Effect of a High Carbohydrate Pre-Exercise Meal on Metabolic and Performance-Related Parameters in Male Athletes Following Two Different Strategies to Improve Fat Utilization: an Exploratory Examination

The purpose of this additional examination of a larger intervention was to determine the effects of a carbohydrate-rich pre-exercise meal on metabolic and performance-related parameters in a group of male endurance athletes, who had previously followed either a high fat low carbohydrate (HFLC; n=6) or high carbohydrate low glycaemic (LGI; n=6) diet for 4 weeks. Participants continued their regular training routine during the intervention. Respiratory exchange ratio (RER), lactate concentrations ([La−]), substrate oxidation rates at rest and during a cycle ergometry with incremental workload were determined in the fasted state and 2h after consuming a carbohydrate-rich (2g per kg of body mass) pre-exercise meal. Power output at lactate thresholds, peak oxygen uptake (V̇O2peak), absolute and relative peak power during the incremental test were assessed. After consuming the pre-exercise meal, both groups showed increased levels of RER, [La−] and carbohydrate oxidation at rest and during the incremental test (p<0.05; Cohen’s d>0.8), and an improved V̇O2peak (p<0.05; Cohen’s d>0.5). RmANOVA revealed significant group differences in metabolic parameters. Despite meaningful baseline differences ([La-]: p=0.133; ηp2=0.185; RER: p=0.037; ηp2=0.367; carbohydrate oxidation: p=0. 041; ηp2=0.355) upregulation of carbohydrate metabolism was more pronounced in the LGI subgroup compared to the HFLC group after 4-weeks intervention, in both fasted ([La-]: p=0.130; ηp2=0.214; RER: p=0.001; ηp2=0.713; carbohydrate oxidation: p=0.001; ηp2=0.684) and postprandial states ([La-]: p=0.036; ηp2=0.369; RER: p=0.001; ηp2=0.705; carbohydrate oxidation: p=0.001; ηp2=0.665). Peak power during the final incremental test was slightly higher in the LGI subgroup compared with the HFLC subgroup (p=0.320; ηp2=0.100). In this group of male endurance athletes, a LGI diet seemed to result in more favourable performance metrics as compared to a HFLC diet despite increases in carbohydrate availability before undertaking the performance test likely due to the ability to sustain higher workloads in training.