Sex Differences in the Relationship Between Baroreflex Effectiveness Index and Spontaneous Cardiac Baroreflex Sensitivity

Baroreflex effectiveness index (BEI) is a relatively new measure used to assess cardiac baroreflex function. It is unclear whether BEI provides independent or complementary information compared to traditional spontaneous cardiac baroreflex sensitivity (BRS) measures. PURPOSE: The purpose of this project was to begin to explore the relationship between BEI and BRS in young adults and to investigate the impact of sex on these potential relationships. We hypothesized that there would be a positive correlation between BEI and BRS in both males and females. METHODS: We studied 45 young healthy adults, 17 males (24 ± 4 years) and 28 females (23 ± 4 years). Heart rate (ECG) and beat-to-beat arterial blood pressure (finger photoplethysmography) were continuously recorded during a five-minute resting baseline. Spontaneous cardiac BRS was measured using the Sequence Method, by identifying the gain of the relationship between systolic blood pressure and RRI from sequence(s) of three or more consecutive heartbeats in which systolic blood pressure and RRI change in the same direction. BEI was quantified as the ratio of the number of baroreflex-driven ramps relative to all systolic blood pressure ramps. RESULTS: BEI (Male: 0.65 ± 0.14, Female: 0.61 ± 0.13; mean ± SD, p=0.27) and BRS (Male: 21.3 ± 8.4, Female: 27.27 ± 12.6, p=0.09) between groups was not different. There was no significant relationship between BEI and BRS among all participants (r= 0.13, p= 0.36). However, sex-specific analysis data revealed a positive correlation in our male group (r= 0.57, p=0.01), and no relationship in our female group (r= 0.03, p=0.84). CONCLUSION: These preliminary data suggest that the relationship between BEI and BRS may be sex-dependent

Leisure-Time Physical Activity before and during Pregnancy Is Associated with Improved Insulin Resistance in Late Pregnancy

A total of 83 third trimester pregnant women were recruited to examine the role of pre-pregnancy versus late-pregnancy physical activity on maternal insulin resistance. Principal component analysis plots demonstrated a distinction between the high and low Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) groups. The variation was driven primarily by exercise prior to and during pregnancy. Specifically, higher levels of physical activity prior to pregnancy was associated with a lower HOMA-IR and is not modified by other variables. Women who were active prior to pregnancy were more active during pregnancy. These results suggest that being active before pregnancy may be a good strategy for mitigating the risk of insulin resistance during late pregnancy

Effects of prenatal exercise on fetal heart rate, umbilical and uterine blood flow: a systematic review and meta-analysis

Objective To perform a systematic review and meta-analysis examining the influence of acute and chronic prenatal exercise on fetal heart rate (FHR) and umbilical and uterine blood flow metrics. Design Systematic review with random-effects meta-analysis and meta-regression. Data sources Online databases were searched up to 6 January 2017. Study eligibility criteria Studies of all designs were included (except case studies) if published in English, Spanish or French, and contained information on the population (pregnant women without contraindication to exercise), intervention (subjective or objective measures of frequency, intensity, duration, volume or type of exercise, alone [“exercise-only”] or in combination with other intervention components [eg, dietary; “exercise + co-intervention”]), comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and outcomes (FHR, beats per minute (bpm); uterine and umbilical blood flow metrics (systolic:diastolic (S/D) ratio; Pulsatility Index (PI); Resistance Index (RI); blood flow, mL/min; and blood velocity, cm/s)). Results ‘Very low’ to ‘moderate’ quality evidence from 91 unique studies (n=4641 women) were included. Overall, FHR increased during (mean difference (MD)=6.35bpm; 95% CI 2.30 to 10.41, I2=95%, p=0.002) and following acute exercise (MD=4.05; 95% CI 2.98 to 5.12, I2=83%, p\u3c0.00001). The incidence of fetal bradycardia was low at rest and unchanged with acute exercise. There were no significant changes in umbilical or uterine S/D, PI, RI, blood flow or blood velocity during or following acute exercise sessions. Chronic exercise decreased resting FHR and the umbilical artery S/D, PI and RI at rest. Conclusion Acute and chronic prenatal exercise do not adversely impact FHR or uteroplacental blood flow metrics

The effects of superimposed tilt and lower body negative pressure on anterior and posterior cerebral circulations

Steady-state tilt has no effect on cerebrovascular reactivity to increases in the partial pressure of end-tidal carbon dioxide (PETCO2). However, the anterior and posterior cerebral circulations may respond differently to a variety of stimuli that alter central blood volume, including lower body negative pressure (LBNP). Little is known about the superimposed effects of head-up tilt (HUT; decreased central blood volume and intracranial pressure) and headdown tilt (HDT; increased central blood volume and intracranial pressure), and LBNP on cerebral blood flow (CBF) responses. We hypothesized that (a) cerebral blood velocity (CBV; an index of CBF) responses during LBNP would not change with HUT and HDT, and (b) CBV in the anterior cerebral circulation would decrease to a greater extent compared to posterior CBV during LBNP when controlling PETCO2. In 13 male participants, we measured CBV in the anterior (middle cerebral artery, MCAv) and posterior (posterior cerebral artery, PCAv) cerebral circulations using transcranial Doppler ultrasound during LBNP stress (−50 mmHg) in three body positions (45°HUT, supine, 45°HDT). PETCO2 was measured continuously and maintained at constant levels during LBNP through coached breathing. Our main findings were that (a) steady-state tilt had no effect on CBV responses during LBNP in both the MCA (P = 0.077) and PCA (P = 0.583), and (b) despite controlling for PETCO2, both the MCAv and PCAv decreased by the same magnitude during LBNP in HUT (P = 0.348), supine (P = 0.694), and HDT (P = 0.407). Here, we demonstrate that there are no differences in anterior and posterior circulations in response to LBNP in different body positions

The Effects of Physical Activity on Arterial Stiffness during Pregnancy: An Observational Study

The objective of the present study was to investigate the relationship between moderate-to-vigorous physical activity (MVPA) and arterial stiffness in pregnancy. Thirty-nine women participated in this study resulting in 68 measurements in non-pregnant (NP; n=21), first (TM1; n=8), second (TM2; n=20), and third trimesters (TM3; n=19). Compliance, distensibility, elasticity, β-stiffness, and carotid to femoral (central) and carotid to finger (peripheral) pulse wave velocity (PWV) were assessed. MVPA was measured using accelerometry. Multilevel linear regressions adjusted for multiple tests per participant using random effects to generate β coefficients and 95% confidence intervals (CI) were performed. Distensibility, elasticity, β-stiffness, central- and peripheral-PWV did not differ between pregnant and non-pregnant assessments. Carotid artery compliance was higher in TM2 compared to NP. Central PWV (β Coef: -0.14, 95% CI: -0.27, -0.02) decreased from early to mid-pregnancy and increased in late pregnancy. Meeting the MVPA guidelines was significantly associated with central-PWV (Adj. β Coef: -0.34, 95% CI: -0.62, -0.06, p=0.016), peripheral-PWV (Adj. β Coef: -0.54, 95% CI: -0.91, -0.16, p=0.005), and distensibility (Adj. β Coef: -0.001, 95% CI: -0.002, -0.0001, p=0.018), in pregnancy. These results suggest that MVPA may be associated with improved (i.e. reduced) arterial stiffness in pregnancy. Novelty Bullets • Central PWV, distensibility, compliance, elasticity, and -stiffness, but not peripheral PWV, exhibited curvilinear relationships with gestational age • Central and peripheral PWV were lower in pregnant women who met the physical activity guidelines of 150 minutes of moderate-to-vigorous physical activity per weekThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Maternal cardioautonomic responses during and following exercise throughout pregnancy

Blood pressure regulation during pregnancy is poorly understood. Cardiovagal baroreflex gain (BRG) is an important contributor to blood pressure regulation via its influence on heart-rate. Heart-rate fluctuations occur in response to various physiological stimuli and can be measured using heart-rate variability (HRV). It is unclear how these mechanisms operate during pregnancy, particularly related to exercise. We examined BRG and HRV prior to, during, and following prenatal exercise. Forty-three pregnant (n=10 first trimester [TM1], n=17 second trimester [TM2]; n=16 third trimester [TM3]) and 20 non-pregnant (NP) women underwent an incremental peak exercise test. Beat-by-beat blood pressure (photoplethysmography) and heart-rate (lead II ECG) were measured throughout. BRG (slope of the relationship between fluctuations in systolic blood pressure and R-R interval) and HRV (root mean square of the successive differences; RMSSD) were assessed at rest, during steady-state exercise (EX), and during active recovery. BRG decreased with gestation and was lower in TM3 compared to NP (17.9±6.9 vs 24.8±7.4 ms/mmHg, p=0.017). BRG was reduced during EX in all groups. Resting HRV (RMSSD) also decreased with gestation and was lower in TM3 compared to NP (29±17 vs 48±20 ms, pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author