Differences in sympathoadrenal, hormonal, and metabolic adaptation to submaximal and maximal arm and leg work...

During work on land adaptational reactions of circulation and hormones are influenced by the body position, the activated muscle mass, and the working extremities. The aim of this study was to explore the additional effect of water immersion during swimming on cardiocirculatory, metabolic, and hormonal regulation under different working conditions. Twelve young men not specifically trained in swimming underwent swimming tests on 3 different days. They had to swim breast stroke in total as well as isolated with legs or arms only each for 10 min at submaximal intensity and 150 m or 100 m at maximal intensity. This study was focused on changes of catecholamines (CA), heart rate (HR), blood pressure (BP), glucose, lactate, plasma renin activity (PRA), and plasma aldosterone (PA). Additionally, parameters of the electrolyte-volume homeostasis were investigated. Norepinephrine (NE) and epinephrine (EPI) increased during swimming under submaximal and maximal conditions. The augmentation of CA and HR was the highest after swimming whole stroke and the lowest after swimming arm stroke only. They were related to intensity within one type of swimming and showed a dependence on muscle mass independent from lactate or glucose levels when the different types of swimming were compared, although a positive correlation between CA and lactate levels was found. The BP was higher after leg work than after arm work, contrary to observations done on land regarding the comparable submaximal work loads. We suppose that this is an effect of water immersion and the horizontal body position whereby the central hemodynamic circulation becomes stabilized.(ABSTRACT TRUNCATED AT 250 WORDS)