Continuous measurement of blood pressure, heart rate and left ventricular performance during and after isometric exercise in head-out water immersion

Experiments were performed to determine the changes in blood pressure (BP), heart rate (HR) and left ventricular function during and after isometric knee extension during thermoneutral (35°C) head-out water immersion (HWI) or in air. Seven healthy male subjects mean age 24 (SD 3) years kept their knees extended (60% maximal voluntary extension) until they reached exhaustion. The mean BP at rest was 80 (SD 10) and 78 (SD 8) mmHg 10.7 (SD 1.33) and 10.4 (SD 1.07) kPa] in air and during HWI, respectively, (NS). They increased progressively (P < 0.01) during contraction and reached maximal values of 148 (SD 22) and 143 (SD 26) mmHg 19.7 (SD 2.93) and 19.1 (SD 3.47) kPa] in air and in HWI, respectively, (NS). The mean HR at rest was 74 (SD 8) and 70 (SD 11) beats·min^–1 in air and in HWI, respectively, (NS). They also increased progressively (P < 0.01) and reached 126 (SD 14) and 118 (SD 17) beats·min^–1 in air and in HWI, respectively, (NS). The changes in BP and HR during contraction in HWI tended to be smaller than those in air (NS). Left ventricular end diastolic diameters (dd) at rest in HWI were greater than those in air and were maintained at higher values during and after isometric contraction. In contrast, dd decreased during isometric contraction in air (P < 0.01). The change of left ventricular systolic diameters (d _s) in HWI was no different to those in air. From these findings, isometric exercise in thermoneutral HWI would seem to be characterized by a greater d _d than in air and this could be useful for patients with deconditioning effects such as orthostatic hypotension.