O2 uptake and muscle deoxygenation kinetics during the transition to moderate-intensity exercise in different phases of the menstrual cycle in young adult females

O(2) uptake (VO2) kinetics were examined during the follicular (F) and luteal (L) phases of the menstrual cycle to determine if there was an effect of altered sex hormones on the (VO2) response to moderate-intensity exercise. Seven healthy women (age 21 +/- 2 years; mean +/- SD) performed six transitions from 20 W to moderate-intensity exercise (approximately 90% theta L) during the F and L phase. VO2 was measured breath-by-breath and deoxyhemoglobin/myoglobin (Delta HHb) was determined by near infrared spectroscopy. Progesterone and estrogen were significantly (P < 0.05) elevated during the L compared to F phase. VO2 kinetics (tau VO2) were not different in the two phases of the menstrual cycle (F, 22 +/- 5 s; L, 22 +/- 6 s; 95% confidence intervals +/-4 s) nor was the time course of the Delta HHb response (F, TD 11 +/- 2 s, tau 11 +/- 3 s; L, TD 12 +/- 2 s, tau 12 +/- 11 s; tau HHb 95% confidence intervals +/-3 s). Respiratory exchange ratio (RER) was not different between phases for baseline or steady-state exercise and the blood lactate response to exercise was not different. In conclusion, VO2 kinetics at the onset of moderate-intensity exercise are not affected by the phase of the menstrual cycle in young females suggesting either no change in, or no effect of metabolic activation on the on-transient kinetics of moderate-intensity exercise. Additionally, the similar adaptation of Delta HHb in combination with unchanged VO2 suggests that there were no differences in the adaptation of local muscle O(2) delivery.

Effect of repeated boluses of intravenous omeprazole and primed infusions of ranitidine on 24-hour intragastric pH in healthy human subjects

The aim of this study was to identify dosage regimens using intravenous omeprazole and ranitidine that would elevate and consistently maintain intragastric pH > 6 in the first 24 hr of therapy. In 19 healthy, fasting human subjects using continuous 24-hr gastric pH-metry, we studied two dosages of primed infusions of ranitidine (50 mg bolus followed by infusion of either 3 or 6 mg/kg body wt/24 hr) and six regimens of intravenous omeprazole (80-200 mg in 24 hr in two to five boluses). Only the two ranitidine infusions and high doses of omeprazole (> or = 160 mg/day as four or five boluses) raised the intragastric median pH above 5.4. There was no significant difference in the median intragastric pH after high dose ranitidine and high doses of omeprazole. Considerable interindividual variation in intragastric pH was observed after omeprazole therapy. The percentage of intragastric pH > 6.0 during the 24-hr study was lower after omeprazole (35-42%) than after high-dose ranitidine (58%). We conclude that it is possible to raise intragastric pH > 6.0 by use of either primed ranitidine infusion or by repeated boluses of omeprazole. However, maintenance of this high pH in the first 24 hr is difficult with both, more so with omeprazole.