Alterations in the morning plasma levels of hormones and the endocrine responses to bicycle exercise during prolonged strain. The significance of energy and sleep deprivation

Abstract

The relative significance of physical exercise, energy and sleep deprivation for the morning levels of hormones and the endocrine response to short-term bicycle exercise were investigated in 24 male cadets during a 5-day military training course. Significant increases in the morning levels of noradrenaline, adrenaline, and dopamine, and a decrease in PRL were ascribed mainly to physical strain. Cortisol and hGH increased, whereas insulin and glucose decreased mainly due to energy deficiency. Pulse rate after the bicycle test was unchanged and similar in all groups in spite of increased catecholamine responses. The increased catecholamine response was mainly due to physical strain. The cortisol response to the bicycle test was increased in all groups, and energy deficiency caused slower postexercise recovery. The incremental hGH response to the exercise test was unchanged in the energy-deficient subjects but abolished in the wellfed subjects. The results suggest that the endocrine responses during long-lasting exhausting strain were mainly due to physical exertion and energy deficiency, whereas sleep deprivation did not play any major role.Physical exercise is known to elicit a multitude of endocrine and metabolic responses appropriate for energy mobilization and cardiovascular adaptation. Thus, there is a gradual increase in the plasma levels of noradrenaline, adrenaline, dopamine and pulse rate with increasing exercise intensity (1,2). The serum levels of cortisol and growth hormone are known to increase when a certain workload is exceeded (3-6). Short-term physical exercise has variable effects on serum prolactin (7-10), and a decrease has been shown during long-term exereise (11). Serum insulin decreases during shortterm exercise, and glucose is slightly increased (10,12).Only moderate peripheral endocrine and meta¬ bolic alterations have been found during sleep deprivation (13). Cortisol, hGH and PRL have been shown to increase during night-time, but the dis¬ tinction between the effect of sleep and the natural circadian rhythm is difficult. It seems, however, as if sleep as such increases the serum levels of hGH and cortisol (13,14).In contrast to sleep deprivation, energy defi¬ ciency causes profound changes in the metabolic and endocrine state of the human body (15)(16)(17).There are alterations both in the secretion and degradation of hormones and metabolites. The action of hormones on target tissues is altered as are the energy stores. hGH and cortisol have been shown to increase during starvation, whereas the thyroid function is decreased (18,19).Previously, considerable endocrine and meta¬ bolic alterations have been documented during a 5-day military training course with heavy physical exercise, sleep and energy deficiency (10)(11)(12)14,20,21). Some of these results were found to be depen¬ dent on sleep and/or nutritional factors as studied in separate courses where the cadets were given either extra amounts of sleep or additional food supplies. In these courses, blood samples were drawn immediately ...

Field studies of exercise and food deprivation

“…Similar findings are evident in obese patients on a very low calorie diet [31]. Other metabolic changes, such as a progressive increase in total cholesterol levels in the Ranger students and increasing insulin resistance in Norwegian cadets, may be related to other counterregulatory mechanisms directed towards preserving lean mass in the face of large energy deficits [8,32].…”

Effects of dietary protein content on IGF-I, testosterone, and body composition during 8 days of severe energy deficit and arduous physical activity

“…However, it must be recognized that the dietary intervention involved only modest differences in protein consumption between groups. It has been postulated that the decline of testosterone contributes to preservation of normoglycemia by enhancing alanine availability for gluconeogenesis (24,25). The maintenance of normal glucose concentrations during these times is important given the lack of time to eat and the paucity of food.…”

Influência da suplementação de carboidrato na função imune de judocas durante o treinamento

“…Apesar de os resultados observados aqui estarem de acordo com os de outros estudos (19,20) , a influência desses hormônios na contagem de células sanguíneas não está totalmente esclarecida (21) . No presente estudo, apesar de ser observada menor leucocitose ao final do exercício no grupo CHO, as concentrações de cortisol não diferiram entre os grupos CHO e PLA.…”

“…No presente estudo, apesar de ser observada menor leucocitose ao final do exercício no grupo CHO, as concentrações de cortisol não diferiram entre os grupos CHO e PLA. Opstad et al (19) observaram que os níveis de cortisol se elevam durante o ciclismo de longa duração, entretanto, a influência dos hormônios na contagem de células, provavelmente, está associada à interação entre corticosteróides (cortisol) e catecolaminas (adrenalina e noradrenalina).…”