Thermoregulation in hypertensive men exercising in the heat with water ingestion.

G.A Ribeiro,E Silami-Garcia,L.O.C Rodrigues,F.F.O Camargos,M.C.V Moreira,M.R.S Pascoa

doi:10.1590/s0100-879x2004000300019

G.A Ribeiro, E Silami-Garcia + Show 4 more

Open Access

https://doi.org/10.1590/s0100-879x2004000300019

Copy DOI

Abstract

Hydration is recommended in order to decrease the overload on the cardiovascular system when healthy individuals exercise, mainly in the heat. To date, no criteria have been established for hydration for hypertensive (HY) individuals during exercise in a hot environment. Eight male HY volunteers without another medical problem and 8 normal (NO) subjects (46 +/- 3 and 48 +/- 1 years; 78.8 +/- 2.5 and 79.5 +/- 2.8 kg; 171 +/- 2 and 167 +/- 1 cm; body mass index=26.8 +/- 0.7 and 28.5 +/- 0.6 kg/m2; resting systolic (SBP)=142.5 and 112.5 mmHg and diastolic blood pressure (DBP)=97.5 and 78.1 mmHg, respectively) exercised for 60 min on a cycle ergometer (40% of VO2peak) with (500 ml 2 h before and 115 ml every 15 min throughout exercise) or without water ingestion, in a hot humid environment (30 masculine C and 85% humidity). Rectal (Tre) and skin (Tsk) temperatures, heart rate (HR), SBP, DBP, double product (DP), urinary volume (Vu), urine specific gravity (Gu), plasma osmolality (Posm), sweat rate (S R), and hydration level were measured. Data were analyzed using ANOVA in a split plot design, followed by the Newman-Keuls test. There were no differences in Vu, Posm, Gu and S R responses between HY and NO during heat exercise with or without water ingestion but there was a gradual increase in HR (59 and 51%), SBP (18 and 28%), DP (80 and 95%), Tre (1.4 and 1.3%), and Tsk (6 and 3%) in HY and NO, respectively. HY had higher HR (10%), SBP (21%), DBP (20%), DP (34%), and Tsk (1%) than NO during both experimental situations. The exercise-related differences in SBP, DP and Tsk between HY and NO were increased by water ingestion (P<0.05). The results showed that cardiac work and Tsk during exercise were higher in HY than in NO and the difference between the two groups increased even further with water ingestion. It was concluded that hydration protocol recommended for NO during exercise could induce an abnormal cardiac and thermoregulatory responses for HY individuals without drug therapy.

Highlights

During exercise, the increased metabolism and heat production require an increased cardiac output which is achieved through higher stroke volume and heart rate and through adjustments in systemic blood flow
The results showed that cardiac work and Tsk during exercise were higher in HY than in NO and the difference between the two groups increased even further with water ingestion
The increased metabolism and heat production require an increased cardiac output which is achieved through higher stroke volume and heart rate and through adjustments in systemic blood flow

Summary

Introduction

The increased metabolism and heat production require an increased cardiac output which is achieved through higher stroke volume and heart rate and through adjustments in systemic blood flow. Heat stress during exercise represents an overload for the cardiovascular system because muscle and skin circulation must compete for blood flow. The rise in cardiac output directed at the skin lowers both central venous pressure and stroke volume because of the shift in blood volume inside the cutaneous veins, leading to a compensatory tachycardia [1,2]. Since hypertensive subjects show higher blood pressure levels during exercise for a specific muscular strain [5], arterial hypertension is expected to impose an extra overload on the cardiovascular system during acute exercise [6]

Objectives

Methods

Results

Conclusion