Salt restriction lowers blood pressure at rest and during exercise without altering peripheral hemodynamics in hypertensive individuals

Abstract

Dietary salt restriction is a well-established approach to lower blood pressure and reduce cardiovascular disease risk in hypertensive individuals. However, little is currently known regarding the effects of salt restriction on central and peripheral hemodynamic responses to exercise in those with hypertension. Therefore, this study sought to determine the impact of salt restriction on the central and peripheral hemodynamic responses to static-intermittent handgrip (HG) and dynamic single-leg knee extension (KE) exercise in individuals with hypertension. Twenty-two subjects (14 men and 8 women, 51 ± 10 yr, 173 ± 11 cm, 99 ± 23 kg) forewent their antihypertensive medication use for at least 2 wk before embarking on a 5-day liberal salt (LS: 200 mmol/day) diet followed by a 5-day restricted salt (RS: 10 mmol/day) diet. Subjects were studied at rest and during static intermittent HG exercise at 15, 30, and 45% of maximal voluntary contraction and KE exercise at 40, 60, and 80% of maximum KE work rate. Salt restriction lowered resting systolic blood pressure (supine: −12 ± 12 mmHg, seated: −17 ± 12 mmHg) and diastolic blood pressure (supine: −3 ± 9 mmHg, seated: −5 ± 7 mmHg, P < 0.05). Despite an ~8 mmHg lower mean arterial blood pressure during both HG and KE exercise following salt restriction, neither central nor peripheral hemodynamics were altered. Therefore, salt restriction can lower blood pressure during exercise in subjects with hypertension, reducing the risk of cardiovascular events, without impacting central and peripheral hemodynamics during either arm or leg exercise. NEW & NOTEWORTHY This is the first study to examine the potential blood pressure-lowering benefit of a salt-restrictive diet in individuals with hypertension without any deleterious effects of exercising blood flow. While mean arterial pressure decreased by ~8 mmHg following salt restriction, these findings provide evidence for salt restriction to provide protective effects of reducing blood pressure without inhibiting central or peripheral hemodynamics required to sustain arm or leg exercise in subjects with hypertension.

Recent advances in exercise pressor reflex function in health and disease

“…Furthermore, a recent human study found that salt restriction lowered resting and exercise BP in patients with hypertension without impacting central and peripheral hemodynamics during arm or leg exercise. However, BP responsiveness (change values) was not altered in this salt restriction study (Ratchford et al, 2019).…”

Salt Restriction and Angiotensin-Converting Enzyme Inhibitor Improve the Responsiveness of the Small Artery in Salt-Sensitive Hypertension

“…Although previous studies [23][24][25] have shown that high salt intake negatively impacts the response of resistant arteries to vasoactive agents, there was a lack of research focusing on the improvement effects of switching from a high-to low-salt diet in vivo. In a human study [26], found that salt reduction improved endothelium-dependent vasodilation [26] but did not improve arterial stiffness [27] and showed no impact on central and peripheral hemodynamics during exercise [28]. Perhaps it is quite impractical in human studies to design sophisticated procedures to observe the effects of salt restriction on vascular function.…”

The damaging duo: Obesity and excess dietary salt contribute to hypertension and cardiovascular disease

“…Specifically, plasma volume expansion with salt loading is associated with reduced MSNA, which may sensitize α‐adrenergic receptors and heighten the vasoconstrictor response to a given MSNA input 173,175,211 . Other work details that dietary salt restriction attenuates BP during isometric handgrip and dynamic lower body exercise 212,213 and that high salt augments BP during dynamic lower body exercise 157 . Importantly, exaggerated BP responses during physical stressors (e.g., acute exercise) are prognostic of hypertension risk, CV events, and CV mortality 214–221 .…”