What mechanisms lower blood pressure during and after moderate‑intensity aerobic exercise that induces sweating in adults with pre‑hypertension or stage 1 hypertension?

Blood Pressure-Lowering Mechanisms Activated by Aerobic Exercise and Sweating

Moderate-intensity aerobic exercise that induces sweating lowers blood pressure primarily through sustained peripheral vascular resistance reduction (via enhanced nitric oxide bioavailability and vasodilation in working muscles), decreased sympathetic nervous system activity, and suppression of the renin-angiotensin system, with these effects persisting for up to 24 hours after each session. 1, 2

Primary Hemodynamic Mechanisms

Peripheral Vascular Resistance Reduction

• Vasodilation in active skeletal muscles is the dominant acute mechanism, causing systemic vascular resistance to decrease by approximately 7% during and after aerobic exercise. 2
• This vasodilation results in diastolic blood pressure remaining stable or falling slightly during the exercise bout itself, while systolic pressure rises progressively with intensity. 1, 3
• The reduction in peripheral resistance persists into the post-exercise hypotensive period, which lasts up to 24 hours and underlies the long-term benefit when exercise is performed on most days. 1

Vascular and Endothelial Adaptations

• Enhanced nitric oxide bioavailability is a key chronic adaptation that sustains lower systemic vascular resistance over weeks to months of regular training. 1
• Aerobic training specifically increases nitrite and nitrate levels (markers of nitric oxide production) and improves brachial artery flow-mediated dilation by approximately 1.7% after 12 weeks. 4
• Endothelin-1 levels decrease with aerobic training, removing a potent vasoconstrictor influence on blood vessels. 4

Neurohormonal Mechanisms

Sympathetic Nervous System Suppression

• Plasma noradrenaline decreases by 29% with regular aerobic endurance training, reflecting reduced sympathetic outflow to blood vessels and the heart. 2
• This sympathetic withdrawal contributes to both lower resting heart rate and reduced hemodynamic stress (heart rate × systolic blood pressure) during submaximal activities. 5

Renin-Angiotensin System Downregulation

• Plasma renin activity falls by 20% after aerobic training programs, diminishing angiotensin II-mediated vasoconstriction and aldosterone-driven sodium retention. 2

Anti-Inflammatory Mechanisms

• Aerobic exercise uniquely reduces markers of chronic low-level inflammation including C-reactive protein, monocyte chemoattractant protein-1, vascular cell adhesion molecule-1, and lectin-like oxidized LDL receptor-1. 4
• These inflammatory mediators contribute to endothelial dysfunction and arterial stiffness; their reduction supports sustained blood pressure lowering. 4

Metabolic and Body Composition Effects

• Body weight decreases by 1.2 kg, waist circumference by 2.8 cm, and body fat percentage by 1.4% with aerobic training programs. 2
• Insulin resistance (HOMA index) improves by 0.31 units, and muscle glucose uptake increases during contraction, indirectly supporting vascular health. 5, 2
• Visceral adipose tissue reduction occurs even without changes in total body weight, addressing metabolic syndrome components that elevate blood pressure. 5

Intensity-Dependent Effects

• Moderate-intensity exercise (50–70% of maximal heart rate) consistently lowers blood pressure across all hypertensive categories. 1
• Higher exercise intensity (up to 70% of VO₂max) yields greater reductions in both systolic and diastolic blood pressure compared with lower intensities. 1
• The sweating threshold typically occurs at moderate-to-vigorous intensities where these hemodynamic and neurohormonal mechanisms are maximally engaged. 1

Magnitude and Time Course of Blood Pressure Reduction

• Acute post-exercise hypotension begins immediately after a single session and persists for approximately 24 hours, explaining why daily or near-daily exercise is most effective. 1
• Chronic adaptations emerge after 12 weeks of regular training, producing average reductions of 7–8 mmHg systolic and 4–5 mmHg diastolic in hypertensive patients. 1
• Even in resistant hypertension (blood pressure ≥140/90 mmHg despite ≥3 medications), aerobic exercise decreases daytime ambulatory systolic and diastolic blood pressure by 6 and 3 mmHg, respectively. 6

Clinical Implications

• These mechanisms operate additively with antihypertensive medications, allowing some patients to reduce medication burden while maintaining blood pressure control. 1, 4
• The sympathetic and renin-angiotensin suppression explains why aerobic exercise benefits extend beyond blood pressure to reduce cardiac morbidity by 5–9%, stroke by 8–14%, and all-cause mortality by 4% for every 3 mmHg systolic reduction. 5
• Resistance training alone produces smaller blood pressure reductions (3–3.5 mmHg) because it does not engage the same degree of peripheral vasodilation or neurohormonal suppression as aerobic exercise. 5, 2

Common Pitfalls

• Beta-blockers and certain antihypertensives blunt heart rate response to exercise, requiring intensity targets to be adjusted based on perceived exertion rather than heart rate formulas. 1
• Vigorous or high-intensity exercise may transiently increase cardiovascular risk in hypertensive individuals despite greater long-term blood pressure reductions; careful risk-benefit assessment is required before prescribing high-intensity protocols. 1
• The blood pressure-lowering effect is attenuated if exercise frequency falls below 3–4 days per week, because the 24-hour post-exercise hypotensive window does not provide continuous coverage. 1, 7