Acute effects of isocaloric cycling sessions performed continuously and accumulated on blood pressure in prehypertensive individuals

Abstract

Introduction: The regular practice of aerobic exercise has been recommended as a key conduct in the prevention and non-pharmacological treatment of hypertension. There is evidence that chronic reductions in blood pressure (BP) due to the continued practice of exercise programs are due largely to the sum of the acute effects of the training sessions. However, gaps remain in relation to the effects of the manner of execution (continuous vs. accumulated) and exercise volume (as measured by energy expenditure) of aerobic exercise on BP and cardiac autonomic control in pre-hypertensive individuals. Objective: The aim of the present study was to investigate the acute responses of BP and cardiac autonomic control after isocaloric bouts of cycling performed continuously and accumulated in prehypertensive individuals. Methods: This study was conducted on a sample of prehypertensive individuals, aged 20-40 years. Each subject visited the laboratory five times. On the first visit, subjects participated in an orientation session to familiarize them with equipment and test protocols, completed a pre-participation questionnaire for cardiovascular risk and were screened for BP to ensure they met the study inclusion criteria. On the second visit, anthropometric measurements were taken followed by resting oxygen uptake (VO2), BP and heart rate variability (HRV) assessments for 60 min (control session). On the third visit, maximal cardiopulmonary exercise test (CPET) on a cycle ergometer was performed for determining VO2max. On two subsequent visits, subjects underwent a continuous bout (CONT) with 400 kcal and an accumulated bout split into two x 200 kcal (INTER1 and INTER2) at 75% of VO2 reserve. BP and cardiac autonomic control were monitored 10 min before and for 60 min after each exercise bout and control session in a supine position. Results: Compared to control session, systolic BP (SBP), diastolic BP (DBP) and mean arterial pressure (MAP) decreased similarly after CONT (SBP: Δ-3.4 mmHg, P < 0.001; MAP: Δ-2.5 mmHg, P = 0.001) and INTER2 (SBP: Δ-4.4 mmHg, P < 0.001; DBP: Δ-2.7 mmHg, P = 0.045; MAP: Δ-3.3 mmHg, P = 0.001). However, INTER2 elicited greater postexercise hypotension (PEH) than INTER1 (SBP and MAP: Δ-2.0 and Δ-1.8 mmHg, respectively, P < 0.05). Concomitant to PEH, sympathetic (low frequency band, LF) and parasympathetic (high frequency band, HF) activity increased (P < 0.001) and decreased (P < 0.001), respectively, from baseline, increasing the sympathovagal balance (LF:HF ratio) (P < 0.001) that was inversely related to ΔSBP and ΔDBP (r = -0.64 to -0.71; P < 0.05). Conclusion: Continuous or accumulated bouts of cycling matched by energy expenditure elicit similar PEH; however, lower BP decreases were also observed after cycling bout involving lower exercise volume (INTER1: 200 kcal). The results also indicate that the recovery pattern of cardiac autonomic control may have an important role in eliciting PEH.