Oxygen Uptake Capacity Research Articles

Thermal index parameter investigation of coal–oxygen adsorption during low-temperature oxidation of coal

Oxidative spontaneous combustion is an inherent property of coal. In which, coal oxygen adsorption heat is the decisive speed step of coal spontaneous combustion self-acceleration process, and coal oxygen adsorption heat is closely related to coal pore structure. By utilising an automatic physicochemical adsorption instrument, it was found that the form of pore existence in coal was dominated by mesopores, that the pore structure, oxygen uptake capacity and temperature varied non-linearly, and that pore size was positively correlated with pore volume; Using a self–built air adsorption calorimetric experimental system, it was found that when oxygen was involved in the adsorption reaction, the presence of oxygen would lead to a significant time lag in the adsorption equilibrium. Additionally, the transition temperature of coal adsorption mode has been determined to be 40 °C, shedding light on the mechanism behind the thermal self-accelerating reaction of coal oxygen adsorption; Using the correlation method, it was obtained that the index affecting the physical adsorption heat release is the percentage of mesopore volume in the coal, while the index affecting the chemical adsorption heat release is the pore size. The research findings are anticipated to offer theoretical backing for advancing flame-resistant materials.

Mediative role of body mass index in cardiorespiratory fitness-associated vascular remodeling in youth.

Data on fitness-associated arterial remodeling in children is limited. We assessed the relation between cardiorespiratory fitness (CRF) and intima-media thickness (IMT), diameter, IMT:diameter-ratio (IDR), and tensile stress of the common carotid artery (CCA) in 697 healthy German schoolchildren. Further, we explored how body mass index (BMI) may influence these associations. We measured the vascular parameters with a high-resolution ultrasound device. We determined CRF using the FITNESSGRAM® PACER test and calculated each child's allometrically scaled peak oxygen uptake capacity (VO2peak). VO2peak, reflecting CRF, showed positive direct effects on IMT (girls: p < 0.001; boys: p = 0.02) and diameter in girls (p < 0.001). Considering BMI as a mediator, higher CRF was indirectly linked to decreases in IMT (girls: p = 0.04; boys: p = 0.02) and diameter (both p < 0.001), reflecting a competitive mediation. CRF indirectly mitigated the BMI-associated decrease in IDR (both p < 0.001) and increase in tensile stress (both p < 0.001) without affecting any of these parameters directly. CRF appears to be linked to uniform arterial remodeling with balanced hemodynamics and to further alleviate BMI-associated, potentially adverse vascular alterations, highlighting its significant role in cardiovascular health in youth. Data on CRF-associated arterial remodeling in youth is limited. Higher VO2peak, reflecting higher CRF, was positively associated with IMT in girls and boys and diameter in girls. These direct effects were counteracted by the indirect BMI-mediated effect of CRF on IMT and diameter, reflecting a competitive mediation. A higher CRF indirectly mitigated the BMI-associated decrease in IDR and increase in tensile stress without directly affecting any of these parameters. Our findings indicate homogenous remodeling and balanced hemodynamics with increasing CRF-and opposite effects with increasing BMI.

Waste biomass-derived activated carbons for selective oxygen adsorption

Activated carbons (ACs) derived from waste rice husk ash (RHA) exhibit remarkable potential for selective oxygen adsorption. The pore morphology of the prepared materials was characterized utilizing BET measurement, t-plot, and BJH-plot suggesting a linear relation between activation temperature and mesopore volume, whereas, micropore volume decreases at activation beyond 550 °C. FT-IR spectroscopy confirms their non-polar surface. Notably, AC-600 achieves an outstanding O2/N2 (0.21/0.78) of 152.7 at 0.01 bar at 25 °C, owing to the non-polar nature of the surface, favouring oxygen adsorption due to its low quadrupole moment. Additionally, the mixed micro and mesoporous structure of AC-600 significantly enhance the oxygen adsorption, showing an ∼18.4% (or 1.2-fold) increase compared to AC-500. However, a ∼32.3% decrease in oxygen uptake was observed for AC-800 due to excessive “burn-off”. Adsorption selectivity, assessed with Ideal Adsorption Solution Theory (IAST) and fitted to the Freundlich isotherm model, and adsorption kinetics, analysed using the pseudo-second-order Lagergren and Webber-Morris intraparticle diffusion models, highlighted the impact of activation temperature on the porosity of the material. Understanding the surface chemistry and pore morphology of activated carbon offers deeper insights to enhance oxygen uptake capacity, advancing the development of sustainable, industrially viable materials for oxygen production.

The Variability of the Components of Fitness along the Menstrual Cycle.

This study aims to determine the variability of the components of fitness along the menstrual cycle (MC) of physically active eumenorrheic women. Fifteen subjects were monitored along two consecutive MCs through the calendar-based counting method in combination with a urine luteinizing hormone surge kit. Subjects were tested at the early follicular phase (EFP), pre-ovulatory or late follicular phase (LFP), and post-ovulatory or mid-luteal phase (MLP). In each session, the back squat one-repetition maximum (1-RM), maximum fat oxidation (MFO), maximum oxygen uptake (VO2max) and acute recovery capacity were determined. The results revealed a wide variability among components of fitness and a low to high variability among subjects (acute recovery: 3.6% [range 1.5 to 9.5%]; back squat 1-RM: 6.1% [range 2.2 to 11%]; VO2max: 6.6% [range 1.1 to 15%]; MFO: 23% [range 4.6 to 35%]). Despite the individual nature, considering the number and magnitude of the responses in each MC phase, VO2max and acute recovery capacity tended to be enhanced at the LFP, the MFO at the MLP, and the back squat 1-RM remained stable along the MC. Thus, practitioners are aware of which components are susceptible to change along the MC phase, but an individual monitoring is recommended.

Changes in real-world walking speed following 60-day bed-rest

The aim of this work was to explore whether real-world walking speed (RWS) would change as a consequence of 60-day bed-rest. The main hypothesis was that daily RWS would decrease after the bed-rest, with a subsequent recovery during the first days of re-ambulation. Moreover, an exploratory analysis was done in order to understand whether there is an agreement between the loss in RWS after bed-rest and the loss in the maximum oxygen uptake capacity (VO2max), or the loss in maximal vertical jump power (JUMP) respectively. Twenty-four subjects were randomly assigned to one of three groups: a continuous artificial gravity group, an intermittent artificial gravity group, or a control group. The fitted linear mixed effects model showed a significant decrease (p < 0.001) of RWS after the 60-day bed-rest and a subsequent increase (p < 0.001) of RWS during the 14-day recovery period in the study facility. No or little agreement was found between the loss in RWS and the loss in VO2max capacity or the loss in maximal vertical jumping power (RWS vs. VO2max: p = 0.81, RWS vs. JUMP: p = 0.173). Decreased RWS after bed-rest, with a follow-up recovery was observed for all three groups, regardless of the training intervention. This suggests that RWS, also in these settings, was able to reflect a de-conditioning and follow-up recovery process.

Hemoglobin Mass and Blood Volume in Swimming: A Comparison Between Highly Trained, Elite, and World-Class Swimmers.

Total hemoglobin mass (tHbmass) and blood volume (BV) are important determinants of maximal oxygen uptake and endurance capacity. Higher-caliber endurance athletes usually possess higher tHbmass and BV values. This study aimed to compare tHbmass and BV among swimmers of diverse competitive calibers and distances. Thirty swimmers (16 female and 14 male) participated in the study: 3 were tier 5, world class (869 [59] FINA points); 15 were tier 4, elite/international (853 [38] points); and 12 were tier 3, highly trained/national (808 [35] points). They specialized in competition distances ranging from 200m to open-water 10km. Between February 2019 and February 2020, all swimmers had their tHbmass and BV measured by carbon monoxide rebreathing 1 to 6 times and participated in multiple competitions and race events. Relative tHbmass and BV were not different (P > .05) between tiers among women or among men (pooled tHbmass values 14.5 [0.5], 12.5 [1.5], 12.6 [2.3]g/kg for tier 5, tier 4, and tier 3, respectively). No differences were observed in relative tHbmass (P = .215) and BV (P = .458) between pool and open-water swimmers or between 200-, 400-, and 1500-m specialists (P > .05). No significant correlations were found between the highest measured absolute or relative tHbmass and BV and the highest FINA points scored over the follow-up period (R = -.42-.17, P = .256-.833), irrespective of competition distance. tHbmass and BV values did not differ between swimmers of different calibers or among competition distances. Furthermore, these values did not correlate with FINA points, either in males or in females. The present results indicate that hematological characteristics may have a lesser impact on swimming performance than on land-based endurance sports.

Assessing aerobic endurance in elite female cricket players

To assess and compare the aerobic endurance levels of elite female cricket players from Bangladesh and India. This study’s participants were 50 elite female cricket players (ages 18-30 years), with 25 players from each country. They were all considered elite players based on their performance and experience in national and international cricket tournaments. To measure aerobic endurance fitness, the participants underwent a Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1), which is widely used to measure an individual's maximal oxygen uptake (VO2max) and aerobic capacity. The data collected were analysed using descriptive statistics and inferential statistics. The test of Normality, mean, and standard deviation were calculated for each group, and a t-test was used to compare the mean scores of the two groups. A p-value of less than .05 is considered statistically significant. The data were analysed using the statistical software SPSS version 26. The study found that the Indian female cricket players had a significantly higher aerobic endurance fitness level than the Bangladeshi players. The mean VO2max of the Indian players was 46.76 ml/kg/min, while the Bangladeshi players' mean VO2max was 43.60 ml/kg/min. Additionally, the Indian players had a higher mean score in total distance covered in YYIRT1 (1233.6 m) than the Bangladeshi players (857.6). These differences were found to be statistically significant (p &lt; .05). These findings suggest that there may be a difference in the training and preparation methods between the two countries, leading to a higher aerobic endurance fitness level among Indian players.

The dependence of maximum oxygen uptake and utilization (V̇O2 max) on hemoglobin-oxygen affinity and altitude.

Oxygen transport from the lungs to peripheral tissue is dependent on the affinity of hemoglobin for oxygen. Recent experimental data have suggested that the maximum human capacity for oxygen uptake and utilization (V̇O2 max) at sea level and altitude (~3000 m) is sensitive to alterations in hemoglobin-oxygen affinity. However, the effect of such alterations on V̇O2 max at extreme altitudes remains largely unknown due to the rarity of mutations affecting hemoglobin-oxygen affinity. This work uses a mathematical model that couples pulmonary oxygen uptake with systemic oxygen utilization under conditions of high metabolic demand to investigate the effect of hemoglobin-oxygen affinity on V̇O2 max as a function of altitude. The model includes the effects of both diffusive and convective limitations on oxygen transport. Pulmonary oxygen uptake is calculated using a spatially-distributed model that accounts for the effects of hematocrit and hemoglobin-oxygen affinity. Systemic oxygen utilization is calculated assuming Michaelis-Menten kinetics. The pulmonary and systemic model components are solved iteratively to compute predicted arterial and venous oxygen levels. Values of V̇O2 max are predicted for several values of hemoglobin-oxygen affinity and hemoglobin concentration based on data from humans with hemoglobin mutations. The model predicts that increased hemoglobin-oxygen affinity leads to increased V̇O2 max at altitudes above ~4500 m.

Oxygen production at intermediate temperatures using Ca2AlMnO5+δ double perovskite-type oxides

Double-perovskite Ca2AlMnO5+δ exhibits promising oxygen uptake and release capacity at intermediate temperatures (400–700 °C), which makes it an interesting candidate for in situ oxygen production in an integrated gasification combined cycle (IGCC) process. Experiments were conducted at 10 bars by alternating gas feeds of air and various sweep gases to a packed bed filled with 300 g of granular oxygen carrier materials. These realistic operating conditions demonstrated that 15–20% oxygen can be introduced to the sweep gas, which is sufficient for autothermal gasification of solid fuels in IGCC. Argon performed slightly better than CO2 as a sweep gas, presumably because of some CO2 absorption or the higher O2 partial pressure of CO2 that inhibited O2 release. Further O2 concentration increases can be expected from increasing the temperature under reduction by feeding a fuel gas to combust with the released O2, but experiments with H2 did not produce the desired effect because the combustion reaction was too slow at the optimal reactor temperature (~ 600 °C). In general, the reduction stage was more prone to kinetic limitations, as illustrated by a significant decrease in O2 concentration when the sweep flowrate was increased. A longer oxidation stage to fully charge the oxygen carrier also increased O2 concentrations in the sweep, but this requires a process integration such as IGCC where the large quantity of warm depleted air can be effectively utilized. Furthermore, the enthalpy of oxidation of Ca2AlMnO5+δ was obtained from density functional theory modeling, equilibrium conditions in thermogravimetric analysis, packed bed experiments and directly from differential scanning calorimetry. The enthalpy of oxidation obtained by these techniques range from − 166 to − 196 kJ mol−1 O2.

Effect of resistance training on HbA1c and other cardiovascular risk factors in patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Obesity, hypertension, hyperlipidemia, and other cardiovascular risk factors are commonly clustered in patients with diabetes type II (T2DM). As a result, patients with T2DM are at increased cardiovascular (CV) risk. Exercise therapy is recommended in the prevention and management of patients with T2DM. In the last decade, dynamic resistance training has attracted more interest as an exercise therapy in the management of patients with diabetes. Though, the primary outcome in these intervention trials has mostly been glycated hemoglobin (HbA1c). Given the high prevalence of other CV risk factors in patients with T2DM, knowledge on the impact of dynamic resistance training on the overall CV risk profile of these patients is important. Purpose To perform a systematic review with meta-analysis to investigate the effects of resistance training on HbA1c and other traditional cardiovascular risk factors in patients with T2DM. Methods and analyses A systematic search was conducted in the electronic databases MEDLINE, Embase, SPORTdiscus and PEDro from the earliest date available until the first of September 2021 to identify peer reviewed randomized controlled trials investigating the effect of resistance training on HbA1C in adults with T2DM. Primary outcome was HbA1C. Secondary outcomes included traditional CV risk factors (i.e. blood pressure, blood lipids, body composition) and physical fitness (muscle strength, exercise capacity). Effect sizes were calculated using random effect models. Data are reported as weighted mean and 95% confidence limits. Results Fourteen trials could be included in the meta-analysis. Resistance training was found to significantly reduce HbA1c [-0.35 % (95% CL -0.61 to -0.11)], systolic blood pressure [-4.6 mmHg (95%CL -8.7 to -0.39)], diastolic blood pressure -2.25 (95%CL -4.45 to -0.048)) and body fat (-0 0.038). Muscle strength was significantly improved in the three studies reporting this outcome. Other cardiovascular risk factors including fasting plasma glucose, high-density-lipoprotein, low-density-lipoprotein, triglycerides and peak oxygen uptake capacity (VO2 peak) remained unchanged after resistance training in patients with T2DM. Conclusion The available data suggests that resistance training can exert favorable effects on HbA1C but also on blood pressure, body composition and muscle strength of patients with type 2 diabetes. Further research is needed to determine the impact of different resistance training characteristics such as volume, frequency and type of training on the overall CV risk profile of patients with type 2 diabetes.

An isotopic study on oxygen uptake/exchange over ceria-praseodymia mixed oxides with pulse experiments using 18O2: Implications on soot combustion activities in the GDI (Gasoline Direct Injection) context

This research work focuses on a preliminary study of the behaviour of several ceria-praseodymia mixed oxides along with three model catalysts under isotopic oxygen pulses at different temperatures in an attempt to investigate their ability to interact with 18O2 (uptaking/releasing/exchanging) with their own lattice oxygen, under conditions which could simulate those existing in GDI exhaust gases. Furthermore, these ceria-praseodymia mixed oxides were studied to explore their responses towards soot combustion under two consecutive 18O2 pulses at 500 °C. It was observed that the capacity of oxygen activation and uptake is very dependent on the nature of the catalyst. Ce1−xPrxO2-δ catalysts present different responses in the O2 activation and uptake processes, as a function of temperature, praseodymium content and method of preparation. Moreover, some of these ceria-praseodymia formulations exhibited high soot combustion activity with a marked intervention of unlabelled active oxygen species during the inert period after the 18O2 pulse.

The role of cell size in shaping responses to oxygen and temperature in fruit flies

Abstract The body size of an animal is strongly coupled to key ecological traits such as fecundity, mortality and growth. Ectothermic animals mature at smaller body sizes in warmer conditions and under low oxygen availability (hypoxia). Whether these responses result from changes in cell size and cell number (which together determine body size) and how such cellular responses may help ectotherms cope with heat and hypoxia is poorly understood. The theory of optimal cell size postulates that cell size imposes constraints on oxygen delivery: Differences in cell size result in differences in membrane surface‐to‐volume ratio, which impact the capacity of cells to take up oxygen and has consequences for growth rate and hence body size. Here, using inbred lines of fruit flies Drosophila melanogaster, which exhibit differences in cell size, we demonstrate that thermal responses in body size are magnified under hypoxia and in lines of flies that exhibit larger cell size. Furthermore, reductions in body size were partly manifested via reductions in cell size, resulting in a coupling between the body mass and cell size of flies. The coupling between cell size and body size was tighter under conditions where oxygen is expected to become limited, that is, warm or hypoxia, supporting the idea that capacity for oxygen uptake is causally related to organismal growth and the resulting body size. Our data indicate that the benefits of diffusive oxygen uptake due to the higher surface‐to‐volume ratios in smaller cells can help explain the temperature‐size rule in this species. Read the free Plain Language Summary for this article on the Journal blog.

TREINAMENTO DE RESISTÊNCIA APLICADO NO ENSINO DE KUNG FU

ABSTRACT Introduction Many studies have explored different training methods to improve cardiorespiratory capacity, ensuring better oxygen demand to help students develop better sports skills and teaching outcomes. Objective Explore the effects of applying resistance training on kung fu teaching. Methods 40 kung fu athletes were selected as research volunteers. They were randomly divided into experimental and control groups; both were trained in a cardiopulmonary resistance protocol for 8 weeks, three times a week, using a breathing trainer. The control group trained at 20%, while the experimental group had their training at 50% of full capacity. Results The maximal inspiratory pressure, FEV1 / FVC, and mvv15 of the lung function indices increased significantly in the experimental group; the forced capacity and maximal ventilation of the oxygen uptake capacity indices also increased significantly. The blood oxygen saturation and the blood flow perfusion index of the oxygen utilization capacity indices had significant differences between the groups; the central balance and flexibility indices also showed significant differences. Conclusion After cardiopulmonary endurance training, the athletes’ capacity was significantly improved, inferring a benefit in the quality of kung fu teaching. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Investigation of Physiological Exercise Parameters and Sleep Status of Elite Karate Athletes

Aim: The aim of this study was to determine sleep quality and exercise-related physiological parameters (heart rate, heart rate reserve, cardiac output, blood pressure, maximum oxygen uptake capacity) of elite karate athletes in Trabzoninvolved. Materials and Methods: Ten athletes, 3 girls and 7 boys, who are interested in karate at an elite level in Trabzon, participated in the study. Anthropometric measurements and body mass index measurements were made. Cardiopulmonary exercise test (CPET) was performed with a gradually increasing intensity (15W/min) bicycle ergometer test protocol. In this study, sleep parameters of the athletes were obtained by using the physical activity measurement holter (Sensewear Armband). Results: The mean age of the individuals was 17.8±1.39 years (n=10), the mean height was 169.0±8.1 cm (n=10), the mean weight was 63.99±7.64 kg (n=10), and the mean body mass index was 22.41 kg/m² (n=10) was. Average value for oxygen consumption (VO₂) at maximum workload level 43±8 ml/kg/min (n=10, 99±12% of predicted), average maximum power 197±27.50 Watts (n=10, 92%±% predicted) 14), mean minute ventilation (VE) 103±28 L/min (n=10, 95±22% of predicted), mean heart rate (HR) 181±12 beats/min (n=10, % predicted) 93±7) and mean oxygen (O₂) heart rate at maximum workload level was 15.20±2.90 ml/beat (n=10, 115.1±17.75% of predicted). The average lying down time of the athletes was 8 hours 8 minutes ±2 hours 26 minutes (n=9), sleep time was 6 hours 9 minutes±2 hours 30 minutes (n=9), and sleep efficiency was 74±12%. Conclusion: The findings of this study show that the participating athletes had a good aerobic capacity and a good training level for the sport branch they are were engaged

ANÁLISE DA RESISTÊNCIA CARDIOPULMONAR SOB DIFERENTES CARGAS EM EXERCÍCIOS AERÓBICOS

ABSTRACT Introduction The key objective of aerobic exercise is enhancing cardiorespiratory endurance. On the national gymnastics plan implementation, the idea of lifelong sports was gradually accepted by the masses, and the aerobic gymnastics concept was sweeping the world. Objective Analyze the cardiorespiratory endurance responses in female college students under different frequencies in aerobic exercise. Methods 20 female professors and civilian women were randomly selected and divided into two groups. The experimental group performed 45 and 90 minutes of aerobic exercise to analyze changes in cardiopulmonary function before and after each exercise. Results After 16 weeks of aerobic exercise with different loads, all young women who had participated in the program training showed a significant increase in vital capacity and maximal oxygen uptake capacity. The vital capacity of the 90-min aerobic exercise group was significantly higher than that of the 45-min aerobic exercise group (P&lt;0.05). Conclusion The establishment of a cardiorespiratory endurance response model can accurately analyze the effects of different aerobic exercise frequencies on cardiorespiratory endurance. Evidence Level II; Therapeutic Studies – Investigating the results.

Abstract 10388: Impact Of Right Ventricular Function On Cardiopulmonary Exercise Capacity In Mitral Regurgitation Patients Undergoing Transcatheter Mitral Valve Repair

Background/Objectives: To investigate the role of right ventricular (RV) function on exercise capacity in patients undergoing transcatheter mitral valve repair (TMVR) we aimed to perform cardiopulmonary exercise testing (CPET) and to show a correlation between an improved RV function and maximal and submaximal exercise capacity. Methods: Constant work rate exercise time testing (CWRET) reflects submaximal/endurance exercise capacity, which is more likely to be relevant for daily life activities, and gives a more differentiated physiologic insight into the nature of exercise intolerance. Thus, 28 Patients with mitral regurgitation (MR) and symptomatic heart failure (NYHA≥II) underwent CPET by assessment of maximal oxygen uptake (peak VO 2 ) and submaximal exercise capacity (at 75% of maximal achieved work rate in the initial incremental exercise test) accompanied by echocardiography prior to TMVR and 3 months post-procedure. Results: Mean age of the patients was 75.0±8.7 years and 32.1% of them were female. One patient presented a reduction of MR &lt;2 grades. RV function (assessed with fractional area change, tricuspid annular plane systolic excursion, longitudinal strain of the RV free wall and S`) was at least moderately impaired in 25% of the patients. The submaximal exercise capacity of these patients was impaired, but did not significantly differ (416.4±359.6sec vs. 296.1 ±216.5sec; p=0.152) compared to patients without a deteriorated RV function. Three months after intervention, exercise time at 75% of maximal achieved work rate significantly improved (from 337.4±262.2sec to 517.4±393. sec p=0.006), reflecting a gain in submaximal exercise tolerance. peak VO 2 showed a positive trend, but no statistically significant difference (10.3±3.1ml/min/kg vs. 11.3±3.4ml/min/kg; p=0.056). RV function (at least 2 of 4 parameters) improved in 35.7% and these patients showed a significantly higher submaximal exercise time increasement (471.7±153.9sec vs. 82.7±47.0sec, p=0.003). Discussion/Conclusions: TMVR may have a beneficial effect on RV remodeling. Furthermore, submaximal exercise capacity is significantly increased, reflecting an improvement especially regarding daily life activities in MR patients and impaired RV function.

Chronic experimental hyperoxia elevates aerobic scope: a valid method to test for physiological oxygen limitations in fish.

Experimental hyperoxia has been shown to enhance the maximum oxygen uptake capacity of fishes under acute conditions, potentially offering an avenue to test prominent physiological hypotheses attempting to explain impacts of climate warming on fish populations (e.g., gill-oxygen limitation driving declines in fish size). Such benefits of experimental hyperoxia must persist under chronic conditions if it is to provide a valid manipulation to test the relevant hypotheses, yet the long-term benefits of experimental hyperoxia to oxygen uptake capacity have not been examined. Here, the authors measured aerobic metabolic performance of Galaxias maculatus upon acute exposure to hyperoxia (150% air saturation) and after 5months of acclimation, at both 15°C and 20°C. Acute hyperoxia elevated aerobic scope by 74%-94% relative to normoxic controls, and an elevation of 58%-73% persisted after 5months of hyperoxia acclimation. When hyperoxia-acclimated fish were acutely transitioned back to normoxia, they maintained superior aerobic performance compared with normoxic controls, suggesting an acclimation of the underlying metabolic structures/processes. In demonstrating the long-term benefits of experimental hyperoxia on the aerobic performance of a fish, the authors encourage the use of such approaches to disentangle the role of oxygen in driving the responses of fish populations to climate warming.

Remote ischemic preconditioning enhances aerobic performance by accelerating regional oxygenation and improving cardiac function during acute hypobaric hypoxia exposure.

Remote ischemic preconditioning (RIPC) may improve exercise performance. However, the influence of RIPC on aerobic performance and underlying physiological mechanisms during hypobaric hypoxia (HH) exposure remains relatively uncertain. Here, we systematically evaluated the potential performance benefits and underlying mechanisms of RIPC during HH exposure. Seventy-nine healthy participants were randomly assigned to receive sham intervention or RIPC (4 × 5 min occlusion 180 mm Hg/reperfusion 0 mm Hg, bilaterally on the upper arms) for 8 consecutive days in phases 1 (24 participants) and phase 2 (55 participants). In the phases 1, we measured the change in maximal oxygen uptake capacity (VO2max) and muscle oxygenation (SmO2) on the leg during a graded exercise test. We also measured regional cerebral oxygenation (rSO2) on the forehead. These measures and physiological variables, such as cardiovascular hemodynamic parameters and heart rate variability index, were used to evaluate the intervention effect of RIPC on the changes in bodily functions caused by HH exposure. In the phase 2, plasma protein mass spectrometry was then performed after RIPC intervention, and the results were further evaluated using ELISA tests to assess possible mechanisms. The results suggested that RIPC intervention improved VO2max (11.29%) and accelerated both the maximum (18.13%) and minimum (53%) values of SmO2 and rSO2 (6.88%) compared to sham intervention in hypobaric hypoxia exposure. Cardiovascular hemodynamic parameters (SV, SVRI, PPV% and SpMet%) and the heart rate variability index (Mean RR, Mean HR, RMSSD, pNN50, Lfnu, Hfnu, SD1, SD2/SD1, ApEn, SampEn, DFA1and DFA2) were evaluated. Protein sequence analysis showed 42 unregulated and six downregulated proteins in the plasma of the RIPC group compared to the sham group after HH exposure. Three proteins, thymosin β4 (Tβ4), heat shock protein-70 (HSP70), and heat shock protein-90 (HSP90), were significantly altered in the plasma of the RIPC group before and after HH exposure. Our data demonstrated that in acute HH exposure, RIPC mitigates the decline in VO2max and regional oxygenation, as well as physiological variables, such as cardiovascular hemodynamic parameters and the heart rate variability index, by influencing plasma Tβ4, HSP70, and HSP90. These data suggest that RIPC may be beneficial for acute HH exposure.

Effects Of Specific Exercise Training During 120 Days Isolation On Physiological Kinetics And Inhibitory Control

PURPOSE: Long-term isolation is known for the detrimental effects of inactivity and decreased external stimuli on physical and cognitive systems, which is relevant for space travel in microgravity but also for pandemic-related isolation periods. Exercise countermeasures are investigated in terrestrial analog settings concerning feasibility, time efficiency, and overall beneficial effects on cardiorespiratory and cognitive fitness (i.e., positive exercise-cognition interaction). In terrestrial settings, interval (INT) and continuous (CON) treadmill exercise showed positive effects on heart rate (HR) and oxygen uptake (V̇O2) capacities and kinetics, but research for space application is still pending. We expected (I) negative effects of isolation on cognitive performance and (II) physical fitness improvements, especially from INT. METHODS: Six participants (34 ± 6 years, 3 females) spent 120 days in isolation on a simulated journey to the moon (SIRIUS-19). 8 weeks of CON, followed by 8 weeks of INT aerobic exercise on a treadmill were conducted in a crossover design. Cardiorespiratory capacities, kinetics (HR, V̇O2), and cognitive performance (Flanker task measuring inhibitory control) were assessed with an exercise protocol, including pseudo-random binary sequences (PRBS), constant work-rate phases (Rest, 3, 6, 9 km h-1, recovery), and incremental exercise for Pre, Post, and five times during isolation (ANOVA: time x phase). RESULTS: Peak values for HR (P = 0.025), V̇O2 (P = 0.012), and respiratory exchange ratio (P = 0.001) had significant time effects with lower values during isolation. Kinetics of HR and V̇O2 improved during the mission with slightly better effects for INT (both p < 0.05). Inhibitory control was not altered by 120 days of isolation. CONCLUSIONS: This study proved the successful implementation of cognitive testing within our endurance exercise test. Positive effects for INT and CON aerobic exercise were confirmed for HR, but not for V̇O2 kinetics during isolation periods. We assume the lack of general physical activity is merely compensated for by the applied exercise countermeasure, at least in 1G contexts. Currently, additional exercise modalities (i.e., strength training, passive treadmill exercise) are investigated during a consecutive 240-day mission (SIRIUS-21).

Larger Nile tilapia struggle in hot water

When your metabolism depends on the temperature of your surroundings, climate change represents a unique and alarming challenge. As temperatures increase, your metabolic rate rises too, requiring that you consume more oxygen to maintain your body at a faster pace. ‘At warmer temperatures, larger individuals may be prone to limitations in their capacity for oxygen uptake’, says David McKenzie, at the CNRS's Centre for Marine Biodiversity Exploitation and Conservation, Montpellier, France, with the consequence that larger fish may struggle to survive at higher temperatures. ‘If true, this would be important in projecting how global warming will affect fish populations’, says McKenzie; the size distribution of fish populations could become smaller as temperatures rise. ‘But evidence is lacking’, McKenzie admits. So, he and colleagues from the Federal University of São Carlos, Brazil, decided to find out how well Nile tilapia (Oreochromis niloticus), ranging in size from 21 to 313 g, managed to keep swimming at high speed as the temperature rose. First, the team tested how resilient the resting fish were as the water temperature rose. Initially, the fish began behaving erratically but eventually they toppled over when the temperature was too high. However, the largest fish were as resilient as the smallest; getting enough oxygen was not an issue when the fish were resting. ‘They may lose their balance for another reason when they are warmed up while resting in a tank’, McKenzie says.He and his colleagues then set the fish a challenge, encouraging them to swim at 85% of their top speed while the researchers gently increased the water temperature, and they found that the largest animals struggled most as the temperature rose. They gave up swimming at lower temperatures (around 37°C), while the smaller fish managed to keep going at temperatures up to 39.5°C. And when the team investigated the fish's oxygen consumption as the temperature increased, they found the largest fish got out of breath at far lower oxygen consumption rates (∼18 mmol O2 kg−1 h−1) than their smaller counterparts (41 mmol O2 kg−1 h−1).So, larger tilapia struggle to keep swimming as the temperature rises and they seem to find it difficult to get enough oxygen, which could have implications for the size of fish in future populations. McKenzie suspects that ‘Global warming may favour the small’, as smaller individuals may be able to take the heat while larger fish may have more trouble surviving in hot water.