Lactate, Fructose and Glucose Oxidation Profiles in Sports Drinks and the Effect on Exercise Performance

Abstract

Exogenous carbohydrate oxidation was assessed in 6 male Category 1 and 2 cyclists who consumed CytoMax™ ( C) or a leading sports drink ( G) before and during continuous exercise (CE). C contained lactate-polymer, fructose, glucose and glucose polymer, while G contained fructose and glucose. Peak power output and VO ₂ on a cycle ergometer were 408±13 W and 67.4±3.2 mlO ₂·kg ⁻¹·min ⁻¹. Subjects performed 3 bouts of CE with C, and 2 with G at 62% VO ₂peak for 90 min, followed by high intensity (HI) exercise (86% VO ₂peak) to volitional fatigue. Subjects consumed 250 ml fluid immediately before (−2 min) and every 15 min of cycling. Drinks at −2 and 45 min contained 100 mg of [U- ¹³C]-lactate, -glucose or -fructose. Blood, pulmonary gas samples and ¹³CO ₂ excretion were taken prior to fluid ingestion and at 5,10,15,30,45,60,75, and 90 min of CE, at the end of HI, and 15 min of recovery. HI after CE was 25% longer with C than G (6.5±0.8 vs. 5.2±1.0 min, P<0.05). ¹³CO ₂ from the −2 min lactate tracer was significantly elevated above rest at 5 min of exercise, and peaked at 15 min. ¹³CO ₂ from the −2 min glucose tracer peaked at 45 min for C and G. ¹³CO ₂ increased rapidly from the 45 min lactate dose, and by 60 min of exercise was 33% greater than glucose in C or G, and 36% greater than fructose in G. ¹³CO ₂ production following tracer fructose ingestion was greater than glucose in the first 45 minutes in C and G. Cumulative recoveries of tracer during exercise were: 92%±5.3% for lactate in C and 25±4.0% for glucose in C or G. Recoveries for fructose in C and G were 75±5.9% and 26±6.6%, respectively. Lactate was used more rapidly and to a greater extent than fructose or glucose. CytoMax significantly enhanced HI.