High-Dose Nitrate Supplementation Attenuates the Increased Blood Pressure Responses to Isometric Blood Flow Restriction Exercise in Healthy Males

The effect of nitrate (NO₃⁻) supplementation on blood pressure (BP) responses during large muscle mass isometric and ischaemic exercise in healthy young adults is unclear. The aim of the present study was to assess the effect of 5-day supplementation of NO₃⁻ on BP responses during a short isometric contraction and a sustained ischaemic contraction. In a randomised, double-blinded, crossover design, 14 healthy active young adults underwent BP measurements after 5 days of either NO₃⁻ (NIT) or placebo (PLA) supplementation. Beat-by-beat BP was measured at pre- and post-exercise rest, and during a short (20 s) isometric contraction at 25% maximal strength and throughout a sustained ischaemic contraction. Plasma nitrite (NO₂⁻) concentration increased significantly after NO₃⁻ supplementation compared to placebo (475 ± 93 nmol·L⁻¹ vs. 198 ± 46 nmol·L⁻¹, p < 0.001, d = 3.37). Systolic BP was significantly lower at pre- (p = 0.051) and post-exercise rest (p = 0.006), during a short isometric contraction (p = 0.030), and throughout a sustained ischaemic contraction (p = 0.040) after NO₃⁻ supplementation. Mean arterial pressure was significantly lower at pre- (p = 0.004) and post-exercise rest (p = 0.043), during a short isometric contraction (p = 0.041), and throughout a sustained ischaemic contraction (p = 0.021) after NO₃⁻ supplementation. Diastolic BP was lower at pre-exercise rest (p = 0.032), but not at post-exercise rest, during a short isometric contraction, and during a sustained ischaemic contraction (all p > 0.05). Five days of NO₃⁻ supplementation elevated plasma NO₂⁻ concentration and reduced BP during a short isometric contraction and a sustained ischaemic contraction in healthy adults. These observations indicate that multiple-day nitrate supplementation can decrease BP at rest and attenuate the increased BP response during isometric exercise. These findings support that NO₃⁻ supplementation is an effective nutritional intervention in reducing SBP and MAP in healthy young males during submaximal exercise.