| dc.description.abstract | This study examined the impact of a high carbohydrate (HCHO) and high fat (HFAT) diet in combination with nitrate supplementation on oxygen uptake kinetics and performance during severe-intensity exercise. Ten healthy and physically active males were assigned in a double-blind, randomized, crossover design to consume HCHO (74% carbohydrate, 16% protein, 10% fat), HFAT (9% carbohydrate, 19% protein, 72% fat), along with 8 mmol of nitrate (NIT) or placebo (PL) over 4 days preceding the completion of a time-to-exhaustion trial (TTE) in the severe-intensity exercise domain. Cycling baseline RER in HCHO was significantly higher (~17%) compared to HFAT (P<0.05) and fat oxidation rates were 4-fold higher in HFAT (P<0.05) whereas CHO oxidation rates were 2-fold higher in HCHO (P<0.05). Resting plasma [NO3-] increased significantly (~812%) in NIT (24.45±7.45 µM) compared to PL (2.68±0.54 µM) in HCHO, and by (~1023%) in NIT (30.33±7.88 µM) compared to PL (2.70±0.77 µM) in HFAT (P<0.05). Resting plasma [NO2-] increased by ~88% in NIT (697±343 nM) compared to PL (370±121 nM) in HCHO (P<0.05) and by ~47% in NIT (521±221 nM) compared to PL (353±247 nM) in HFAT (P>0.05). Cycling baseline V ̇O2 was significantly lower in HCHO+PL (994±107 ml/min) when compared to HFAT+NIT (1037±122 ml/min, P<0.05) and HFAT+PL (1072±134 ml/min, P<0.05). V ̇O2 cycling baseline in HCHO+NIT (1008±145 ml/min) was significantly lower compared to HFAT+PL (1072±134 ml/min, P<0.05). There were no significant differences in V ̇O2 peak between conditions (P>0.05). V ̇O2 was higher across the rest-to-exercise transition in HFAT resulting in earlier attainment of V ̇O2 peak and shorter TTE. TTE was shorter in HFAT+NIT (154±40 s) and HFAT+PL (159±39 s) compared to HCHO+NIT (174±35 s, P<0.05) and HCHO+PL (186±39 s, P<0.05). These findings suggest that 4 days of a HFAT diet elevates V ̇O2 and impairs performance relative to HCHO during severe-intensity exercise. Additionally, the macronutrient content of diet impacts on the ability to convert [NO3-] to [NO2-], with this being more favourable in the HCHO compared to the HFAT diet. | en_GB |
