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Hormonal studies of pituitary-testicular function in insulin-dependent diabetes mellitus were examined at rest and during moderate exercise to assess whether diabetes per se caused abnormalities of nocturnal penile tumescence and androgen function in men with normal sexual function. The present study compared 10 healthy men and eight men with Type I diabetes mellitus in whom normal sexual function was determined by clinical history. Urinary gonadotropin excretion, semen analysis and diurnal variation of serum glucose, prolactin, testosterone and free testosterone were determined in both groups. In addition, the serum levels of testosterone, free testosterone, prolactin, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were measured at rest, during 45 minutes of exercise on a bicycle ergometer at 50% of the subjects previously determined maximal oxygen uptake (VO2 max) and during a 30-minute recovery period. Nocturnal penile tumescence and parameters of semen analysis were similar in both groups. Urinary FSH excretion and serum FSH were higher (P less than or equal to 0.01) in the diabetic subjects while urinary LH excretion was similar. Diurnal variation of serum prolactin, testosterone and free testosterone were similar in both groups. Exercise produced a significant (P less than or equal to 0.01) increase in maximal free and total testosterone in both groups without changes in serum FSH or LH. Prolactin increased significantly (P less than or equal to 0.01) during exercise in the diabetic group only. We conclude that, for the most part, the pituitary-testicular axis and nocturnal penile tumescence under basal conditions and the pituitary-testicular axis during moderate exercise are similar in healthy males and insulin-dependent diabetic males with normal sexual function.

Healthy children evidence smaller values of cardiorespiratory function than adults, but these are in proportion to the smaller body size. At birth, the distribution of muscle fibres and the activity of enzymes in muscle are different from in adults, but these differences disappear at about age 6. On the other hand, muscle fibre thickness increases from birth to about 18 years of age and this is concurrent with increases in muscular strength. The increase in maximal oxygen consumption (VO2max) that accompanies growth and maturation in the human has been attributed in the main to appreciating muscle mass. During exercise, heart rate and cardiac output increase in the child as in the adult, but the heart rate in the child is greater and the stroke volume smaller. Furthermore, the arteriovenous difference in oxygen is greater in the exercising child than in the adult. Children also evidence a diminished blood pressure response to exercise. It seems that control of ventilation at exercise is the same in children as in adults, but exercise ventilation has been reported to be less efficient in the child. The young are less capable of regulating core temperature at exercise than adults and are more readily dehydrated. Very limited data suggest that muscle energy substrate storage and utilisation in children are such that they are less capable of anaerobic metabolism than adults. Generally, children respond to aerobic training as do adults, but such training in the first decade of life has been reported to have negligible effects. Blood lipid levels in children seem to be favourably influenced by persistent endurance activity. Ventilatory efficiency of children at exercise is augmented by aerobic training. Maximal values of ventilation and breathing frequency are increased in children and youth by endurance training. Conflicting data exist regarding the influence of training upon the child's vital capacity. Pulmonary diffusion capacity in well trained children has been seen to be greater than in untrained youngsters and many workers have reported increased VO2max as an outcome of endurance training. Limited data indicate that the nature of training may alter muscle fibre distribution in youthful athletes, and that muscle fibre hypertrophy can be induced in the young by means of strength and power training.(ABSTRACT TRUNCATED AT 400 WORDS)

We measured physical working capacity at a heart rate of 170 bpm (PWC₁₇₀) and diffusing capacity for carbon monoxide (DL_co) in two groups of children ranging in age from 9 to 17 years. One group was formed of highly trained competitive swimmers and the other of age, sex and size matched untrained counterparts. Bicycle ergometry was used to establish PWC₁₇₀. The DL_co was measured at rest (Dl_{co rest}) and while pedalling at 170 bpm (DL_{co ex}). The PWC₁₇₀, DL_{co rest} and DL_{co ex} were significantly higher in swimmers than in non-swimmers. Repeated measurements in the same subjects show that individual increases in DL_{co rest} and DL_{co ex} were the result of both growth and training.

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