Maximal Oxygen Uptake Rate Research Articles

Influence of load increase rate during incremental test on aerobic performance indicators

Maximum oxygen consumption is an informative indicator of aerobic performance, and its assessment is associated with a significant investment of time. The paper compares the results of maximum tests with a stepwise increasing load with different duration of one load step: 15, 30, 60, 120 and 240 s. Maximum oxygen uptake, total operating time, and pair-wise relationship of protocols were assessed. There was no statistically significant difference in maximum oxygen uptake rate in protocols of different duration. Also, all the studied protocols showed a high correlation with each other (r = 0.92–0.97).

Method dependency of maximum oxygen uptake rate and its repeatability in the Gulf killifish, Fundulus grandis.

The maximum rate at which fish can take up oxygen from their environment to fuel aerobic metabolism is an important feature of their physiology and ecology. Methods to quantify maximum oxygen uptake rate (ṀO2), therefore, should reliably and reproducibly estimate the highest possible ṀO2 by an individual or species under a given set of conditions (peak ṀO2). This study determined peak ṀO2 and its repeatability in Gulf killifish, Fundulus grandis, subjected to three methods to elevate metabolism: swimming at increasing water speeds, during recovery after an exhaustive chase, and after ingestion of a large meal. Estimates of peak ṀO2 during swimming and after an exhaustive chase were repeatable across two trials, whereas peak ṀO2 after feeding was not. Peak ṀO2 determined by the three methods was significantly different from one another, being highest during swimming, lowest after an exhaustive chase, and intermediate after feeding. In addition, peak ṀO2 during recovery from an exhaustive chase depended on the length of time of recovery: in nearly 60% of the trials, values within the first hour of the chase were lower than those measured later. A novel and important finding was that an individual's peak ṀO2 was not repeatable when compared across methods. Therefore, the peak ṀO2 estimated for a group of fish, as well as the ranking of individual ṀO2 within that group, depends on the method used to elevate aerobic metabolism.

Environmental variation associated with overwintering elicits marked metabolic plasticity in a temperate salmonid, Salvelinus fontinalis.

Poleward winters commonly expose animals, including fish, to frigid temperatures and low food availability. Fishes that remain active over winter must therefore balance trade-offs between conserving energy and maintaining physiological performance in the cold, yet the extent and underlying mechanisms of these trade-offs are not well understood. We investigated the metabolic plasticity of brook char (Salvelinus fontinalis), a temperate salmonid, from the biochemical to whole-animal level in response to cold and food deprivation. Acute cooling (1°Cday-1) from 14°C to 2°C had no effect on food consumption but reduced activity by 77%. We then assessed metabolic performance and demand over 90 days with exposure to warm (8°C) or cold winter (2°C) temperatures while fish were fed or starved. Resting metabolic rate (RMR) decreased substantially during initial cooling from 8°C to 2°C (Q10=4.2-4.5) but brook char exhibited remarkable thermal compensation during acclimation (Q10=1.4-1.6). Conversely, RMR was substantially lower (40-48%) in starved fish, conserving energy. Thus, the absolute magnitude of thermal plasticity may be masked or modified under food restriction. This reduction in RMR was associated with atrophy and decreases in in vivo protein synthesis rates, primarily in non-essential tissues. Remarkably, food deprivation had no effect on maximum oxygen uptake rates and thus aerobic capacity, supporting the notion that metabolic capacity can be decoupled from RMR in certain contexts. Overall, our study highlights the multi-faceted energetic flexibility of Salvelinus spp. that likely contributes to their success in harsh and variable environments and may be emblematic of winter-active fishes more broadly.

The Oxidative Phosphorylation and Cytoskeleton Proteins of Mouse Ovaries after 96 Hours of Hindlimb Suspension.

The purpose of this study was to assess oxidative phosphorylation (OXPHOS) in mouse ovaries, determine the relative content of proteins that form the respiratory chain complexes and the main structures of the cytoskeleton, and determine the mRNA of the corresponding genes after hindlimb suspension for 96 h. After hindlimb suspension, the maximum rate of oxygen uptake increased by 133% (p < 0.05) compared to the control due to the complex I of the respiratory chain. The content of mRNA of genes encoding the main components of the respiratory chain increased (cyt c by 78%, cox IV by 56%, ATPase by 69%, p < 0.05 compared with the control). The relative content of cytoskeletal proteins that can participate in the processes of transport and localization of mitochondria does not change, with the exception of an increase in the content of alpha-tubulin by 25% (p < 0.05) and its acetylated isoform (by 36%, p < 0.05); however, the mRNA content of these cytoskeletal genes did not differ from the control. The content of GDF9 mRNA does not change after hindlimb suspension. The data obtained show that short-term exposure to simulated weightlessness leads to intensification of metabolism in the ovaries.

Supplemental oxygen does not improve growth but can enhance reproductive capacity of fish.

Fish tend to grow faster as the climate warms but attain a smaller adult body size following an earlier age at sexual maturation. Despite the apparent ubiquity of this phenomenon, termed the temperature-size rule (TSR), heated scientific debates have revealed a poor understanding of the underlying mechanisms. At the centre of these debates are prominent but marginally tested hypotheses which implicate some form of 'oxygen limitation' as the proximate cause. Here, we test the role of oxygen limitation in the TSR by rearing juvenile Galaxias maculatus for a full year in current-day (15°C) and forecasted (20°C) summer temperatures while providing half of each temperature group with supplemental oxygen (hyperoxia). True to the TSR, fish in the warm treatments grew faster and reached sexual maturation earlier than their cooler conspecifics. Yet, despite supplemental oxygen significantly increasing maximum oxygen uptake rate, our findings contradict leading hypotheses by showing that the average size at sexual maturation and the adult body size did not differ between normoxia and hyperoxia groups. We did, however, discover that hyperoxia extended the reproductive window, independent of fish size and temperature. We conclude that the intense resource investment in reproduction could expose a bottleneck where oxygen becomes a limiting factor.

Gill surface area allometry does not constrain the body mass scaling of maximum oxygen uptake rate in the tidepool sculpin, Oligocottus maculosus.

The gill oxygen limitation hypothesis (GOLH) suggests that hypometric scaling of metabolic rate in fishes is a consequence of oxygen supply constraints imposed by the mismatched growth rates of gill surface area (a two-dimensional surface) and body mass (a three-dimensional volume). GOLH may, therefore, explain the size-dependent spatial distribution of fish in temperature- and oxygen-variable environments through size-dependent respiratory capacity, but this question is unstudied. We tested GOLH in the tidepool sculpin, Oligocottus maculosus, a species in which body mass decreases with increasing temperature- and oxygen-variability in the intertidal, a pattern consistent with GOLH. We statistically evaluated support for GOLH versus distributed control of [Formula: see text] allometry by comparing scaling coefficients for gill surface area, standard and maximum [Formula: see text] ([Formula: see text],Standard and [Formula: see text],Max, respectively), ventricle mass, hematocrit, and metabolic enzyme activities in white muscle. To empirically evaluate whether there is a proximate constraint on oxygen supply capacity with increasing body mass, we measured [Formula: see text],Max across a range of Po2s from normoxia to Pcrit, calculated the regulation value (R), a measure of oxyregulatory capacity, and analyzed the R-body mass relationship. In contrast with GOLH, gill surface area scaling either matched or was more than sufficient to meet [Formula: see text] demands with increasing body mass and R did not change with body mass. Ventricle mass (b = 1.22) scaled similarly to [Formula: see text],Max (b = 1.18) suggesting a possible role for the heart in the scaling of [Formula: see text],Max. Together our results do not support GOLH as a mechanism structuring the distribution of O. maculosus and suggest distributed control of oxyregulatory capacity.

The influence of verbal encouragement on heart rate, maximum oxygen uptake, and distance covered in young male adults during beep test

Communication and motivation from physical education teachers is an important part of physical education classes. Therefore, it is necessary to look for suitable and effective methods to maximize students’ effort and performance. This study aimed to investigate the changes in aerobic performance after applying verbal encouragement (VE) to the beep test for university students. A group of 397 male students with average body mass index (BMI) 24.81 ± 5.88 and age 19.1 ± 1.3 was randomly selected for this study. Students were divided into two groups: physically active (237 PAS) and non-active students (160 NAS). These students underwent a beep test with and without VE in a counterbalancing manner. A Wilcoxon signed-rank test was employed to find differences between the distance covered, maximum oxygen uptake and maximum heart rates after verbal VE and without stimulus (WS) in a beep test. The results showed that all students improved in the distance covered after VE compared to WS in the beep test (47.3 m, 5.53%, p &lt; 0.0001), NAS (34.2 m, 4.44%, p = 0.013) and PAS (60.2 m, 6.62%, p &lt; 0.0001). All students also increased maximal heart rate (beats per minute—BPM) values after VE stimulus compared to WS in the same test (1.01 BPM, 0.51%, p = 0.001) and PAS (1.58 BPM, 0.80%, p = 0.001). Only the NAS group did not significantly improve in maximal heart rate. These findings indicate that VE (“go-go or faster-faster”) applied every 60 seconds is more effective for improving endurance than without any stimulus and that VE improved performance statistically the same in both groups (NAS, PAS). Therefore, the positive effect of VE is similar to NAS and PAS.

Tolerance of an acute warming challenge declines with body mass in Nile tilapia: evidence of a link to capacity for oxygen uptake.

It has been proposed that larger individuals within fish species may be more sensitive to global warming, as a result of limitations in their capacity to provide oxygen for aerobic metabolic activities. This could affect size distributions of populations in a warmer world but evidence is lacking. In Nile tilapia Oreochromis niloticus (n=18, mass range 21-313 g), capacity to provide oxygen for aerobic activities (aerobic scope) was independent of mass at an acclimation temperature of 26°C. Tolerance of acute warming, however, declined significantly with mass when evaluated as the critical temperature for fatigue from aerobic swimming (CTSmax). The CTSmax protocol challenges a fish to meet the oxygen demands of constant aerobic exercise while their demands for basal metabolism are accelerated by incremental warming, culminating in fatigue. CTSmax elicited pronounced increases in oxygen uptake in the tilapia but the maximum rates achieved prior to fatigue declined very significantly with mass. Mass-related variation in CTSmax and maximum oxygen uptake rates were positively correlated, which may indicate a causal relationship. When fish populations are faced with acute thermal stress, larger individuals may become constrained in their ability to perform aerobic activities at lower temperatures than smaller conspecifics. This could affect survival and fitness of larger fish in a future world with more frequent and extreme heatwaves, with consequences for population productivity.

Estimated energy expenditure and training intensity in young female artistic gymnasts

Aim: This study determined the energy expenditure and effort intensity of athletes during women's artistic gymnastics training sessions. Methods: Ten gymnasts (age 10.9 ± 1.7 years) performed a test to estimate the maximum rate of oxygen uptake (VO2max), during which the maximum heart rate (HRmax) was also obtained. The heart rate (HR) of these gymnasts was recorded during five training sessions and then used to estimate the exercise intensity and energy expenditure. Results: Mean duration of training sessions was 4.08 ± 0.42 h, with mean HR corresponding to 137 ± 8 bpm or 69.0 ± 3.5% of HRmax. Gymnasts spent less training time at 90-100% HRmax compared to the other HR ranges (p < 0.05). Time spent at 60-70% and 70-80% was higher compared to 80-90% HRmax (p = 0.012 and p = 0.001, respectively). The training impulse was 239.2 ± 35.4 AU. Estimated energy expenditure was 768.3 ± 168.5 kcal, metabolic rate was 3.1 ± 0.6 kcal/min, and the metabolic equivalent of task (MET) corresponded to 6.1 ± 0.6. Conclusion: Young gymnasts performed prolonged and moderate-intensity training sessions that generated high energetic demands. This information is beneficial to gymnasts since the coaching team can use the data to control the training load and prescribe a proper diet.

Vitreoscilla Haemoglobin: A Tool to Reduce Overflow Metabolism.

Overflow metabolism is a phenomenon extended in nature, ranging from microbial to cancer cells. Accumulation of overflow metabolites pose a challenge for large-scale bioprocesses. Yet, the causes of overflow metabolism are not fully clarified. In this work, the underlying mechanisms, reasons and consequences of overflow metabolism in different organisms have been summarized. The reported effect of aerobic expression of Vitreoscilla haemoglobin (VHb) in different organisms are revised. The use of VHb to reduce overflow metabolism is proposed and studied through flux balance analysis in E. coli at a fixed maximum substrate and oxygen uptake rates. Simulations showed that the presence of VHb increases the growth rate, while decreasing acetate production, in line with the experimental measurements. Therefore, aerobic VHb expression is considered a potential tool to reduce overflow metabolism in cells.

Caracterización del proceso biológico de sulfuro oxidación: un enfoque de respirometría de pulsos in situ y microrespirometria de pulsos ex situ

During the optimization of environmental biotechnology processes, it is important to count on proper and reliable information about the kinetic and stoichiometric parameters of the microorganisms. In this work, the biological sulfide oxidation process was assessed under two novel dynamic pulse respirometric approaches: in-situ pulse respirometry conducted in airlift bioreactor and ex-situ pulse respirometry carried out in microreactors (microrespirometry) with samples taken from the airlift bioreactor. The process was characterized in terms of the growth yield, substrate oxidation yield, maximum oxygen uptake rate, affinity constant, and mass transfer coefficient. The in-situ pulse respirometry showed to be a reproducible technique that allowed the determination of the kinetic and stoichiometric parameters besides the detection of mass transfer limitations in the airlift bioreactor, however, its use in biological sulfide oxidation is limited to a few experiments and experimental conditions with significant time investment. On the other hand, the ex-situ pulse microrespirometry allowed the acquisition of a higher amount of information under a broader range of sulfide concentrations (from 5 to 60 mg H2S L-1) and experimental conditions such as different pH values. The results obtained showed that the ex-situ microrespirometry technique would be preferable over in-situ pulse respirometry for the proper and reliable characterization of the sulfide oxidation process.

How important is V̇O2max when climbing Mt. Everest (8,849 m)?

The maximal rate of oxygen uptake (V̇O2max) of humans declines with increasing altitude, but represents the upper limit of aerobic endurance performance at low and high altitude as well. Before Reinhold Messner and Peter Habeler climbed Mt. Everest first (1978) without supplemental oxygen, physiologists have doubted whether this would be possible due to insufficient V̇O2max remaining when approaching the summit (8849 m). Subsequently, several studies evaluated the decline in the V̇O2max levels at real and simulated extreme altitudes. However, the potential influence of the preexisting individual sea level V̇O2max remained largely unconsidered. Based on available studies and case observations, here we discuss the observed and expected decline of V̇O2max up to 8849 m dependent on the individual sea level V̇O2max. It is concluded that a high sea level V̇O2max and an only moderate decline of arterial oxygen saturation and associated V̇O2max with increasing altitude, due to appropriate acclimatization and ascent strategies, enable certain mountaineers to climb 8,000er summits and even the Everest without supplemental oxygen.

A study on the prediction of maximal oxygen consumption (VO2 max) among male and female medical college student population using bicycle ergometer

The maximal rate of oxygen uptake (VO2 max) is an important determinant of cardio-respiratory fitness and aerobic performance. Maximal oxygen uptake (VO2max) is an important, independent predictor of cardiovascular health and mortality. The present study was conducted in the Dept. of Physiology, GSL Medical College, East Godavari Dist., Andhra Pradesh, India. The study was conducted to establish prediction norms for VO2 max from physical parameters among sedentary young healthy student subjects (n = 72) consisting of male (n = 36) and female (n = 36) students of Medical College belonging to age group 18 – 24 years. The study was aimed to compare and correlate the measured parameters with the predicted parameters of V·O2max using a sub maximal cycle ergometry test. The parameters studied were age, gender, height, weight, systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), mean arterial pressure (MAP). The predicted VO2 max was calculated in male (n = 36) and female (n = 36) subjects during multistage sub maximal exercise test with bicycle Ergometer using the modified Astrand-Rhyming Nomogram. The present study results showed that mean heart beat rate, SBP and DBP variables can be identified as the good indicators on prediction of maximal oxygen consumption (VO2 max) using bicycle ergometer among males and female subjects though male individuals showed higher VO2 max values of mean body weight, height compared to female subjects however, was statistically not significant. Future research should focus on the variables involved in the prediction equations by stratification of subjects to obtain a large range of values for the variable (s) investigated. It was not possible to do this with the subjects such as age, weight and height participating in this project because the variables used were not easily stratified.

Theoretical analysis of the 12 min Cooper’s test to estimate the maximal oxygen uptake rate

The Cooper’s test is an indirect approach to estimate the maximal oxygen uptake rate (V̇O2,max) from the maximum distance covered in 12 min exhaustive physical activity. Despite its widespread usage, the 12 min Cooper’s test has been scarcely analyzed to assess its validity and potential extensions. The aim of the present work is to obtain a mathematical derivation of the Cooper’s equation from a model based on energy conservation and on Newton’s second law where resistive and propulsion forces are considered. The main result showed that the Cooper’s equation is a particular case of a more general equation, which was validated with field data already published in the literature. Overall, it is concluded that the Cooper’s equation is valid over a limited range of distances covered by the 12 min Cooper’s test.

Effect of Mathematical Modeling and Fitting Procedures on the Assessment of Critical Speed and Its Relationship With Aerobic Fitness Parameters.

An accurate estimation of critical speed (CS) is important to accurately define the boundary between heavy and severe intensity domains when prescribing exercise. Hence, our aim was to compare CS estimates obtained by statistically appropriate fitting procedures, i.e., regression analyses that correctly consider the dependent variables of the underlying models. A second aim was to determine the correlations between estimated CS and aerobic fitness parameters, i.e., ventilatory threshold, respiratory compensation point, and maximal rate of oxygen uptake. Sixteen male runners performed a maximal incremental aerobic test and four exhaustive runs at 90, 100, 110, and 120% of the peak speed of the incremental test on a treadmill. Then, two mathematically equivalent formulations (time as function of running speed and distance as function of running speed) of three different mathematical models (two-parameter, three-parameter, and three-parameter exponential) were employed to estimate CS, the distance that can be run above CS (d′), and if applicable, the maximal instantaneous running speed (smax). A significant effect of the mathematical model was observed when estimating CS, d′, and smax (P < 0.001), but there was no effect of the fitting procedure (P > 0.77). The three-parameter model had the best fit quality (smallest Akaike information criterion) of the CS estimates but the highest 90% confidence intervals and combined standard error of estimates (%SEE). The 90% CI and %SEE were similar when comparing the two fitting procedures for a given model. High and very high correlations were obtained between CS and aerobic fitness parameters for the three different models (r ≥ 0.77) as well as reasonably small SEE (SEE ≤ 6.8%). However, our results showed no further support for selecting the best mathematical model to estimate critical speed. Nonetheless, we suggest coaches choosing a mathematical model beforehand to define intensity domains and maintaining it over the running seasons.

Influence of simulated hypogravity on oxygen uptake during treadmill running.

Prolonged exposure to microgravity during spaceflights leads to severe deterioration in the physical performance of astronauts. To understand the effectiveness of existing in‐flight daily countermeasures and to plan exercise onboard the International Space Station, we compared supine treadmill running to traditional upright treadmill running on earth. Specifically, we assessed the cardiorespiratory responses to conventional upright running to the responses to supine treadmill running under 0.3 g, 0.6 g, and 1 g of body weight in younger (20–30 years, n = 14, 8 females) and older healthy adults (50–60 years, n = 12, 6 females). Maximal cardiorespiratory capacity was additionally evaluated by performing an incremental running protocol on each treadmill. Maximum speed was greater for 0.3 g and 0.6 g in supine than for upright running (18.5 km/h (1.1) and 15.9 (3.1) vs 13.2 (2.4) p < 0.001). In contrast, maximum oxygen uptake (V˙O2max) and maximum heart rate (HRmax) were greater in upright running than in all supine conditions (Upright treadmill running vs S1.0G vs S0.6G vs S0.3G, 41.7 ml kg−1 min−1 (7.2) vs 30.5 (6.6) vs 32.9 (7.0) vs 30.9 (5.2), p < 0.001 and 171 beats min−1 (14) vs 152 (24) vs 155 (20) vs 152 (18), p < 0.001, respectively). The reduction in V˙O2max was remarkably similar across all three supine conditions, could not be increased by higher running speeds and can be well explained by reduced ground reaction forces (GRF). Thus, although a gravity‐related restriction of pulmonary gas exchange or perfusion of the legs when exercising in the supine position can be suspected, findings are also explicable on grounds of the vertical treadmill mechanics. Reduced loading will constitute a substantial limitation to V˙O2 in space with implications for crew health and the physical deterioration of astronauts.

Egzersiz Testinin Ekshale Karbon Monoksit Oranı Üzerindeki Akut Etkisi

Objective: The aim of this study is to analyze the acute effect of exercise on the rate of exhaled carbon monoxide (CO) in healty young smokers. Material and Methods: Twenty four male smokers were included in the study. Pulmonary functions of the participants were evaluated by spirometer forced expiratory volume in one second (FEV1), forced vital capacity (FVC), FEV1/FVC, peak flow rate (PEF) and forced expiratory flow at 25 to 75% of FVC (FEF 25%-75%). Exercise testing was performed by using bicycle ergometer. Maximal load, maximum oxygen uptake (VO2max), rest and maximal heart rate were recorded. CO levels before and after the test were mesured with portable breath CO monitor. CO levels and changes were assessed and compared on the exercise test day and rest day (without exercise test). Results: 25% of the participants have dyspnea, 20.8% have cough and 50% have sputum complaints. The results of the pulmonary function test and exercise test of young healthy smokers are as follows: % FEV1=89.7±9.9, % FEV1/FVC=87.4±8.2, % PEF=77.4±9.5, mean rest heart rate=94.8±9.8 bpm, mean maximal heart rate=170.3±9.7 bpm and mean VO2max=30.9±6.5 mL/min/kg. There is a statistically significant difference between the first and the second CO values of the participants measured on both days (p<0.001). There is a significant difference between the mean change of CO on the exercise test day and rest day (p<0.001). Conclusion: Our results show that smoking causes respiratory symptoms, impaired cardiopulmonary responses to exercise and increased CO level and exercise increases to the exhaled CO rate in young and healthy male.

Contrasting effects of constant and fluctuating pCO2 conditions on the exercise physiology of coral reef fishes

Ocean acidification (OA) is predicted to affect the physiology of some fishes. To date, most studies have investigated this issue using stable pCO2 levels based on open ocean projections. Yet, most shallow, nearshore systems experience temporal and spatial pCO2 fluctuations. For example, pCO2 on coral reefs is highest at night and lowest during the day, but as OA progresses, both the average pCO2 and magnitude of fluctuations are expected to increase. We exposed four coral reef fishes – Lutjanus fulviflamma, Caesio cuning, Abudefduf whitleyi, and Cheilodipterus quinquelineatus – to ambient, stable elevated, or fluctuating elevated pCO2 conditions for 9–11 days. Then, we measured swimming performance, oxygen uptake rates, and haematological parameters during the day and at night. When compared to ambient pCO2 conditions, L. fulviflamma, C. cuning, and A. whitleyi exposed to fluctuating elevated pCO2 increased swimming performance, maximum oxygen uptake rates, and aerobic scope, regardless of time of day; whereas, the only nocturnal species studied, C. quinquelineatus, decreased maximum oxygen uptake rates and aerobic scope. Our findings suggest that exposure to fluctuating or stable elevated pCO2 can physiologically benefit some coral reef fishes; however, other species, such as the cardinalfish examined here, may be more sensitive to future OA conditions.

Effect of continuous positive airway pressure on maximal exercise capacity in patients with obstructive sleep apnea: a systematic review and meta-analysis.

Exercise capacity is impaired in obstructive sleep apnea (OSA). There are conflicting reports on the effect of continuous positive airway pressure (CPAP) on maximal exercise capacity. The objective of this review was to determine if there is a change in exercise capacity and anaerobic threshold following CPAP treatment in OSA patients. We conducted a systematic review and meta-analyses to summarize the changes in peak rate of oxygen uptake (V̇O₂ peak) or maximum rate of oxygen uptake (V̇O2 max) and anaerobic threshold (AT) during cardiopulmonary exercise testing following CPAP intervention in patients with OSA. A systematic literature review was conducted to identify published literature on markers of V̇O₂ peak, V̇O₂ max, and AT pre- vs post-CPAP using a web-based literature search of PubMed/MEDLINE, Embase, CINAHL, and Cochrane review (CENTRAL) databases. Two independent reviewers screened the articles for data extraction and analysis. The total search of all the databases returned 470 relevant citations. Following application of eligibility criteria, 6 studies were included in the final meta-analysis for V̇O₂ peak, 2 studies for V̇O₂ max, and five studies for AT. The meta-analysis showed a mean net difference in V̇O₂ peak between pre- and post-CPAP of 2.69 mL·kg-1·min-1, P = .02, favoring treatment with CPAP. There was no difference in V̇O₂ max or AT with CPAP treatment (mean net difference 0.66 mL·kg-1·min-1 [P = .78] and -144.98 mL·min-1 [P = .20] respectively). There is a paucity of high-quality studies investigating the effect of CPAP on exercise capacity. Our meta-analysis shows that V̇O₂ peak increases following CPAP treatment in patients with OSA, but we did not observe any change in V̇O₂ max or AT. Our findings should be considered preliminary and we recommend further randomized controlled trials to confirm our findings and to clarify the peak and maximum rates of oxygen uptake adaptations with CPAP therapy.

Thermal tolerance and hypoxia tolerance are associated in blacktip reef shark (Carcharhinus melanopterus) neonates.

Thermal dependence of growth and metabolism can influence thermal preference and tolerance in marine ectotherms, including threatened and data-deficient species. Here, we quantified the thermal dependence of physiological performance in neonates of a tropical shark species (blacktip reef shark, Carcharhinus melanopterus) from shallow, nearshore habitats. We measured minimum and maximum oxygen uptake rates (ṀO2 ), calculated aerobic scope, excess post-exercise oxygen consumption and recovery from exercise, and measured critical thermal maxima (CTmax), thermal safety margins, hypoxia tolerance, specific growth rates, body condition and food conversion efficiencies at two ecologically relevant acclimation temperatures (28 and 31°C). Owing to high post-exercise mortality, a third acclimation temperature (33°C) was not investigated further. Acclimation temperature did not affect ṀO2 or growth, but CTmax and hypoxia tolerance were greatest at 31°C and positively associated. We also quantified in vitro temperature (25, 30 and 35°C) and pH effects on haemoglobin-oxygen (Hb-O2) affinity of wild-caught, non-acclimated sharks. As expected, Hb-O2 affinity decreased with increasing temperatures, but pH effects observed at 30°C were absent at 25 and 35°C. Finally, we logged body temperatures of free-ranging sharks and determined that C. melanopterus neonates avoided 31°C in situ We conclude that C. melanopterus neonates demonstrate minimal thermal dependence of whole-organism physiological performance across a seasonal temperature range and may use behaviour to avoid unfavourable environmental temperatures. The association between thermal tolerance and hypoxia tolerance suggests a common mechanism warranting further investigation. Future research should explore the consequences of ocean warming, especially in nearshore, tropical species.