Abstract

Exercise-induced increases in peripheral beta-endorphin concentration are mainly associated both with changes in pain perception and mood state and are possibly of importance in substrate metabolism. A better understanding of opioid function during exercise can be achieved by investigating changes in beta-endorphin concentrations dependent upon intensity and duration of physical exercise and in comparison to other stress hormones. Published studies reveal that incremental graded and short term anaerobic exercise lead to an increase in beta-endorphin levels, the extent correlating with lactate concentration. During incremental graded exercise beta-endorphin levels increase when the anaerobic threshold has been exceeded or at the point of an overproportionate increase in lactate. In endurance exercise performed at steady-state between lactate production and elimination, blood beta-endorphin levels do not increase until exercise duration exceeds approximately 1 h, the increase being exponential thereafter. Beta-Endorphin and ACTH are secreted simultaneously during exercise, followed by a delayed release of cortisol. It is not yet clear whether a relationship exists between catecholamines and beta-endorphin. These results support a possible role of beta-endorphin in changes of mood state and pain perception during endurance sports. In predominantly anaerobic exercise the behaviour of beta-endorphin depends on the degree of metabolic demand, suggesting an influence of endogenous opioids on anaerobic capacity or acidosis tolerance. Verf.-R.