Steady-state cerebral blood flow regulation at altitude: interaction between oxygen and carbon dioxide.

High-altitude ascent imposes a unique cerebrovascular challenge due to two opposing blood gas chemostimuli. Specifically, hypoxia causes cerebral vasodilation, whereas respiratory-induced hypocapnia causes vasoconstriction. The conflicting nature of these two superimposed chemostimuli presents a challenge in quantifying cerebrovascular reactivity (CVR) in chronic hypoxia. During incremental ascent to 4240 m over 7 days in the Nepal Himalaya, we aimed to (a) characterize the relationship between arterial blood gas stimuli and anterior, posterior and global (g)CBF, (b) develop a novel index to quantify cerebral blood flow (CBF) in relation to conflicting steady-state chemostimuli, and (c) assess these relationships with cerebral oxygenation (rSO2). On rest days during ascent, participants underwent supine resting measures at 1045 m (baseline), 3440 m (day 3) and 4240 m (day 7). These measures included pressure of arterial (Pa)CO2, PaO2, arterial O2 saturation (SaO2; arterial blood draws), unilateral anterior, posterior and gCBF (duplex ultrasound; internal carotid artery [ICA] and vertebral artery [VA], gCBF [{ICA + VA} × 2], respectively) and rSO2 (near-infrared spectroscopy). We developed a novel stimulus index (SI), taking into account both chemostimuli (PaCO2/SaO2). Subsequently, CBF was indexed against the SI to assess steady-state cerebrovascular responsiveness (SS-CVR). When both competing chemostimuli are taken into account, (a) SS-CVR was significantly higher in ICA, VA and gCBF at 4240 m compared to lower altitudes, (b) delta SS-CVR with ascent (1045 m vs. 4240 m) was higher in ICA vs. VA, suggesting regional differences in CBF regulation, and (c) ICA SS-CVR was strongly and positively correlated (r = 0.79) with rSO2 at 4240 m.

Exercise for the prevention and treatment of low back, pelvic girdle and lumbopelvic pain during pregnancy: a systematic review and meta-analysis.

OBJECTIVE: The purpose of this review was to investigate the relationship between prenatal exercise, and low back (LBP), pelvic girdle (PGP) and lumbopelvic (LBPP) pain. 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 eligible (except case studies and reviews) if they were 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 outcome (prevalence and symptom severity of LBP, PGP and LBPP). RESULTS: The analyses included data from 32 studies (n=52 297 pregnant women). 'Very low' to 'moderate' quality evidence from 13 randomised controlled trials (RCTs) showed prenatal exercise did not reduce the odds of suffering from LBP, PGP and LBPP either in pregnancy or the postpartum period. However, 'very low' to 'moderate' quality evidence from 15 RCTs identified lower pain severity during pregnancy and the early postpartum period in women who exercised during pregnancy (standardised mean difference -1.03, 95% CI -1.58, -0.48) compared with those who did not exercise. These findings were supported by 'very low' quality evidence from other study designs. CONCLUSION: Compared with not exercising, prenatal exercise decreased the severity of LBP, PGP or LBPP during and following pregnancy but did not decrease the odds of any of these conditions at any time point.

Prenatal exercise is not associated with fetal mortality: a systematic review and meta-analysis.

OBJECTIVE: To perform a systematic review of the relationship between prenatal exercise and fetal or newborn death. 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 they were 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 outcome (miscarriage or perinatal mortality). RESULTS: Forty-six studies (n=2 66 778) were included. There was 'very low' quality evidence suggesting no increased odds of miscarriage (23 studies, n=7125 women; OR 0.88, 95% CI 0.63 to 1.21, I2=0%) or perinatal mortality (13 studies, n=6837 women, OR 0.86, 95% CI 0.49 to 1.52, I2=0%) in pregnant women who exercised compared with those who did not. Stratification by subgroups did not affect odds of miscarriage or perinatal mortality. The meta-regressions identified no associations between volume, intensity or frequency of exercise and fetal or newborn death. As the majority of included studies examined the impact of moderate intensity exercise to a maximum duration of 60 min, we cannot comment on the effect of longer periods of exercise. SUMMARY/CONCLUSIONS: Although the evidence in this field is of 'very low' quality, it suggests that prenatal exercise is not associated with increased odds of miscarriage or perinatal mortality. In plain terms, this suggests that generally speaking exercise is 'safe' with respect to miscarriage and perinatal mortality.

Effects of prenatal exercise on incidence of congenital anomalies and hyperthermia: a systematic review and meta-analysis.

OBJECTIVE: To investigate the relationships between exercise and incidence of congenital anomalies and hyperthermia. DESIGN: Systematic review with random-effects meta-analysis . DATA SOURCES: Online databases were searched from inception up to 6 January 2017. STUDY ELIGIBILITY CRITERIA: Studies of all designs were eligible (except case studies and reviews) if they were published in English, Spanish or French, and contained information on 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 [e.g., dietary; "exercise + co-intervention"]), comparator (no exercise or different frequency, intensity, duration, volume or type of exercise) and outcome (maternal temperature and fetal anomalies). RESULTS: This systematic review and meta-analysis included 'very low' quality evidence from 14 studies (n=78 735) reporting on prenatal exercise and the odds of congenital anomalies, and 'very low' to 'low' quality evidence from 15 studies (n=447) reporting on maternal temperature response to prenatal exercise. Prenatal exercise did not increase the odds of congenital anomalies (OR 1.23, 95% CI 0.77 to 1.95, I2=0%). A small but significant increase in maternal temperature was observed from pre-exercise to both during and immediately after exercise (during: 0.26°C, 95% CI 0.12 to 0.40, I2=70%; following: 0.24°C, 95% CI 0.17 to 0.31, I2=47%). SUMMARY/CONCLUSIONS: These data suggest that moderate-to-vigorous prenatal exercise does not induce hyperthermia or increase the odds of congenital anomalies. However, exercise responses were investigated in most studies after 12 weeks' gestation when the risk of de novo congenital anomalies is negligible.

Impact of prenatal exercise on maternal harms, labour and delivery outcomes: a systematic review and meta-analysis.

OBJECTIVE: To perform a systematic review of the relationships between prenatal exercise and maternal harms including labour/delivery outcomes. DESIGN: Systematic review with random effects meta-analysis and meta-regression. DATASOURCES: Online databases were searched up to 6 January 2017. STUDY ELIGIBILITY CRITERIA: Studies of all designs were included (except case studies) if they were 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), comparator (no exercise or different frequency, intensity, duration, volume and type of exercise, alone ["exercise-only"] or in combination with other intervention components [e.g., dietary; "exercise + co-intervention"]) and outcome (preterm/prelabour rupture of membranes, caesarean section, instrumental delivery, induction of labour, length of labour, vaginal tears, fatigue, injury, musculoskeletal trauma, maternal harms (author defined) and diastasis recti). RESULTS: 113 studies (n=52 858 women) were included. 'Moderate' quality evidence from exercise-only randomised controlled trials (RCTs) indicated a 24% reduction in the odds of instrumental delivery in women who exercised compared with women who did not (20 RCTs, n=3819; OR 0.76, 95% CI 0.63 to 0.92, I 2= 0 %). The remaining outcomes were not associated with exercise. Results from meta-regression did not identify a dose-response relationship between frequency, intensity, duration or volume of exercise and labour and delivery outcomes. SUMMARY/CONCLUSIONS: Prenatal exercise reduced the odds of instrumental delivery in the general obstetrical population. There was no relationship between prenatal exercise and preterm/prelabour rupture of membranes, caesarean section, induction of labour, length of labour, vaginal tears, fatigue, injury, musculoskeletal trauma, maternal harms and diastasis recti.

Effectiveness of exercise interventions in the prevention of excessive gestational weight gain and postpartum weight retention: a systematic review and meta-analysis.

OBJECTIVE: Gestational weight gain (GWG) has been identified as a critical modifier of maternal and fetal health. This systematic review and meta-analysis aimed to examine the relationship between prenatal exercise, GWG and postpartum weight retention (PPWR). DESIGN: Systematic review with random effects meta-analysis and meta-regression. Online databases were searched up to 6 January 2017. STUDY ELIGIBILITY CRITERIA: Studies of all designs in English, Spanish or French were eligible (except case studies and reviews) if they contained information on the population (pregnant women without contraindication to exercise), intervention (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 or type of exercise) and outcomes (GWG, excessive GWG (EGWG), inadequate GWG (IGWG) or PPWR). RESULTS: Eighty-four unique studies (n=21 530) were included. 'Low' to 'moderate' quality evidence from randomised controlled trials (RCTs) showed that exercise-only interventions decreased total GWG (n=5819; -0.9 kg, 95% CI -1.23 to -0.57 kg, I2=52%) and PPWR (n=420; -0.92 kg, 95% CI -1.84 to 0.00 kg, I2=0%) and reduced the odds of EGWG (n=3519; OR 0.68, 95% CI 0.57 to 0.80, I2=12%) compared with no exercise. 'High' quality evidence indicated higher odds of IGWG with prenatal exercise-only (n=1628; OR 1.32, 95% CI 1.04 to 1.67, I2=0%) compared with no exercise. CONCLUSIONS: Prenatal exercise reduced the odds of EGWG and PPWR but increased the risk of IGWG. However, the latter result should be interpreted with caution because it was based on a limited number of studies (five RCTs).

Prenatal exercise for the prevention of gestational diabetes mellitus and hypertensive disorders of pregnancy: a systematic review and meta-analysis.

OBJECTIVE: Gestational diabetes mellitus (GDM), gestational hypertension (GH) and pre-eclampsia (PE) are associated with short and long-term health issues for mother and child; prevention of these complications is critically important. This study aimed to perform a systematic review and meta-analysis of the relationships between prenatal exercise and GDM, GH and PE. 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 [e.g., dietary; "exercise + co-intervention"]), Comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and Outcomes (GDM, GH, PE). RESULTS: A total of 106 studies (n=273 182) were included. 'Moderate' to 'high'-quality evidence from randomised controlled trials revealed that exercise-only interventions, but not exercise+cointerventions, reduced odds of GDM (n=6934; OR 0.62, 95% CI 0.52 to 0.75), GH (n=5316; OR 0.61, 95% CI 0.43 to 0.85) and PE (n=3322; OR 0.59, 95% CI 0.37 to 0.9) compared with no exercise. To achieve at least a 25% reduction in the odds of developing GDM, PE and GH, pregnant women need to accumulate at least 600 MET-min/week of moderate-intensity exercise (eg, 140 min of brisk walking, water aerobics, stationary cycling or resistance training). SUMMARY/CONCLUSIONS: In conclusion, exercise-only interventions were effective at lowering the odds of developing GDM, GH and PE.

Glucose responses to acute and chronic exercise during pregnancy: a systematic review and meta-analysis.

OBJECTIVE: To perform a systematic review and meta-analysis to explore the relationship between prenatal exercise and glycaemic control. 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 and reviews) if they were 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 acute or chronic exercise, alone ('exercise-only') or in combination with other intervention components (eg, dietary; 'exercise+cointervention') at any stage of pregnancy), comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and outcome (glycaemic control). RESULTS: A total of 58 studies (n=8699) were included. There was 'very low' quality evidence showing that an acute bout of exercise was associated with a decrease in maternal blood glucose from before to during exercise (6 studies, n=123; mean difference (MD) -0.94 mmol/L, 95% CI -1.18 to -0.70, I2=41%) and following exercise (n=333; MD -0.57 mmol/L, 95% CI -0.72 to -0.41, I2=72%). Subgroup analysis showed that there were larger decreases in blood glucose following acute exercise in women with diabetes (n=26; MD -1.42, 95% CI -1.69 to -1.16, I2=8%) compared with those without diabetes (n=285; MD -0.46, 95% CI -0.60 to -0.32, I2=62%). Finally, chronic exercise-only interventions reduced fasting blood glucose compared with no exercise postintervention in women with diabetes (2 studies, n=70; MD -2.76, 95% CI -3.18 to -2.34, I2=52%; 'low' quality of evidence), but not in those without diabetes (9 studies, n=2174; MD -0.05, 95% CI -0.16 to 0.05, I2=79%). CONCLUSION: Acute and chronic prenatal exercise reduced maternal circulating blood glucose concentrations, with a larger effect in women with diabetes.

Impact of prenatal exercise on both prenatal and postnatal anxiety and depressive symptoms: a systematic review and meta-analysis.

OBJECTIVE: To examine the influence of prenatal exercise on depression and anxiety during pregnancy and the postpartum period. 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 they were 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), Comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and Outcome (prenatal or postnatal depression or anxiety). RESULTS: A total of 52 studies (n=131 406) were included. 'Moderate' quality evidence from randomised controlled trials (RCTs) revealed that exercise-only interventions, but not exercise+cointerventions, reduced the severity of prenatal depressive symptoms (13 RCTs, n=1076; standardised mean difference: -0.38, 95% CI -0.51 to -0.25, I2=10%) and the odds of prenatal depression by 67% (5 RCTs, n=683; OR: 0.33, 95% CI 0.21 to 0.53, I2=0%) compared with no exercise. Prenatal exercise did not alter the odds of postpartum depression or the severity of depressive symptoms, nor anxiety or anxiety symptoms during or following pregnancy. To achieve at least a moderate effect size in the reduction of the severity of prenatal depressive symptoms, pregnant women needed to accumulate at least 644 MET-min/week of exercise (eg, 150 min of moderate intensity exercise, such as brisk walking, water aerobics, stationary cycling, resistance training). SUMMARY/CONCLUSIONS: Prenatal exercise reduced the odds and severity of prenatal depression.

Impact of prenatal exercise on neonatal and childhood outcomes: a systematic review and meta-analysis.

OBJECTIVE: We aimed to identify the relationship between maternal prenatal exercise and birth complications, and neonatal and childhood morphometric, metabolic and developmental outcomes. 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 eligible (except case studies and reviews) if published in English, Spanish or French, and contained information on the relevant population (pregnant women without contraindication to exercise), intervention (subjective/objective measures of frequency, intensity, duration, volume or type of exercise, alone ('exercise-only') or in combination with other intervention components (eg, dietary; 'exercise+cointervention')), comparator (no exercise or different frequency, intensity, duration, volume, type or trimester of exercise) and outcomes (preterm birth, gestational age at delivery, birth weight, low birth weight (<2500 g), high birth weight (>4000 g), small for gestational age, large for gestational age, intrauterine growth restriction, neonatal hypoglycaemia, metabolic acidosis (cord blood pH, base excess), hyperbilirubinaemia, Apgar scores, neonatal intensive care unit admittance, shoulder dystocia, brachial plexus injury, neonatal body composition (per cent body fat, body weight, body mass index (BMI), ponderal index), childhood obesity (per cent body fat, body weight, BMI) and developmental milestones (including cognitive, psychosocial, motor skills)). RESULTS: A total of 135 studies (n=166 094) were included. There was 'high' quality evidence from exercise-only randomised controlled trials (RCTs) showing a 39% reduction in the odds of having a baby >4000 g (macrosomia: 15 RCTs, n=3670; OR 0.61, 95% CI 0.41 to 0.92) in women who exercised compared with women who did not exercise, without affecting the odds of growth-restricted, preterm or low birth weight babies. Prenatal exercise was not associated with the other neonatal or infant outcomes that were examined. CONCLUSIONS: Prenatal exercise is safe and beneficial for the fetus. Maternal exercise was associated with reduced odds of macrosomia (abnormally large babies) and was not associated with neonatal complications or adverse childhood outcomes.

Prenatal exercise (including but not limited to pelvic floor muscle training) and urinary incontinence during and following pregnancy: a systematic review and meta-analysis.

OBJECTIVE: To examine the relationships between prenatal physical activity and prenatal and postnatal urinary incontinence (UI). 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 they were 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 [e.g., dietary; "exercise + co-intervention"]), Comparator (no exercise or different frequency, intensity, duration, volume and type of exercise) and Outcome (prenatal or postnatal UI). RESULTS: 24 studies (n=15 982 women) were included. 'Low' to 'moderate' quality evidence revealed prenatal pelvic floor muscle training (PFMT) with or without aerobic exercise decreased the odds of UI in pregnancy (15 randomised controlled trials (RCTs), n=2764 women; OR 0.50, 95% CI 0.37 to 0.68, I2=60%) and in the postpartum period (10 RCTs, n=1682 women; OR 0.63, 95% CI 0.51, 0.79, I2=0%). When we analysed the data by whether women were continent or incontinent prior to the intervention, exercise was beneficial at preventing the development of UI in women with continence, but not effective in treating UI in women with incontinence. There was 'low' quality evidence that prenatal exercise had a moderate effect in the reduction of UI symptom severity during (five RCTs, standard mean difference (SMD) -0.54, 95% CI -0.88 to -0.20, I2=64%) and following pregnancy (three RCTs, 'moderate' quality evidence; SMD -0.54, 95% CI -0.87 to -0.22, I2=24%). CONCLUSION: Prenatal exercise including PFMT reduced the odds and symptom severity of prenatal and postnatal UI. This was the case for women who were continent before the intervention. Among women who were incontinent during pregnancy, exercise training was not therapeutic.

Blood Glucose During High Altitude Trekking in Young Healthy Adults.

Reid, Ly-Anh, Jordan L Rees, Miranda Kimber, Marina James, Graeme M Purdy, Megan Smorschok, Lauren E Maier, Normand G. Boulé, Trevor A. Day, Margie H. Davenport, and Craig D. Steinback. Blood glucose during high altitude trekking in young healthy adults. High Alt Med Biol. 00:00-00, 2024. Introduction: High altitude trekking is becoming more popular and accessible to an increased number of people. Simultaneously, there is a worldwide rise in the prevalence of metabolic diseases. The purpose of this study was to examine the impact of a gradual trekking ascent to high altitude on continuous glucose monitoring outcomes including fasting, mean 24-hour, postprandial, and post-75 g modified oral glucose tolerance test. This study also investigated the relationship between physical activity intensity, high altitude, and glucose concentrations. Methods: Individuals (n = 9) from Alberta, Canada participated in a 2-week trek in the Khumbu Valley in Nepal, ascending by foot from 2,860 m to 5,300 m (∼65 km) over 10 days. A standardized 75 g oral glucose load was given to participants at four different altitudes (1,130 m, 3,440 m, 3,820 m, 5,160 m). Physical activity (Actigraph accelerometry) and interstitial glucose (iPro2, Medtronic) were measured continuously during the trek. Results: Fasting and mean 24-hour glucose concentrations were not different between altitudes. However, 2-hour post dinner glucose and 2-hour post lunch glucose, AUC concentrations were different between altitudes. The relationship between physical activity intensity and glucose was not influenced by increasing altitudes. Conclusion: Our findings suggest that glucose regulation is largely preserved at high altitude; however, inconsistency in our postprandial glucose concentrations at altitude warrants further investigation.

Longitudinal study of cerebral blood flow regulation during exercise in pregnancy.

Cerebrovascular adaptation to pregnancy is poorly understood. We sought to assess cerebrovascular regulation in response to visual stimulation, hypercapnia and exercise across the three trimesters of pregnancy. Using transcranial Doppler (TCD) ultrasound, middle and posterior cerebral artery mean blood velocities (MCAvmean and PCAvmean) were measured continuously at rest and in response to (1) visual stimulation to assess neurovascular coupling (NVC); (2) a modified Duffin hyperoxic CO2 rebreathe test, and (3) an incremental cycling exercise test to volitional fatigue in non-pregnant (n = 26; NP) and pregnant women (first trimester [n = 13; TM1], second trimester [n = 21; TM2], and third trimester [n = 20; TM3]) in total 47 women. At rest, MCAvmean and PETCO2 were lower in TM2 compared to NP. PCAvmean was lower in TM2 but not TM1 or TM3 compared to NP. Cerebrovascular reactivity in MCAvmean and PCAvmean during the hypercapnic rebreathing test was not different between pregnant and non-pregnant women. MCAvmean continued to increase over the second half of the exercise test in TM2 and TM3, while it decreased in NP due to differences in ΔPETCO2 between groups. Pregnant women experienced a delayed decrease in MCAvmean in response to maximal exercise compared to non-pregnant controls which was explained by CO2 reactivity and PETCO2 level.

Spleen reactivity during incremental ascent to altitude.

The spleen contains a reservoir of red blood cells that are mobilized into circulation when under physiological stress. Despite the spleen having an established role in compensation to acute hypoxia, no previous work has assessed the role of the spleen during ascent to high altitude. Twelve participants completed 2 min of handgrip exercise at 30% of maximal voluntary contraction at 1,045, 3,440, and 4,240 m. In a subset of eight participants, an infusion of phenylephrine hydrochloride was administered at a dosage of 30 µg/l of predicted blood volume at each altitude. The spleen was imaged by ultrasound via a 2- to 5.5-MHz curvilinear probe. Spleen volume was calculated by the prolate ellipsoid formula. Finger capillary blood samples were taken to measure hematocrit. Spleen images and hematocrit were taken both before and at the end of both handgrip and phenylephrine infusion. No changes in resting spleen volume were observed between altitudes. At low altitude, the spleen contracted in response to handgrip [272.8 ml (SD 102.3) vs. 249.6 ml (SD 105.7), P = 0.009], leading to an increase in hematocrit (42.6% (SD 3.3) vs. 44.3% (SD 3.3), P = 0.023] but did not contract or increase hematocrit at the high-altitude locations. Infusion of phenylephrine led to spleen contraction at all altitudes, but only lead to an increase in hematocrit at low altitude. These data reveal that the human spleen may not contribute to acclimatization to chronic hypoxia, contrary to its response to acute sympathoexcitation. These results are explained by alterations in spleen reactivity to increased sympathetic activation at altitude. NEW & NOTEWORTHY The present study demonstrated that, despite the known role of the human spleen in increasing oxygen delivery to tissues during acute hypoxia scenarios, the spleen does not mobilize red blood cells during ascent to high altitude. Furthermore, the spleen's response to acute stressors at altitude depends on the nature of the stressor; the spleen's sensitivity to neurotransmitter is maintained, while its reflex response to stress is dampened.

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 through 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 with regard 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 nonpregnant (NP) women underwent an incremental peak exercise test. Beat-by-beat blood pressure (photoplethysmography) and heart rate (lead II electrocardiogram) were measured throughout. BRG (the slope of the relationship between fluctuations in systolic blood pressure and the 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 the TM3 group than in the NP group (17.9 ± 6.9 ms/mm Hg vs 24.8 ± 7.4 ms/mm Hg, p = 0.017). BRG was reduced during EX in all groups. Resting HRV (RMSSD) also decreased with gestation and was lower in the TM3 group than in the NP group (29 ± 17 ms vs 48 ± 20 ms, p < 0.001). RMSSD was blunted during EX in all groups compared with rest. During active recovery, RMSSD was further blunted compared with EX in the NP group but not during pregnancy (TM1, TM2, and TM3). Compared with the nonpregnant controls, the pregnant women had lower BRG and HRV at rest, but comparable cardioautonomic control during both exercise and active recovery following peak exercise.

Maternal Physical Activity Is Associated With Improved Blood Pressure Regulation During Late Pregnancy.

BACKGROUND: Cardiovagal baroreflex gain (cBRG) reflects an individual's ability to buffer swings in blood pressure. It is not well understood how this mechanism is influenced by physical activity in pregnancy. Because pregnant women tend to engage in low levels of moderate-to-vigorous physical activity (MVPA) and high levels of sedentary behaviour, we sought to determine the influence of MVPA and sedentary behaviour on cBRG and mean arterial pressure (MAP) in pregnancy. METHODS: Fifty-eight third trimester (31.9 ± 3.0 weeks) normotensive pregnant women (31.2 ± 2.8 years) were tested. Heart rate (electrocardiogram) and blood pressure (systolic blood pressure and MAP; finger photoplethysmography) were collected on a beat-by-beat basis, and averaged over 3 minutes of rest. Spontaneous cBRG was calculated as the slope of the relationship between fluctuations in systolic blood pressure and heart rate. Objective measures of MVPA and sedentary behaviour were collected over a 7-day period using an ActiGraph accelerometer (model wGTX3-BT; ActiGraph LLC, Pensacola, FL). RESULTS: Participants spent 67.5 ± 7.9% of waking hours engaged in sedentary behaviour, and performed 68.6 ± 91.9 minutes of MVPA per week. Sedentary behaviour was not related to cBRG (r = -0.035; P = 0.793) or MAP (r = -0.033; P = 0.803). However, MVPA was positively associated with cBRG (r = 0.315; P = 0.016), but not MAP (r = -0.115; P = 0.389). The association between MVPA and cBRG remained significant after controlling for age, pre-pregnancy body mass index, gestational age, and wear time (r = 0.338; P = 0.013), indicating that women who engaged in greater amounts of MVPA showed increased cBRG. CONCLUSIONS: Our data suggest that increased MVPA, but not necessarily reduced sedentary behaviour, might be beneficial for reflex control of blood pressure during pregnancy.

Addressing gaps in physician knowledge regarding transgender health and healthcare through medical education.

BACKGROUND: Transgender people (those people whose sex at birth does not "match" their felt gender identity) are a priority group for healthcare as they experience high rates of discrimination and related illnesses. Despite this, there is a trend of poor healthcare access for trans people due, in large part, to the denial of care on the part of physicians. A small body of literature is beginning to suggest that this denial of care may be due to a lack of physician knowledge as well as, in some cases, to transphobia. There is a dearth of research in Canada, however, exploring whether and/or how knowledge gaps create barriers to quality care, and whether medical education can attend to these gaps while and through addressing gender normativity. METHODS: To fill these gaps in the literature, we undertook a qualitative study with 30 trans identified people and 11 physicians (N=41) in Winnipeg, Manitoba. Methods included semi-structured individual interviews and focus groups. Data were transcribed and analyzed with NVivo qualitative data software using iterative methods. RESULTS: An overwhelming finding of this study was a lack of physician knowledge, as reported both by trans people and by physicians, that resulted in a denial of trans-specific care and also impacted general care. Transphobia was also identified as a barrier to quality care by both trans people and physicians. Physicians were open to learning more about trans health and healthcare. CONCLUSIONS: The findings suggest a pressing need for better medical education that exposes students to basic skills in trans health so that they can become competent in providing care to trans people. This learning must take place alongside anti-transphobia education. Based on these findings, we suggest key recommendations at the close of the paper for providing quality trans health curriculum in medical education.