Influence of dietary nitrate supplementation on local sweating and cutaneous vascular responses during exercise in a hot environment

Abstract

Purpose

We investigated the influence of inorganic nitrate ( \({\text{NO}}_{3}^{ - }\) ) supplementation on local sweating and cutaneous vascular responses during exercise in hot conditions.

Method

Eight healthy, young subjects were assigned in a randomized, double-blind, crossover design to receive \({\text{NO}}_{3}^{ - }\) -rich beetroot (BR) juice (140 mL/day, containing ~ 8 mmol of \({\text{NO}}_{3}^{ - }\) ) and \({\text{NO}}_{3}^{ - }\) -depleted placebo (PL) juice (140 mL/day, containing ~ 0.003 mmol of \({\text{NO}}_{3}^{ - }\) ) for 3 days. On day 3 of supplementation, subjects cycled at an intensity corresponding to 55% of \(\dot{V}\) O_2max for 30 min in hot conditions (30 °C, 50% relative humidity). Chest and forearm sweat rate (SR) and skin blood flow (SkBF), were measured continuously. Cutaneous vascular conductance (CVC) was calculated by SkBF/mean arterial pressure (MAP).

Results

Prior to exercise, plasma \({\text{NO}}_{3}^{ - }\) (21 ± 6 and 581 ± 161 µM) and nitrite ( \({\text{NO}}_{2}^{ - }\) , 87 ± 28 and 336 ± 156 nM) concentrations were higher after BR compared to PL supplementation (P ≤ 0.011, n = 6). Oesophageal, mean skin, and mean body temperatures during exercise were not different between conditions. In addition, BR supplementation did not affect SR, SkBF, and CVC during exercise. A lower MAP was found after 30 min of exercise following BR supplementation (112 ± 6 and 103 ± 6 mmHg for PL and BR, respectively, P = 0.021).

Conclusion

These results suggest that inorganic \({\text{NO}}_{3}^{ - }\) supplementation, which increases the potential for O₂-independent NO production, does not affect local sweating and cutaneous vascular responses, but attenuates blood pressure in young healthy subjects exercising in a hot environment.

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