None listed
Conditions
Brief summary
Endurance training stimulates many muscular adaptations such as an increase in mitochondrial content and enzyme activity, which enhance an athlete’s ability to utilise both fat and carbohydrate as energy sources during exercise. When exercising continuously at low to moderate intensities (50-60% of maximal aerobic capacity [VO2max]) the energy for muscular work comes predominately from fat-based fuels, with less reliance on carbohydrate-based fuels (Romijn et al., 1993). However, athletes typically compete at higher intensities (>80% of VO2max). At such work rates, there is a reliance on carbohydrate-based fuels for oxidative metabolism. For example, O’Brien et al (1993) reported 97% of energy from carbohydrate-based fuels when running a marathon (42.2 km) in 2 h 45 minutes, in comparison to a 68% contribution when running the distance in 3 h 45 minutes. Whilst well-trained individuals may be more efficient at utilising fat-based fuels during training, at race pace in events lasting 90-100 minutes carbohydrate-based fuels are the major source for muscle metabolism. However, to date few investigations have determined the contributions of fat and carbohydrate to fuel metabolism during races lasting ~90 minutes. The current study will quantify substrate utilisation during simulated half-marathon time trials and determine if blocking fatty acid metabolism (lipolysis) will impair performance in well-trained runners. We hypothesise that blocking lipolysis by administration of Nicotinic Acid during a half-marathon time trial will not affect performance.
Interventions
Participants will complete four experimental trials, each consisting of a maximal self-paced half-marathon. Trials will be completed using a double blinded, Latin squared design and will be separated by a minimum of 7 days. Two trials will be commenced in a fed state and two in an unfed state (fasted state following an 8-10 h overnight fast) and in each condition participants will be administered either Nicotinic Acid or a placebo given in capsules. A standardised diet will be provided for the 2
Participants will complete four experimental trials, each consisting of a maximal self-paced half-marathon. Trials will be completed using a double blinded, Latin squared design and will be separated by a minimum of 7 days. Two trials will be commenced in a fed state and two in an unfed state (fasted state following an 8-10 h overnight fast) and in each condition participants will be administered either Nicotinic Acid or a placebo given in capsules. A standardised diet will be provided for the 24 h preceding each trial, before participants report to the ACU laboratory at 07:00 h. Upon arrival participants will have a cannula inserted into the antecubital vein in the arm to enable blood sampling (6 mL). During the “fed” trials participants will be provided with a standardised high carbohydrate breakfast (2 g/kg carbohydrate, 30 g protein and 10 g fat) 2.5 hours prior to commencing the half-marathon, followed by either Nicotonic Acid (total of 15 mg/kg body mass) or placebo capsules (no active compounds). The fasted trials will be completed under the same conditions but without the consumption of the standardised breakfast. During the fed trials participants will also be provided 60 g of carbohydrate per hour at 20 minute intervals using a commercially available sports drink. The volume of water consumed during the first trial will be recorded and repeated for all subsequent trials. There will be 7-10 days between each trial.
Sponsors
Prof John Hawley
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Educational / counselling / training
Masking
Blinded (masking used) (Subject, Caregiver)
Eligibility
Sex/Gender
Male
Age
18 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
Aged 18-35 yr Able to run a half-marathon within 90 minutes VO2max greater than 60 mL/kg/min No pre-existing medical conditions or chronic injuries Not currently using any prohibited substance on the World-Anti Doping Agency List.
Exclusion criteria
Anyone with pre-existing medical conditions or chronic injuries Anyone using any prohibited substance on the World Anti-Doping Agency List. Anyone with a discrepancy in the cardiovascular risk assessment questionnaire
Outcome results
None listed