Acute Exercise Effects on Arterial Stiffness and Cardiovagal Modulation in Adults

All participants were randomly assigned to 1 of 4 experimental conditions using a randomized block scheme (https://www.randomizer.org/). Participants completed 4 separate intervention sessions, each consisting of an initial rest, a group fitness class of either indoor cycling, resistance training, combined exercise training, or no exercise (CON), followed by a recovery period. A minimum of 72 hours between sessions was ensured. Body composition and cardiorespiratory fitness for each participant were evaluated before and after the CON session, respectively.

Each session began with 20 minutes of supine rest on a cushioned examination table, with resting energy expenditure (REE) measured by indirect calorimetry (K5, Cosmed, Rome, Italy) and heart rate (HR) and blood pressure (BP) recorded continuously using digital plethysmography (Finapres, NOVA, Finapres Medical Systems, Amsterdam, The Netherlands). This was followed by: 1) Regional assessments of PWV and pulse wave analysis of the carotid, brachial, femoral, and distal arteries on the right side of the body using applanation tonometry (Complior 2.0, Alam Medical; Saint Quentin Fallavier, France); and 2) Assessment of heart rate variability (HRV) and baroreflex sensitivity (BRS) indices using the Finapres NOVA 5 ECG lead module. Following these assessments, participants engaged in a 45-minute group fitness class, while activity energy expenditure (AEE) was continuously measured by indirect calorimetry (K5, Cosmed, Rome, Italy). In the CON session, participants remained comfortably seated for 45 minutes, maintaining a good posture. After each group fitness class, participants immediately returned to the examination table and recovered in the supine position for 30 minutes, during which local and regional stiffness, HRV, and baroreflex sensitivity (BRS) were re-evaluated at 10-, 20-, and 30-minute intervals during recovery and compared to those at rest. Participants were blinded to the order of the experimental interventions until arrival at the laboratory. All sessions were conducted in the morning to minimize potential diurnal variation. Participants were also instructed not to ingest any food or drink (except water) 4 hours before the sessions and to avoid alcohol, caffeine, and exercise for at least 24 hours preceding each session.

Based on a medium effect size of 0.154 derived from published changes in aortic PWV within-between modes of exercise (23), an a priori power analysis suggested that 22 participants were required (11 per group) to detect significant differences within-between groups, conditions, and time points (1-β = 80%, α = 0.05).

Inclusion criteria

• Physically active, as assessed by the International Physical Activity Questionnaire (IPAQ)
• Experience in both aerobic and resistance exercise (∼3-4 times/week, for more than 3 months).
• Healthy or perceived to be healthy based on the sport's medical examination or the preparticipation screening process, Physical Activity Readiness Questionnaire for Everyone (PARQ+).

Exclusion criteria

• Any form of cardiovascular disease
• More than one cardiovascular disease risk factor
• Resting hypertension (SBP >140 mmHg, DBP > 90 mmHg)
• Any prescription medication use that may influence vascular and autonomic response to exercise
• Being an athlete
• Currently smoking.