The Impact of Exercise Training on Muscle Sympathetic Nerve Activity: A Systematic Review and Meta-Analysis.

The purpose of this systematic review and meta-analysis was to examine the effects of exercise training on muscle sympathetic nerve activity (MSNA) in humans. Studies included exercise interventions (randomized controlled trials [RCTs], non-randomized controlled trials [non-RCTs] or pre-to-post intervention) that reported on adults (>18 years) where MSNA was directly assessed using microneurography, and relevant outcomes were assessed (MSNA [total activity, burst frequency, burst incidence, amplitude], heart rate, blood pressure [systolic blood pressure, diastolic blood pressure, or mean blood pressure], and aerobic capacity [maximal or peak oxygen consumption]). 40 intervention studies (n=1,253 individuals) were included. RCTs of exercise compared to no exercise illustrated that those randomized to the exercise intervention had a significant reduction in MSNA burst frequency and incidence compared to controls. This reduction in burst frequency was not different between individuals with cardiovascular disease compared to those without. However, the reduction in burst incidence was greater in those with cardiovascular disease (9 RCTs studies, n = 234, MD -21.08 bursts/100 hbs; 95% CI -16.51, -25.66; I2 = 63%) compared to those without (6 RCTs, n = 192, MD -10.92 bursts/100 hbs; 95% CI -4.12, -17.73; I2 = 76%). Meta-regression analyses demonstrated a dose-response relationship where individuals with higher burst frequency and incidence pre-intervention had a greater reduction in values post-intervention. These findings suggest that exercise training reduces muscle sympathetic nerve activity, which may be valuable for improving cardiovascular health.

Impact of heavy resistance training on pregnancy and postpartum health outcomes.

INTRODUCTION AND HYPOTHESIS: Participation in Olympic weightlifting, the Valsalva maneuver, and acute or prolonged supine weightlifting during pregnancy are cautioned against; however, these recommendations are based on expert opinions as opposed to empirical evidence. The aim of this study was to examine the training and health outcomes of individuals who engaged in heavy resistance training during pregnancy. METHODS: A total of 679 individuals who lifted at least 80% one-repetition maximum during pregnancy participated in an online survey. RESULTS: Participants were primarily recreational athletes (88%, 332 out of 675) engaged in CrossFit™ (61%, 410 out of 675) and/or weightlifting (49%, 332 out of 675) during pregnancy. Most participants reported no complications during pregnancy or delivery (66%, 388 out of 589), whereas 57% (241 out of 426) reported urinary incontinence following pregnancy. Participants who maintained pre-pregnancy training levels until delivery reported significantly less reproductive complications than those who ceased training levels prior to delivery (p = 0.006). Most respondents engaged in Olympic lifting (72%, 311 out of 432) and lifting in a supine position (71%, 306 out of 437), whereas fewer reported use of the Valsalva maneuver during pregnancy (34%, 142 out of 412). Most returned to weightlifting following delivery (89%, 400 out of 447, average: 3.2 ± 3.0 months), including Olympic lifting (81%, 300 out of 372, average: 4.0 ± 3.4 months) and Valsalva (62%, 213 out of 341, average: 4.5 ± 3.6 months). CONCLUSIONS: Individuals who engaged in heavy prenatal resistance training had typical perinatal and pelvic floor health outcomes that were not altered whether they engaged in, or avoided Olympic lifting, Valsalva or supine weightlifting.

Health Outcomes after Pregnancy in Elite Athletes: A Systematic Review and Meta-analysis.

PURPOSE: This study aimed to evaluate postpartum maternal health and training outcomes of females who were competing or training as elite athletes before or during pregnancy. METHODS: Online databases were searched up to August 26, 2020. Studies of any design and language were eligible if they contained information on the relevant population (postpartum athletes [any period after pregnancy]), exposure (engaged in the highest level of sport immediately before or during pregnancy), comparators (sedentary/active controls), and outcomes: maternal (breastfeeding initiation and duration, postpartum weight retention or loss, bone mineral density, low back or pelvic girdle pain, incontinence [prevalence or severity of stress, urge or mixed urinary incontinence, fecal incontinence], injury, anemia, diastasis recti, breast pain, depression, anxiety) and training (<6 wk time to resume activity, training volume or intensity, performance level). RESULTS: Eleven studies (n = 482 females, including 372 elite athletes) were included. We identified "very low" certainty evidence demonstrating a higher rate of return to sport before 6 wk postpartum among elite athletes compared with nonelite athletes (n = 145, odds ratio = 6.93, 95% confidence interval = 2.73-17.63, I2 = 11). "Very low" certainty evidence from three studies (n = 179) indicated 14 elite athletes obtained injuries postpartum (7 stress fractures, 9 "running injuries"). "Very low" certainty evidence from five studies (n = 262) reported that 101 (40.5%) elite athletes experienced improved performance postpartum. CONCLUSION: Compared with controls, "very low" quality evidence suggests that elite athletes return to physical activity early in the postpartum period and may have an increased risk of injury. Additional high-quality evidence is needed to safely guide return to sport of elite athletes in the postpartum period.

Cardioautonomic control in healthy singleton and twin pregnancies.

In conjunction with significant cardiovascular adaptation, changes in cardioautonomic balance, specifically greater sympathetic activation and vagal withdrawal, are considered normal adaptations to healthy singleton pregnancy. Cardiovascular adaptation to twin pregnancy is more profound than that of singleton pregnancies; however, the changes in cardioautonomic control during multifetal gestation are unknown. To address this gap, beat-by-beat blood pressure (photoplethysmography) and heart rate (lead II electrocardiogram) were measured continuously in 25 twin pregnancies and 25 singleton pregnancies (matched for age, prepregnancy body mass index, and gestational age) during 10 min of rest. Data extracted from a 3- to 5-min period were used to analyze heart rate variability (HRV), blood pressure variability (BPV), cardiovagal baroreflex gain, and cardiac intervals as indicators of cardioautonomic control. Independent t tests were used to determine statistical differences between groups (α = 0.05), and the false rate discovery was determined to adjust for multiple comparisons. Resting heart rate was greater in twin compared with singleton pregnancies (91 ± 10 vs. 81 ± 10 beats/min; P = 0.001), but blood pressure was not different. Individuals with twin pregnancies had lower HRV, evidenced by lower standard deviation of R-R intervals (32 ± 11 vs. 47 ± 18 ms; P = 0.001), total power (1,035 ± 810 vs. 1,945 ± 1,570 ms2; P = 0.004), and high frequency power (224 ± 262 vs. 810 ± 806 ms2; P < 0.001) compared with singleton pregnancies. There were no differences in cardiac intervals, BPV, and cardiovagal baroreflex gain between groups. Our findings suggest that individuals with twin pregnancies have greater sympathetic and lower parasympathetic contributions to heart rate and that cardiac, but not vascular, autonomic control is impacted during twin compared with singleton pregnancy.NEW & NOTEWORTHY Individuals with healthy twin pregnancies had lower overall heart rate variability compared with those with singleton pregnancies at similar gestational ages. These results suggest a greater sympathetic and reduced parasympathetic contribution to cardiac control in twin pregnancies. Baseline heart rate was elevated, while arterial pressure and spontaneous cardiovagal baroreflex gain were not different between groups. This was result of the upward resetting of the cardiovagal baroreflex during healthy twin pregnancy, thus maintaining arterial pressure.

Knowledge translation and social media: Twitter data analysis of the 2019 Canadian Guideline for Physical Activity throughout Pregnancy.

OBJECTIVES: Despite extensive evidence demonstrating the benefits of prenatal physical activity (PA), inefficient knowledge translation may contribute to low rates of PA during pregnancy. This study aimed to examine the impact of the 2019 Canadian Guideline for Physical Activity throughout Pregnancy (hereafter Guideline) on knowledge transmission via Twitter. METHODS: Tweets containing keywords regarding prenatal PA were mined using the Twitter Application Programming Interface 1 month prior to (PRE), and 2 months following (POST-Month1 and Month2) Guideline release (October 18, 2018). The volume, user and location of Tweets relevant to prenatal PA were analyzed. RESULTS: In this 3-month period, 19,944 Tweets were collected. After randomization to select 10% of the sample, 1995 Tweets were analyzed. Tweets related to prenatal PA increased following Guideline release (PRE = 318/674 [45%]; POST-Month1 = 377/755 [50%]); however, this was not sustained into POST-Month2 (202/566 [36%]). The main users Tweeting about prenatal PA were categorized as 'General Population' (33%), whereas top users Tweeting about the Guideline were 'Academics' (25%), 'Exercise Specialists' (27%) and 'Medical Professionals' (20%). POST-Guideline, Tweets originated from users in 42 countries (PRE = 28). CONCLUSIONS: Twitter can be an effective tool for knowledge transmission of PA guidelines to a variety of end-users around the globe.

RéSUMé: OBJECTIFS: Malgré les nombreuses preuves démontrant les avantages de l'activité physique (AP) prénatale, l'application inefficace de ces connaissances pourrait contribuer aux faibles taux d'AP pendant la grossesse. Dans notre étude, nous avons examiné l'impact de l'édition 2019 des Directives canadiennes en matière d'activité physique pendant la grossesse (ci-après Directives) sur la transmission des connaissances via Twitter. MéTHODE: Les minimessages contenant des mots clés en lien avec l'AP prénatale ont été explorés à l'aide de l'interface de programmation de l'application Twitter un mois avant (PRÉ) et deux mois après (POST-Mois1 et POST-Mois2) la date de parution des Directives (le 18 octobre 2018). Le volume, les utilisateurs et utilisatrices et le lieu géographique des minimessages en lien avec l'AP prénatale ont été analysés. RéSULTATS: Au cours de cette période de trois mois, 19 944 minimessages ont été collectés. Après une sélection aléatoire de 10 % de l'échantillon, 1 995 mini messages ont été analysés. Les minimessages liés à l'AP prénatale ont augmenté après la parution des Directives (PRÉ = 318/674 [45 %]; POST-Mois1 = 377/755 [50 %]), mais cette augmentation ne s'est pas maintenue le deuxième mois suivant la parution (POST-Mois2 = 202/566 [36 %]). Les principaux utilisateurs et utilisatrices ayant publié des minimessages sur Twitter au sujet de l'AP prénatale étaient catégorisés comme faisant partie de la « population générale ¼ (33 %), mais les principaux utilisateurs et utilisatrices ayant publié des minimessages sur les Directives étaient des « universitaires ¼ (25 %), des « spécialistes de l'exercice ¼ (27 %) et des « professionnels de la santé ¼ (20 %). Après la parution des Directives (POST), les minimessages provenaient d'utilisateurs et d'utilisatrices situés dans 42 pays (PRÉ = 28). CONCLUSIONS: Twitter peut être un outil efficace de transmission des connaissances sur les directives en matière d'AP à un éventail d'utilisateurs et d'utilisatrices du monde entier.