moderate dose of watercress and red radish does not reduce oxygen consumption during graded exhaustive exercise

objective: very recent studies have reported positive effects of dietary nitrate on the oxygen consumption during exercise. this research aimed to study the effect of moderate dose of high-nitrate vegetables, watercress (nasturtium officinale) and red radish (raphanus sativus) compared with a control group on the incremental treadmill exercise test following a standard bruce protocol controlled by computer. materials and methods: group 1 consumed 100 g watercress (n=11, 109.5 mg nitrate/day), and group 2 consumed 100 g red radish (n=11, mg 173.2 mg nitrate/day) for seven days, and control group (n=14) was prohibited from high nitrate intake. results: during exercise, watercress group showed significant changes in the maximum values of respiratory exchange ratio (rer) (p<0.05), end-tidal o2 fraction (feto2) (p<0.05), and energy consumption from carbohydrate (p<0.01). red radish group had a significant increase in the vco2 (p<0.01), rer (p<0.01), vt (p<0.05), vco2/kg (p<0.05), and energy consumption from carbohydrates (p<0.01). when all groups in the same workload were normalized by the subject’s body mass, watercress had a significant increase in the total expired co2 (p<0.05), rer (p<0.05), feto2 (p<0.05), and energy consumption from carbohydrates (p<0.05) compared with the control group. similar comparison between red radish and control group revealed a significant increase during pre-test in the total co2 production (p<0.05), vco2 (p<0.05), rer (p<0.01), vt (p<0.05), and vco2/kg (p<0.05). conclusion: current results indicate higher carbon dioxide production in the experimental groups in the same workload. this might have a negative impact on the exercise performance. further investigations with controlled exercise program will be necessary.