Sex, gender and the pulmonary physiology of exercise

Biological Sex Differences in the Perception of CO2-Induced Air Hunger

INTRODUCTION

Biological sex may mediate 'dyspnoea' during submaximal exercise, but whether it mediates air hunger (AH), a highly unpleasant form of dyspnoea, remains unclear.

METHOD

Forty healthy adults (twenty females) completed 6-min of quiet breathing (rest) followed by a hyperoxic CO2 rebreathing task to evoke AH. AH intensity (AH-I) and unpleasantness (AH-U) were measured every 30-s. The Multidimensional Dyspnoea Profile (MDP) was administered after CO2 rebreathing.

RESULTS

Compared to males, AH-I and AH-U thresholds occurred at lower PETCO2 in females (AH-I: 44.15±2.81 vs 48.90±4.47mmHg, P < 0.001; AH-U: 43.86±2.57 vs 47.59±2.75mmHg, P < 0.001) and after a smaller increase in PETCO2 above resting PETCO2 (AH-I: 7.04±2.63 vs 10.08±5.28mmHg, P = 0.027; AH-U: 6.75±2.22 vs 8.77±2.99mmHg, P = 0.020). AH-I and AH-U were higher in females than males at standardised absolute V̇E of 25, 30 and 35L/min (P < 0.05). AH-U, but not AH-I, remained higher (main effect of sex, P = 0.026) in females than males at standardised relative V̇E of 20, 25, and 30% MVV. More females (n=9) than males (n=4) terminated CO2 rebreathing due to maximal AH perception (P = 0.001). Compared to males, females reported greater intensities of 'mental effort/concentration' (7±3 vs 4±3), 'tight/constricted lungs' (6±3 vs 2±2), and 'breathing work/effort' (6±2 vs 4±3) (all P < 0.05) on the MDP.

CONCLUSION

Our findings suggest that sex differences exist in the perception of AH, which are not entirely accounted for by sex differences in ventilatory capacity.

Diaphragm blood flow: new avenues for human translation

The rhythmic contraction of the diaphragm facilitates continuous pulmonary ventilation essential for life. Adequate blood flow to the diaphragm is critical to continuously support contractile function, as an imbalance in nutritive supply and demand can lead to diaphragm insufficiency, patient morbidity, and mortality. Given oxygen supply to the diaphragm is key to its function, it is no surprise that more than 200 animal studies have investigated diaphragm blood flow ([Formula: see text]) regulation over the past century. This work has advanced our understanding of the diaphragm's circulatory control (i.e., regional blood flow heterogeneity and mechanical impediment) and response to a variety of conditions, including eupnea, exercise, hypoxia, hypercapnia, hemorrhage, mechanical ventilation, and pharmacological interventions. However, due to the relative inaccessibility of the diaphragm, few studies have been conducted in humans since [Formula: see text] measurements have historically required highly invasive and technically challenging techniques that are not conducive to routine use. Thus, our current understanding of [Formula: see text] is informed almost exclusively by animal work with conflicting findings, and its translation to humans is hindered by species-dependent variability in diaphragmatic structure and function. Novel approaches have been developed to quantify respiratory muscle blood flow in humans using minimally invasive techniques. More recently, contrast-enhanced ultrasound (CEUS) is a promising approach for quantifying [Formula: see text] in humans, independent from other respiratory muscles. Using novel approaches to quantify [Formula: see text] in humans, future research can aim to advance our understanding of [Formula: see text] in humans in health and disease, including exercise, sex-based comparisons, and critical care.

Sex differences in the physiological and perceptual responses to face masks during exercise

Despite consistent evidence that face masks (FMs) increase dyspnea during exercise, few studies have examined the sex differences in the physiological and perceptual responses to FMs. In a randomized, crossover design, 32 healthy individuals (16 females; 23 ± 3 yr) completed incremental cycling tests on two visits with either no mask or a surgical FM. Dyspnea intensity and unpleasantness were assessed using the 0-10 category-ratio Borg scale. Diaphragmatic electromyography, esophageal pressure (Peso), and transdiaphragmatic pressure (Pdi) were measured using a nasogastric catheter to estimate neural inspiratory drive and respiratory muscle effort. Surface electromyography (EMG) was measured on the sternocleidomastoid and scalene muscles. FMs resulted in a steeper increase in dyspnea unpleasantness in males compared with females across the 0%-100% work rate (estimate = 1.5 CR10, P = 0.0048), with no significant difference in the effect of the FM on dyspnea intensity between sexes (P > 0.05). Males had a greater increase in Peso and Pdi with FMs compared with females across work rate (-3.8 cmH2O, P = 0.0088; -4.7 cmH2O, P = 0.011, respectively) and a greater increase in sternocleidomastoid activation from 40%-60% work rate (WR) (all P < 0.05). In addition, moisture accumulation pre- versus postexercise (P = 0.01) was significantly greater in males compared with females. FMs resulted in a similar absolute reduction in exercise time in both sexes although it was only statistically significant in females (P = 0.006). This study highlights that males likely experience greater dyspnea unpleasantness with FMs due to higher flows and ventilations, which increase mask resistance and, combined with greater moisture accumulation, elevate respiratory muscle effort and accessory muscle activation. Nonetheless, the absolute impact on exercise duration appears similar between sexes.NEW & NOTEWORTHY During the coronavirus disease 2019 pandemic, numerous studies evaluated the effects of face masks on the physiological and perceptual responses to exercise. However, the symptoms of breathlessness and associated physiological mechanisms were largely neglected. In addition, our understanding of whether face masks affected males and females differently was particularly limited. We found that sex-specific physiological responses can guide exercise and face mask strategies to improve comfort and performance for individuals engaging in prolonged, intense workouts.

The age and gender-dependent changes in pulmonary arterial flow distribution: A cardiac magnetic resonance flow study

OBJECTIVE

To investigate whether the pulmonary artery blood flow distribution in the normal population changes depending on age and gender using the Cardiac Magnetic Resonance Phase Contrast Imaging method.

MATERIALS AND METHODS

A total of 62 healthy volunteers aged 20-60 years were included in the study between September 2020 and November 2021. Participants were first divided into two groups according to their age (group 120-40 years old, group 2: 40-60 years old). Then, each group was divided into two according to gender (groups 1A, 1B and groups 2A, 2B). After routine MR sequences of mediastinum and heart (True Fast Imaging with Steady State Free Precession, short axis for heart (SA), 4-chamber, 2-chamber and 3-chamber CINE sequence). Phase Contrast imaging was performed to Main Pulmonary Artery (MPA), right PA and left PA. On the phase contrast (PC) images obtained, flow velocity, forward flow, backward flow and net forward flow volume and gradient were calculated for each artery. With these data, the distribution ratio for both pulmonary arteries was calculated. Measurements were made simultaneously by two radiologists.

RESULTS

In phase contrast sequence evaluation; No statistically significant correlation was found between RPA/LPA distribution ratio and Group 1 (p > 0.05). A moderate and positive correlation was found statistically between RPA/LPA distribution ratio and Group 2 (r:0.42, p:0.04). No statistically significant correlation was found between the RPA/LPA distribution ratio and the gender variable (p:0.59).

CONCLUSION

The distribution ratio of pulmonary blood flow to both lungs in healthy volunteers can be measured using PC-CMR without the need for invasive procedures. Knowing the normal distribution ratios according to age in the population can be used for the early diagnosis of pathological conditions.

Association between body roundness index and weight-adjusted waist index with asthma prevalence among US adults: the NHANES cross-sectional study, 2005-2018

This study investigated the connection between asthma in US individuals and their body roundness index (BRI) and weight-adjusted waist index (WWI). According to data from the 2005-2018 National Health and Nutrition Examination Survey (NHANES), 3609 of the 25,578 persons in the survey who were 18 years of age or older reported having asthma. After adjusting for all confounders, the probability of asthma prevalence increased by 8% for every unit rise in BRI (OR = 1.08, 95% CI 1.06,1.11). The probability of asthma prevalence increased by 16% for every unit rise in WWI (OR = 1.16, 95% CI 1.08,1.25). The BRI and WWI indices were associated with prevalence and were nonlinearly correlated. The inflection points for threshold saturation effects were 4.36 and 10.69, respectively (log-likelihood ratio test, P < 0.05). Relationship subgroup analyses showed that the positive associations between BRI and WWI and asthma were generalized across populations and there was no significant interaction in most subgroups. In addition, sensitivity analyses verified the robustness of these results, further confirming the conclusion of BRI and WWI as independent risk factors for asthma. Finally, receiver operating characteristic (ROC) analysis showed that BRI outperformed WWI in predicting asthma, suggesting the potential of BRI in early asthma screening. Overall, BRI and WWI are independent risk factors for asthma with important clinical applications.

Bolstering the Prognostic Utility of Coronary Risk Assessments with PAI: A Physical Activity Metric

PURPOSE

Personal activity intelligence (PAI) translates heart rate during physical activity (PA) into a weekly score, which credits vigorous over low- and moderate-intensity PA. We prospectively investigated the association between PAI and fatal and nonfatal coronary heart disease (CHD) in self-reported healthy participants from Norway, with specific reference to improving the accuracy of conventional coronary risk assessment.

METHODS

We studied 40,961 healthy adults (56% women) from the population-based Trøndelag Health Study (the HUNT study). Individual data were linked to hospital and cause of death registries. The weekly PAI score of each participant was divided into four groups (PAI scores of 0, ≤50, 51-99, or ≥100). Adjusted hazard ratios and 95% confidence intervals for fatal and nonfatal CHD related to PAI were estimated using Cox proportional hazard regression analyses.

RESULTS

During a median follow-up period of 13.1 yr (interquartile range, 12.7-13.6), 3303 (3109 nonfatal, 194 fatal) CHD events occurred. Compared with the inactive group (0 PAI), weekly PAI scores at baseline of 51-99 and ≥100 were associated with a lower risk of CHD [0.80 (0.71-0.91) and 0.86 (0.78-0.95), respectively]. By adding PAI to traditional risk factors, the net reclassification improvement of CHD was 0.472 ( P < 0.001).

CONCLUSIONS

PAI was inversely associated with CHD risk among healthy participants at baseline, and its cardioprotective effect persisted across diverse risk factor profiles. A PAI score >50 was substantially associated with a reduced risk of CHD. These findings have implications for improving the accuracy of conventional coronary risk assessments with PAI.

Assessment of Neural Respiratory Drive Using Surface Electromyography Parameters of Parasternal Muscles in Three Different Body Positions Among Healthy Young Adults: A Cross-Sectional Study

OBJECTIVES

The neural respiratory drive (NRD) is a critical determinant of breathlessness, influenced by the balance between ventilatory load and respiratory muscle capacity. This study aimed to evaluate the impact of body positions on NRD in young healthy adults (18-50 years) and to identify the optimal position for assessing NRD among the healthy subjects.

METHODS

Surface electromyography (sEMG) data from the 2nd intercostal space parasternal muscle was collected in supine, sitting, and standing positions among young healthy adults. NRD parameters, including EMG Para max% and Neural Respiratory Drive Index (NRDI), were analysed and compared among positions using ANOVA.

RESULTS

Significant differences in NRD values were observed across body positions, with standing vs. supine vs. sitting yielding higher values in both sexes respectively (Males: 5.113±0.437, 4.404±0.576, 4.913±0.623; P<0.001 and Females: 7.444±0.416, 6.435±0.266, 6.748±0.390; P<0.001). Post hoc analysis reveals significant difference in standing vs supine vs sitting position. These findings highlight the influence of body position on NRD measurements.

CONCLUSIONS

The study emphasizes the importance of considering body position when evaluating NRD in healthy individuals. These factors should also be taken into account in clinical assessments to ensure accurate interpretation of NRD and related respiratory functions.

Sex differences in anaerobic performance in CrossFit® athletes: a comparison of three different all-out tests

Background

Athletic performance can be influenced by various factors, including those related to biological sex. Various scientific disciplines have studied the observed differences in athletic performance between men and women. Moreover, anaerobic performance refers to the capacity of the human body to generate energy quickly and efficiently during high-intensity and short-duration activities. It is associated with the ability to perform explosive actions and the capacity for rapid recovery between repeated efforts. Anaerobic performance is a determining factor for performance in high-intensity sports and those with predominantly lower intensity but intermittent peaks of higher intensity. One high-intensity sport that has experienced exponential growth and attracts increasing numbers of participants yearly is commercially known as CrossFit® (CF). Therefore, the primary purpose of this study was to determine the anaerobic performance differences between sexes in CF athletes in terms of absolute and relative values.

Methods

A cross-sectional study was conducted over 2 weeks. Fifty CrossFit® athletes (25 men and 25 women) voluntarily participated in the study. They were subjected to body composition analysis and three maximal effort tests to measure anaerobic performance: a cycle ergometer test, a continuous jump test and a squat test.

Results

Significant differences were found in all the variables of absolute peak power and relative to body mass in the three tests. In values adjusted to lean and muscle mass, significant differences were only found in the cycle ergometer test but not in the other two. In mean power variables, significant differences were found in all the variables studied, except for the mean power adjusted to muscle mass in the squat test. In conclusion, this study's results indicate that differences between sexes in absolute and relative peak powers measured in all tests evaluated are explained by the amount of lean and muscle mass. However, mean powers show significant differences in all variables except for the one related to muscle mass in the squat test.

Normative values for lung, bronchial sizes, and bronchus-artery ratios in chest CT scans: from infancy into young adulthood

OBJECTIVE

To estimate the developmental trends of quantitative parameters obtained from chest computed tomography (CT) and to provide normative values on dimensions of bronchi and arteries, as well as bronchus-artery (BA) ratios from preschool age to young adulthood.

MATERIALS AND METHODS

Two independent radiologists screened a dataset of 1160 chest CT scans, initially reported as normal, from participants aged 0 to 24 years. Using an automated deep learning-based algorithm, we computed the following bronchus and artery parameters: bronchial outer diameter (Bout), bronchial inner diameter (Bin), adjacent pulmonary artery diameter (A), bronchial wall thickness (Bwt), bronchial wall area (BWA), and bronchial outer area (BOA). From these parameters, we computed the following ratios: Bout/A, Bin/A, Bwt/A, Bwt/Bout, and BWA/BOA. Furthermore, mean lung density, total lung volume, and the square root of wall area of bronchi with a 10-mm lumen perimeter (Pi10) were obtained. The effects on CT parameters of age, sex, and iodine contrast were investigated using mixed-effects or regression model analyses.

RESULTS

375 normal inspiratory chest CT scans (females / males = 156 / 219; mean age [SD] 12.7 [5.0] years) met the inclusion criteria. Bout and Bin progressively increased with age (all p < 0.05), but Bwt, Bout/A, Bin/A, Bwt/A, Bwt/Bout, or BWA/BOA did not. Total lung volume and mean lung density continuously increased with age (both p < 0.001), while Pi10 did not exhibit such a trend. Bout, total lung volume, and mean lung density were the only parameters that differed between males and females, all higher in males than females (all p < 0.03). The presence of iodinated contrast led to greater values for Bwt, Bwt/Bout, and BWA/BOA, but lower values for Bin, Bout/A, Bin/A, and Bwt/A (all p < 0.01).

CONCLUSION

Quantitative CT parameters of both lung parenchyma and bronchi exhibit growth-related changes, but from 6 to 24 years ratios between bronchus and artery dimensions remain constant. Contrast-enhanced CT scans affect the assessment of lung parenchyma and bronchial size. We propose age and technique-dependent normative values for bronchial dimensions and wall thickness.

KEY POINTS

Question What are the developmental trends of quantitative lung CT parameters in patients from childhood into young adulthood? Findings The ratio between bronchus and pulmonary artery dimensions demonstrates consistent values across age groups, indicating synchronized growth between bronchi and paired pulmonary arteries. Clinical relevance Our findings highlight the importance of standardized CT protocol and volume acquisition, and emphasize the need for ongoing collection of normal chest CT scans to refine the proposed reference values.

The impact of diurnal temperature range on the risk of hospitalizations in a low-income setting: the case of the Central Coast of Vietnam

The study aims to evaluate the effects of diurnal temperature range (DTR) on all causes, cardiovascular and respiratory conditions in the Central Coast of Vietnam, a tropical, low-income region with high DTR exposure but limited research. Daily hospital admission data from the largest hospitals in three provinces were analyzed alongside meteorological data. A time-series analysis using a generalized linear distributed lag model was conducted to examine the non-linear DTR-hospitalization association. A random-effect meta-analysis using restricted maximum likelihood was performed to calculate the pooled effects across three provinces. Stratified analyses by gender, age, season and natural disaster occurrence were conducted to identify vulnerable subpopulations. The multi-province pooled effects indicated that a 1 °C increase in DTR raised the risk of hospitalizations for all causes and respiratory diseases by 1.5% [1.2-1.8%] and 0.5% [0.0-1.0%], at lag 0-6 days. The effects of DTR on cardiovascular diseases, as well as those stratified by subgroups, were not statistically significant. Additionally, DTR had a greater adverse effect during the dry season and in the presence of natural disaster. Females and the elderly were slightly more susceptible to respiratory admissions, while males and younger individuals had a higher risk of all-cause admissions due to greater DTR effects. DTR was an independent risk factor for the exacerbation of all and specific causes, particularly among the susceptible subgroups. The findings suggested that it is necessary to take preventive measures to protect these at-risk populations from the adverse effects of extreme DTR exposure.

Physiological effects of high-flow nasal cannula during sustained high-intensity exercise in healthy volunteers: a randomised crossover trial

Introduction

High-flow nasal cannula (HFNC) has increased exercise capacity in patients with chronic respiratory diseases. However, it remains unknown whether HFNC impacts respiratory physiological variables during exercise. This study aimed to evaluate the effect of HFNC on respiratory physiological variables during sustained high-intensity exercise in healthy volunteers.

Methods

We performed a single-centre, open-label, randomised crossover trial to compare HFNC (60 L·min-1) and Sham-HFNC (2 L·min-1) interventions during a constant work rate exercise (CWRET) through randomised order. The primary outcome was change in oesophageal pressure (ΔP oes), and the secondary outcomes were other variables of inspiratory effort, ventilation distribution, ventilatory variables and clinical assessment. We evaluated volunteers at seven time points (baseline=T0; CWRET=T1-T2-T3 (1, 4 and 6 min); cooldown period=T4-T5-T6 (1, 6 and 10 min)) in both interventions.

Results

14 healthy volunteers (50% women; age: 22 (21-27) years) were enrolled. Mean differences in ΔP oes decreased to favour the HFNC intervention compared to Sham-HFNC at T2 (-2.8 cmH2O; 95% CI -5.3 to -0.3), as well as the simplified oesophageal pressure-time product (sPTP) per minute at T2 (-86.1 cmH2O·s·min-1; 95% CI -146.2 to -26.1) and T3 (-79.9 cmH2O·s·min-1; 95% CI -142.3 to -17.6). The standard deviation of the Regional Ventilation Delay index was also lower with HFNC compared to Sham-HFNC (T1: -1.38; 95% CI -1.93 to -0.83; T2: -0.71; 95% CI -1.27 to -0.16). There was decreased dyspnoea to favour the HFNC, but sPTP per breath, spatial distribution ventilation indexes, ventilatory variables and clinical assessments were nonsignificant between interventions.

Conclusion

HFNC intervention reduces respiratory effort and dyspnoea and improves temporal ventilation distribution in healthy volunteers during CWRET.

Effects of sitting position on ventilation distribution determined by electrical impedance tomography in ventilated ARDS patients

OBJECTIVE

The study aimed to evaluate the improvements in pulmonary ventilation following a sitting position in ventilated ARDS patients using electrical impedance tomography.

METHODOLOGY

A total of 17 patients with ARDS under mechanical ventilation participated in this study, including 8 with moderate ARDS and 9 with severe ARDS. Each patient was initially placed in the supine position (S1), transitioned to sitting position (SP) for 30 min, and then returned to the supine position (S2). Patients were monitored for each period, with parameters recorded.

MAIN OUTCOME MEASURES

The primary outcome included the spatial distribution parameters of EIT, regional of interest (ROI), end-expiratory lung impedance (ΔEELI), and parameters of respiratory mechanics.

RESULTS

Compared to S1, the SP significantly altered the distribution in ROI1 (11.29 ± 4.70 vs 14.88 ± 5.00 %, p = 0.003) and ROI2 (35.59 ± 8.99 vs 44.65 ± 6.97 %, p ＜ 0.001), showing reductions, while ROI3 (39.71 ± 11.49 vs 33.06 ± 6.34 %, p = 0.009), ROI4 (13.35 ± 8.76 vs 7.24 ± 5.23 %, p ＜ 0.001), along with peak inspiratory pressure (29.24 ± 3.96 vs 27.71 ± 4.00 cmH2O, p = 0.036), showed increases. ΔEELI decreased significantly ventrally (168.3 (40.33 - 189.5), p ＜ 0.0001) and increased significantly dorsally (461.7 (297.5 - 683.7), p ＜ 0.0001). The PaO2/FiO2 ratio saw significant improvement in S2 compared to S1 after 30 min in the seated position (108 (73 - 130) vs 96 (57 - 129) mmHg, p = 0.03).

CONCLUSIONS

The sitting position is associated with enhanced compliance, improved oxygenation, and more homogenous ventilation in patients with ventilated ARDS compared to the supine position.

IMPLICATIONS FOR CLINICAL PRACTICE

It is important to know the impact of postural changes on patient pulmonary ventilation in order to standardize safe practices in critically ill patients. It may be helpful in the management among ventilated patients.

Study of Physiological Adaptations in Vertical Kilometer Runners: Focus on Cardiorespiratory and Local Muscle Demands

Background: Research into key performance factors in trail running, particularly in vertical kilometer (VK) races, is crucial for effective training and periodization. However, recent studies on metabolic and cardiorespiratory responses during VK races, especially using field tests, are limited. Objectives: Therefore, the aim of this study is to evaluate the metabolic and cardiorespiratory responses during a VK field test, identifying differences based on sex and performance level, as well as key performance factors and their deterioration due to fatigue. Fifteen trained trail runners (ten males and five females, 19 to 38 years old) perform a VK race. Methods: The global physiological response is evaluated using the portable gas analyzer Cosmed K5 and the local response using near-infrared spectroscopy technology. Results: In gender comparisons, the ANCOVA test shows significant differences (p < 0.05) in the ventilation, tidal volume, expiratory time-to-inspiratory time ratio, inspiratory flow rate, end-tidal CO2 partial pressure, heart rate, oxygen pulse, and total hemoglobin. Additionally, the performance comparison reveals significant differences in the variables' velocity, oxygen consumption, carbon dioxide production, ventilation, dead space-to-tidal volume ratio, total time of the breathing cycle, expiratory time-to-inspiratory time ratio, inspiratory duty cycle, expiratory fractions of CO2, quadriceps saturation index, and VE/VCO2 ratio. Finally, the correlation analysis shows oxygen consumption (r = -0.80 mean; r = -0.72 peak), carbon dioxide production (r = -0.91 mean; r = -0.75 peak), expiratory time-to-inspiratory time ratio (r = 0.68 peak), ventilation (r = -0.58 mean), and quadriceps saturation index (r = 0.54 mean; r = -0.76 coefficient of variation) as the key performance factors in the VK race. Conclusions: Overall, the physiological analysis indicates the importance of local muscular adaptations and respiratory system capacity in this type of short-duration race.

Mediated relationship between Vitamin D deficiency and reduced pulmonary function by copper in Taiwanese young adults

BACKGROUND

Vitamin D deficiency is prevalent worldwide and associated with worse outcomes in various lung diseases. This study examines the association between vitamin D deficiency and pulmonary function in healthy young adults.

METHODS

This prospective cohort study (2017-2019) explored the impact of vitamin D deficiency on pulmonary function in a community-based young adult population. Pulmonary function was assessed via spirometry, with serum 25-hydroxyvitamin D [25(OH)D] and urinary copper levels quantified. Multivariate regression was used to estimate the relationship between vitamin D levels and lung function, with mediation analysis evaluating copper's role.

RESULTS

The study included 1034 participants, average age 33.45 years, 41.93 % male. The median 25(OH)D level was 19.20 ng/mL (Interquartile Range: 13.48-24.90 ng/mL). Over half (54.74 %) had 25(OH)D levels below 20 ng/mL. Higher 25(OH)D levels were associated with better forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁). Trends suggested subgroup differences, but these were not statistically significant, indicating a consistent effect of 25(OH)D on pulmonary function across groups. SEM analysis suggested urinary copper as a mediator between 25(OH)D levels and FVC.

CONCLUSION

Vitamin D deficiency is significantly associated with reduced pulmonary function in young adults in Taiwan.

Diaphragm Assessment by Multimodal Ultrasound Imaging in Healthy Subjects

Background

In recent years, diaphragm ultrasound (DUS) has been used to identify diaphragm dysfunction in the intensive care unit (ICU). However, there are few studies on DUS parameters to evaluate function, normal ranges, and influencing factors in population. The aim of this study is to provide a methodological reference for clinical evaluation of diaphragm function by measuring different DUS parameters in a healthy population.

Methods

A descriptive study was conducted 212 (105 males, 107 females) subjects with normal spirometry underwent ultrasound imaging in this study. The diaphragm contraction and motion related parameters and shear wave velocity (SWV) were measured in the supine position. The effects of gender, age, body mass index (BMI) and lifestyle on diaphragm ultrasound parameters were analyzed.

Results

The diaphragm thickness at end-expiration (DT-exp) was 0.14 ±0.05 cm, the diaphragm thickness at end- inspiration (DT-insp) was 0.29±0.10 cm, with thickening fraction (TF) was 1.11±0.54. The diaphragm excursion (DE) was 1.68±0.37cm and diaphragm velocity was 1.45±0.41 cm/s during calm breathing. During deep breathing, the DE was 5.06±1.40cm and diaphragm velocity was 3.20±1.18 cm/s. The Diaphragm shear modulus-longitudinal view were Mean16.72±4.07kPa, Max25.04±5.58kPa, Min11.06±3.88kPa, SD2.56±0.98. The results of diaphragmatic measurement showed that the DT of males was significantly greater than that of females (P< 0.05), but there was no significant difference in TF. The DT-insp (r=0.155, P= 0.024) and the DT-exp (r=0.252, P=0.000) were positively correlated with age, and the DE during calm breathing was negatively correlated with age (r=-0.218, P= 0.001) and BMI (r=-00.280, P= 0.000). The DE (R=0.371, P=0.000) and velocity (R=0.368, P=0.000) during deep breathing were correlated with lifestyle.

Conclusion

Our study provides normal reference values of the diaphragm and evaluates the influence of gender, age, body mass index and lifestyle on diaphragmatic morphology.

Sex- and age-adjusted reference values for dynamic inspiratory constraints during incremental cycle ergometry

Activity-related dyspnea in chronic lung disease is centrally related to dynamic (dyn) inspiratory constraints to tidal volume expansion. Lack of reference values for exertional inspiratory reserve (IR) has limited the yield of cardiopulmonary exercise testing in exposing the underpinnings of this disabling symptom. One hundred fifty apparently healthy subjects (82 males) aged 40-85 underwent incremental cycle ergometry. Based on exercise inspiratory capacity (ICdyn), we generated centile-based reference values for the following metrics of IR as a function of absolute ventilation: IRdyn1 ([1-(tidal volume/ICdyn)] x 100) and IRdyn2 ([1-(end-inspiratory lung volume/total lung capacity] x 100). IRdyn1 and IRdyn2 standards were typically lower in females and older subjects (p<0.05 for sex and age versus ventilation interactions). Low IRdyn1 and IRdyn2 significantly predicted the burden of exertional dyspnea in both sexes (p<0.01). Using these sex and age-adjusted limits of reference, the clinician can adequately judge the presence and severity of abnormally low inspiratory reserves in dyspneic subjects undergoing cardiopulmonary exercise testing.

Fitness Level- and Sex-Related Differences in Pulmonary Limitations to Maximal Exercise in Normoxia and Hypoxia

PURPOSE

Both maximal-intensity exercise and altitude exposure challenge the pulmonary system that may reach its maximal capacities. Expiratory flow limitation (EFL) and exercise-induced hypoxemia (EIH) are common in endurance-trained athletes. Furthermore, because of their smaller airways and lung size, women, independently of their fitness level, may be more prone to pulmonary limitations during maximal-intensity exercise, particularly when performed in hypoxic conditions. The objective of this study was to investigate the impact of sex and fitness level on pulmonary limitations during maximal exercise in normoxia and their consequences in acute hypoxia.

METHODS

Fifty-one participants were distributed across four different groups according to sex and fitness level. Participants visited the laboratory on three occasions to perform maximal incremental cycling tests in normoxia and hypoxia (inspired oxygen fraction = 0.14) and two hypoxic chemosensitivity tests. Pulmonary function and ventilatory capacities were evaluated at each visit.

RESULTS

EIH was more prevalent (62.5% vs 22.2%, P = 0.004) and EFL less common (37.5% vs 70.4%, P = 0.019) in women than men. EIH prevalence was different ( P = 0.004) between groups of trained men (41.7%), control men (6.7%), trained women (50.0%), and control women (75.0%). All EIH men but only 40% of EIH women exhibited EFL. EFL individuals had higher slope ratio ( P = 0.029), higher ventilation (V̇ E ) ( P < 0.001), larger ΔVO 2max ( P = 0.019), and lower hypoxia-related V̇ E increase ( P < 0.001).

CONCLUSIONS

Women reported a higher EIH prevalence than men, regardless of their fitness level, despite a lower EFL prevalence. EFL seems mainly due to the imbalance between ventilatory demands and capacities. It restricts ventilation, leading to a larger performance impairment during maximal exercise in hypoxic conditions.

Separation of ventilation and perfusion of electrical impedance tomography image streams using multi-dimensional ensemble empirical mode decomposition

Objective.In the future, thoracic electrical impedance tomography (EIT) monitoring may include continuous and simultaneous tracking of both breathing and heart activity. However, an effective way to decompose an EIT image stream into physiological processes as ventilation-related and cardiac-related signals is missing.Approach.This study analyses the potential ofMulti-dimensional Ensemble Empirical Mode Decompositionby application of theComplete Ensemble Empirical Mode Decomposition with Adaptive Noiseand a novel frequency-based combination criterion for detrending, denoising and source separation of EIT image streams, collected from nine healthy male test subjects with similar age and constitution.Main results.In this paper, a novel approach to estimate the lung, the heart and the perfused regions of an EIT image is proposed, which is based on theRoot Mean Square Errorbetween the index of maximal respiratory and cardiac variation to their surroundings. The summation of the indexes of the respective regions reveals physiologically meaningful time signals, separated into the physiological bandwidths of ventilation and heart activity at rest. Moreover, the respective regions were compared with the relative thorax movement and photoplethysmogram (PPG) signal. In linear regression analysis and in the Bland-Altman plot, the beat-to-beat time course of both the ventilation-related signal and the cardiac-related signal showed a high similarity with the respective reference signal.Significance.Analysis of the data reveals a fair separation of ventilatory and cardiac activity realizing the aimed source separation, with optional detrending and denoising. For all performed analyses, a feasible correlation of 0.587 to 0.905 was found between the cardiac-related signal and the PPG signal.

Recommendations for Women in Mountain Sports and Hypoxia Training/Conditioning

The (patho-)physiological responses to hypoxia are highly heterogeneous between individuals. In this review, we focused on the roles of sex differences, which emerge as important factors in the regulation of the body's reaction to hypoxia. Several aspects should be considered for future research on hypoxia-related sex differences, particularly altitude training and clinical applications of hypoxia, as these will affect the selection of the optimal dose regarding safety and efficiency. There are several implications, but there are no practical recommendations if/how women should behave differently from men to optimise the benefits or minimise the risks of these hypoxia-related practices. Here, we evaluate the scarce scientific evidence of distinct (patho)physiological responses and adaptations to high altitude/hypoxia, biomechanical/anatomical differences in uphill/downhill locomotion, which is highly relevant for exercising in mountainous environments, and potentially differential effects of altitude training in women. Based on these factors, we derive sex-specific recommendations for mountain sports and intermittent hypoxia conditioning: (1) Although higher vulnerabilities of women to acute mountain sickness have not been unambiguously shown, sex-dependent physiological reactions to hypoxia may contribute to an increased acute mountain sickness vulnerability in some women. Adequate acclimatisation, slow ascent speed and/or preventive medication (e.g. acetazolamide) are solutions. (2) Targeted training of the respiratory musculature could be a valuable preparation for altitude training in women. (3) Sex hormones influence hypoxia responses and hormonal-cycle and/or menstrual-cycle phases therefore may be factors in acclimatisation to altitude and efficiency of altitude training. As many of the recommendations or observations of the present work remain partly speculative, we join previous calls for further quality research on female athletes in sports to be extended to the field of altitude and hypoxia.

Hemorheological, cardiorespiratory, and cerebrovascular effects of pentoxifylline following acclimatization to 3,800 m

Pentoxifylline is a nonselective phosphodiesterase inhibitor used for the treatment of peripheral artery disease. Pentoxifylline acts through cyclic adenosine monophosphate, thereby enhancing red blood cell deformability, causing vasodilation and decreasing inflammation, and potentially stimulating ventilation. We conducted a double-blind, placebo-controlled, crossover, counter-balanced study to test the hypothesis that pentoxifylline could lower blood viscosity, enhance cerebral blood flow, and decrease pulmonary artery pressure in lowlanders following 11-14 days at 3,800 m. Participants (6 males/10 females; age, 27 ± 4 yr old) received either a placebo or 400 mg of pentoxifylline orally the night before and again 2 h before testing. We assessed arterial blood gases, venous hemorheology (blood viscosity, red blood cell deformability, and aggregation), and inflammation (TNF-α) in room air (end-tidal oxygen partial pressure, ∼52 mmHg). Global cerebral blood flow (gCBF), ventilation, and pulmonary artery systolic pressure (PASP) were measured in room air and again after 8-10 min of isocapnic hypoxia (end-tidal oxygen partial pressure, 40 mmHg). Pentoxifylline did not alter arterial blood gases, TNF-α, or hemorheology compared with placebo. Pentoxifylline did not affect gCBF or ventilation during room air or isocapnic hypoxia compared with placebo. However, in females, PASP was reduced with pentoxifylline during room air (placebo, 19 ± 3; pentoxifylline, 16 ± 3 mmHg; P = 0.021) and isocapnic hypoxia (placebo, 22 ± 5; pentoxifylline, 20 ± 4 mmHg; P = 0.029), but not in males. Acute pentoxifylline administration in lowlanders at 3,800 m had no impact on arterial blood gases, hemorheology, inflammation, gCBF, or ventilation. Unexpectedly, however, pentoxifylline reduced PASP in female participants, indicating a potential effect of sex on the pulmonary vascular responses to pentoxifylline.NEW & NOTEWORTHY We conducted a double-blind, placebo-controlled study on the rheological, cardiorespiratory and cerebrovascular effects of acute pentoxifylline in healthy lowlanders after 11-14 days at 3,800 m. Although red blood cell deformability was reduced and blood viscosity increased compared with low altitude, acute pentoxifylline administration had no impact on arterial blood gases, hemorheology, inflammation, cerebral blood flow, or ventilation. Pentoxifylline decreased pulmonary artery systolic pressure in female, but not male, participants.

Sex Differences in Association of Physical Activity With All-Cause and Cardiovascular Mortality

BACKGROUND

Although physical activity is widely recommended for reducing cardiovascular and all-cause mortality risks, female individuals consistently lag behind male individuals in exercise engagement.

OBJECTIVES

The goal of this study was to evaluate whether physical activity derived health benefits may differ by sex.

METHODS

In a prospective study of 412,413 U.S. adults (55% female, age 44 ± 17 years) who provided survey data on leisure-time physical activity, we examined sex-specific multivariable-adjusted associations of physical activity measures (frequency, duration, intensity, type) with all-cause and cardiovascular mortality from 1997 through 2019.

RESULTS

During 4,911,178 person-years of follow-up, there were 39,935 all-cause deaths including 11,670 cardiovascular deaths. Regular leisure-time physical activity compared with inactivity was associated with 24% (HR: 0.76; 95% CI: 0.73-0.80) and 15% (HR: 0.85; 95% CI: 0.82-0.89) lower risk of all-cause mortality in women and men, respectively (Wald F = 12.0, sex interaction P < 0.001). Men reached their maximal survival benefit of HR 0.81 from 300 min/wk of moderate-to-vigorous physical activity, whereas women achieved similar benefit at 140 min/wk and then continued to reach a maximum survival benefit of HR 0.76 also at ∼300 min/wk. Sex-specific findings were similar for cardiovascular death (Wald F = 20.1, sex interaction P < 0.001) and consistent across all measures of aerobic activity as well as muscle strengthening activity (Wald F = 6.7, sex interaction P = 0.009).

CONCLUSIONS

Women compared with men derived greater gains in all-cause and cardiovascular mortality risk reduction from equivalent doses of leisure-time physical activity. These findings could enhance efforts to close the "gender gap" by motivating especially women to engage in any regular leisure-time physical activity.

Dysanapsis is not associated with exertional dyspnoea in healthy male and female never-smokers aged 40 years and older

In healthy adults, airway-to-lung (i.e., dysanapsis) ratio is lower and dyspnoea during exercise at a given minute ventilation (V̇E) is higher in females than in males. We investigated the relationship between dysanapsis and sex on exertional dyspnoea in healthy adults. We hypothesized that females would have a smaller airway-to-lung ratio than males and that exertional dyspnoea would be associated with airway-to-lung ratio in males and females. We analyzed data from n = 100 healthy never-smokers aged ≥40 years enrolled in the Canadian Cohort Obstructive Lung Disease (CanCOLD) study who underwent pulmonary function testing, a chest computed tomography scan, and cardiopulmonary exercise testing. The luminal area of the trachea, right main bronchus, left main bronchus, right upper lobe, bronchus intermedius, left upper lobe, and left lower lobe were 22%-37% smaller (all p < 0.001) and the airway-to-lung ratio (i.e., average large conducting airway diameter relative to total lung capacity) was lower in females than in males (0.609 ± 0.070 vs. 0.674 ± 0.082; p < 0.001). During exercise, there was a significant effect of V̇E, sex, and their interaction on dyspnoea (all p < 0.05), indicating that dyspnoea increased as a function of V̇E to a greater extent in females than in males. However, after adjusting for age and total lung capacity, there were no significant associations between airway-to-lung ratio and measures of exertional dyspnoea, regardless of sex (all r < 0.34; all p > 0.05). Our findings suggest that sex differences in airway size do not contribute to sex differences in exertional dyspnoea.

Blood-pool MRI assessment of myocardial microvascular reactivity

Purpose

The ability to non-invasively image myocardial microvascular dilation and constriction is essential to assessing intact function and dysfunction. Yet, conventional measurements based on blood oxygenation are not specific to changes in blood volume. The purpose of this study was to extend to the heart a blood-pool MRI approach for assessing vasomodulation in the presence of blood gas changes and investigate if sex-related differences exist.

Methods

Animals [five male and five female healthy Sprague Dawley rats (200-500 g)] were intubated, ventilated, and cycled through room air (normoxia) and hypercapnia (10% CO2) in 10-minute cycles after i.v. injection of blood-pool agent Ablavar (0.3 mmol/kg). Pre-contrast T1 maps and T1-weighted 3D CINE were acquired on a 3 Tesla preclinical MRI scanner, followed by repeated 3D CINE every 5 min until the end of the gas regime. Invasive laser Doppler flowmetry of myocardial perfusion was performed to corroborate MRI results.

Results

Myocardial microvascular dilation to hypercapnia and constriction to normoxia were readily visualized on T1 maps. Over 10 min of hypercapnia, female myocardial T1 reduced by 20% (vasodilation), while no significant change was observed in the male myocardium. After return to normoxia, myocardial T1 increased (vasoconstriction) in both sexes (18% in females and 16% in males). Laser Doppler perfusion measurements confirmed vasomodulatory responses observed on MRI.

Conclusion

Blood-pool MRI is sensitive and specific to vasomodulation in the myocardial microcirculation. Sex-related differences exist in the healthy myocardium in response to mild hypercapnic stimuli.

Neuropeptide stimulation of physiological and immunological responses in precision-cut lung slices

Organotypic lung slices, sometimes known as precision-cut lung slices (PCLS), provide an environment in which numerous cell types and interactions can be maintained outside the body (ex vivo). PCLS were maintained ex vivo for up to a week and demonstrated health via the presence of neurons, maintenance of tissue morphology, synthesis of mucopolysaccharides, and minimal cell death. Multiple phenotypes of neuronal fibers were present in lung slices with varied size, caliber, and neurotransmitter immunoreactivity. Of the neuropeptides present in fibers, calcitonin gene-related peptide (CGRP) was the most prevalent. Exposing PCLS to recombinant CGRP resulted in the proliferation and dispersion of CD19+ B cells in slices taken selectively from females. The number of granules containing immunoreactive (ir) surfactant protein C (SPC), which are representative of alveolar type 2 cells, increased in slices from females within 24 h of exposure to CGRP. Additionally, ir-SPC granule size increased in slices from males and females across 48 h of exposure to CGRP. Exposure of PCLS to exogenous CGRP did not alter the number of solitary pulmonary neuroendocrine cells (PNEC) but did result in neuroendocrine bodies that had significantly more cells. Neuronal fiber numbers were unchanged based on ir-peripherin; however, ir-CGRP became non-detectable in fibers while unchanged in PNECs. The effects of exogenous CGRP provide insight into innate immune and neuroendocrine responses in the lungs that may be partially regulated by neural fibers. The sex-dependent nature of these changes may point to the basis for sex-selective outcomes among respiratory diseases.

Physiological responses to treadmill exercise in size- and fitness-matched male and female firefighter applicants

Physiological responses during a standardised treadmill test for structural firefighting employment were compared in 41 pairs of size-matched, male and female applicants. Applicants wore personal exercise clothing, running shoes, and fire protective ensemble with self-contained breathing apparatus (added mass 21.2 ± 1.0 kg). Applicants walked at 1.56 m·s-1, completing a 5-min warm-up, 8-min at 10% grade, and then, progressive 1-min stages to exhaustion. The cut-score required completion of 13-min of exercise. Up to the cut-score, no differences in heart rate, oxygen uptake or minute ventilation were detected between sexes. At time 12:30-13:00 min, V̇O2 was 45.7 ± 0.6 vs. 44.2 ± 0.5 mL·kg-1·min-1 (body mass) for males and females, respectively. Despite similar physiological responses at minute 13, females worked at higher fractions of peak than males (p < 0.05). A second analysis compared a subset of 27 fitness-matched (V̇O2peak) male-female pairs. Fitness-matching further reduced or eliminated most observed differences in physiological responses, except small differences in breathing pattern. Practitioner Summary: Physiological responses during a standardised treadmill test for firefighter applicants were investigated in male and female applicants matched on size and fitness. Absolute responses to exercise were the same for both sexes when size-matched, but relative intensity was higher for females. Fitness-matching reduced or eliminated most previously observed differences. Abbreviations: NFPA: National Fire Protection Association; V̇O2: rate of oxygen consumption; V̇O2peak: rate of oxygen consumption at peak exercise; PAR-Q+: Physical Activity Readiness Questionnaire Plus; SCBA: self-contained breathing apparatus; ANOVA: analysis of variance; V̇E: minute ventilation; V̇Epeak: minute ventilation at peak exercise; V̇E/V̇O2: ventilatory equivalent for oxygen.

Physiological association of the breakpoint with the duration of hyperventilation

OBJECTIVES

To determine the relationship of body mass index (BMI) with breath-holding time (BHT) as well as that of BHT with the duration of hyperventilation (DOH) in young healthy adults.

METHODS

An observational study was performed at Shalamar Medical and Dental College, Lahore, Pakistan, between May 2021 and June 2022. Healthy first-year Bachelor of Medicine, Bachelor of Surgery students aged 18-22 years, with a normal BMI were included. Spirometric measurements were taken through a spirometer pod connected to a pneumotachometer (model: Power Lab 26T). Body mass index was calculated as the weight (kg) to height (m2) ratio. Pearson correlation, linear regression, and t tests were applied using SPSS.

RESULTS

A total of 101 subjects participated, comprising of 44 men and 57 women. A weak negative association was found between BMI and BHT in all subjects (r= -0.08, p=0.34), in men (r= -0.24, p=0.11), and in women (r= -0.092, p=0.497). Furthermore, a strong association was observed between BHT and DOH in all subjects (r=0.64, p=0.000), in men (r=0.604, p=0.000), and in women (r=0.518, p=0.000). Moreover, a nonsignificant weak inverse linear regression was found between the BMI and BHT of all subjects (β= -0.087, p=0.38), of men (β= -0.241, p=0.11), and of women (β= -0.092, p=0.49). Lastly, a significantly strong positive regression was observed between the BHT and DOH of all subjects (β=0.637, p=0.000), of men (β=0.604, p=0.000), and of women (β=0.518, p=0.000).

CONCLUSION

No association was found between BMI and BHT. A strong positive association was observed between BHT and DOH in all healthy young people.

Correlations between gustatory, trigeminal, and olfactory functions and nasal airflow

PURPOSE

To determine the relationship of chemosensory screening and nasal airflow tests among the same set of participants, and to determine other factors that are related to the outcomes of these tests.

METHODS

Participants had no chemosensory complaints. Structured medical history was taken. Participants underwent 5 screening tests: q-sticks (orthonasal olfaction), q-powders (retronasal olfaction), trigeminal lateralization test, taste sprays, and peak nasal inspiratory flow (PNIF). Ratings of smell/taste ability and nasal airflow were obtained using visual analogue scales (VAS). Composite sinusitis symptoms and significance of olfaction questionnaire scores were also determined.

RESULTS

Four hundred participants were included in the study, 156 men, 244 women; aged 18-82 years (mean: 46). The q-powders and taste spray scores were weakly positively correlated with all the other chemosensory tests and PNIF. However, chemosensory test scores were not correlated with VAS, composite sinusitis symptoms, and significance of olfaction questionnaire scores. Various tests showed significant decrease starting at specific ages (in years, PNIF and trigeminal lateralization: 40, q-powders: 60, and q-sticks: 70).

CONCLUSION

Chemosensory screening tests and self-rated chemosensory function showed no correlation in participants without chemosensory complaints. In addition, gustatory function appeared to be correlated with olfactory and trigeminal function but also with nasal airflow, and nasal airflow was related not only to olfactory but also to trigeminal and taste function. Over all, the results suggest that chemosensory functions (orthonasal olfactory, trigeminal, retronasal olfactory, gustatory) and nasal airflow are correlated with each other, which we propose may be possibly mediated, at least in part, through central nervous system interactions.

Methods to Detect Volatile Organic Compounds for Breath Biopsy Using Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry

Volatile organic compounds (VOCs) are byproducts from metabolic pathways that can be detected in exhaled breath and have been reported as biomarkers for different diseases. The gold standard for analysis is gas chromatography-mass spectrometry (GC-MS), which can be coupled with various sampling methods. The current study aims to develop and compare different methods for sampling and preconcentrating VOCs using solid-phase microextraction (SPME). An in-house sampling method, direct-breath SPME (DB-SPME), was developed to directly extract VOCs from breath using a SPME fiber. The method was optimized by exploring different SPME types, the overall exhalation volume, and breath fractionation. DB-SPME was quantitatively compared to two alternative methods involving the collection of breath in a Tedlar bag. In one method, VOCs were directly extracted from the Tedlar bag (Tedlar-SPME) and in the other, the VOCs were cryothermally transferred from the Tedlar bag to a headspace vial (cryotransfer). The methods were verified and quantitatively compared using breath samples (n = 15 for each method respectively) analyzed by GC-MS quadrupole time-of-flight (QTOF) for compounds including but not limited to acetone, isoprene, toluene, limonene, and pinene. The cryotransfer method was the most sensitive, demonstrating the strongest signal for the majority of the VOCs detected in the exhaled breath samples. However, VOCs with low molecular weights, including acetone and isoprene, were detected with the highest sensitivity using the Tedlar-SPME. On the other hand, the DB-SPME was less sensitive, although it was rapid and had the lowest background GC-MS signal. Overall, the three breath-sampling methods can detect a wide variety of VOCs in breath. The cryotransfer method may be optimal when collecting a large number of samples using Tedlar bags, as it allows the long-term storage of VOCs at low temperatures (-80 °C), while Tedlar-SPME may be more effective when targeting relatively small VOCs. The DB-SPME method may be the most efficient when more immediate analyses and results are required.

Exploring the association of physical activity with the plasma and urine metabolome in adolescents and young adults

BACKGROUND

Regular physical activity elicits many health benefits. However, the underlying molecular mechanisms through which physical activity influences overall health are less understood. Untargeted metabolomics enables system-wide mapping of molecular perturbations which may lend insights into physiological responses to regular physical activity. In this study, we investigated the associations of habitual physical activity with plasma and urine metabolome in adolescents and young adults.

METHODS

This cross-sectional study included participants from the DONALD (DOrtmund Nutritional and Anthropometric Longitudinally Designed) study with plasma samples n = 365 (median age: 18.4 (18.1, 25.0) years, 58% females) and 24 h urine samples n = 215 (median age: 18.1 (17.1, 18.2) years, 51% females). Habitual physical activity was assessed using a validated Adolescent Physical Activity Recall Questionnaire. Plasma and urine metabolite concentrations were determined using ultra-high-performance liquid chromatography-tandem mass spectroscopy (UPLC-MS/MS) methods. In a sex-stratified analysis, we conducted principal component analysis (PCA) to reduce the dimensionality of metabolite data and to create metabolite patterns. Multivariable linear regression models were then applied to assess the associations between self-reported physical activity (metabolic equivalent of task (MET)-hours per week) with single metabolites and metabolite patterns, adjusted for potential confounders and controlling the false discovery rate (FDR) at 5% for each set of regressions.

RESULTS

Habitual physical activity was positively associated with the "lipid, amino acids and xenometabolite" pattern in the plasma samples of male participants only (β = 1.02; 95% CI: 1.01, 1.04, p = 0.001, adjusted p = 0.042). In both sexes, no association of physical activity with single metabolites in plasma and urine and metabolite patterns in urine was found (all adjusted p > 0.05).

CONCLUSIONS

Our explorative study suggests that habitual physical activity is associated with alterations of a group of metabolites reflected in the plasma metabolite pattern in males. These perturbations may lend insights into some of underlying mechanisms that modulate effects of physical activity.

Voluntary activation of the diaphragm after inspiratory pressure threshold loading

After a bout of isolated inspiratory work, such as inspiratory pressure threshold loading (IPTL), the human diaphragm can exhibit a reversible loss in contractile function, as evidenced by a decrease in transdiaphragmatic twitch pressure (PDI,TW ). Whether or not diaphragm fatigability after IPTL is affected by neural mechanisms, measured through voluntary activation of the diaphragm (D-VA) in addition to contractile mechanisms, is unknown. It is also unknown if changes in D-VA are similar between sexes given observed differences in diaphragm fatigability between males and females. We sought to determine whether D-VA decreases after IPTL and whether this was different between sexes. Healthy females (n = 11) and males (n = 10) completed an IPTL task with an inspired duty cycle of 0.7 and targeting an intensity of 60% maximal transdiaphragmatic pressure until task failure. PDI,TW and D-VA were measured using cervical magnetic stimulation of the phrenic nerves in combination with maximal inspiratory pressure maneuvers. At task failure, PDI,TW decreased to a lesser degree in females vs. males (87 ± 15 vs. 73 ± 12% baseline, respectively, p = 0.016). D-VA decreased after IPTL but was not different between females and males (91 ± 8 vs. 88 ± 10% baseline, respectively, p = 0.432). When all participants were pooled together, the decrease in PDI,TW correlated with both the total cumulative diaphragm pressure generation (R2  = 0.43; p = 0.021) and the time to task failure (TTF, R2 = 0.40; p = 0.30) whereas the decrease in D-VA correlated only with TTF (R2  = 0.24; p = 0.041). Our results suggest that neural mechanisms can contribute to diaphragm fatigability, and this contribution is similar between females and males following IPTL.

Blood shifts between body compartments during submaximal exercise with induced expiratory flow limitation in healthy humans

External expiratory flow limitation (EFLe) can be applied in healthy subjects to mimic the effects of chronic obstructive pulmonary disease during exercise. At maximal exercise intensity, EFLe leads to exercise intolerance owing to respiratory pump dysfunction limiting venous return. We quantified blood shifts between body compartments to determine whether such effects can be observed during submaximal exercise, when the load on the respiratory system is milder. Ten healthy men (25.2 ± 3.2 years of age, 177.3 ± 5.4 cm in height and weighing 67.4 ± 5.8 kg) exercised at 100 W (∼40% of maximal oxygen uptake) while breathing spontaneously (CTRL) or with EFLe. We measured respiratory dynamics with optoelectronic plethysmography, oesophageal (P_es ) and gastric (P_ga ) pressures with balloon catheters, and blood shifting between body compartments with double body plethysmography. During exercise, EFLe resulted in the following changes: (i) greater intrabreath blood shifts between the trunk and the extremities [518 ± 221 (EFLe) vs. 224 ± 60 ml (CTRL); P < 0.001] associated with lower P_es during inspiration (r = 0.53, P < 0.001) and higher P_ga during expiration (r = 0.29, P < 0.024); and (ii) a progressive pooling of blood in the trunk over time (∼700 ml after 3 min of exercise; P < 0.05), explained by a predominant effect of lower inspiratory P_es (r = 0.54, P < 0.001) over that of increased P_ga . It follows that during submaximal exercise, EFLe amplifies the respiratory pump mechanism, with a prevailing contribution from lower inspiratory P_es over increased expiratory P_ga , drawing blood into the trunk. Whether these results can be replicated in chronic obstructive pulmonary disease patients remains to be determined. KEY POINTS: External expiratory flow limitation (EFLe) can be applied in healthy subjects to mimic the effects of chronic obstructive pulmonary disease and safely study the mechanisms of exercise intolerance associated with the disease. At maximal exercise intensity with EFLe, exercise intolerance results from high expiratory pressures altering the respiratory pump mechanism and limiting venous return. We used double body plethysmography to quantify blood shifting between the trunk and the extremities and to examine whether the same effects occur with EFLe at submaximal exercise intensity, where the increase in expiratory pressures is milder. Our data show that during submaximal exercise, EFLe amplifies the respiratory pump mechanism, each breath producing greater blood displacements between the trunk and the extremities, with a prevailing effect from lower inspiratory intrathoracic pressure progressively drawing blood into the trunk. These results help us to understand the haemodynamic effects of respiratory pressures during submaximal exercise with expiratory flow restriction.

Step-adaptive sound guidance enhances locomotor-respiratory coupling in novice female runners: A proof-of-concept study

Introduction

Many runners struggle to find a rhythm during running. This may be because 20-40% of runners experience unexplained, unpleasant breathlessness at exercise onset. Locomotor-respiratory coupling (LRC), a synchronization phenomenon in which the breath is precisely timed with the steps, may provide metabolic or perceptual benefits to address these limitations. It can also be consciously performed. Hence, we developed a custom smartphone application to provide real-time LRC guidance based on individual step rate.

Methods

Sixteen novice-intermediate female runners completed two control runs outdoors and indoors at a self-selected speed with auditory step rate feedback. Then, the runs were replicated with individualized breath guidance at specific LRC ratios. Hexoskin smart shirts were worn and analyzed with custom algorithms to estimate continuous LRC frequency and phase coupling.

Results

LRC guidance led to a large significant increase in frequency coupling outdoor from 26.3 ± 10.7 (control) to 69.9 ± 20.0 % (LRC) "attached". There were similarly large differences in phase coupling between paired trials, and LRC adherence was stronger for the indoor treadmill runs versus outdoors. There was large inter-individual variability in running pace, preferred LRC ratio, and instruction adherence metrics.

Discussion

Our approach demonstrates how personalized, step-adaptive sound guidance can be used to support this breathing strategy in novice runners. Subsequent investigations should evaluate the skill learning of LRC on a longer time basis to effectively clarify its risks and advantages.

The Effects of Zumba Fitness® on Respiratory Function and Body Composition Parameters: An Eight-Week Intervention in Healthy Inactive Women

BACKGROUND

Women are considered less active than men, and a sedentary lifestyle particularly affects middle-aged women and affects their overall health. Recommending group fitness programs that have a positive effect on women's overall health is an important strategy of any health policy. Thus, the purpose of this study was to investigate how the Zumba Fitness^® workout affects healthy inactive women's respiratory function and body composition.

METHODS

The research was conducted for eight weeks on a sample of 41 females aged 35 to 45 divided into two groups: experimental (21 subjects: age 38.52 ± 2.29) and control (20 subjects: age 39.45 ± 3.01). They were tested before, four weeks, and eight weeks after the intervention period. The respiratory functions were tested using spirometry and the body composition parameters by the Tanita body analyzer. The experimental group practiced Zumba Fitness^® three times per week for 60 min (24 training sessions in total). The control group was not physically active during the intervention period.

RESULTS

After the Zumba Fitness^® program, the experimental group showed a significant improvement in the following respiratory function parameters: forced expiratory volume in the first second (M = 4.02 ± 0.69; MD = 0.65, p = 0.01, ES = 0.14), vital capacity (M = 4.10 ± 0.65: MD = -0.63, p = 0.03, ES = 0.11) and lung age (M = 30.95 ± 10.30; MD = 8.52, p = 0.04, ES = 0.10). The body composition parameters were significantly decreased: body mass (M = 60.09 ± 7.57; MD = 6.32, p = 0.03, ES = 0.11), body mass index (M = 20.44 ± 2.63; MD = 2.61, p = 0.01, ES = 0.13) and fat mass (M = 16.07 ± 4.87; MD = 3.95, p = 0.03, ES = 0.11).

CONCLUSIONS

The results of the current study suggest that the Zumba Fitness^® workout is a beneficial exercise method not only for reducing body parameters but also for improving respiratory function in inactive women.

The effects of a respiratory training mask on steady-state oxygen consumption at rest and during exercise

No studies have directly measured ventilatory and metabolic responses while wearing a respiratory training mask (RTM) at rest and during exercise. Eleven aerobically fit adults (age: 21 ± 1 years) completed a randomized cross-over study while wearing an RTM or control mask during cycling at 50% Wmax. An RTM was retrofitted with a gas collection tube and set to the manufacturer's "altitude resistance" setting of 6,000 ft (1,800 m). Metabolic gas analysis, ratings of perceived exertion, and oxygen saturation (SpO2) were measured during rest and cycling exercise. The RTM did not affect metabolic, ventilation, and SpO2 at rest compared to the control mask (all, effect of condition: P > 0.05). During exercise, the RTM blunted respiratory rate and minute ventilation (effect of condition: P < 0.05) compared to control. Similar increases in VO2 and VCO2 were observed in both conditions (both, effect of condition: P > 0.05). However, the RTM led to decreased fractional expired O2 and increased fractional expired CO2 (effect of condition: P < 0.05) compared to the control mask. In addition, the RTM decreased SpO2 and increased RPE (both, effect of condition: P < 0.05) during exercise. Despite limited influence on ventilation and metabolism at rest, the RTM reduces ventilation and disrupts gas concentrations during exercise leading to modest hypoxemia.

Reference values of impulse oscillometry (IOS) for healthy Chinese children aged 4-17 years

OBJECTIVE

To establish the predicted value of pulmonary function determined by impulse oscillometry (IOS) in children (4-17 years old) in China.

METHODS

A total of 6270 healthy children aged 4-17 years in China were included. The Master Screen IOS pulmonary function device (Jaeger Co, Germany) was used to detect the respiratory impedance (Zrs), resonant frequency (Fres), respiratory system resistance (Rrs) and respiratory system reactance (Xrs) at various oscillation frequencies, and the indices above were analysed. Stepwise multivariate regression was used to establish the regression equation of related parameters of IOS in different sexes, ages, height, and weight.

RESULTS

The differences in the main IOS parameters between different age stages were statistically significant regardless of sex (P < 0.05). The stepwise multivariate regression analysis showed that IOS parameters were related to height, age, and weight, and most IOS parameters were most closely related to height (the absolute value of the regression coefficient was the largest). With increasing age and height, the values of Z₅, R₅, R₂₀, R₅-R₂₀, and Fres decreased, while the value of X₅ increased. Through height, age, and weight, we obtained the normal predicted values equation of children's IOS parameters. Compared with the other reference equations, our reference equation is more suitable for Chinese children.

CONCLUSIONS

The study revealed the reference values of IOS parameters in healthy Chinese children. In the evaluation of results for lung function measurements, this predicted value equation is more consistent with the characteristics of Chinese children than other reference equations.

CLINICAL TRIAL

ChiCTR: 1800019029.