Change in plasma creatine kinase: Creatine kinase was measured in samples taken before, immediately after and 1 hours after the exercise challenge. Creatine kinase was measured by using a commercial colorimetric kit (Sigma) in a 96-well UV/vis plate reader (Molecular Devices). Increased plasma creatine kinase is a well-established index of exercise induced muscle damage. In a similar study, cyclists riding at 85% VO2 max until exhaustion after glycogen depletion the previous day had less plasma creatine kinase when they consumed chocolate milk as a recovery drink compared to a carbohydrate replacement beverage.