Respiratory exchange ratio

Four weeks before competition in the 2023 Marathon des Sables, a 6-stage, ~250 km running event in the Sahara Desert, we examined the effects of a 7-day intake of New Zealand blackcurrant extract (210 mg anthocyanins per day) on 1 h treadmill running-induced physiological and metabolic responses in the heat (~34 °C, relative humidity: ~30%) in non-acclimatized amateur female and male athletes (age: 23, 38 yrs, BMI: 24.2, 28.4 kg·m-2 , body fat%: 29.2, 18.8%, V˙O2max : 50.1, 52.1 mL·kg-1 ·min-1 )...

OBJECTIVE: We investigated how changes in 24-h respiratory exchange ratio (RER) and substrate oxidation during fasting versus an energy balance condition influence subsequent ad libitum food intake. METHODS: Forty-four healthy, weight-stable volunteers (30 male and 14 female; mean [SD], age 39.3 [11.0] years; BMI 31.7 [8.3] kg/m2 ) underwent 24-h energy expenditure measurements in a respiratory chamber during energy balance (50% carbohydrate, 30% fat, and 20% protein) and 24-h fasting...

Stable carbon isotopes are a powerful tool to study photosynthesis. Initial applications consisted of determining isotope ratios of plant biomass using mass spectrometry. Subsequently, theoretical models relating C isotope values to gas exchange characteristics were introduced and tested against instantaneous online measurements of 13 C photosynthetic discrimination. Beginning in the twenty-first century, laser absorption spectroscopes with sufficient precision for determining isotope mixing ratios became commercially available...

In a randomized controlled cross-over study ten male runners (26.7 ± 4.9 years; recent 5-km time: 18:37 ± 1:07 min:s) performed an incremental treadmill test (ITT) and a 3-km time trial (3-km TT) on a treadmill while wearing either carbon fiber insoles with downwards curvature or insoles made of butyl rubber (control condition) in light road racing shoes (Saucony Fastwitch 9). Oxygen uptake, respiratory exchange ratio, heart rate, blood lactate concentration, stride frequency, stride length and time to exhaustion were assessed during ITT...

The nose of the mammals is responsible for filtering, humidifying, and heating the air before entering the lower respiratory tract. This conditioning avoids, notably, dehydration of the bronchial and alveolar mucosa. However, since this conditioning is not perfect, exercising in cold air can induce lung inflammation, both for human and non-human mammals. This work aims to compare the air conditioning in the noses of various mammals during inspiration. We build our study on computational fluid dynamics simulations of the heat exchanges in the lumen of the upper respiratory tract of these mammals...

PURPOSE: Cardiorespiratory fitness (CRF) measured by peak oxygen consumption (VO2peak) declines with aging and correlates with mortality and morbidity. Cardiopulmonary Exercise Testing (CPET) is the criterion method to assess CRF, but its feasibility, validity and reliability in older adults is unclear. Our objective was to design and implement a dependable, safe and reliable CPET protocol in older adults. METHODS: VO2peak was measured by CPET, performed using treadmill exercise in 875 adults ≥70 years in the Study of Muscle, Mobility and Aging (SOMMA)...

Background: The use of the prone position (PP) has been widespread during the COVID-19 pandemic. While it has demonstrated benefits, including improved oxygenation and lung aeration, the factors influencing the response in terms of gas exchange to PP remain unclear. In particular, the association between baseline quantitative Computed Tomography (qCT) scan results and gas exchange response to PP in intubated, mechanically ventilated subjects with COVID-19 ARDS is unknown. The present study aimed to compare baseline qCT results between subjects responding to PP in terms of oxygenation or carbon dioxide (CO2 ) clearance and those who did not...

The asymptote (critical power; CP) and curvature constant (W') of the hyperbolic power-duration relationship can predict performance within the severe-intensity exercise domain. However, the extent to which these parameters relate to skeletal muscle mitochondrial content and respiratory function is not known. Fifteen males (peak O2 uptake, 52.2 ± 8.7 mL kg-1  min-1 ; peak work rate, 366 ± 40 W; and gas exchange threshold, 162 ± 41 W) performed three to five constant-load tests to task failure for the determination of CP (246 ± 44 W) and W' (18...

BACKGROUND: Superimposed high-frequency jet ventilation (SHFJV) is suitable for respiratory motion reduction and essential for effective lung tumor ablation. Fluid filling of the target lung wing one-lung flooding (OLF) is necessary for therapeutic ultrasound applications. However, whether unilateral SHFJV allows adequate hemodynamics and gas exchange is unclear. AIM: To compared SHFJV with pressure-controlled ventilation (PCV) during OLF by assessing hemodynamics and gas exchange in different animal positions...

BACKGROUND: Mechanical ventilation with variable tidal volumes (V-VCV) has the potential to improve lung function during general anesthesia. We tested the hypothesis that V-VCV compared to conventional volume-controlled ventilation (C-VCV) would improve intraoperative arterial oxygenation and respiratory system mechanics in patients undergoing thoracic surgery under one-lung ventilation (OLV). METHODS: Patients were randomized to V-VCV (n = 39) or C-VCV (n = 39)...

PURPOSE: Garlic extract (GA) is purported to enhance antioxidant and anti-inflammatory activity and glucose regulation in humans. The present study investigated the effects of post-exercise GA supplementation on GLUT4 expression, glycogen replenishment, and the transcript factors involved with mitochondrial biosynthesis in exercised human skeletal muscle. METHODS: The single-blinded crossover counterbalanced study was completed by 12 participants. Participants were randomly divided into either GA (2000 mg of GA) or placebo trials immediately after completing a single bout of cycling exercise at 75% Maximal oxygen uptake (VO2max ) for 60 minutes...

Patients with sickle cell disease (SCD) display lower slope coefficients of the oxygen uptake (V_O2) vs. work rate (W) relationship (delineating an O2 uptake/demand mismatch) and a poor metabolic flexibility. Because endurance training (ET) increases the microvascular network and oxidative enzymes activity including one involved in lipid oxidation, ET might improve the slope coefficient of the V_O2 vs. W curve and the metabolic flexibility of SCD patients. ET may also contribute to improve patient post-exercise cardiopulmonary and metabolic recovery...

BACKGROUND: Ratio of arterial pressure of oxygen and fraction of inspired oxygen (P/F ratio) together with the fractional dead space (Vd /Vt ) provides a global assessment of pulmonary gas exchange. The aim of this study was to assess the potential value of these variables to prognosticate 90-day survival in patients with COVID-19 associated ARDS admitted to the Intensive Care Unit (ICU) for invasive ventilatory support. METHODS: In this single-center observational, retrospective study, P/F ratios and Vd /Vt were assessed up to 4 weeks after ICU-admission...

The causes and consequences of excess exercise ventilation (EEV) in patients with fibrosing interstitial lung disease (f-ILD) were explored. Twenty-eight adults with f-ILD and 13 controls performed an incremental cardiopulmonary exercise test. EEV was defined as ventilation-carbon dioxide output (⩒E-⩒CO2 ) slope ≥36L/L. Patients showed lower pulmonary function and exercise capacity compared to controls. Lower DLCO was related to higher ⩒E-⩒CO2 slope in patients (P<0.05)...

The control of feeding and physical activity is tightly linked and coordinated. However the underlying mechanisms are unclear. One of the major regulatory systems of feeding behaviour involves neuropeptide Y (NPY) signalling, with the signalling mediated through NPY Y4 receptor also known to influence activity. Here we show that mice globally lacking the Npy4r (Npy4r-/- ) in the absence of access to a running wheel behaved WT-like with regards to food intake, energy expenditure, respiratory exchange ratio and locomotion regardless of being fed on a chow or high fat diet...

PURPOSE: To assess (1) whether and how a higher maximal lactate steady state (MLSS) at higher cycling cadence (RPM) comes along with higher absolute and/or fractional carbohydrate combustion (CHOMLSS), respectively, and (2) whether there is an interrelation between potential RPM-dependent MLSS effects and the maximally achievable RPM (RPMMAX). METHODS: Twelve healthy males performed incremental load tests to determine peak power, peak oxygen uptake, and 30-minute MLSS tests at 50 and 100 per minute, respectively, to assess RPM-dependent MLSS, corresponding power output, CHOMLSS responses, and 6-second sprints to measure RPMMAX...

The purpose of this study was to compare roller skiing economy during different training phases in Nordic combined (NC) athletes and determine the aerobic and anaerobic factors responsible for changes in skiing economy. Seven elite NC athletes underwent incremental load tests on a large buried treadmill in both spring and autumn using roller skis. Measurements included oxygen uptake, respiratory exchange ratio, and blood lactate concentration. Roller skiing economy was calculated from aerobic and anaerobic energy system contributions, and overall roller skiing economy was determined by combining the two...

OBJECTIVE: Relapses of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis are important events that can cause organ dysfunction and reduce quality of life. Understanding the effects of the initial treatments for ANCA-associated vasculitis on the subsequent risk of relapse may help guide monitoring and treatment. METHODS: We performed a post hoc analysis of participants with severe ANCA-associated vasculitis enrolled in an international two-by-two factorial randomized controlled trial comparing the effects of plasma exchange (PLEX) to no PLEX and a regimen of reduced glucocorticoid exposure to a standard regimen...

Chlorella supplementation is reported to improve V˙O2max following extended supplementation periods (~3 weeks). However, there is little research on its impact over submaximal exercise intensities and following shorter supplementation regimens. This study aimed to investigate the efficacy of 6 g/day 2-day chlorella supplementation on exercise performance in healthy young adults. Twenty young healthy adults (Males = 16, Females = 4) (Age 22 ± 6 years, V˙O2max 42.7 ± 9.6 mL/(kg·min)) were recruited for this double-blinded, randomised cross-over study...

Free-breathing abdominal chemical exchange saturation transfer (CEST) has great potential for clinical application, but its technical implementation remains challenging. This study aimed to propose and evaluate a free-breathing abdominal CEST sequence. The proposed sequence employed respiratory gating (ResGat) to synchronize the data acquisition with respiratory motion and performed a water presaturation module before the CEST saturation to abolish the influence of respiration-induced repetition time variation...