Comparison of blood lipids, lipoproteins, anthropometric measures, and resting and exercise cardiovascular responses in children, 6-7 years old

The purpose of this investigation was to determine sex differences and interrelationships in anthropometric, blood lipids and lipoproteins, steady rate and maximal bicycle ergometric measures in boys (N = 38) and girls (N= 28) ages 6 to 7 years. After adjusting for a significantly (P P -1 whereas no differences (P> 0.05) existed in preexercise and maximal heart rates. Multiple regression analyses resulted in weak but significant (P P r = 0.46) was obtained for the girls. These data indicate that sex differences exist for selected ergometric, anthropometric, and blood lipid and lipoprotein measures as early as 6 years. Also, the association among blood lipid and lipoprotein measures may differ between boys and girls.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24221/1/0000480.pd

Effects of follicular phase exercise on luteinizing hormone pulse characteristics in sedentary eumenorrhoeic women

OBJECTIVE Current studies reveal little regarding the Inception of exercise-induced LH changes during physical training. This study aimed to assess the susceptibility of the hypothalamic–pituitary axis to the acute physical stress of exercise in untrained, physically inactive women. The acute effects of submaximal endurance exercise upon the pulsatile LH secretion in the follicular phase were compared with those accompanying leisurely strolling for a similar time period. SUBJECTS All subjects were eumenorrhoelc, as determined by biphasic temperature patterns, detection of the urinary LH surge, and mid-luteal serum progesterone levels. Subjects were not physically active and had little history of strenuous exercise ( V o 2 max = 38·0 ± 1·8) (mean ± SEM) ml/kg/min). DESIGN All women completed a 13·5-hour pulsatility test which included three consecutive 20-minute runs on a treadmill at 50, 60 and 70% of the subjects’maximum oxygen uptake ( n = 16). Six of these same subjects completed a separate test on another occasion in which one hour of leisurely strolling was substituted for exercise. Blood was sampled every 10 minutes via an indwelling cannula for 4·5 hours before and 8 hours after one hour of exercise and or strolling. MEASUREMENTS A pulse algorithm (Pulsar) was used to quantify LH pulse characteristics. RESULTS Exercise produced no significant effects upon LH pulse frequency or mean serum LH concentration. However, exercise of moderate intensity caused a significant increase in LH pulse amplitude ( P < 0·05). Strolling produced no significant changes in LH secretion. CONCLUSION Acute exercise of moderate intensity in the follicular phase of untrained women is an insufficient stimulus to inhibit the GnRH pulse generator in the post-exercise period, yet may produce a slight stimulatory effect on the amount of LH released per pulsePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73507/1/j.1365-2265.1994.tb02794.x.pd

The Acute and Chronic Effects of Marathon Training on the Function of the Hypothalamic - Pituitary - Gonadal Axis of Male Runners (Reproductive System, Testosterone, Gonadotropins).

The long-term and acute effects of marathon running on the reproductive system of male runners, specifically the hypothalamic-pituitary-gonadal axis, is not well understood. While evidence is available for women runners demonstrating alterations of this axis resulting in menstrual cycle disorders, such evidence is lacking for men. The purpose of the present investigation was to examine the effect of marathon training on the hypothalamic-pituitary-gonadal axis of competitive male marathon runners. Both the cumulative and acute effects of training were examined by measuring testosterone, luteinizing hormone (LH), and follicle stimulating hormone (FSH) concentrations, and the secretory pattern of LH during basal conditions and during a two-hour run. In addition, pituitary and testicular sensitivity was examined with the administration of gonadotropin releasing hormone (GnRH) and human chorionic gonadotropin (hCG), respectively. While there was no cumulative effect of marathon training on testosterone concentrations of the runners, the hypothalamic-pituitary axis was affected. The LH pulse frequency was significantly lower, and mean LH concentrations were significantly higher in the runners. In response to stimulation with three increasing doses of GnRH, the percent rise in LH was lower in the runners than in the controls, indicating some impariment of the hypothalamic-pituitary axis. There were no other differences between groups for testosterone, FSH, or prolactin concentrations, nor for LH pulse amplitude. In addition, testicular responsiveness to a bolus injection of hCG was similar for both groups. The two-hour exercise bout had little effect on the hypothalamic-pituitary-gonadal axis. Testosterone concentrations increased significantly by 40 minutes of running and remained elevated for the duration of the run. However, in the absence of any alterations in LH and FSH concentrations, the rise was due more to decreased metabolic clearance of testosterone than to increased testosterone secretion. The pulsatile secretion of LH and FSH was unaffected by the exercise bout.Ph.D.Physical educationUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160690/1/8520937.pd