Blood pressure alters during the normal menstrual cycle

Test-retest reliability of exercise blood pressure and the workload-indexed systolic blood pressure slope in healthy males and females

The reliability of blood pressure (BP) measured during submaximal and maximal exercise, and confounding effects of biological sex, remain to be fully established but have implications for using exercise BP as a cardiovascular risk factor. We hypothesize that exercise BP test-retest reliability will not differ between sexes but will be higher during submaximal compared to maximal exercise. Eighty-four participants (22 ± 5 yr; 36 females) completed two maximal treadmill tests (modified Bruce protocol) separated by ≥2 days. Exercise BP was measured every 90 s using automated auscultation (Tango M2 monitor). Breath-by-breath oxygen uptake was analyzed. Test-retest reliability was assessed using two-way, mixed-effects, consistency, single-rater intraclass correlation coefficient (ICC) analysis on the total group and separated by sex at submaximal and maximal exercise. Systolic BP during submaximal (ICC = 0.65 [0.49-0.76], P < 0.01) and maximal (ICC = 0.66 [0.52-0.77], P < 0.01) exercise both displayed substantial reliability between visits. In contrast, the SBP/MET slope showed poor submaximal (ICC = 0.12 [-0.09-0.33], P = 0.13) but substantial maximal (ICC = 0.63 [0.48-0.75], P < 0.01) exercise reliability. Females showed substantial reliability in submaximal systolic BP (ICC = 0.73 [0.53-0.85], P < 0.01) and peak systolic BP (ICC = 0.74 [0.54-0.87], P < 0.01) and SBP/MET slope (ICC = 0.78 [0.60-0.88], P < 0.01); the submaximal SBP/MET slope had fair reliability (ICC = 0.28 [-0.06-0.56], P = 0.05). Males showed moderate reliability in submaximal systolic BP (ICC = 0.53 [0.26-0.72], P < 0.01) and peak systolic BP (ICC = 0.41 [0.15-0.62], P < 0.01) and SBP/MET slope (ICC = 0.48 [0.22-0.67], P < 0.01); the submaximal SBP/MET slope had poor reliability (ICC = 0.06 [-0.18-0.31], P = 0.32). Systolic BP showed similar reliability during submaximal and maximal exercise, with females demonstrating higher reliability in exercise systolic BP compared to males.NEW & NOTEWORTHY Limited work has assessed the reliability of exercise blood pressure (BP) in young healthy males and females. Our results demonstrate that systolic BP test-retest reliability did not differ between submaximal and maximal exercise. Sex-specific analysis found that females had higher reliability in exercise systolic BP than males. Despite the acceptable average reliability, exercise BP measured using automated auscultation possesses wide confidence intervals, which impact sample size requirements in future trials.

Breaks in Sitting Time: Effects on Continuously Monitored Glucose and Blood Pressure

PURPOSE

We examined the effects of interrupting prolonged sitting with multiple 2-min walking breaks or one 30-min continuous walking session on glucose control and ambulatory blood pressure (ABP).

METHODS

Ten overweight/obese, physically inactive participants (five men; 32 ± 5 yr; BMI, 30.3 ± 4.6 kg·m) participated in this randomized four-trial crossover study, with each trial performed on a separate, simulated workday lasting 9 h: 1) 30 min of continuous moderate-intensity (30-min MOD) walking at 71% ± 4% HRmax; 2) 21 × 2 min bouts of moderate-intensity (2-min MOD) walking at 53% ± 5% HRmax, each performed every 20 min (42 min total); 3) 8 × 2 min bouts of vigorous-intensity (2-min VIG) walking at 79% ± 4% HRmax, each performed every hour (16 min total); 4) 9 h of prolonged sitting (SIT). Participants underwent continuous interstitial glucose monitoring and ABP monitoring during and after the simulated workday spent in the laboratory, with primary data analysis from 12:30 h to 07:00 h the next morning.

RESULTS

Compared with SIT (5.6 ± 1.1 mmol·L), mean 18.7-h glucose was lower during the 2-min MOD (5.2 ± 1.1 mmol·L) and 2-min VIG (5.4 ± 0.9 mmol·L) trials and mean 18.7-h glucose during the 30-min MOD trial (5.1 ± 0.8 mmol·L) was lower than all other trials (P < 0.001). Postprandial glucose was approximately 7% to 13% lower during all trials compared with SIT (P < 0.001), with 30-min MOD having the greatest effect. Only the 30-min MOD trial was effective in reducing systolic ABP from 12:30 to 07:00 h (119 ± 15 mm Hg) when compared with SIT (122 ± 16 mm Hg; P < 0.05).

CONCLUSIONS

Replacing sitting with 2-min MOD walking every 20 min or 2 min of vigorous-intensity walking every hour during a simulated workday reduced 18.7 h and postprandial glucose, but only 30-min MOD walking was effective for reducing both glucose and systolic ABP.

Systemic and renal hemodynamic changes in the luteal phase of the menstrual cycle mimic early pregnancy

Blood pressure decreases during early pregnancy in association with a decrease in peripheral vascular resistance and increases in renal plasma flow and glomerular filtration rate. These early changes suggest a potential association with corpora lutea function. To determine whether peripheral vasodilation occurs following ovulation, we studied 16 healthy women in the midfollicular and midluteal phases of the menstrual cycle. A significant decrease in mean arterial pressure in the midluteal phase of the cycle (midfollicular of 81.7 +/- 2.0 vs. midluteal of 75.4 +/- 2.3 mmHg, P < 0.005) was found in association with a decrease in systemic vascular resistance and an increase in cardiac output. Renal plasma flow and glomerular filtration rate increased. Plasma renin activity and aldosterone concentration increased significantly in the luteal phase accompanied by a decrease in atrial natriuretic peptide concentration. Serum sodium, chloride, and bicarbonate concentrations and osmolarity also declined significantly in the midluteal phase of the menstrual cycle. Urinary adenosine 3',5'-cyclic monophosphate (cAMP) excretion increased in the luteal compared with the follicular phase, whereas no changes in urinary cGMP or NO2/NO3 excretion were found. Thus peripheral vasodilation occurs in the luteal phase of the normal menstrual cycle in association with an increase in renal plasma flow and filtration. Activation of the renin-angiotensin-aldosterone axis is found in the luteal phase of the menstrual cycle. These changes are accompanied by an increase in urinary cAMP excretion indicating potential vasodilating mediators responsible for the observed hemodynamic changes.

Haemodynamic responses to nonhypotensive central hypovolaemia induced by lower body negative pressure in men and women

Haemodynamic responses to low levels of lower body negative pressure (LBNP) were investigated in two groups of healthy, normotensive volunteers (8 men and 8 women) during two repeated experimental runs on two occasions, the latter determined by the different phases of the menstrual cycle in the women. The data consisted of systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean blood pressure (MBP), pulse rate (fc), forearm blood flow (FBF) and forearm vascular conductance (FC). The resting cardiovascular status was similar in men and women, except that women had a significantly higher fc than men. LBNP (1.3, 2.7 and 4 kPa) had no significant effect on any BP variable or on fc. However, FBF and FC were reduced at all levels of LBNP. Significant overshoots in FBF and FC were seen in all subjects following the release of LBNP of 2.7 and 4 kPa and, in most cases, after release of LBNP of 1.3 kPa. There were no significant gender differences in any of the responses to LBNP. Furthermore, none of the cardiovascular variables measured showed significant differences between the follicular and luteal phases of the menstrual cycle in women, either at rest or during exposure to LBNP, and the responses in the men on the two occasions were not different. These findings indicate that gender differences in responses to LBNP hypothesized previously are not apparent during and after exposure to low levels of LBNP.