Comparing Vascular Responses to Aerobic Exercise With and Without Blood Flow Restriction in Young and Older Adults

Condition(s) studied

Investigational drug(s) / intervention(s)

Low Intensity Aerobic Exercise with Blood Flow Restriction (LIAE+BFR): In the LIAE+BFR condition, participants will walk on a treadmill for 20 minutes at 30-40% of heart rate reserve (HRR), with a pneumatic cuff inflated to 1.3 times the individual's ankle systolic blood pressure, using a 5cm wide x 75cm long commercial cuff around each upper thigh. Treadmill speed will be adjusted dynamically to maintain target intensities, while the incline remains at 1%. Heart Rate, the Modified Borg Rate of Perceived Exertion scale, and the Rating of perceived discomfort will be continuously monitored throughout both exercise sessions to ensure adherence to the prescribed intensity levels.

High Intensity Interval Exercise (HIIE): In the HIIE condition, participants will perform a 20 minutes treadmill-based HIAE, alternating between 60-seconds high-intensity intervals at 60-89% HRR and 60-second active recovery intervals at 40-50% HRR. Treadmill speed will be adjusted dynamically to maintain target intensities, while the incline remains at 1%. Heart Rate, the Modified Borg Rate of Perceived Exertion scale, and the Rating of perceived discomfort will be continuously monitored throughout both exercise sessions to ensure adherence to the prescribed intensity levels.

Study summary

Aging is a major risk factor for cardiovascular disease (CVD), contributing to progressive macrovascular and microvascular dysfunction. Macrovascular impairments, such as arterial stiffening and endothelial dysfunction, reduce nitric oxide (NO) bioavailability, leading to hypertension and impaired blood flow regulation. Microvascular dysfunction exacerbates cardiovascular decline by compromising capillary perfusion and tissue oxygenation, increasing susceptibility to ischemic events. Preserving vascular function is essential for maintaining cardiovascular health in aging populations.

Low-intensity aerobic exercise (LIAE) improves cardiovascular health and mobility, particularly in populations unable to perform high-intensity exercise. However, LIAE alone often fails to induce significant vascular adaptations, such as improved arterial compliance or endothelial function, highlighting the need for optimized interventions.

Blood Flow Restriction (BFR) enhances vascular adaptations during low-intensity exercise by inducing localized hypoxia, stimulating endothelial function and arterial remodeling. While BFR may transiently increase blood pressure and arterial stiffness, its vascular benefits resemble those of high-intensity exercise at lower workloads. However, research on BFR's acute vascular effects during aerobic exercise in older adults remains limited.

Current studies have focused on perceptual and hemodynamic responses to LIAE+BFR but lack direct assessments of macrovascular (e.g., flow-mediated slowing) and microvascular function. Older adults may exhibit distinct vascular responses, yet data are scarce. This study examines acute vascular responses to LIAE+BFR and high-intensity interval exercise (HIIE) in young and older adults.

Hypothesis:

1. BFR combined with LIAE will elicit greater acute microvascular and macrovascular responses in older adults than in younger adults.
2. These responses will be comparable to HIIE without BFR, suggesting BFR enhances LIAE's efficacy to high-intensity levels.
3. Any transient vascular dysfunction (e.g., increased arterial stiffness) will normalize within 30 minutes post-exercise, supporting safety in aging populations.

Eligibility

Primary outcome measure(s)

• Change in macrovascular function — At rest and re-evaluated 5- and 30-minutes into recovery following the experimental conditions
  We will use the slowing of the pulse wave velocity (PWV) recorded between the upper arm and the wrist as an index of macrovascular function. PWV is inversely related to arterial distensibility; a widening of the brachial artery cross-section will cause a drop in post-occlusive PWV. Macrovascular function will be evaluated using EndoFMS (Vicorder, Berlin, Germany), and the response parameters are PWVmin and PWV% change from pre-occlusion values. The percentage change from initial PWV is called FMS. The default cuff placement is a 10 cm brachial cuff on the upper arm and a 7 cm wrist cuff on the selected limb. The test is performed with the patient lying horizontally, the right arm extended at a 60-degree angle, and the hand rotated palm up. After the patient relaxes, the test starts with a target occlusion pressure 30 mmHg above systolic pressure. Brachial PWV is measured between the wrist and upper arm over 10 minutes, with a 5-minute occlusion period.
• Change in central arterial stiffness — At rest and re-evaluated 5- and 30-minutes into recovery following the exercise condition
  To measure arterial stiffness, we will assess carotid-femoral pulse wave velocity (cPWV) using a Vicorder module (Berlin, Germany). Participants will be in a reclined position, with a minimum of 10 minutes of rest. A 100 mm blood pressure cuff will encircle the upper thigh, and a 30 mm partial cuff will be applied around the neck at the level of the carotid arteries, above the thyroid prominence. The direct path length will be measured from the suprasternal angle to the middle of the femoral blood pressure cuff by the same operator. Both cuffs will be simultaneously inflated to 60 mm Hg to capture femoral and carotid waveforms. Continuous recordings will be obtained beat-to-beat for at least 3 minutes. Automated software will determine the wave\'s foot using an intersecting tangent algorithm. The time delay between the foot of the carotid and femoral waveforms will provide the average TT every 3.5 seconds.
• Change in blood pressure — At rest and re-evaluated after each set and 5- and 30-minutes into recovery following the exercise condition
  The brachial artery pulse waveform obtained oscillometrically, will be analyzed using the Pulse Wave Analysis (PWA) function of the Vicorder® device (Berlin, Germany), and the aortic waveform calculated using a transfer function. This enables calculation of arterial system parameters, including cSBP, augmentation pressure (AugPress), augmentation index (AugInd), central peripheral pressure (cPP), cardiac output, and total peripheral resistance. Initial waves will be omitted, and good-quality consecutive pulse waves will be analyzed.
• Change in microvascular function — At rest and re-evaluated 5- and 30-minutes into recovery following the exercise condition
  Microvascular function will be assessed using EndoCheckPAR (Vicorder, Berlin, Germany). Participants will be in a supine position with their arms comfortably positioned. Changes in the peripheral arterial dilation ratio (PAR) signal to reactive hyperemia (RH) will be measured at the fingertip with photoplethysmographs and an inflating device controlled by a computer algorithm. The RH procedure consists of a 30-second calibration, a 5-minute baseline recording, followed by 5 minutes of blood flow occlusion of the test arm using an upper arm blood pressure cuff inflated to 30 mmHg above the patient's systolic brachial pressure. After cuff deflation, the PAR tracing will be recorded for another 3 minutes. The software automatically normalizes this ratio to the concurrent signal from the contralateral, non-occluded forearm to correct for confounding variables. This ratio is then multiplied with a baseline correction factor to obtain Measured Peak, Max Reference Peak, and Max PAR.

Trial sites (1)

More Egas Moniz - Cooperativa de Ensino Superior, CRL trials in Portugal

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