Maximum Rate Research Articles

Visual behavior of racing bike cyclists in multi-tasking situations

Distracted biking can have serious repercussions for the rider such as accidents. The purpose of the present experiment was to determine the effect of visually monitoring two parameters, the cadence, and the heart rate on a bike computer fixed on a racing bike, and simultaneously detect hazardous traffic situations. Individuals (n = 20) were instructed to ride a racing bike that was fitted onto a roller trainer. After conducting a bicycle step test to assess the maximal heart rate (HFmax), participants were assigned to a within subject-design on a separate day. They were instructed to perform the riding task in two single-task conditions (only watching the traffic at the video with occluded or without occluded bike computer), two multi-tasking conditions (monitoring the cadence of 70 RPM or 90 RPM, monitoring the heart rate, and observing the traffic) and one control condition (no instructions). Percentage dwell time of the eye movements, the constant error from the target cadence, keeping the heart rate in an interval of 50% - 70% of the HFmax, and percentage of the recognized hazard traffic situations were analyzed. The analysis indicated that monitoring the parameters on the bike computer induced no significant decline in perceived hazardous traffic situations.

No Sex Differences in Perceptual Responses to High-Intensity Interval Training or Sprint Interval Training.

Coe, LN and Astorino, TA. No sex differences in perceptual responses to high-intensity interval training or sprint interval training. J Strength Cond Res 36(6): 1025-1032, 2024-High-intensity interval training (HIIT) elicits similar and, in some cases, superior benefits vs. moderate-intensity continuous training (MICT). However, HIIT is typically more aversive than MICT because of the higher intensity and in turn, greater blood lactate accumulation (BLa). This study explored potential sex differences in perceptual responses to acute HIIT and sprint interval training. Fifteen men (age and V̇O2max = 29 ± 8 years and 39 ± 3 ml·kg-1·min-1) and 13 women (age and V̇O2max = 22 ± 2 years and 38 ± 5 ml·kg-1·min-1) who are healthy and recreationally active initially underwent testing of maximal oxygen uptake (V̇O2max) on a cycle ergometer. In randomized order on 3 separate occasions, they performed the 10 × 1-minute protocol at 85% of peak power output, 4 × 4-minute protocol at 85-95% maximal heart rate (%HRmax), or reduced exertion high intensity interval training consisting of 2 "all-out" 20-second sprints at a load equal to 5% body mass. Before and throughout each protocol, rating of perceived exertion (rating of perceived exertion [RPE] 6-20 scale), affective valence (+5 to -5 of the Feeling Scale), and BLa were assessed. Five minutes postexercise, enjoyment was measured using the Physical Activity Enjoyment scale survey. Results showed no difference in RPE (p = 0.17), affective valence (0.27), or enjoyment (p = 0.52) between men and women. Blood lactate accumulation increased in response to all protocols (p < 0.001), and men showed higher BLa than women (p = 0.03). Previous research suggests that interval exercise protocols are not interchangeable between men and women, yet our data reveal that men and women having similar V̇O2max exhibit no differences in perceptual responses to interval exercise.

Physiological and Locomotor Profiling Enables to Differentiate Between Sprinters, 400-m Runners, and Middle-Distance Runners.

Thron, M, Woll, A, Doller, L, Quittmann, OJ, Härtel, S, Ruf, L, and Altmann, S. Physiological and locomotor profiling enables to differentiate between sprinters, 400-m runners, and middle-distance runners. J Strength Cond Res XX(X): 000-000, 2024-Different approaches exist for characterizing athletes, e.g., physiological and locomotor profiling. The aims of this study were to generate and compare physiological and locomotor profiles of male and female runners and to evaluate relationships between the different approaches. Thirty-four highly trained adolescent and young adult female and male athletes (n = 11 sprinters; n = 11,400-m runners; n = 12 middle-distance runners) performed two 100-m sprints on a running track to determine maximal sprinting speed (MSS) and maximal lactate accumulation rate (ċLamax). A cardiopulmonary exercise test was performed on a treadmill to determine maximal aerobic speed (MAS) and maximal oxygen uptake (V̇o2max). Anaerobic speed reserve (ASR) was calculated as the difference between MSS and MAS. Group comparisons were conducted with a 2-way ANOVA (discipline × sex; p < 0.05) and Bonferroni post hoc tests and Cohen's d as effect size. Parameters were correlated by Pearson's correlation coefficients. Maximal aerobic speed and V̇o2max were higher in 400-m and middle-distance runners compared with sprinters (p ≤ 0.02; -2.24 ≤ d ≤ -1.29). Maximal sprinting speed and ċLamax were higher in sprinters and 400-m runners compared with middle-distance runners (0.03 ≤ p ≤ 0.28; 0.73 ≤ d ≤ 1.23). Anaerobic speed reserve was highest in sprinters and lowest in middle-distance runners (p ≤ 0.03; 1.24 ≤ d ≤ 2.79). High correlations were found between ASR and MAS, MSS, and ċLamax (p < 0.01; -0.55 ≤ r ≤ 0.91) and between ċLamax and MSS (p < 0.01; r = 0.74). Our results indicate that athletes of different sprinting and running disciplines show differing physiological and locomotor profiles, and that the parameters of these approaches are related to each other. This can be of interest for assessing strengths and weaknesses (e.g., for talent identification) or training prescription in these disciplines.

Cardiac resynchronization therapy using endocardial versus trans-coronary sinus, epicardial left ventricular pacing: the Epi-Endo study

Abstract Aims Some studies have suggested that cardiac resynchronization therapy (CRT) using endocardial left ventricular (LV) pacing (Endo-CRT) is superior to a conventional transvenous, epicardial CRT (Epi-CRT). To determine whether, in CRT recipients, endocardial LV pacing is haemodynamically superior to trans-coronary vein (trans-CV) LV epicardial pacing. Methods and results At implantation patients (n=16; aged 68.9±8.32 years; 13 male) underwent Epi-CRT and Endo-CRT in basal, mid and apical myocardial segments, delivered using the trans-CS lead and an intra-cavitary, roving EP catheter to achieve juxtapositions of the epicardial and endocardial side of the LV free wall respectively. Myocardial scar was quantified using cardiovascular magnetic resonance. An acute haemodynamic response (AHR) was defined as a ≥10% increase in the maximal rate of rise of LV pressure (%LV dP/dtmax) in relation to RV pacing (DOO). When the 84 paired segments were taken together, the %ΔLV dP/dtmax was higher with Endo-CRT than with Epi-CRT (9.9±8,6% vs 7.9±8.3% respectively, p&amp;lt;0.002; 52.3% vs 28.6% responders [p&amp;lt;0.045). However, Endo-CRT was not always superior to epi-CRT in individual patients. For example, in basal segments, only 5/10 (50%) patients were converted from non-responders with epi-CRT to responders with endo-CRT whereas 1/4 (25%) epi-CRT responder was converted to a non-responder with endo-CRT (Figure). There was no difference in ΔLV dP/dtmax between Epi-CRT and endo-CRT in segments with myocardial scar. Conclusions On average, endo-CRT provides a better AHR than epi-CRT. Within patients, however, endo-CRT is not always better.Epicardial versus Endocardial CRT

Photocatalytic degradation of Direct Black 10 B dye in aqueous phase using nanophotocatalyst

ABSTRACT In this study, the photocatalytic degradation of an aqueous solution containing a mixture of Direct Black 10 B dye using titanium dioxide (TiO2) as a catalyst was investigated. The degradation of Direct Black 10 B dye was studied for several parameters, including the catalyst, dosage, initial concentration of dye, and pH. Variable catalyst quantities (0.25, 0.50, 0.75, 1, and 1.25 g), pH (3, 5, 9, and 11), and beginning dye concentration were used in the studies (62.5, 125, 250 and 500 ppm). 0.75 g/litre of catalyst was found to be the ideal dose. The ideal catalyst concentration was determined to be 0.75 g/litre, and the maximal dye decolourization rate was further studied in a basic media, i.e. at pH 9 Blue turned into grey and finally white in the acidic medium, whereas blue turned into pink and then white in the basic medium. After 3 hours 98% of the colour was completely removed at this optimal point. The Langmuir, Freundlich and Temkin isotherms were examined. The langmuier isothers with regression coefficient 0.99 is best fitted as compared to Freundlich and Temkin isotherms. The findings of the kinetic analysis suggest that the Pseudo Second order with regression coefficient 0.9923 is best suited as compared with the pseudo first order and Intra-particle diffusion model.

Adjunctive hiking bouts during 8 weeks regular sailing training improves cardiorespiratory and muscular responses during hiking emulation in highly trained sailors

AbstractTo investigate the effects of 8‐week hiking bench training on cardiorespiratory and muscular responses of highly trained sailors during hiking emulation. Twenty‐four sailors were assigned into two groups: the hiking bench training group (HTG, n = 12) and the control group (CG, n = 12). Both groups maintained their regular training with the HTG performed two additional hiking bench training sessions per week for 8 weeks, while the CG performed an equivalent duration of on‐water sailing training. Physiological responses were assessed by performing four successive 3‐min hiking bouts on a sailing emulation ergometer before and after the 8‐week training period. Comparing the pretest, both groups exhibited a significant decrease (p &lt; 0.05) in the percentage of maximal oxygen uptake (%VO2max) and maximal heart rate (%HRmax); the HTG experienced a greater decrease in %VO2max in bouts 2 and 3. The root mean square (RMS) of rectus femoris (RF), vastus lateralis (VL), rectus abdominis (RA), and external oblique decreased significantly (p &lt; 0.05), whereas the mean power frequency (MPF) of RF, VL, and RA exhibited an increasing trend. The RMS of RF and RA in HTG were lower than those in CG in the initial three bouts; VL and EA in HTG were lower than those in CG in bouts 1 and 2 (p &lt; 0.05). The MPF of RA in HTG was significantly increased in bouts 2, 3, and 4 (p &lt; 0.05). Eight‐week hiking bench training could improve hiking economy and the activation of lower limb and trunk muscles delaying the onset of fatigue in sailors.

Aerobic high‐intensity interval training and maximal strength training in patients with unspecific musculoskeletal disorders improve V̇O2peak and maximal strength more than moderate training

AbstractImproving peak oxygen uptake (V̇O2peak) and maximal strength are key objectives of rehabilitation for patients with unspecific musculoskeletal disorders (MSDs). Although high‐intensity training yield superior outcomes for these factors, patients with MSDs may not tolerate high‐intensity due to pain and fear. Therefore, we examined the effect and feasibility of incorporating aerobic high‐intensity intervals (HIITs) and maximal strength training (MST) in a standard clinical rehabilitation program for patients with unspecific MSDs. 73 patients (45 ± 10 years) with MSDs partaking in a standard, public, and 4‐week rehabilitation program were randomized to high‐intensity training (HG: 4 × 4 minutes intervals at ∼90% of maximal heart rate; HRmax, and 4 × 4 repetitions leg press at ∼90% of 1 repetition maximum; 1RM, with maximal intended velocity) or keep todays treatment of low‐to moderate‐intensity training (MG: various cycling, walking, and/or running activities at ∼70%–80% of HRmax and 3 × 8 − 10 repetitions leg press at ∼75% of 1RM without maximal intended velocity). HG improved V̇O2peak (12 ± 7%) and leg press 1RM (43 ± 34%) more than moderate‐intensity group (V̇O2peak; 5 ± 6%, 1RM; 19 ± 18%, both p &lt; 0.001). We observed that no adverse events and no between‐group differences in dropout rate or self‐reported quality of life (both p &gt; 0.05). There were positive correlations between improved V̇O2peak and improved physical (p = 0.024) and emotional (0.016) role functioning. We conclude that both high‐intensity interval training and MST are feasible and improve V̇O2peak and maximal strength more than standard low‐to moderate‐intensity treatment of patients with unspecific MSDs. Our findings suggest that high‐intensity training should be implemented as a part of standard clinical care of this patient population.

Wagner diagram for modeling O2pathway - calculation and graphical display by the Helsinki O2pathway tool.

Maximal O2uptake (V̇O2max) reflects the individual's maximal rate of O2transport and utilization through the integrated whole-body pathway composed of the lungs, heart, blood, circulation, and metabolically active tissues. As such, V̇O2maxis strongly associated with physical capacity as well as overall health and thus acts as one predictor of physical performance and as a vital sign in determination of status and progress of numerous clinical conditions. Quantifying the contribution of single parts of the multistep O2pathway to V̇O2maxprovides mechanistic insights into exercise (in)tolerance and into therapy-, training-, or disuse-induced adaptations at individual or group levels. We developed a desktop application (Helsinki O2Pathway Tool - HO2PT) to model numerical and graphical display of the O2pathway based on the "Wagner diagram" originally formulated by Peter D. Wagner and his colleagues.&#xD;Approach: The HO2PT was developed and programmed in Python to integrate the Fick principle and Fick's law of diffusion into a computational system to import, calculate, graphically display, and export variables of the Wagner diagram.&#xD;Main results: The HO2PT models O2pathway both numerically and graphically according to the Wagner diagram and pertains to conditions under which the mitochondrial oxidative capacity of metabolically active tissues exceeds the capacity of the O2transport system to deliver O2to the mitochondria. The tool is based on the Python open source code and libraries and freely and publicly available online for Windows, macOS, and Linux operating systems.&#xD;Significance: The HO2PT offers a novel functional and demonstrative platform for those interested in examining V̇O2maxand its determinants by using the Wagner diagram. It will improve access to and usability of Wagner's and his colleagues' integrated physiological model and thereby benefit users across the wide spectrum of contexts such as scientific research, education, exercise testing, sports coaching, and clinical medicine.&#xD.

Construction of n-n heterojunction copper manganese spinel/mesoporous WO3 photocatalyst for efficient H2 evolution rate from aqueous glycerol

Mesoporous metal oxides can expedite charge separation and mobility and give enormous active sites for H2 production. Herein, n-n heterojunction CuMn2O4/WO3 nanocomposites were constructed by a sol-gel procedure employing F-127 surfactant. The synthesized CuMn2O4/WO3 photocatalysts have been evaluated for H2 evolution from aqueous glycerol as an electron donor under visible illumination. XRD patterns of the synthesized CuMn2O4/WO3 nanocomposite manifested the formation of the monoclinic structure of WO3 and crystalline cubic CuMn2O4 spinel. The TEM image of WO3 NPs showed quasi-spherical ∼10–20 nm and CuMn2O4 NPs ∼10 nm were regularly dispersed on the surface of WO3. The optimum 12%CuMn2O4/WO3 nanocomposite exhibited a significant enhancement photocatalytic ability with the maximal H2 evolution rate (2856.6 μmol h−1g−1), which is about of 14.4 -fold higher than WO3 NPs. The optimal photocatalyst dosage is 2.4 g/L with a large evolution rate of 3427.2 μmol h−1g−1. The close interfacial connection existing between CuMn2O4 and WO3 with S-scheme mechanism and active charge separation generated the high H2 yield. The H2 evolution experiments for 45 h using CuMn2O4/WO3 nanocomposite are stable with high efficiency after five cyclings. This superb H2 evolution rate was utilized from the design of proper bandgap energy; the fostered light harvest, and the enhancement of separation efficiency photocarriers. The resultant CuMn2O4/WO3 nanocomposites exhibit a favorable photocatalyst for sustainability where it is effectively utilized in glycerol by-product through the renewable solar illumination to produce H2 and cleanly water concomitantly.

S‐Scheme g‐C3N4/CdS Heterostructures Grafting Single Pd Atoms for Ultrafast Charge Transport and Efficient Visible‐Light‐Driven H2 Evolution

AbstractEmerging step‐scheme (S‐scheme) heterostructures hold unique superiority in steering directional charge transport and reinforcing redox capacity, yet rational modification of S‐scheme heterostructures by single atoms (SAs) for efficient photocatalytic H2 evolution is rarely reported. In this work, Pd SAs‐modulated organic–inorganic g‐C3N4/CdS S‐scheme heterostructures are designed and prepared by a one‐pot mechanochemical approach allowing for g‐C3N4 nanosheets/CdS nanoparticles to confine atomically dispersed Pd co‐catalysts. The g‐C3N4/CdS S‐scheme charge‐transfer pathway is corroborated by a combination of in situ irradiated X‐ray photoelectron spectroscopy, electron paramagnetic resonance, and Kelvin probe force microscopy. Density functional theory (DFT) calculations, high‐angle annular dark‐field scanning transmission electron microscopy, and X‐ray absorption fine structure identify Pd‐S3 and Pd‐N2 atomic moieties underpinned by the electronic interaction between Pd SAs and g‐C3N4/CdS heterostructures, in which the d‐band center of Pd SAs is optimized for proton adsorption thermodynamically. Further, the g‐C3N4/CdS S‐scheme heterostructures alongside Pd SAs in concert boost the rapid migration of photogenerated electrons (1.05 ps) via Pd─S and Pd─N bond‐derived channels. A maximal H2 evolution rate of 85.66 mmol h−1 g−1 is achieved by 1 wt% Pd‐20 wt% g‐C3N4/CdS hierarchical composites. This work may guide the design of high‐efficiency S‐scheme‐based photocatalysts for solar‐to‐H2 conversion and beyond.

Conduit Flow Compensates for Impaired Left Atrial Passive and Booster Functions in Advanced Diastolic Dysfunction.

Quantification of left atrial (LA) conduit function and its contribution to left ventricular (LV) filling is challenging because it requires simultaneous measurements of both LA and LV volumes. The functional relationship between LA conduit function and the severity of diastolic dysfunction remains controversial. We studied the role of LA conduit function in maintaining LV filling in advanced diastolic dysfunction. We performed volumetric and flow analyses of LA function across the spectrum of LV diastolic dysfunction, derived from a set of consecutive patients undergoing multiphasic cardiac computed tomography scanning (n=489). From LA and LV time-volume curves, we calculated 3 volumetric components: (1) early passive emptying volume; (2) late active (booster) volume; and (3) conduit volume. Results were prospectively validated on a group of patients with severe aortic stenosis (n=110). The early passive filling progressively decreased with worsening diastolic function (P<0.001). The atrial booster contribution to stroke volume modestly increases with impaired relaxation (P=0.021) and declines with more advanced diastolic function (P<0.001), thus failing to compensate for the reduction in early filling. The conduit volume increased progressively (P<0.001), accounting for 75% of stroke volume (interquartile range, 63-81%) with a restrictive filling pattern, compensating for the reduction in both early and booster functions. Similar results were obtained in patients with severe aortic stenosis. The pulmonary artery systolic pressure increased in a near-linear fashion when the conduit contribution to stroke volume increased above 60%. Maximal conduit flow rate strongly correlated with mitral E-wave velocity (r=0.71; P<0.0001), indicating that the increase in mitral E wave in diastolic dysfunction represents the increased conduit flow. An increase in conduit volume contribution to stroke volume represents a compensatory mechanism to maintain LV filling in advanced diastolic dysfunction. The increase in conduit volume despite increasing LV diastolic pressures is accomplished by an increase in pulmonary venous pressure.

Effect of Heat Acclimatization, Heat Acclimation, and Intermittent Heat Training on Maximal Oxygen Uptake.

Maximal oxygen uptake (VO2max) is an important determinant of endurance performance. Heat acclimation/acclimatization (HA/HAz) elicits improvements in endurance performance. Upon heat exposure reduction, intermittent heat training (IHT) may alleviate HA/HAz adaptation decay; however, corresponding VO2max responses are unknown. VO2max is maintained after HAz/HA; IHT mitigates decrements in aerobic power after HAz/HA. Interventional study. Level 3. A total of 27 male endurance runners (mean ± SD; age, 36 ± 12 years; body mass, 73.03 ± 8.97 kg; height, 178.81 ± 6.39 cm) completed VO2max testing at 5 timepoints; baseline, post-HAz, post-HA, and weeks 4 and 8 of IHT (IHT4, IHT8). After baseline testing, participants completed HAz, preceded by 5 days of HA involving exercise to induce hyperthermia for 60 minutes in the heat (ambient temperature, 39.13 ± 1.37°C; relative humidity, 51.08 ± 8.42%). Participants were assigned randomly to 1 of 3 IHT groups: once-weekly, twice-weekly, or no IHT. Differences in VO2max, velocity at VO2max (vVO2), and maximal heart rate (HRmax) at all 5 timepoints were analyzed using repeated-measure analyses of variance with Bonferroni corrections post hoc. No significant VO2max or vVO2 differences were observed between baseline, post-HAz, or post-HA (P = 0.36 and P = 0.09, respectively). No significant group or time effects were identified for VO2max or vVO2 at post-HA, IHT4, and IHT8 (P = 0.67 and P = 0.21, respectively). Significant HRmax differences were observed between baseline and post-HA tests (P < 0.01). No significant group or time HRmax differences shown for post-HA, IHT4, and IHT8 (P = 0.59). VO2max was not reduced among endurance runners after HA/HAz and IHT potentially due to participants' similar aerobic training status and high aerobic fitness levels. HAz/HA and IHT maintain aerobic power in endurance runners, with HAz/HA procuring reductions in HRmax.

Evaluation of learning curves for contact laser vaporization of the prostate using the 980 nm diode laser for benign prostatic hyperplasia.

We investigated the background of patients who underwent contact laser vaporization of the prostate (CVP) surgery and the learning curve of the operators. A total of 207 patients who underwent CVP surgery for benign prostatic hyperplasia between August 2018 and March 2023 were included in this study. Patient background, perioperative results, pre- and postoperative urinary flow tests, and complications were collected retrospectively. We enrolled 12 doctors who were divided into expert (five doctors) and novice (seven doctors) groups based on the number of TURP experiences before CVP. The median patient age was 73 years (51-92 years) and prostate volume was 56 cc (15-190 cc) with no difference between the expert and novice groups. Complications included urinary retention (eight cases), hematuria (four), urinary tract infection (four), intraoperative perforation (two), and postoperative stricture (one). Both cases of intraoperative perforation occurred in the novice group. The expert group had a significantly shorter operative time (38 vs. 66 min) and a higher operative efficacy of prostate volume divided by operative time (1.43 vs. 0.88 cc/min). Postoperatively, IPSS, quality of life scores, and postvoid residual urine volume decreased, and maximal flow rate increased; however, there was no significant difference between the groups. The expert group showed stable operative time and operative efficacy after about five to eight cases, while the novice group showed stable after about 15 cases. Our findings suggest that CVP was safely performed at our hospital, and operators with limited experience in TURP can achieve stable perioperative results.

Does mild chronic obstructive pulmonary disease need a standard pulmonary rehabilitation program? A case report

Background: Patients with mild chronic obstructive pulmonary disease (COPD) are usually not recommended for a standard pulmonary rehabilitation (PR)program based on the GOLD guideline in mild COPD GOLD A classification. Especially, the scientific evidence on exercise capacity that can be identified for recruitment in PR programs has been less reported. Thus, a preliminary case study to identify the exercise capacity under cardiopulmonary responses by aerobic exercise testing among patients in mild COPD GOLD A classification was the aim of this study. Objective: To evaluate the cardiopulmonary responses from exercise capacity testing in individual COPD patients with mild COPD GOLD A Classification. Materials and methods: Four participants with mild COPD GOLD A performed an exercise endurance capacity test at home using Spot Marching Exercise Test (SMT), marching on the spot with high hip and arm raising. The load of SMT was indicated by a controlled stepping rate at 70, 80, 90, 100, and 110 steps/min. Every participant performed Incremental SMT (ISMT) with every 3 min incremental load, and the Constant SMT (CSMT) at the peak load. Both exercise tests were terminated at symptom limit. Resting time between ISMT and CSMT was at least 30 minutes. Cardiopulmonary exercise responses, Borg perceived breathlessness (RPB) and exertion (RPE) were monitored every minute during the exercise test. The duration of exercises was recorded. Results: Peak exercise capacity using ISMT was low with the end exercise load at 70, 80, 80, and 90 steps/min which is equivalent to moderate to high intensity at 81%, 62%, 65% and 93% of age-predicted maximum heart rate (HRmax). The exercise test was stopped by breathlessness at RPB 7, 8, 6, and 5. Respiratory rates (RR) were 36, 26, 38, and 38 breaths/min. With CSMT, the results showed very short exercise duration 1.78, 4.60, 2.15, and 2.47 mins with RPB 7, 8, 5, and 5 and RR of 33, 27, 34, and 41 breaths/min respectively. Conclusion: This preliminary report reveals that all four mild COPD GOLD A show low exercise capacity and very poor exercise endurance that should identify the appropriated standard PR program in the future.

Effect of body mass index on exercise capacity following pediatric heart transplantation.

Obesity and impaired exercise tolerance following heart transplantation increase the risk of post-transplant morbidity and mortality. The aim of this study was to evaluate the effect of body mass index on markers of exercise capacity in pediatric heart transplant recipients and compare this effect with a healthy pediatric cohort. A retrospective analysis of cardiopulmonary exercise test data between 2004 and 2022 was performed. All patients exercised on a treadmill using the Bruce protocol. Inclusion criteria included patients aged 6-21 years, history of heart transplantation (transplant cohort) or no cardiac diagnosis (control cohort) at the time of testing, and a maximal effort test. Patients were further stratified within these two cohorts as underweight, normal, overweight, and obese based on body mass index groups. Two-way analyses of variance were performed with diagnosis and body mass index category as the independent variables. A total of 250 exercise tests following heart transplant and 1963 exercise tests of healthy patients were included. Heart transplant patients across all body mass index groups had higher resting heart rate and lower maximal heart rate, heart rate recovery at 1 min, exercise duration, and peak aerobic capacity (VO2peak). Heart transplant patients in the normal and overweight body mass index categories had higher VO2peak and exercise duration when compared to underweight and obese patients. Underweight status and obesity are strongly associated with lower VO2peak and exercise duration in heart transplant patients. Normal and overweight heart transplant patients had the best markers of exercise capacity.

Reliability of power output, maximal rate of capillary blood lactate accumulation, and phosphagen contribution time following 15-s sprint cycling in amateur cyclists.

Based on Mader's mathematical model, the rate of capillary blood lactate concentration (νLamax) following intense exercise is thought to reflect the maximal glycolytic rate. We aimed to investigate the reliability of important variables of Mader's model (i.e. power output, lactate accumulation, predominant phosphagen contribution time frames (tP Cr)) and resulting νLamax values derived during and after a 15-s cycling sprint. Fifty cyclists performed a 15-s all-out sprint test on a Cyclus2 ergometer three times. The first sprint test was considered a familiarization trial. Capillary blood was sampled before and every minute (for 8 min) after the sprint to determine νLamax. Test-retest analysis between T2 and T3 revealed excellent reliability for power output (Pmean and Ppeak; ICC = 0.99, 0.99), ∆La and νLamax with tPCr of 3.5 s (ICC = 0.91, 0.91). νLamax calculated with tPCr = tP peak (ICC = 0.87) and tP Cr = tPpeak-3.5% (ICC = 0.79) revealed good reliability. tPpeak and tPpeak-3.5% revealed only poor and moderate reliability (ICC = 0.41, 0.52). Power output and ∆La are reliable parameters in the context of this test. Depending on tPCr, reliability of νLamax varies considerably with tP Cr of 3.5 s showing excellent reliability. We recommend standardization of this type of testing especially tP Cr.

Visualization of intracellular ice formation and growth in mouse oocytes

BACKGROUND: Characterization of intracellular ice formation (IIF) in oocytes during the freezing and thawing processes will contribute to optimizing their cryopreservation. However, the observation of the ice formation process in oocytes is limited by the spatiotemporal resolution of the cryomicroscope systems. OBJECTIVE: To observe the intracellular icing of oocytes during cooling and rewarming, and to study the mechanism of formation and growth of intracellular ice in oocytes. MATERIALS AND METHODS: Mouse oocytes were frozen at different cooling rates to induce intracellular ice formation using a cryomicroscopy system consisting of a microscope equipped with a cryogenic cold stage, an automatic cooling system, a temperature control system, and a high-speed camera. The growth patterns of intracellular ice in oocytes were analyzed from the images recorded. Finally, the growth rate of intracellular ice formation in oocytes was calculated using an automatic intracellular ice tracking method.RESULTS: The IIF temperature decreased gradually with the increase in cooling rate. Initiation sites of IIF could be classified into three categories: marginal type, internal type and coexisting type. There was a strong predominance for ice crystal initiation site in the oocytes, with up to 80% of the initiation sites located in the marginal region. The intracellular ice growth modes of darkening and twitching cells were characterized by “spreading” and “clustering”, respectively. In addition, twitching cells started to recrystallize during rewarming, while darkening cells did not. The instantaneous maximal growth rate of ice crystals in twitching cells was about 10 times higher than that in darkening cells. CONCLUSION: By visualising the growth of ice crystals in mouse oocytes during cooling and rewarming, we obtained valuable information on the kinetics of ice formation and melting in these cells. This information can help us understand how ice formation and melting affect the viability and quality of oocytes after cryopreservation.

Quantifying flow regime impacts on hydrodynamic heat transfer in rough-walled rock fractures

Hydrodynamic heat transfer in rock fractures is crucial for many geophysical processes and engineering activities, notably in harnessing geothermal energy. Despite extensive research, characterizing hydrodynamic heat transfer in rock fractures, complicated by their geometric heterogeneity, remains a formidable challenge. To address this challenge, we experimentally investigated the hydrodynamic heat transfer in rock fractures with diverse geometric features at steady-state elevated temperatures. We found that both heterogeneous fracture geometry and elevated temperatures promote the transition of fracture flow from a linear to nonlinear regime. This flow regime transition enhances the heterogeneity of heat transfer intensity within the fracture and exacerbates the increase in heat transfer efficiency with flow rate. At a fortyfold increase in flow rate, the heat transfer coefficient in the most heterogeneous fracture rises by approximately 72 times, compared to about 28 times in the least heterogeneous one. Leveraging experimental data, we developed parametric models linking heat transfer coefficients, outflow temperature, and heat recovery rate to flow rate and geometric features, yielding a theoretical formulation for the maximal heat recovery rate. By introducing the concept of an energy conversion rate, we quantitatively evaluated the effect of nonlinear flow resistance on heat extraction feasibility, revealing that energy conversion rates in highly heterogeneous fractures can be up to 452 times lower than in less heterogeneous ones. This highlights the pivotal role of flow resistance in heat extraction feasibility. Our findings are instrumental for understanding and predicting the hydrodynamic heat transfer within fractured geothermal reservoirs and analogous hydro-thermal systems.

The effects of wearing face masks on the perception and mood of male healthy male adults during treadmill running: A pilot study.

In the past few years, the face mask has been recommended for the prevention of exposing others to COVID-19. Wearing a face mask may have the potential to increase dyspnea and discomfort during exercise; however, controversy exists on whether wearing face masks during exercise affects exercise performance, perception, and mood in runners. We investigated the physiological and perceptual responses of healthy male adults who had experienced long-distance running while exercising at different intensities. Nine healthy young adults who were long-distance runners wearing surgical face mask conducted an incremental treadmill protocol. The protocol was three 6-min stages (20%, 40%, and 60% of maximal heart rate, respectively). The rating of perceived exertion (RPE) and the feeling scale (FS) were measured. RPE was higher in mask condition than in unmask condition (No mask vs. Face mask, light; 8.22 vs. 8.78, p = 0.615, middle; 10.00 vs. 10.78, p = 0.345, high; 12.33 vs. 13.67, p = 0.044.), while FS was not different between conditions. The present study shows that wearing a mask may increase rating of perceived exertion and discomfort when the exercise intensity exceeds a certain threshold in healthy male adults who have experienced long-distance running.

Characterization of an in vitro model to study CD4+ T cells metabolism in dairy cows

Dairy cows are susceptible to several health disorders throughout their lactation. Objectives were to characterize an in vitro model to study bioenergetic measures in CD4+ T lymphocytes in dairy cows. Twenty-four healthy mid-lactating multiparous Holstein dairy cows were enrolled at a mean (±standard deviation) of 234 ± 22 d in milk (DIM). Cows were blocked according to DIM and blood was collected to isolate peripheral blood mononuclear cells followed by magnetic separation of CD4+ T lymphocytes using bovine specific monoclonal antibodies. The isolated CD4+ T lymphocytes from each cow were split into 2 tubes and randomly assigned to incubate in an assay medium as control (CON) or with a combination of phorbol myristate acetate and ionomycin (PMA+IMY) to evaluate metabolic function under resting and activated state. Mitochondrial and glycolytic functional kinetics were recorded in CD4+ T lymphocytes based on real-time measurement of oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) under basal conditions and in response to complex V inhibitor (oligomycin), a protonophore uncoupler (BAM 15), and complex I and complex III inhibitors (rotenone and antimycin A). The mean (±SD) viability and purity of CD4+ T lymphocytes was 92.5 ± 2.9% and 95.2 ± 2.9%, respectively. The basal OCR in CD4+ T lymphocytes treated with PMA+IMY was greater than CON; nevertheless, the maximal respiration rate (CON = 58.0 vs. PMA+IMY = 47.3 ± 5.7 pmol/min) and sparing respiratory capacity rate (CON = 42.0 vs. PMA+IMY = 28.7 ± 4.2 pmol/min) were decreased in activated CD4+ T lymphocytes. The ECAR in CD4+ T lymphocytes increased progressively over time in PMA+IMY compared with CON, which indicated an increase in aerobic glycolysis in PMA+IMY compared with CON (CON = 46.9 vs. PMA+IMY = 86.4 ± 7.0 pmol/min). Activated CD4+ T lymphocytes exhibit a metabolic switch from oxidative phosphorylation to aerobic glycolysis, which may support rapid cell proliferation. The results observed in this experiment demonstrate the sensitivity of the technique to detect changes in metabolic function under different cellular conditions, providing a robust framework to study immuno-metabolism in dairy cattle.