Effects of pre-exercise carbohydrate consumption on metabolism during exercise

It is well documented that consuming carbohydrates (CHO) prior to exercise has been shown to alter metabolism. There are many ways that CHO ingestion affects substrate utilization and blood glucose dynamics at the start of exercise. Changes in the concentrations of blood glucose, insulin, glucagon, free fatty acids (FFAs) as well as varying utilizations of different substrates have been observed. Each of these responses is reflective of the body’s capacity to maintain homeostasis through different physiological conditions and demands. PURPOSE: The aim is to deduce how varying amounts (approximately 0, 12.5, 25 and 50g for a 70 kg person) of pre-exercise sucrose ingestion effects metabolism including blood glucose concentration and fat oxidation during 30 minutes of moderate intense exercise. METHODS: This will be a randomized crossover study. After the initial assessment of baseline data (VO2peak), participants will be asked to perform four cycling trials at 50% of VO2peak for 30 minutes. Forty-five minutes before each exercise trial, participants will consume 0, 12.5, 25 and 50g (for a 70kg person) of sucrose. VO2 and VCO2 will be collected for 15 minutes prior to exercise and for the entire 30 minutes of cycling. Blood glucose will be obtained through the finger prick method and collected directly prior to exercise, 5, 15 and 30 minutes into cycling. Heart rate and rate of perceived exertion will be measured every 5 minutes of exercise. DISCUSSION: It is speculated that a small dose (12.5g for a 70kg person) of pre-exercise sucrose consumption will be able to demonstrate a decline in blood glucose concentration during exercise with a step-wise reduction in fat oxidation. This dose response curve will display the sensitivity of metabolism to ingested sucrose.