Compensation Point Research Articles

An undergraduate laboratory to study exercise thresholds.

In exercise physiology, laboratory components help students connect theoretical concepts to their own exercise experiences and introduce them to data collection, analysis, and interpretation using classic techniques. Most courses include a lab protocol that involves exhaustive incremental exercise during which expired gas volumes and concentrations of oxygen and carbon dioxide are measured. During these protocols, there are characteristic alterations in gas-exchange and ventilatory profiles that give rise to two exercise thresholds: the gas exchange threshold (GET) and the respiratory compensation point (RCP). The ability to explain why these thresholds occur and how they are identified are fundamental to learning in exercise physiology and requisite to the understanding of core concepts including exercise intensity, prescription, and performance. Proper identification of GET and RCP requires the assembly of 8 data plots. In the past, the burden of time and expertise required to process and prepare data for interpretation has been a source of frustration. In addition, students often express a desire for more opportunities to practice/refine their skills. The objective of this article is to share a blended laboratory model that features the "Exercise Thresholds App" - a free online resource that eliminates post-processing of data and provides a bank of profiles on which end-users can practice threshold identification skills with immediate feedback. In addition to including pre-laboratory and post-laboratory recommendations, we present student accounts of understanding, engagement, and satisfaction following completion of the laboratory experience and introduce a new quiz feature of the app to assist instructors with evaluating student learning.

Occurrence of distinctive cells and effects of irradiance on vascular formation in leaves of shade-tolerant C4 grass Paspalum conjugatum.

The denser leaf vasculature of C4 plants than of C3 plants may suit rapid export of assimilates associated with their higher photosynthetic rate. However, some C4 grasses have partially reduced leaf vasculature with vascular bundle (VB)-free bundle-sheath cells called distinctive cells (DCs). The shade-tolerant C4 grass Paspalum conjugatum has such a reduced leaf vascular system with DCs. We examined whether irradiance during growth affects vascular formation in leaves of P. conjugatum grown under 100%, 30%, or 14% sunlight for 1 month alongside the C4 grass maize. Under all conditions, P. conjugatum leaves had partially reduced vasculature: DCs and incomplete small VBs without phloem occurred between VBs with a normal structure consisting of both xylem and phloem. Shaded plants had less phloem in the small VBs than the full-sunlit plants. In maize, however, all VBs always had both xylem and phloem under all light conditions. The net photosynthetic rate of both grasses was reduced under shade; that of P. conjugatum was always lower than that of maize under all light conditions, but was reduced less by shade than that of maize. The light compensation point was lower in P. conjugatum than in maize, indicating that P. conjugatum acclimatizes better to low light. The reduction of phloem in VBs of P. conjugatum may be an acclimatization to shade, because dense vasculature may be expensive for C4 plants growing in environments where the higher photosynthetic rate is not realized.

Compensation behaviors and magnetic properties of an ising-type bilayer graphyne nanoribbon

In this work, we employ Monte Carlo method to examine the compensation behaviors and magnetic properties of an Ising-type bilayer graphyne nanoribbon. Consideration is given to how the magnetic characteristics of the system are affected by the length of the graphyne nanoribbon and the number of Monte Carlo steps. The influence of different parameters such as exchange coupling, crystal field, temperature and external magnetic field on the studied system are investigated. It is presented that the system can show the interesting behaviors such as double compensation points and multi-loop hysteresis behaviors under certain parameters. These may offer theoretical reference for multi-state magnetic recording.

Oxygen Uptake Kinetics and Time Limit at Maximal Aerobic Workload in Tethered Swimming.

This study aimed to apply an incremental tethered swimming test (ITT) with workloads (WL) based on individual rates of front crawl mean tethered force (Fmean) for the identification of the upper boundary of heavy exercise (by means of respiratory compensation point, RCP), and therefore to describe oxygen uptake kinetics (VO2k) and time limit (tLim) responses to WL corresponding to peak oxygen uptake (WLVO2peak). Sixteen swimmers of both sexes (17.6 ± 3.8 years old, 175.8 ± 9.2 cm, and 68.5 ± 10.6 kg) performed the ITT until exhaustion, attached to a weight-bearing pulley-rope system for the measurements of gas exchange threshold (GET), RCP, and VO2peak. The WL was increased by 5% from 30 to 70% of Fmean at every minute, with Fmean being measured by a load cell attached to the swimmers during an all-out 30 s front crawl bout. The pulmonary gas exchange was sampled breath by breath, and the mathematical description of VO2k used a first-order exponential with time delay (TD) on the average of two rest-to-work transitions at WLVO2peak. The mean VO2peak approached 50.2 ± 6.2 mL·kg-1·min-1 and GET and RCP attained (respectively) 67.4 ± 7.3% and 87.4 ± 3.4% VO2peak. The average tLim was 329.5 ± 63.6 s for both sexes, and all swimmers attained VO2peak (100.4 ± 3.8%) when considering the primary response of VO2 (A1' = 91.8 ± 6.7%VO2peak) associated with the VO2 slow component (SC) of 10.7 ± 6.7% of end-exercise VO2, with time constants of 24.4 ± 9.8 s for A1' and 149.3 ± 29.1 s for SC. Negative correlations were observed for tLim to VO2peak, WLVO2peak, GET, RCP, and EEVO2 (r = -0.55, -0.59, -0.58, -0.53, and -0.50). Thus, the VO2k during tethered swimming at WLVO2peak reproduced the physiological responses corresponding to a severe domain. The findings also demonstrated that tLim was inversely related to aerobic conditioning indexes and to the ability to adjust oxidative metabolism to match target VO2 demand during exercise.

Competition regulates mango fruiting above a floral density threshold

Mango flowering is interannually variable and temperature dependent. Flowering intensity declines with increasing pre-flowering temperatures associated with global warming, potentially limiting yields. Additionally, floral density that does not contribute to greater yield represents an unnecessary drain on plant resources such as nutrients, water, and carbohydrates. This can lead to reduced fruit bearing capacity in later stages of cropping or contribute to interannual yield variation.The objective of this work was to identify the floral density compensation point (FDCP), above which additional flowering becomes redundant, and below which surplus carbohydrates are partitioned to existing flowers, fruit, vegetative growth, or stored. Over two growing seasons, the number of inflorescences on 32 Calypso® mango trees in Dimbulah, Australia were thinned by up to 95%, resulting in floral densities between 0.09 and 4.14 inflorescences per trunk cross sectional area (cm2). Fruit yield, number, composition, vegetative growth, and starch concentration in terminal growth units were measured for each of the trees.Calypso® mango trees have excess floral density, beyond the maximum fruit biomass the tree can support to harvest. Below the FDCP, the tree is unable to compensate for low numbers of inflorescences, and floral density was strongly positively correlated with fruit number and yield, and strongly negatively correlated with fruit per panicle and total soluble solids concentration of ripe fruit. Above the FDCP fruit yield, number and total soluble solids concentration were only weakly related to floral density as they appear limited by carbohydrate availability rather than flowering. Fruit weight, vegetative regrowth of fruiting and non-fruiting terminals, and the starch concentration in terminal growth units were less dependent upon the FDCP and changed continuously across the floral densities evaluated. This information will be valuable for managing mango flowering under current and future climates.

Investigating the Impact of Temperature on Magnetic-Field Behavior of Thin-Film Three-Layer Systems Co/Cu/Co and Co/Gd/Co

This paper presents the results of investigating the impact of temperature on the magnetic properties of Co/Gd/Co and Co/Cu/Co thin-film three-layer systems obtained via ion-plasma magnetron sputtering. The following features of the studied samples were found. In particular, when the temperature changes from 100 to 300[Formula: see text]K, the coercive force of studied systems decreases. The magnetic moment of Co/Cu/Co sample does not dependent on temperature. Strong influence of temperature on the magnetic properties of the studied samples is observed. In particular, a compensation point was found at temperature [Formula: see text][Formula: see text]K for a Co/Gd/Co sample with thickness of gadolinium of 9.0[Formula: see text]nm.

Effects of site dilution on Compensation in Ising Spin-1/2 trilayered triangular Ferrimagnets with non-equivalent planes

Using Monte Carlo simulations with the Metropolis algorithm, the magnetic and thermodynamic behaviours of a spin-1/2, trilayered ferrimagnetic system on triangular monolayers with quenched nonmagnetic impurities are studied. Two different theoretical atoms, A and B, make up the ABA and AAB types of distinct configurations. Like atoms (A-A and B-B) interact ferromagnetically, while unlike atoms (A-B) interact antiferromagnetically. Only the A-layers are randomly site-diluted with dilution percentages ranging from 5% to 45%. Such diluted magnetic thin systems exhibit magnetic compensation which depends sensitively on the concentration of impurities. The phase diagram in the Hamiltonian parameter space related to the occurrence of magnetic compensation phenomenon and the effect of site dilution is discussed in detail. Special attention is given to the mathematical dependencies of compensation temperature on the concentration of nonmagnetic impurities. Depending upon the concentration of nonmagnetic impurities, the compensation and critical points shift with the equilibrium magnetic behaviours changing between distinct ferrimagnetic behaviours. For each combination of the coupling strengths, with values of the impurity concentration above a threshold, compensation appears where previously was absent. Suggested mathematical formulae show how threshold impurity concentration relies on Hamiltonian parameters.

STUDY REGARDING THE IMPORTANCE OF MONITORING PHYSIOLOGICAL PARAMETERS IN ELITE FENCING

Introduction. Fencing is a sport that requires psychomotor skills, explosive power, movement speed, reaction speed and physical endurance. Epée and foil fencers have higher aerobic capacity than sabre fencers, whereas épée and foil fencers have similar aerobic capacity. In fact, this can be due to more aerobic nature of épée and foil weapons compared with sabre. Measurement of maximum oxygen uptake (VO2max) is the standard index of cardiorespiratory fitness, but is practical only in a laboratory setting. Over time, numerous VO2 tests have shown that VO2max is a quantifiable and reproducible parameter of the cardiorespiratory system’s ability to meet maximum oxygen requirements. Objective. The aim of this study is to show the importance of monitoring physiological parameters by the Bruce protocol in elite fencing, specifically women’s épée, in order to manage the physical training plan. Methodology. Cardiopulmonary fitness is monitored in dynamic conditions by testing VO2max with the Bruce protocol of the COSMED treadmill Ergometer. This study was carried out over period of 8 weeks in 2021. It should be mentioned that these tests were performed after a specific training plan adapted to the pandemic period. Were included 4 female épée fencers, members of the Romanian National Fencing Team, aged between 22 and 36 years and with outstanding results at national and international levels. Results. From the total of tested physiological parameters were selected the protocol parameters (speed, treadmill incline, time) and metabolic parameters (absolute oxygens consumed (ml/min), maximum oxygens consumed (ml/min/kg), metabolic equivalents, respiratory coefficient, heart rate). These indicators were assessed for anaerobic threshold, respiratory compensation point and at the end of the test. The evolution of these parameters was followed between tests for each subject. Discussions and conclusions. The Bruce Protocol estimates maximal oxygen consumption (VO2 max) as a measure of the athlete's aerobic capacity during sustained effort. In this context, the obtained results highlight an increase of the cardiorespiratory fittness to the women’s épée, an efficient distribution of the oxygen to the tissues and a better adaptation of the cardiac function to the effort. In conclusion, the cardiorespiratory capacity monitoring through the Bruce Protocol can be an important guideline for the physical training to the elite épée fencers.

“Impact of aging on maximal oxygen uptake adjusted for lower limb lean mass, total body mass, and absolute values in runners”

Performance in endurance sports decreases with aging, which has been primarily attributed to cardiovascular and musculoskeletal aging; however, there is still no clear information on the factors that are most affected by aging. The aim of this study was to compare two groups of runners (< 50 and > 50 years of age) according to their absolute, weight-adjusted maximal oxygen uptake (V̇O2max), lower limb lean mass-adjusted V̇O2max, ventilatory threshold, and respiratory compensation point (RCP). A total of 78 male recreational long-distance runners were divided into Group 1 (38.12 ± 6.87 years) and Group 2 (57.55 ± 6.14 years). Participants were evaluated for body composition, V̇O2max, VT, and RCP. Group 1 showed higher absolute and body mass-adjusted V̇O2max (4.60 ± 0.57 l·min−1 and 61.95 ± 8.25 ml·kg−1·min−1, respectively) than Group 2 (3.77 ± 0.56 l·min−1 and 51.50 ± 10.22 ml·kg−1·min−1, respectively), indicating a significant difference (p < 0.001, d = − 1.46 and p < 0.001, d = − 1.16). Correspondingly, Group 1 showed a significantly higher lower limb lean mass–adjusted V̇O2max (251.72 ± 29.60 ml·kgLM−1·min−1) than Group 2 (226.36 ± 43.94 ml·kgLM−1·min−1) (p = 0.008, d = − 0.71). VT (%V̇O2max) (p = 0.19, d = 0.19) and RCP (%V̇O2max) (p = 0.24, d = 0.22) did not differ between the groups. These findings suggest that both variables that are limited by central or peripheral conditions are negatively affected by aging, but the magnitude of the effect is higher in variables limited by central conditions. These results contribute to our understanding of how aging affects master runners.

Effects of Acid Rain Stress on the Physiological and Biochemical Characteristics of Three Plant Species

The physiological and biochemical indicators of plants reflect the plant’s adaptation to environmental changes and provide information for the planting and management of acid-resistant tree species. To analyze the responses of typical tree species to recent changes in acid rain conditions in Jinyun Mountain, Chongqing, we focused on three representative tree species in the Jinyun Mountain area of Chongqing: Pinus massoniana, Phyllostachys edulis, and Cinnamomum camphora. A mixed acid rain experiment with five gradients of natural rainfall (NR) and pH values of 7.0, 4.5, 3.5, and 2.5 was conducted in May 2021. The changes in physiological and biochemical indicators (net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, light saturation point, light compensation point, apparent quantum efficiency, dark respiration rate, soluble sugar, starch, soluble protein, proline, malondialdehyde, and antioxidant enzyme activity) were determined. The results show the following: 1. Compared with other treatments, NR and slightly acidic rain increased the relative chlorophyll content in plant seedlings. 2. The synthesis of soluble sugars, starches, and soluble proteins was inhibited to different degrees in the three species under acid rain stress at pH ≤ 3.5. 3. The enzyme activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) initially increased and then decreased with an increase in acidity. 4. Acid rain treatments with pH ≤ 4.5 reduced the net photosynthetic rate (Pn) of plants; the higher the acidity, the lower the Pn. Conclusion: A comprehensive comparison of the indicators revealed that NR and mild acid rain enhanced the plant seedlings’ physiological and biochemical characteristics. A pH of 3.5 was the threshold where acid rain had an adverse effect on Pinus massoniana, Phyllostachys edulis, and Cinnamomum camphora. The high indicator values for NR indicate that these tree species have adapted to current conditions in the Jinyun Mountain area of Chongqing. This study provides new information for selecting tree species adapted to the acid rain environment in Jinyun Mountain, Chongqing.

Reproducibility (reliability and agreement) of ventilatory threshold and peak responses during cardiopulmonary exercise test in people with stroke

ABSTRACT Background A cardiopulmonary exercise test (CPET) is used to determine the ventilatory thresholds and to directly assess cardiorespiratory capacity. However, its reproducibility should be tested in people with stroke as sequelae imposed by the stroke may induce important variations among and within each subject, affecting the reproducibility of the physiological responses to CPET. Purpose This cross-sectional repeated measures study design aims to determine the reproducibility of anaerobic threshold (AT), respiratory compensation point (RCP), and maximal cardiorespiratory capacity assessed during a CPET in people with stroke. Methods Twenty-eight subjects with hemiparesis after stroke aging 60 ± 13 years were submitted to two treadmill CPETs with identical protocols. Data Analysis The reproducibility of heart rate (HR) and oxygen consumption (VO2) obtained at AT, RCP, and peak effort was evaluated by systematic error (paired t-test); reliability (ICC and 95% confidence interval); and agreement (typical error and coefficient of variation). Results There were no systematic errors for HR and VO2assessed at AT, RCP, and peak effort (p > 0,05). Reliability was high for these variables during CPET (ICCs > 0.93). Agreement was good for all variables. Typical errors for HR and VO2 assessed at AT, RCP, and peak effort were, respectively, 7, 7, and 8 bpm, and 1.51, 1.44, and 1.57 ml.kg−1.min−1. Coefficients of variation assessed at AT, RCP, and peak effort were, respectively, 5.7, 5.1, and 6.0% for HR and 8.7, 7.3, and 7.5% for VO2. Conclusions HR and VO2 measured at AT, RCP, and peak effort during a treadmill CPET present good reproducibility in people with stroke, showing high reliability and good agreement.

Can the heart rate response at the respiratory compensation point be used to retrieve the maximal metabolic steady state?

ABSTRACT The metabolic rate (VO2) at the maximal metabolic steady state (MMSS) is generally not different from the VO2 at the respiratory compensation point (RCP). Based on this, it is often assumed that the heart rate (HR) at RCP would also be similar to that at MMSS. The study aims to compare the HR at RCP with that at MMSS. Seventeen individuals completed a ramp-incremental test, a series of severe-intensity trials to estimate critical power and two-to-three 30-min trials to confirm MMSS. The HR at RCP was retrieved by linear interpolation of the ramp-VO2/HR relationship and compared to the HR at MMSS recorded at 10, 15, 20, 25 and 30 min. The HR at RCP was 166 ± 12 bpm. The HR during MMSS at the timepoints of interest was 168 ± 8, 171 ± 8, 175 ± 9, 177 ± 9 and 178 ± 10 bpm. The HR at RCP was not different from the HR at MMSS at 10 min (P > 0.05) but lower at subsequent timepoints (P < 0.05) with this difference becoming progressively larger. For all timepoints, limits of agreement were large (~30 bpm). Given these differences and the variability at the individual level, the HR at RCP cannot be used to control the metabolic stimulus of endurance exercise.

Considerations for the Measurement of Respiratory Compensation Point and Critical Power in COPD.

1School of Kinesiology, The University of Western Ontario, London, Ontario, CANADA 2Toronto General Research Institute, Toronto General Hospital, Toronto, Ontario, CANADA 3Lawson Health Research Institute, London, Ontario, CANADA 4Faculty of Kinesiology, The University of Calgary, Calgary, Alberta, CANADA

VO2max prediction based on submaximal cardiorespiratory relationships and body composition in male runners and cyclists: a population study.

Oxygen uptake (VO2) is one of the most important measures of fitness and critical vital sign. Cardiopulmonary exercise testing (CPET) is a valuable method of assessing fitness in sport and clinical settings. There is a lack of large studies on athletic populations to predict VO2max using somatic or submaximal CPET variables. Thus, this study aimed to: (1) derive prediction models for maximal VO2 (VO2max) based on submaximal exercise variables at anaerobic threshold (AT) or respiratory compensation point (RCP) or only somatic and (2) internally validate provided equations. Four thousand four hundred twenty-four male endurance athletes (EA) underwent maximal symptom-limited CPET on a treadmill (n=3330) or cycle ergometer (n=1094). The cohort was randomly divided between: variables selection (nrunners = 1998; ncyclist = 656), model building (nrunners = 666; ncyclist = 219), and validation (nrunners = 666; ncyclist = 219). Random forest was used to select the most significant variables. Models were derived and internally validated with multiple linear regression. Runners were 36.24±8.45 years; BMI = 23.94 ± 2.43 kg·m-2; VO2max=53.81±6.67 mL·min-1·kg-1. Cyclists were 37.33±9.13 years; BMI = 24.34 ± 2.63 kg·m-2; VO2max=51.74±7.99 mL·min-1·kg-1. VO2 at AT and RCP were the most contributing variables to exercise equations. Body mass and body fat had the highest impact on the somatic equation. Model performance for VO2max based on variables at AT was R2=0.81, at RCP was R2=0.91, at AT and RCP was R2=0.91 and for somatic-only was R2=0.43. Derived prediction models were highly accurate and fairly replicable. Formulae allow for precise estimation of VO2max based on submaximal exercise performance or somatic variables. Presented models are applicable for sport and clinical settling. They are a valuable supplementary method for fitness practitioners to adjust individualised training recommendations. No external funding was received for this work.

Investigation of the intrinsic magnetic properties of GdCo4B single crystal: determination of the magnetocrystalline anisotropy from the first-order magnetization processes

We report on the intrinsic magnetic properties of a GdCo4B single crystal as derived from magnetization measurements. The occurrence of a first-order magnetization process (FOMP) in a magnetic field applied perpendicularly to the easy magnetization direction provides an opportunity to determine the anisotropy parameters K1 and K2. To this end, the theoretical approach proposed previously for easy-plane magnets has been adapted for the case of easy-axis compounds exhibiting a FOMP. The obtained anisotropy parameters of GdCo4B are compared with the values deduced by other classical techniques. The presence of a compensation point in the thermal dependence of the spontaneous magnetization has enabled the determination of the exchange field on Gd, Bex = 131 T, which is in good agreement with inelastic neutron scattering results published earlier. Influence of the applied pressure on the anisotropy parameters is quantified using the pressure dependence of the FOMP, revealing a significant sensitivity of the anisotropy parameters to pressure.

SIGN-REVERSING MAGNETOCALORIC EFFECT IN R2Fe10Al7 (R = Dy AND Ho) COMPOUNDS

The magnetic properties of rare-earth ferrimagnetic compounds Dy2Fe10Al7 and Ho2Fe10Al7 with a Th2Zn17 crystal structure have been studied. The temperature dependences of the magnetization and magnetocaloric effect have been examined in the temperature range of 4.2‒300 K in magnetic fields of up to 70 and 18 kOe, respectively. The temperatures of magnetic compensation of the magnetization of the rareearth and iron sublattices have been determined. The magnetocaloric effect has been determined by the direct method. It has been found that the sign of the effect changes near the magnetic compensation point. This phenomenon has an application potential.

Optimization of Nuclear Polarization in an Alkali-Noble Gas Comagnetometer

Self-compensated comagnetometers, employing overlapping samples of spin-polarized alkali and noble gases (for example K-${}^{3}\mathrm{He}$) are promising sensors for exotic beyond-the-standard-model fields and high-precision metrology such as rotation sensing. When the comagnetometer operates in the so-called self-compensated regime, the effective field, originating from contact interactions between the alkali valence electrons and the noble-gas nuclei, is compensated with an applied magnetic field. When the comagnetometer begins operation in a given magnetic field, spin-exchange optical pumping establishes an equilibrium between the alkali electron-spin polarization and the nuclear-spin polarization. Subsequently, when the magnetic field is tuned to the compensation point, the spin polarization is brought out of the equilibrium conditions. This causes a practical issue for long measurement times. We report on a method for closed-loop control of the compensation field. This method allows optimization of the operating parameters, especially magnetic field gradients, in spite of the inherently slow (hours to days) dynamics of the system. With the optimization, higher stable nuclear polarization, longer relaxation times, and stronger electron-nuclear coupling are achieved which is useful for nuclear-spin-based quantum memory, spin amplifiers, and gyroscopes. The optimized sensor demonstrates a sensitivity comparable to the best previous comagnetometer but with four times lower noble-gas density. This paves the way for applications in both fundamental and applied science.

Thickness and composition effects on atomic moments and magnetic compensation point in rare-earth transition-metal thin films

Rare-earth (RE) transition-metal (TM) thin films have exhibited great promise for spintronic applications; however, the variation of their magnetic properties with composition and thickness has yet to be adequately quantified. In this paper, we investigate the atomic magnetic moments of few-nanometer-thick GdCo and TbCo via x-ray magnetic circular dichroism and find a significant decrease in both RE and Co average moments with increasing RE concentration, consistent with a local Co environment model description. We observe a shift in compensation composition to higher RE concentrations as the thickness of GdCo and TbCo films decreases $&lt;10$ nm. Based on the dependence of the saturation magnetization $({M}_{s})$ on temperature and thickness, we posit the existence of an intrinsic unalloyed RE dead layer at room temperature that reduces the effective RE concentration in the remaining alloyed region, resulting in significant, nonzero ${M}_{s}$ in thin films at higher RE concentrations than is observed in thick films. We demonstrate a simple model for RE-TM films that accurately describes ${M}_{s}$ as a function of both RE content and film thickness. In addition, the atomic $g$ factors of GdCo and TbCo are found to vary significantly with RE concentration, largely deviating from their elemental values over the bulk of composition space.

Impact of COVID-19 Infection on Cardiorespiratory Fitness, Sleep, and Psychology of Endurance Athletes-CAESAR Study.

COVID-19 has a deteriorating impact on health which is especially important for endurance athletes (EAs) who need to maintain continuity of training. The illness affects sleep and psychology, which influence sport performance. The aims of this study were: (1) to assess the consequences of mild COVID-19 on sleep and psychology and (2) to assess the consequences of mild COVID-19 on cardiopulmonary exercise test (CPET) results. A total of 49 EAs (males = 43, 87.76%; females = 6, 12.24%; age = 39.9 ± 7.8 years; height = 178.4 ± 6.8 cm; weight = 76.3 ± 10.4 kg; BMI = 24.0 ± 2.6 kg·m-2) underwent a maximal cycling or running CPET pre- and post-COVID-19 and completed an original survey. Exercise performance deteriorated after COVID-19 (maximal oxygen uptake, VO2max = 47.81 ± 7.81 vs. 44.97 ± 7.00 mL·kg·min-1 pre- and post-infection, respectively; p < 0.001). Waking up at night affected the heart rate (HR) at the respiratory compensation point (RCP) (p = 0.028). Sleep time influenced pulmonary ventilation (p = 0.013), breathing frequency (p = 0.010), and blood lactate concentration (Lac) (p = 0.013) at the RCP. The maximal power/speed (p = 0.046) and HR (p = 0.070) were linked to the quality of sleep. Stress management and relaxation techniques were linked with VO2max (p = 0.046), maximal power/speed (p = 0.033), and maximal Lac (p = 0.045). Cardiorespiratory fitness deteriorated after mild COVID-19 and was correlated with sleep and psychological indices. Medical professionals should encourage EAs to maintain proper mental health and sleep after COVID-19 infection to facilitate recovery.

Extraordinary Hall effect of sputtered amorphous ferrimagnetic GdFeCo alloy films

We investigate extraordinary Hall effect of sputtered amorphous ferrimagnetic GdFeCo alloy films using a composite target method. The composite target consists of a FeCo alloy disk and several Gd chips. The alloy film changing from FeCo-rich to Gd-rich phase is realized by manipulating sputtering power during the growth, confirmed by the shift of the compensation point. The sign of the extraordinary Hall resistance is observed to change from positive for FeCo-rich films to negative for Gd-rich films. The reversed sign at magnetic compensation can be ascribed to the combined effect of FeCo and Gd sublattices with opposite sign. A large extraordinary Hall coefficient of 1–2 × 10-8 Ω cm/emu is derived, which is one order in magnitude larger than that in ferromagnetic [Co,CoFe/Pt] multilayers. This sufficiently large extraordinary Hall coefficient indicates amorphous ferrimagnetic GdFeCo alloy films are promising for the applications in perpendicular magnetoelectronic devices.