Effect of physical fitness on vanillylmandelic acid excretion during immersion

Abstract

The effects of 4--6 h head-out immersion on excretion of vanillylmandelic acid (VMA), blood pressure and plasma volume were estimated in 8 endurance-trained (TR) and 8 untrained (UT) subjects. In the trained only a slight increase of VMA excretion occurred (4 h value: +2.7 +/- 10.9 ng/ml GFR), but there was a highly significant increase in the UT (+29.0 +/- 17.2 ng/ml GFR). VMA values during control experiments in supine position tended to decrease in both groups. Systolic and diastolic blood pressure fell by 20 mm Hg after beginning of immersion; in the UT plasma volume was reduced while it remained constant in TR. The results indicate that orthostatic intolerance (o.i.) after immersion is not effected by decreased sympathetic innervation of vessels; in contrast it seems to be partly compensated for by an elevated sympathetic activity at least in the UT. As a main cause for the post-immersion o.i. one might suggest a decrease in renin activity.

Arterial Stress Hormones during Scuba Diving with Different Breathing Gases

“…Feedback from arterial pressure receptors consequently should reduce HR. However, also, constant values during snorkeling (17) and even an increase during head-out immersion have been observed, the latter accompanied by a decrease of arterial blood pressure (e.g., Skipka et al [25], Ulmer et al [30]). …”

“…Because these intracoiporal pressure effects were equal for all experiments, a different change for breathing air, oxygen, or Heliox did not occur. The main reaction during head-out immersion in males seems to be a long-known marked reduction of systolic and diastolic blood pressure as an indicator of reduced peripheral resistance (e.g., Skipka et al [25], Ulmer et al [30]), but measurements during scuba diving seem not to exist.…”

“…However, after 2-A h, catecholamine secretion (measured by vanillylmandelic excretion in urine) had increased markedly, especially in untrained subjects (e.g., Skipka et al [25]). In other immersion experiments, only high pressure (4 or 11 bar) caused similar reactions (4,16,18); interestingly, [noradrenaline] but not [adrenaline] in venous blood increased (18).…”