EFFECT OF A SINGLE SESSION OF ISOMETRIC ELBOW FLEXION ON AMBULATORY BLOOD PRESSURE IN HYPERTENSIVE INDIVIDUALS: A CROSSOVER TRIAL
KEYWORDS: hypertension; ambulatory blood pressure monitoring; post-exercise hypotension; isometric exercise.
INTRODUCTION: The isometric training may contribute to improve the blood pressure levels in hypertensive individuals. However, the acute effects of the isometric training on ambulatory blood pressure are less known.
OBJECTIVE: To analyze the effects of a single session of isometric elbow flexion on ambulatory blood pressure in hypertensive individuals.
METHODS: This is a randomized clinical trial with a crossover design. Twelve inactive hypertensive individuals (♀= 9; 46.8 ± 7.1 years; 27.2 ± 2.7 kg/m²; resting blood pressure 123.0 ± 11.6 / 74.3 ± 6.0 mm Hg) were submitted to two experimental sessions in a randomized order with one-week interval: i) isometric elbow flexion (4 x 1 min, 2 min intervals, 30% one-maximum repetition at 90º); ii) control session (no exercise). Both sessions were performed in the morning and lasted for 12 min. Before and until 30 min after the isometric and control sessions the heart rate variability and blood pressure were measured. Ambulatory blood pressure was measured during 20 h (awake: 12 h; asleep: 8 h) after the isometric and control sessions using an ambulatory blood pressure monitoring device. Systolic, diastolic, and mean blood pressure during the 20 h period were compared between the conditions using a paired t-test. A statistical significance was set at 5%.
RESULTS: There were no differences in systolic (isometric: 126.1 ± 14.7 vs. control: 125.6 ± 11.4 mm Hg; p = 0.810) and diastolic (isometric: 71.0 ± 8.7 vs. control: 71.3 ± 5.7 mm Hg; p = 0.800) during the 20 h period. Also, no differences were found in the awake and asleep period between the isometric and control session (p > 0.05). No changes were found in the heart rate variability indices (RR interval, SDNN, LF, HF, SampleEN). Regarding the blood pressure there was an increase in systolic blood pressure immediately after the isometric exercise session compared to the control session (14,7 mmHg, IC95% 8,7-20,7, p < 0.05).
CONCLUSION: a single session of isometric elbow flexion does not elicit changes on ambulatory blood pressure in hypertensive individuals.