EXERCISE AT LOW-ALTITUDE (JORDAN VALLEY) CAUSES CHANGES IN SERUM LEVELS OF ACTH, INSULIN, CORTISOL AND LACTATE

This study was designed to examine the effects of exercise on adrenoco rticotropic hormone (ACTH) and cortisol at low altitude (350 meters be low sea level) and to compare these effects with those at a moderate l evel altitude (620 meters above sea level). Ten male trained athletes participated in a 21-Km non-competitive race. Serum levels of ACTH, lu teinizing hormone (LH), growth hormone and cortisol were measured befo re and after the race at each of the altitudes. A significant increase in serum levels of ACTH was observed in response to this exercise onl y at low altitude. Serum levels of growth hormone were increased at bo th altitudes. Those of LH were not affected. Serum cortisol levels wer e increased following exercise at both altitudes. It is proposed here that ACTH may play a role in acclimatization to exercise at low altitu des. The role of growth hormone and LH in this conditioning process se ems to be insignificant. Additionally, serum levels of insulin and lac tate were also measured in these experiments. Exercise caused a decrea se in serum insulin levels at both altitudes. Serum levels of lactate were decreased only at low altitude. These changes of serum levels of insulin and lactate suggest a type of metabolic adjustment to meet ene rgy requirements. Changes in energy metabolism can be correlated by ch anges in the ratio of insulin to serum cortisol levels and those of ot her counterregulatory hormones in response to exercise at both altitud es.