The acute effects of exercise intensity and inorganic nitrate supplementation on the Buckberg ratio in postmenopausal females

Menopause increases coronary heart disease risk, in part through reduced oestrogen-mediated nitric oxide (NO) bioavailability. The Buckberg ratio, an index of myocardial oxygen supply-demand balance, in which higher values reflect more favourable myocardial perfusion, is lower in postmenopausal females (PMFs) than in age-matched males. High-intensity exercise enhances NO production and endothelial function more than moderate-intensity exercise, yet PMFs often exhibit blunted vascular adaptations. Inorganic nitrate (NO₃ ⁻) supplementation increases NO bioavailability and improves endothelial function, but its effect on the Buckberg ratio is unknown. We hypothesised that the Buckberg ratio would decline after exercise in an intensity-dependent manner and that this reduction would be attenuated by NO₃ ⁻ supplementation. In a double-blind, randomized design, 24 PMFs (60 ± 5 years; 27.5 ± 5.9 kg/m²; 10 ± 5 years postmenopausal; peak oxygen consumption = 23.9 ± 4.5 mL/kg/min) consumed nitrate-rich beetroot juice (BRJ; n = 12) or nitrate-depleted placebo (PL; n = 12) for ∼2 days, with a final dose 2 h before testing. The Buckberg ratio was measured at rest and every 30 min for 3 h following calorically matched high-intensity exercise (HIE), moderate-intensity exercise (MIE) and non-exercise control (CON) conditions using pulse wave analysis (SphygmoCor) and was calculated from the derived central aortic pressure waveform as the ratio of diastolic to systolic pressure-time integrals, reflecting myocardial oxygen supply relative to demand. Venous blood collected pre- and post-supplementation assessed plasma NO₃ ⁻ and nitrite (NO₂ ⁻). BRJ increased plasma NO₃ ⁻ (64.9 ± 20.8 vs. 1114.2 ± 176.2 µM, P < 0.001) and NO₂ ⁻ (118.3 ± 57.9 vs. 356.8 ± 114.0 nM, P < 0.001). The Buckberg ratio was unchanged during CON but declined after MIE (P < 0.001) and HIE (P < 0.001). BRJ attenuated this decline following HIE (P < 0.001), but not MIE. These findings indicate that acute exercise reduces the Buckberg ratio in PMFs in an intensity-dependent manner, and NO₃ ⁻ supplementation might help to preserve coronary perfusion during higher-intensity exercise stress.