Influence of Exercise in Water on Hormonal, Metabolic and Adrenergic Receptor Changes in Man

Abstract

We investigated hormonal, metabolic, and cardiovascular adaptations as well as changes of α₂- and β₂-adrenergic receptors in response to three different exercise performances in water: 1000 m fin swimming with or without a neoprene suit and, additionally, 600m diving with a breathing apparatus while performing several tasks. Eight male divers participated in the study. Blood samples were taken at rest on land, 10 min after water immersion, immediately after exercise, and after 20 min recovery.

Both free and sulfoconjugated norepinephrine (NE) increased exercise-dependently. Moreover, heat loss in water caused elevation of plasma free NE. Free epinephrine (EPI) increases showed a highly significant correlation with NE except during fin swimming with a neoprene suit where EPI concentrations were constantly higher. ACTH and Cortisol levels rose during exercise and paralleled those of plasma NE. Plasma aldosterone decreased in response to water immersion at rest. Blood volume regulating hormones such as plasma renin, aldosterone, and vasopressin were significantly higher during physical exercise. Moreover, increased pressure conditions during diving caused significantly higher secretion rates of all of these hormones, resulting in a higher systolic blood pressure. This clinical issue might be considered when examining diving ability. Lipolysis was elevated to the same degree after the three exercise schedules had been applied. As expected, plasma glucose also increased during physical activity. The lactate values observed after fin swimming, but not after diving with a breathing apparatus were closely related to NE. The lowest lactate levels were obtained during air-assisted diving. Physical exertion in water was associated with significantly elevated β-adrenergic receptor sites on mononuclear leukocytes correlating well with an increased susceptibility of cyclic adenosine monophosphate (cAMP) to isoproterenol stimulation. Platelet α-adrenoceptors showed no changes.

Key words

physical exercise - diving - free and sulfated catecholamines - hormonal adpatation - adrenergic receptors - water immersion - thermoregulation - air assistance