Journal of Applied Physiology

In contrast to whole-body bioimpedance, which estimates fluid status at a single point in time, thoracic bioimpedance applied by a wearable device could enable continuous measurements. However, clinical experience with thoracic bioimpedance in patients in dialysis is still limited. In order to test the reproducibility of whole-body and thoracic bioimpedance measurements and to compare their relation with hemodynamic changes during hemodialysis, these parameters were measured pre- and end-dialysis in 54 patients during two sessions...

Emphysema is one of the pathological hallmarks of chronic obstructive pulmonary disease. We have recently reported that radiofrequency therapy improves lung function in rodent models of emphysema. However, preclinical data using large animals is necessary for clinical translation. Here, we describe the work performed to establish a unilateral porcine emphysema model. Different doses of porcine pancreatic elastase (PPE) were instilled into the left lung of ten Yucatan pigs. Three additional pigs were used as controls...

In neonatal rhythmic medullary slices, muscarinic acetylcholine receptor (mAChR) activation of hypoglossal (XII) motoneurons that innervate the tongue has a net excitatory effect on XII inspiratory motor output. Conversely, during rapid eye movement sleep in adult rodents, XII motoneurons experience a loss of excitability partly due to activation of mAChRs. This may be mediated by activation of G-protein coupled inwardly rectifying potassium (GIRK) channels. Therefore, this study was designed to evaluate whether muscarinic modulation of XII inspiratory motor output in mouse rhythmic medullary slices includes GIRK channel-mediated inhibition and if so, when this inhibitory mechanism emerges...

While research has largely focused on the effects of physical activity (PA) on the brain, less in known about the influence of the brain on engagement in healthy-living behaviors, such as regular PA. In this secondary analysis of a study of brain activity and participation in healthy-living behaviors, we examined relationships between activation of selected brain networks and PA in persons self-managing chronic conditions. Fifty-eight individuals with chronic conditions underwent functional magnetic resonance imaging while exposed to a protocol consisting of listening to emotion-focused and analytic-focused information and measures of activation of three neuromarkers were obtained: default mode network (DMN), task positive network (TPN), and ventromedial prefrontal cortex (vmPFC)...

UNLABELLED: Increased intrapulmonary shunt(QS /Qt ) and alveolar dead space(VD /VT ) are present in early recovery from COVID-19. We hypothesized patients recovering from severe-critical acute illness(NIH category 3-5) would have greater and longer-lasting increased QS /Qt and VD /VT than patients with mild-moderate acute illness(NIH 1-2). METHODS: 59 unvaccinated patients (33 male, age 52[38-61] years, BMI 28.8[25.3-33.6] kg/m2 ; median[IQR], 44 previous mild-moderate COVID-19, and 15 severe-critical disease), were studied 15-403 days post-acute SARS-CoV-2 infection...

Pregnancy complications are associated with abnormal maternal autonomic regulation. Subsequently, thoroughly understanding maternal autonomic regulation during healthy pregnancy may enable the earlier detection of complications, in turn allowing for the improved management thereof. Under healthy autonomic regulation, reciprocal interactions occur between the cardiac and respiratory systems, i.e., cardiorespiratory coupling (CRC). Here, we investigate for the first time the differences in CRC between healthy pregnant and non-pregnant women...

Ischemia-reperfusion injury (I/R) can inhibit endothelial function and impair nitric oxide bioavailability. We tested the hypothesis that I/R also blunts the rapid and steady-state hyperemic and vasodilatory response to handgrip exercise. Ten subjects (8M/2F; 24±4yr) performed handgrip exercises before and after I/R (20 min of ischemia/20 min of reperfusion) and time control (40 min supine rest) trials. Forearm blood flow (FBF) and vascular conductance (FVC) were assessed with Doppler ultrasound during single forearm contractions and 3 min of rhythmic handgrip exercise...

We applied the recently introduced concept of intra-muscle synergies in spaces of motor units (MUs) to quantify indices of such synergies in the tibialis anterior during ankle dorsiflexion force production tasks and their changes with fatigue. We hypothesized that MUs would be organized into robust groups (MU-modes), which would co-vary across trials to stabilize force magnitude, and the indices of such synergies would drop under fatigue. Healthy, young subjects (n = 14; 7 females) produced cyclical, isometric dorsiflexion forces while surface electromyography was used to identify action potentials of individual MUs...

Comparisons of muscle force output are often performed after normalization to muscle physiological cross-sectional area (CSA). Differences in force per CSA (i.e., specific force) suggest the presence of physiological differences in contractile function. Permeabilized mammalian skeletal muscle fibres frequently exhibit substantial declines in specific force with increasing CSA, suggesting that smaller fibres are intrinsically stronger than larger fibres of the same group. However, the potential for CSA assessment error to account for CSA-dependent differences in specific force has not received adequate attention...

Although in recent years near-infrared spectroscopy has been used in many sports to monitor muscle oxygen saturation (SmO2 ), there is a lack of knowledge about the sex differences in SmO2 during exercise in different muscles. Our study aimed to examine SmO2 differences in muscles between female and male cyclists, during a graded cycling test and at the first and second lactate thresholds. Twenty-five trained cyclists and triathletes [15 males: 23 ±7 years, 1.78 ±0.05 m, 70.2 ±5.3 kg, and 10 females: 22 ±5 years, 1...

Inspiratory muscle strength training (IMST) has shown potential to improve both respiratory and cardiovascular function in health and disease. Less is known about acute hemodynamic responses to a single IMST session, therefore we assessed upper and lower limb blood flow via Doppler ultrasound in the brachial and popliteal arteries, respectively. Mean, anterograde, and retrograde blood flow (BF) and shear rate (SR) were assessed relative to baseline during low-intensity (15% maximal inspiratory pressure - PImax) and high-intensity (75% PImax) IMST...

Oral inorganic nitrate (NO3 - ) supplementation has been shown to increase bioavailable NO and provide potential ergogenic benefits in males, however data in females is scarce. Estrogen increases endogenous NO bioavailability and to fluctuate throughout the menstrual cycle (MC) being lowest in the early follicular phase (EF) and highest during the late follicular phase (LF). This study examined the effects of oral NO3 - supplementation on exercise economy, endurance capacity, and vascular health in young females across the MC...

Heat waves can cause dangerous elevations in body temperature that can compromise cellular function and increase the risk of heat stroke and major cardiovascular events. Visiting a cooling center or other air-conditioned location is commonly recommended by health agencies to protect heat-vulnerable older persons but the associated cellular effects remain underexplored. We evaluated cellular stress responses in peripheral blood mononuclear cells (PBMC) from 19 older adults (71 [SD 2] years; 9 females) before and after a 9-hour heat exposure (40...

Changes in skeletal muscle are an important aspect of overall health. The collection of human muscle to study cellular and molecular processes for research requires a needle biopsy procedure which in itself can induce changes in the tissue. To investigate the effect of repeat tissue sampling, we collected skeletal muscle biopsy samples from vastus lateralis separated by 7 days. Cellular infiltrate, central nucleation, enlarged extracellular matrix and rounding of muscle fibers were used as indices to define muscle damage, and we found that 16/26 samples (61...

CO2 inhalation has been previously reported as a treatment for central sleep apnea both when associated with heart failure or where the cause is unknown. Here we evaluated a novel CO2 supply system using a novel open mask capable of comfortably delivering a constantly inspired fraction of CO2 (FiCO2 ) during sleep. We recruited eighteen patients with central sleep apnea (13 patients with cardiac disease, and 5 patients idiopathic) diagnosed by diaphragm EMG recordings made during overnight full polysomnography (Night 1)...

Endothelial dysfunction is a key phenomenon in COVID-19, induced by direct viral endothelial infection and secondary inflammation, mainly affecting the microvascular circulation. However, few studies described the subcellular aspects of the lung microvasculature and the associated thrombotic phenomena, which are widely present in severe COVID-19 cases. To that end, in this transversal observational study we performed transmission and scanning electron microscopy in nine lung samples of patients that died due to COVID-19, obtained via minimally invasive autopsies in Sao Paulo, Brazil, in 2020...

Mechanosensing and subsequent mechanotransduction are indispensable for muscle plasticity. Nevertheless, a scarcity of literature exists regarding an all-encompassing understanding of the muscle mechanosensing machinery's response to prolonged loading, especially in conditions that resemble a natural physiological state of skeletal muscle. This study aimed to comprehensively explore the effects of prolonged mechanical loading on mechanosensitive components, skeletal muscle characteristics, and metabolism-related gene clusters...

BACKGROUND: Following acute COVID-19, a substantial proportion of patients showed symptoms and sequelae for several months, namely the post-acute sequelae of COVID-19 (PASC) syndrome. Major phenomena are exercise intolerance, muscle weakness and fatigue. We aimed to investigate the physiopathology of exercise intolerance in patients with PASC syndrome by structural and functional analyses of skeletal muscle. METHODS: At least 3 months after infection, non-hospitalized patients with PASC (n=11,ys:54±11; PASC) and patients without long-term symptoms (n=12,ys:49±9; CTRL) visited the laboratory on four non-consecutive days...

Cutaneous input is important in postural control and balance. Aging and diabetes impair skin sensitivity and motor control. Heat application can improve skin sensation, but its influence on motor control remains unknown. This study investigated the effects of heating skin of the foot sole on lower limb cutaneous reflexes. Reflexes were evoked in the tibialis anterior muscle of twenty young, healthy adults before and after heating the foot sole to a maximum of 42 °C. While holding a 15% EMGmax isometric dorsiflexion, a filtered white noise (0-50 Hz) vibration, at 10x perceptual threshold was applied to the heel to stimulate cutaneous mechanoreceptors...

The purpose of this study was to clarify the effect of sex and menstrual cycle phase on celiac artery blood flow during dynamic exercise in healthy young humans. Eleven healthy young females (21±2 yrs, mean±SD) and ten males (23±3 yrs) performed dynamic knee-extension and -flexion exercise at 30% of heart rate reserve for 4-min. The percent changes from baseline (Δ) for mean arterial blood pressure (MAP), mean blood flow (celMBF) in celiac artery, and celiac vascular conductance (celVC) during exercise were calculated...