conducted as a randomized crossover design and consisted of 2 bouts of cycling to exhaustion separated by 4 hours of recovery.
* The first bout consisted of alternating periods of work and recovery in an interval format until glycogen depletion.
* During the 4-hour recovery period, athletes were offered equal volumes of low fat chocolate milk (The Kroger Co) or FR (Gatorade) or CR (Endurox).
* The carbohydrate content of chocolate milk and CR were similar.
* Following the recovery period, the second exercise bout was performed at 70% VO2max until exhaustion to maintain their previous pedal cadence (85 - 100 rpm).
* Cyclists were not allowed to stand on pedals while cycling.
* Investigators were blinded to allocation of fluids, which were in opaque bottles.
* Blood samples from fingertips were taken for lactate levels prior to and on completion of each exercise trial and at 2 hours into the recovery period.
* Subjects were permitted to freely drink water, but no other food was allowed during the recovery period.
* Both time to exhaustion and total work performed during the endurance performance ride were significantly greater (P < .05) in the chocolate milk and FR trials vs the CR trial.
* Subjects cycled 49% and 54% longer following chocolate milk and FR ingestion vs CR ingestion.
* Total amount of work performed was 57% and 48% greater for chocolate milk and FR ingestion vs the CR ingestion.
* No significant differences occurred in any other variables, including heart rate, rating of perceived exertion during the endurance performance trials, and postexercise lactate levels.
* Body mass index and total body water did not differ between treatments.
* Total amount of water consumed was similar for the 3 groups.
* No significant differences occurred in macronutrient content of diets for the athletes before the trial.
Pearls for Practice
* Low-fat chocolate milk and FR ingestion as recovery fluids are associated with greater endurance in terms of time to exhaustion vs a CR for cycling in male endurance athletes.
* Chocolate milk and FR ingestion as recovery fluids are associated with greater work performed at 70% VO2max in male endurance cyclists.
