Background: This study compared the effects of ingesting cereal and nonfat milk (Cereal) and a carbohydrate-electrolyte sports drink (Drink) immediately following endurance exercise on muscle glycogen synthesis and the phosphorylation state of proteins controlling protein synthesis: Akt, mTOR, rpS6 and eIF4E.
Methods: Trained cyclists or triathletes (8 male: 28.0 +/- 1.6 yrs, 1.8 +/- 0.0 m, 75.4 +/- 3.2 kg, 61.0 +/- 1.6 ml O2*kg-1*min-1; 4 female: 25.3 +/- 1.7 yrs, 1.7 +/- 0.0 m, 66.9 +/- 4.6 kg, 46.4 +/- 1.2 mlO2*kg-1*min-1) completed two randomly-ordered trials serving as their own controls. After 2 hours of cycling at 60-65% VO2MAX, a biopsy from the vastus lateralis was obtained (Post0), then subjects consumed either Drink (78.5 g carbohydrate) or Cereal (77 g carbohydrate, 19.5 g protein and 2.7 g fat). Blood was drawn before and at the end of exercise, and at 15, 30 and 60 minutes after treatment. A second biopsy was taken 60 minutes after supplementation (Post60). Differences within and between treatments were tested using repeated measures ANOVA.
Results: At Post60, blood glucose was similar between treatments (Drink 6.1 +/- 0.3, Cereal 5.6 +/- 0.2 mmol/L, p < .05), but after Cereal, plasma insulin was significantly higher (Drink 123.1 +/- 11.8, Cereal 191.0 +/- 12.3 pmol/L, p < .05), and plasma lactate significantly lower (Drink 1.4 +/- 0.1, Cereal 1.00 +/- 0.1 mmol/L, p < .05). Except for higher phosphorylation of mTOR after Cereal, glycogen and muscle proteins were not statistically different between treatments. Significant Post0 to Post60 changes occurred in glycogen (Drink 52.4 +/- 7.0 to 58.6 +/- 6.9, Cereal 58.7 +/- 9.6 to 66.0 +/- 10.0 mumol/g, p < .05) and rpS6 (Drink 17.9 +/- 2.5 to 35.2 +/- 4.9, Cereal 18.6 +/- 2.2 to 35.4 +/- 4.4 %Std, p < .05) for each treatment, but only Cereal significantly affected glycogen synthase (Drink 66.6 +/- 6.9 to 64.9 +/- 6.9, Cereal 61.1 +/- 8.0 to 54.2 +/- 7.2%Std, p < .05), Akt (Drink 57.9 +/- 3.2 to 55.7 +/- 3.1, Cereal 53.2 +/- 4.1 to 60.5 +/- 3.7 %Std, p < .05) and mTOR (Drink 28.7 +/- 4.4 to 35.4 +/- 4.5, Cereal 23.0 +/- 3.1 to 42.2 +/- 2.5 %Std, p < .05). eIF4E was unchanged after both treatments.
Conclusion: These results suggest that Cereal is as good as a commercially-available sports drink in initiating post-exercise muscle recovery.