Clinical Trial in Hypertensive Patients Comparing Two Cardiorespiratory Exercise Protocols, Low-volume Sprint Interval Training (SIT) Versus Moderate-intensity Continuous Training (MICT), to Evaluate Decreases in Ambulatory Blood Pressure and Other Clinical Variables.

Introduction

Cardiovascular disease remains the leading cause of mortality worldwide, with hypertension as a major modifiable risk factor. Exercise is a key non-pharmacological strategy for blood pressure management. While moderate-intensity continuous training (MICT) is well established, Sprint Interval Training (SIT) - characterized by short (10-30 s) bursts of maximal effort - has shown promising metabolic and cardiovascular benefits with significantly shorter session durations.

Despite growing interest, few clinical trials have evaluated SIT in hypertensive populations using ambulatory blood pressure monitoring (ABPM), which provides better prognostic information than office measurements. Furthermore, the biological mechanisms underlying exercise-induced benefits may involve myokines such as interleukin-6 (IL-6) and α-calcitonin gene-related peptide (α-CGRP), both associated with improved cardiometabolic health.

Objectives

Primary objective:

To compare the effect of SIT versus MICT on 24-hour systolic ambulatory blood pressure after 12 weeks of structured exercise.

Secondary objectives:

Assess changes in diastolic, daytime, and nighttime ambulatory blood pressure.

Evaluate office BP, anthropometric variables (weight, waist circumference, body fat percentage), and metabolic profile (lipids, glucose, TG/HDL ratio).

Assess changes in maximal oxygen consumption (VO₂max), non-invasive hemodynamic parameters, and handgrip strength.

Determine post-training serum concentrations of IL-6 and α-CGRP as biomarkers of exercise response.

Analyze acute hemodynamic responses and adherence to training.

Materials and Methods

Design:

Open-label, randomized, parallel-group clinical trial with pre- and post-intervention evaluations.

Population:

Hypertensive adults (30-59 years) attending the Cardio-Metabolic Disease Unit of Hospital San Martín (La Plata, Argentina).

Inclusion criteria

Confirmed hypertension (treated or untreated).

BMI 18.5-34.9 kg/m².

Exclusion criteria

Office BP ≥160/100 mmHg.

Diabetes, chronic kidney disease (eGFR <60 mL/min), coronary or cerebrovascular disease, pregnancy, or severe comorbidities.

Intervention:

Participants undergo a 2-week familiarization phase before randomization into two groups:

MICT group: Continuous cycling at 50-70% of VO₂max, 15-30 minutes per session.

SIT group: 2-4 maximal 20-30-second cycling sprints (≥100% VO₂max) with recovery intervals (2-4 min), total duration ≤15 minutes per session.

Both groups train three times per week for 12 weeks, under professional supervision. Blood pressure, heart rate, and oxygen saturation will be monitored during sessions for safety.

Evaluations:

At baseline and post-intervention:

Office and 24-hour ABPM measurements.

Anthropometry and laboratory tests (lipid profile, glucose, IL-6, α-CGRP via ELISA).

Impedance cardiography and pulse wave velocity for non-invasive hemodynamics.

Graded exercise test to determine VO₂max.

Handgrip strength test.

Sample size:

A total of 14-20 participants (7-10 per group) are required to detect a 5 mmHg difference in 24-hour systolic BP with 80% power and α=0.05.

Statistical analysis:

Between-group comparisons will use t-tests or Wilcoxon rank-sum tests depending on data distribution. Within-group pre/post differences will be analyzed with paired tests. Analyses will follow the intention-to-treat principle, with additional per-protocol analysis for participants achieving ≥75% adherence.

Ethics:

The study is classified as minimal risk and adheres to the Declaration of Helsinki (2024). Approved by the Ethics Committee of Hospital San Martín de La Plata (Reg. No. 070/2019). All participants will provide written informed consent.

Inclusion criteria

• Patients of both sexes between 30-59 years of age who meet the definition of hypertension.

Hypertension will be defined as:

• Those patients who report a history of hypertension and are under pharmacological treatment for it (Angiotensin Converting Enzyme Inhibitors/Angiotensin II Receptor Antagonists/Calcium Channel Blockers/Thiazide Diuretics/Beta Blockers) at the time of the evaluation.

OR

• Patients who report a history of hypertension during the evaluation and who, without pharmacological treatment, have average levels ≥140/90 mmHg will also be considered hypertensive.

Exclusion criteria

• Extreme body mass index (BMI) <18.5 and ≥35.
• Patients with office blood pressure readings ≥160/100 mmHg.
• Patients with high cardiovascular risk conditions such as type II diabetes, chronic kidney disease (<60 milliseconds), history of cerebrovascular disease, coronary artery disease, peripheral arterial disease, or heart failure (Framingham Criteria clinical diagnosis).
• Pregnant or postpartum women up to 3 months old.
• Patients with psychophysical limitations that make exercise difficult.
• Patients with a history of active malignant neoplastic disease under treatment.

Elimination Criteria

-Patients whose pharmacological treatment is initiated or modified during the follow-up after 3 months.