The oxygen uptake efficiency slope does not accurately predict V ˙ O2peak of children - the Arkansas Active Kids study.

Background: Cardiorespiratory fitness (CRF) is a vital indicator of health. However, accurately measuring peak oxygen consumption ( V ˙ O2peak) to determine CRF in children can be challenging. The oxygen uptake efficiency slope (OUES) has been proposed as an alternative metric for predicting V ˙ O2peak in children, but its accuracy and agreement with measured V ˙ O2peak remain unclear. Methods: A post hoc analysis was conducted in 94 children (ages 7-10 years) who completed an incremental cycle ergometer test to measure V ˙ O2peak. Body composition (Dual-energy X-ray absorptiometry) was measured, and fat mass index (FMI, kg/m2) and fat-free mass index (FFMI, kg/m2) were calculated. OUES was determined using all respiratory data (OUES100%) collected during the cycle ergometer test and using data only up to 60% of heart rate reserve (OUES60%HRR). Regression equations to predict V ˙ O2peak (Pred- V ˙ O2peak) were derived from simple and multiple linear regression analysis. Bland-Altman analysis assessed the level of agreement between Pred- V ˙ O2peak and measured V ˙ O2peak. Results: OUES60%HRR (ß = 0.46, p < 0.0001), age (ß = 56.0, p = 0.0004), White race (ß = 173.3, p < 0.0003), FFMI (ß = 0.98.6, p < 0.000), and FMI (ß = -0.40.8, p < 0.000) were retained in the final model. The difference between measured V ˙ O2peak and Pred- V ˙ O2peak was not different from zero (p = 0.999). There was a positive association between the difference of measured V ˙ O2peak and Pred- V ˙ O2peak and the average of the two methods (ß = 0.79, p = 0.0028). Conclusion: There was no mean bias between measured V ˙ O2peak and Pred- V ˙ O2peak. However, magnitude bias was present even after considering other significant predictors of V ˙ O2peak (FMI, FFMI, race, and age) in the regression equation. Caution is advised when using OUES to predict V ˙ O2peak in children.

A Flexible Artificial Spiking Photoreceptor Enabled by a Single VO2 Mott Memristor for the Spike-Based Electronic Retina.

The neuromorphic vision system that utilizes spikes as information carriers is crucial for the formation of spiking neural networks. Here, we present a bioinspired flexible artificial spiking photoreceptor (ASP), which is realized by using a single VO2 Mott memristor that can simultaneously sense and encode the stimulus light into spikes. The ASP has high spike-encoded photosensitivity and ultrawide photosensing range (405-808 nm) with good endurance (>7 × 107) and high flexibility (bending radius ∼5 mm). Then, we put forward an all-spike electronic retina architecture that comprises one layer of ASPs and one layer of artificial optical nerves (AONs) to process the spike information. Each AON consists of a single Mott memristor connected in series with a neuro-transistor that is a multiple-input floating-gate MOS transistor. Simulation results demonstrate that the all-spike electronic retina can successfully segment images with high Shannon entropy, thus laying the foundation for the development of a spike-based neuromorphic vision system.

Hand cooling induces changes in the kinetics of oxygen uptake.

The objective of this investigation was to assess the impact of elevated catecholamine concentrations, induced through cold-water hand immersion, on the oxygen consumption (V̇O2) kinetics during intense exercise, and to contrast this effect with that of the priming effect. Ten active participants underwent three 8-minute constant work rate exercises (CWR) at ∆25%, with one CWR preceded by hand cooling (2 min at 0 °C, HC) and two consecutive CWR to induced priming effect on the second bout (SB). Pulmonary gas exchange and blood samples were analyzed to measure levels of epinephrine (E) and norepinephrine (NE). Results demonstrated a significant increase in the primary phase amplitude of V̇O2 kinetics in response to both hand HC (33.9 mL.min-1.kg-1; CI [32.2;35.7], p < 0.001) and SB (34.6 mL.min-1.kg-1; CI [33.0;36.3], p < 0.001) relative to the control (32.7 mL.min-1.kg-1; CI [31.5;35.1]). Additionally, the amplitude of the V̇O2 slow component was reduced for both HC (3.2 mL.min-1.kg-1; CI [2.2;4.1], p = 0.018) and SB (2.9 mL.min-1.kg-1; CI [1.8;4.2], p = 0.009) in comparison to control (3.9 mL.min-1.kg-1; CI [2.9;4.2]). These findings suggest that the increase in E and NE induced by hand cooling prior to exercise modifies V̇O2 kinetics in a manner akin to the priming effect. This research underscores the potential role of catecholamines in facilitating the priming effect and its subsequent impact on V̇O2 kinetics. However, further studies are necessary to clearly establish this link.

Factores relacionados con la supervivencia en una cohorte de pacientes con enfermedad pulmonar obstructiva crónica grave a largo plazo: relación con la capacidad aeróbica / Related Factors for Survival in a Cohort of Patients with Severe Chronic Obstructive Pulmonary Disease in a Long-Term of Follow-Up: Relationship with Aerobic Capacity

Introducción: Sólo Oga et al. (AJRCCM 2003) relacionaron supervivencia y capacidad aeróbica en pacientes EPOC, pero en hombres y seguimiento a 5 años. Objetivos: Evaluar la supervivencia de una cohorte de pacientes EPOC grave según el consumo de oxígeno pico (VO2p) ajustado al peso. Material y Métodos: Se evaluó la supervivencia a largo plazo desde el diagnóstico de pacientes con EPOC (GOLD). Se midió el VO2p ajustado por peso en prueba cicloergo- métrica máxima (gases espirados). Se usaron técnicas estadísticas convencionales y análisis de supervivencia de LogRank (Mantel-Cox). Resultados: 70 pacientes (27% femenino); edad 68 años (RIQ 63-73); %FEV1 postBD: 39,95±2,09; VO2p: 9,25 ± 3,17 ml/kg/min. GOLD D/B/A 84,3/14,2/1,5%; GOLD II/III/IV: 15,7/61,4/22,9%. A 14 años de seguimiento, 75% había fallecido. Supervivencia: primer cuartilo de VO2p (ml/kg/min) fue 38,5 meses (RIQ 18,25-58,5) y para el cuarto cuartilo 68 meses (RIQ 48-93). A 103 meses, la diferencia en supervivencia fue: primer cuartilo vs. cuarto cuartilo de VO2p (p<0,01) y segundo vs. cuarto cuartilo (p<0,03); a 145 meses entre segundo vs. cuarto cuartilo (p=0,049). En el análisis multivariado, el VO2p alto es un factor protector sobre la mortalidad. En cambio, otras variables independientes como sexo masculino, edad >70, grado de obstrucción bronquial severo y fenotipo exacerbador frecuente se asociaron a mortalidad. Conclusión: A largo plazo, en una cohorte de pacientes hombres y mujeres EPOC grave, en análisis multivariado, el VO2p alto es factor protector sobre la mortalidad. En cambio, otras variables independientes como sexo masculino, edad >70, grado de obstrucción bronquial severo y exacerbador frecuente se asociaron a mortalidad.

Introduction: Only Oga et al. (AJRCCM 2003) related survival and aerobic capacity, but only in chronic obstructive pulmonary disease (COPD) men with 5 years of follow-up. Objective: To determine survival in a cohort of patients with severe COPD due to aerobic capacity (VO2max) adjusted by weight. Methods: Survival of COPD patients was evaluated to long-term (GOLD definition). Patients performed maximal exercise test in cicloergometry (expired gases) evaluating (VO2max). Conventional statistics and Log-Rank survival analysis (Mantel-Cox) were used. Results: We included 70 patients (27% female) followed up 60.77 months (RIQ 29- 87.85); age 68 years (RIQ 63-73); %FEV1 postBD: 39.95±2.09; VO2p: 9.25± 3.17 ml/kg/ min. GOLD D/B/A 84.3/14.2/1.5%; GOLD II/III/IV: 15.7/61.4/22.9%. After 14 years of follow-up, 75% of patients died. Survival: VO2p (ml/kg/min) first quartil was 38.5 months (RIQ 18,25-58,5); second quartil 66 months (RIQ 35-84.5); third quartil 70 months (RIQ 15-96) and fourth quartil 68 months (RIQ 48-93). After 103 months of follow-up, survival was compared: 1st vs 4rd quartil of VO2p (p<0.01) and 2nd vs. 4rd quartil (p<0.03); comparing at 145 months: 2nd vs. 4rd quartil (p=0.049). In a multivariate analysis, high VO2p is a protective factor on mortality, nevertheless other independent variables as male gender, age >70, severe airway obstruction and frequent exacerbators were associated to mortality. Conclusion: At long term of follow-up, a cohort of severe COPD patients (males and fe- males), in multivariate analysis, high VO2p is a protective factor of mortality, nevertheless other independent variables as male gender, age >70, severe airway obstruction and frequent exacerbators were associated to mortality.

Associations among motor competence, health-related fitness, and physical activity in children: A comparison of gold standard and field-based measures.

This study compared the associations among motor competence, health-related fitness, and physical activity measured by gold standard and field-based methods in children. A total of 248 first-grade children (153 boys) aged 6-7 years participated in the study. Motor competence was assessed using the Test of Gross Motor Development, Second Edition (TGMD -2). Gold standard measures were percent body fat using dual-energy X-ray absorptiometry, peak oxygen uptake per weight using a gas analyser, and moderate-to-vigorous physical activity using accelerometers. Field-based measures were body mass index, maximum speed during progressive running on a treadmill, and a physical activity questionnaire. Multiple regression analysis adjusted for age and sex was used to examine the associations of motor competence with one of the health-related variables and compared differences by measurement method. The results indicated that field-based measures models showed lower associations (R2 = 0.02-0.17) than the gold standard (R2 = 0.21-0.27) and lower standardised regression coefficients for sex and motor competence, except for maximum speed. In conclusion, gold standard measures resulted in stronger associations between motor competence, and health-related fitness and physical activity in children. Examining the contribution of motor competence in children's health using field-based tests can underestimate it.

Dual-Tuned Terahertz Absorption Device Based on Vanadium Dioxide Phase Transition Properties.

In recent years, absorbers related to metamaterials have been heavily investigated. In particular, VO2 materials have received focused attention, and a large number of researchers have aimed at multilayer structures. This paper presents a new concept of a three-layer simple structure with VO2 as the base, silicon dioxide as the dielectric layer, and graphene as the top layer. When VO2 is in the insulated state, the absorber is in the closed state, Δf = 1.18 THz (absorption greater than 0.9); when VO2 is in the metallic state, the absorber is open, Δf = 4.4 THz (absorption greater than 0.9), with ultra-broadband absorption. As a result of the absorption mode conversion, a phenomenon occurs with this absorber, with total transmission and total reflection occurring at 2.4 THz (A = 99.45% or 0.29%) and 6.5 THz (A = 90% or 0.24%) for different modes. Due to this absorption property, the absorber is able to achieve full-transmission and full-absorption transitions at specific frequencies. The device has great potential for applications in terahertz absorption, terahertz switching, and terahertz modulation.

Synergistic effect of oxygen defects and calabash-like hollow carbon matrix enables VO2 as high-performance cathode for zinc ion battery.

Vanadium dioxide (VO2) materials exhibit significant theoretical specific capacity, which is ascribed to multi-electron transfer reactions and unique tunneled structures. However, the low electronic conductivity and sluggish reaction kinetics of VO2 have impeded its further development. Hence, in this study, we employed a synergistic strategy of defect engineering and compositing with a calabash carbon matrix to reduce Zn2+ diffusion barriers and accelerate electron transfer. The VO2 cathode provided a high specific capacity at a low rate of 303 mA h g-1 at 0.1 A g-1 after 191 cycles, along with good rate performance (168 mA h g-1 at 10 A g-1) and satisfactory long-term stability (170 mA h g-1 at 1 A g-1 after 1100 cycles). The exhaustive structural analyses indicated that oxygen vacancies accelerated the Zn2+ diffusion rate, while a uniform calabash-like hollow carbon matrix improved electronic conductivity during cycling. Moreover, ex-situ measurements demonstrated that during discharge, the composite cathode transformed to layered Zn3+x(OH)2V2O7·2H2O, which then facilitated the subsequent intercalation of Zn2+. This cooperative strategy advances the practical application of aqueous zinc ion batteries by leveraging vanadium-based electrodes.

Multifunctional Radiation Conditioning Emitter for Laser and Infrared with Adaptive Radiative Cooling.

With the development of technology, multifunctional multiband emitters have been paid much attention due to their wide range of applications, such as LIDAR detection, spectroscopic sensing, and infrared thermal management. However, the development of such emitters is impeded by incompatible structural requirements of different electromagnetic wavebands. Here, we demonstrate coupled modulation between near-infrared (NIR) laser-wavelength and long-wavelength-infrared by constructing a multifunctional emitter (MFE) with a structure of Al/HfO2/VO2, utilizing the phase transition of VO2. The MFE displays excellent thermal modulation capability within the 8-14 µm range, achieving a thermal insulation effect (ε8-14 µm = 0.18) at low temperatures, and heat dissipation effect (ε8-14 µm = 0.64) at high temperatures. The MFE's radiation power regulation capability is 145.06 W m-2 between a temperature of 0 to 60 °C. Moreover, the MFE possesses a large reflectivity modulation value of 0.78 at NIR laser-wavelength (1.06 µm) with a short phase transition time of 1003 ms under 3 W cm-2 laser irradiation. This study provides a guideline for the coordinated control of electromagnetic waves and intelligent collaborative thermal management through simple structural design, thus, having broad implications in energy saving and thermal information processing.

Toughness and Thermoresponsive Hydrogel for Sandwich Smart Window with Adaptive Solar Modulation and Energy Saving.

Thermochromic hydrogels with self-regulating solar transmittance are gaining increasing attention due to their significant potential in the fields of smart windows and energy conservation. Smart windows incorporating viscosity-tough hydrogels as an interlayer exhibit enhanced advantages in resisting external forces. In this study, a tough and thermoresponsive composite hydrogel was developed by incorporating poly(N-isopropylacrylamide) nanoparticles (PNIPAM NPs) and W-doped VO2 into a polyacrylamide-agar (PAM-Agar) double network hydrogel. Upon solar irradiation, thermochromism of PNIPAM NPs could regulate the visible light transmittance of the composite hydrogel and the photothermal effect of W-VO2 contributes to the optical regulation and NIR shielding. The smart window, with the composite hydrogel as an interlayer, demonstrates excellent optical modulation capabilities, with a luminous transmittance (Tum(20 °C)) of 86.81%, high light modulation (ΔTum = 78.89%), a high solar modulation (Tsol) of 83.59%, and a lower critical solution temperature (LCST) of 32.6 °C. The composite hydrogel's superior toughness (0.215 MJ/m3) also enhances the impact resistance of the smart window glass. Additionally, the adhesion between the hydrogel and the glass, with a maximum peeling force of up to 151 N/m (attributed to interactions between the amide groups and the silicon hydroxyl groups), was confirmed through a falling ball experiment. Moreover, the hydrogel exhibits a certain degree of thermal insulation, further promoting its utility in energy-saving applications. In conclusion, this study highlights the significant potential of such composite hydrogels in the development of smart windows for energy-efficient buildings.

VO2MAX, 6-minute walk, and muscle strength each correlate with frailty in US veterans.

Introduction: Frailty often manifests as an increased vulnerability to adverse outcomes, and detecting frailty is useful for informed healthcare decisions. Veterans are at higher risk for developing frailty and at younger ages. The goal of this study was to investigate approaches in Veterans that can better inform the physiologic underpinnings of frailty, including maximal oxygen uptake (VO2max), 6-min walk, muscle strength, and inflammatory biomarkers. Methods: Participants (N = 42) were recruited from the Buffalo VA Medical Center. Inclusion criteria: ages 60-85, male or female, any race, and not having significant comorbidities or cognitive impairment. Outcome measures included: the Fried frailty phenotype, the short physical performance battery (SPPB), quality of life (QOL) using the Q-LES-Q-SF, and the following physiologic assessments: VO2max assessment on an upright stationary bicycle, 6-min walk, and arm and leg strength. Additionally, inflammatory biomarkers (C-reactive protein, IL-6, IL-10, interferon-γ, and TNF-α) were measured using ELLA single and multiplex ELISA. Results: Participants: 70.3 ± 7.4 years of age: 34 males and 8 females, BMI = 30.7 ± 5.4 kg/m2, 26 white and 16 African American. A total of 18 (42.8%) were non-frail, 20 (47.6%) were pre-frail, and 4 (9.5%) were frail. VO2max negatively correlated with Fried frailty scores (r = -0.40, p = 0.03, N = 30), and positively correlated with SPPB scores (r = 0.50, p = 0.005), and QOL (r = 0.40, p = 0.03). The 6-min walk test also significantly correlated with VO2max (r = 0.57, p = 0.001, N = 42) and SPPB (r = 0.55, p = 0.0006), but did not quite reach a significant association with frailty (r = -0.28, p = 0.07). Arm strength negatively correlated with frailty (r = -0.47, p = 0.02, N = 26), but not other parameters. Inflammatory profiles did not differ between non-frail and pre-frail/frail participants. Conclusion: Objectively measured cardiorespiratory fitness was associated with important functional outcomes including physical performance, QOL, and frailty in this group of older Veterans. Furthermore, the 6-min walk test correlated with VO2max and SPPB, but more validation is necessary to confirm sensitivity for frailty. Arm strength may also be an important indicator of frailty, however the relationship to other indicators of physical performance is unclear.

Impact of Body Mass Index and VO2 Max on Symptoms, Physical Activity, and Physical Function in a Multinational Sample of People with HIV.

People with HIV (PWH) are at increased risk for metabolic disorders affecting body mass index (BMI), chronic symptoms, and impaired physical function and capacity. Although physical activity improves health and well-being, PWH often do not meet activity recommendations necessary to achieve these benefits. Despite the known impact of symptoms, physical activity, and physical function on health, little is known about the relationships and interactions between these variables and BMI and maximum oxygen consumption during exercise (VO2 max) in a multinational population of PWH. We examined the relationship of BMI with PROMIS-29 measures, physical activity, strength, flexibility, and VO2 max in a diverse sample of PWH. Additionally, we examined the relationship of VO2 max with PROMIS-29 measures. Data from 810 PWH who participated in a cross-sectional study conducted by the International Nursing Network for HIV Research (Study VII) were analyzed. Participants were recruited from 8 sites across the United States, Thailand, and South Africa. BMI was calculated from collected height and weight data. Physical function and symptoms were assessed using the PROMIS-29 measure. Physical activity was assessed using the 7-day Physical Activity Recall. VO2 max was calculated using sex at birth, age, BMI and the 6-minute Walk Test. Data were analyzed using descriptive, correlational, and regression statistical analyses. Participants had an average age of 49.1 (± 11.1) years, 44% were female, and the average BMI of the sample group was 27 kg/m2 (± 6.7). Increased BMI was associated with decreased 6-minute Walk Test (ß=-2.18, p < 0.001), flexibility (ß=-0.279, p < 0.001), and VO2 max (ß=-0.598, p < 0.001), even after controlling for covariates (age, sex at birth, country, years living with HIV, and antiretroviral therapy status). BMI was not associated with self-reported physical activity. Increased VO2 max was associated with increased physical function (ß = 0.069, p < 0.001), and decreased pain (ß=-0.047, p < 0.006), even after controlling for covariates (country, years living with HIV, and antiretroviral therapy status). Future research should explore development of effective and sustainable symptom self-management interventions in PWH accounting for the potential impact of BMI and VO2 max.

Effects of the Birthplace Altitude and Training Volume on Hematological Characteristics in Youth and Junior Male Colombian Cyclists.

PURPOSE: The long-term development of talent in endurance sports is a topic of interest. Among various factors, the importance of total hemoglobin mass (tHbmass) and the potential benefits of being an altitude-native athlete remain unclear, particularly in young categories. This study aimed to investigate the impact of altitude and training content on hematological characteristics by comparing young male cyclists age 15-16 and 17-18 years who were born and trained at a moderate altitude (ie, greater than or equal to 2500 m; MA) and cyclists who were born and trained at low altitude (below 1000 m; LA). METHODS: tHbmass (in grams and grams per kilogram), measured by using the optimized carbon monoxide rebreathing method during an incremental test on a cycle ergometer; hematocrit percentage, hemoglobin concentration; and erythrocyte, blood, and plasma volume were measured in youth male cyclists age 15-16 years and junior cyclists age 17-18 years who were born and trained at MA versus LA. All variables were analyzed with a 2-way (age [youth cyclist vs junior cyclist] × altitude level [MA vs LA]) analysis of variance with subsequent Tuckey post hoc test. RESULTS AND CONCLUSION: Some altitude-induced benefits were reported in cyclists at age 15-16 years in the MA group with higher values in hematocrit percentage, hemoglobin concentration, and tHbmass (grams per kilogram) (P < .05) than their LA counterparts. This was also observed at age 17-18 years (P < .001), except for tHbmass, wherein no significant difference was found between MA and LA groups. In contrast, plasma volume was lower in MA than LA junior cyclists. NEW FINDINGS: (1) The altitude of birth and residence could generate an advantage in tHbmass in young male cyclists age 15-16 and 17-18 years who train at MA compared with cyclists who are born and train at LA. (2) Altitude-induced benefits in physiological variables (hematocrit percentage, hemoglobin concentration, tHbmass in g·kg-1) were reported in cyclists at age 15-16 years and partially at age 17-18 years. In contrast, plasma volume was lower in MA than in LA junior cyclists. This may impact the strategies for identifying and developing talent in cycling.

Effects of Aerobic Exercise on Cardiopulmonary Function in Postoperative Patients with Congenital Heart Disease: A Meta-analysis.

Background: This meta-analysis aimed to evaluate the impact of aerobic exercise on Peak VO2 (Oxygen Consumption) in postoperative patients with congenital heart disease (CHD). Besides this, we also tried to discover whether the improvement was influenced by patient ages, modes of supervision, types of exercise, the total dose of exercise, intervention periods, and types of CHD. Methods: Following the Population Intervention Comparison Outcome Study Design (PICOS) principle, a comprehensive search of the PubMed, Web of Science, Embase and Cochrane Library databases was conducted for randomized controlled trials (RCTs) evaluating the intervention effects of aerobic exercise on cardiopulmonary function in postoperative CHD patients until December 2023. This meta-analysis and publication bias tests were conducted using Stata 17.0, and the mean differences (MDs) with 95% confidence intervals (CIs) were used as effect sizes in statistics. Results: A total of 15 RCTs (762 cases) were included in this meta-analysis, with 407 cases in the experimental group and 355 cases in the control group. Meta-analysis showed that aerobic exercise had a positive effect on Peak VO2 in postoperative CHD patients (MD = 2.14, 95% CI (1.34, 2.94), p < 0.00001, I2 = 36%). The analysis of subgroups showed that intervention effects of aerobic exercise were superior to the control group when patients were > 18 years old (MD = 2.53, p < 0.00001), ≤ 18 years old (MD = 1.63, p = 0.01), under supervision (MD = 2.23, p < 0.00001), unsupervised (MD = 2.06, p < 0.00400), performing aerobic exercise (MD = 1.87, p = 0.0003), performing aerobic exercise combined with resistance training (MD = 2.57, p < 0.00010), with a total dose of exercise ≥ 1440 minutes (MD = 2.45, p < 0.00010), with the intervention period of 10-12 weeks (MD = 2.31, p < 0.00001), with that > 12 weeks (MD = 1.97, p = 0.00300), or with mixed types of CHD (MD = 2.34, p < 0.00001). Conclusions: This meta-analysis did not deduct points for limitations, inconsistency, indirectness, imprecision, or publication bias, so the quality of evidence was graded as high. Aerobic exercise has a significantly positive impact on improving Peak VO2 in postoperative CHD patients. Moreover, it was found that for patients aged 18 and above, supervised aerobic exercise combined with resistance training, implemented for 10-12 weeks with a total dose of exercise ≥ 1440 minutes, had a better intervention effect on Peak VO2. This finding provided evidence-based medicine for the exercise rehabilitation of postoperative CHD patients, and explored the optimal exercise prescription for clinical practice as well. Clinical Trial registration: Registered on INPLASY No.202440016 (https://inplasy.com).

The Influence of Acute Oral Lactate Supplementation on Responses to Cycle Ergometer Exercise: A Randomized, Crossover Pilot Clinical Trial.

The purpose of this study was to investigate the potential ergogenic effects of an oral lactate supplement. For this double-blind, randomized, placebo-controlled crossover design, fifteen recreational exercisers (nine males, six females) ingested a placebo or a commercially available lactate supplement prior to cycle ergometer exercise. Primary outcomes included peak oxygen uptake (VO2peak; via indirect calorimetry), VO2 at the ventilatory threshold, and work rate at the lactate threshold (arterialized venous blood from a heated hand) determined during incremental exercise to fatigue, and power output during a 20-min cycling time trial. Compared with placebo, the oral lactate supplement (19 ± 1 mg/kg body mass) did not influence VO2peak (placebo: 44.3 ± 7.8 vs. oral lactate: 44.3 ± 7.1 mL/kg/min (mean ± SD); p = 0.87), VO2 at the ventilatory threshold (placebo: 1.63 ± 0.25 vs. oral lactate: 1.65 ± 0.23 L/min; p = 0.82), or work rate at the lactate threshold (placebo: 179 ± 69 vs. oral lactate: 179 ± 59 W; p = 0.41). Throughout the 20-min time trial, the work rate was slightly greater (4%) with oral lactate (204 ± 41 W) compared with placebo (197 ± 41 W; main effect of treatment p = 0.02). Collectively, these data suggest that this commercially available lactate supplement did not acutely influence the physiological responses to incremental cycle ergometer exercise but elicited a modest ergogenic effect during the short-duration time trial.

Impact of sodium-glucose cotransporter-2 inhibitor use on peak VO2 in advanced heart failure patients.

Introduction: Advanced heart failure (HF) is an epidemic that affects multiple organ systems with high morbidity and mortality rates despite optimal medical therapy (OMT) and remains the leading cause of hospitalizations in type 2 diabetes-related cardiovascular disease. The addition of sodium-glucose co-transporter inhibitors (SGLT2i) in treating these patients has seen improved mortality and hospital admission rates. As such, we felt it was important to investigate whether the use of SGLT2i improved functional capacity in patients with HF when compared to OMT by evaluating maximum oxygen consumption (peak VO2) using cardiopulmonary exercise testing (CPET). Methods: We found 94 heart failure patients between August 2020 and August 2021 who underwent CPET before and after treatment at Mayo Clinic in Florida. 50 patients received OMT and 44 received OMT and SGLT2i therapy. CPET results before and after were compared for each group. Results: The baseline ejection fraction was not significantly different between groups, with the OMT group at 38% and the SGLT2i group at 33%, p = 0.10. OMT patients were found to have a significantly lower hemoglobin A1c of 5.7 (5.4-6.1) compared to those with SGLT2i therapy of 6.4 (5.8-7.1), p = 0.01. The baseline peak VO2 was 17.3 ml/kg/min (13.3-21.6) in the OMT group and 17.3 ml/kg/min (14.4-18.9) in the SGLT2i group, p = 0.18, not significantly different. The interesting finding is that the follow-up peak VO2 at one year for the OMT group was 17 ml/kg/min (13.3-21.6), which was not significantly different from the SGLT2i group peak VO2 of 17 ml/kg/min (14.6-19.6), p = 0.19. Our study is the first to compare before and after peak VO2 values of the OMT+SGLT2i group to the patient's own baseline and we found no significant improvement. Conclusion: Our single-center data shows no improvement in functional capacity after the addition of SGLT2i therapy to OMT in patients with advanced heart failure. Improved hospitalization and symptoms may be attributed to other numerous effects of SGLT2i such as volume management.

Impact of Idiopathic Scoliosis on the Cardiopulmonary Capacity of Adolescents.

Chest deformities in children with scoliosis may result in cardiopulmonary disorders, lowering cardiopulmonary capacity levels. However, results regarding the dependence of cardiopulmonary capacity on the severity level of scoliosis remain controversial. We aimed to use dynamic cardiopulmonary exercise testing (CPET) to investigate exercise capacity in reference to spinal deformity in patients with mild or moderate idiopathic scoliosis by means of multivariate analyses. Methods: We included 92 children and adolescents aged 10-17 years with mild and moderate idiopathic scoliosis and 94 healthy peers. The study consisted of three parts: (1) medical record analyses; (2) anthropometric measurements; and (3) CPET. Results: Our results revealed that the mean VO2peak and VO2peak/kg values of the participants with scoliosis were 0.27 L/min and 0.37 mL/min/kg lower than their healthy peers, respectively, regardless of age and gender. Furthermore, the occurrence of scoliosis correlates with a mean decrease in minute ventilation volume by 10.10 L/min, tidal volume by 0.11 L, breathing frequency by 3.78 bpm, and breathing reserve by 14.34%, regardless of the age and gender of the participants. Children and adolescents with mild-to-moderate scoliosis during CPET exhibit a lower ventilation capacity and lower VO2 max than healthy adolescents matched in age but their cardiorespiratory fitness parameters do not depend on the Cobb angle value and the angle rotation of the primary spinal curvature. Conclusions: Physical therapy and activity should be recommended to prevent cardiorespiratory failure in later life in patients with scoliosis. This study may also provide CPET reference values for healthy children and adolescents with scoliosis.

Polarized Raman mapping and phase-transition by CW excitation for fast purely optical characterization of VO2 thin films.

Vanadium dioxide has attracted much interest due to the drastic change of the electrical and optical properties it exhibits during the transition from the semiconductor state to the metallic state, which takes place at a critical temperature of about 68 °C. Much study has been especially devoted to developing advanced fabrication methodologies to improve the performance of VO2 thin films for phase-change applications in optical devices. Films structural and morphological characterisation is normally performed with expensive and time consuming equipment, as x-ray diffractometers, electron microscopes and atomic force microscopes. Here we propose a purely optical approach which combines Polarized Raman Mapping and Phase-Transition by Continuous Wave Optical Excitation (PTCWE) to acquire through two simple measurements structural, morphological and thermal behaviour information on polycrystalline VO2 thin films. The combination of the two techniques allows to reconstruct a complete picture of the properties of the films in a fast and effective manner, and also to unveil an interesting stepped appearance of the hysteresis cycles probably induced by the progressive stabilization of rutile metallic domains embedded in the semiconducting monoclinic matrix.

Effect of Strength and Endurance Training Sequence on Endurance Performance.

This review investigates the effect of two different concurrent training sequences on endurance performance. The sequences investigated are Endurance-Resistance (ER) and Resistance-Endurance (RE). A literature search is conducted of the SPORTDiscus and Medline databases. The included studies are randomized control trials, which compare the effect of ER and RE on at least one endurance performance variable. A PEDro scale is used to assess the methodological quality of the articles in this review. Of a total of 152 articles identified during the initial screening, 15 studies meet the inclusion criteria. These studies include 426 participants (298 males and 128 females), with 212 of the participants training with ER and 214 with RE. The results are presented as the percentage change of the mean from pre- to post-test. All the studies show an improvement in endurance from pre to post for both interventions, except for the RE group in one study. This review finds small and non-conclusive sequence effects between ER and RE, suggesting that the sequence of concurrent training is not of great importance in relation to endurance performance.

VO2-Based Spacecraft Smart Radiator with High Emissivity Tunability and Protective Layer.

In the extreme space environment, spacecraft endure dramatic temperature variations that can impair their functionality. A VO2-based smart radiator device (SRD) offers an effective solution by adaptively adjusting its radiative properties. However, current research on VO2-based thermochromic films mainly focuses on optimizing the emissivity tunability (Δε) of single-cycle sandwich structures. Although multi-cycle structures have shown increased Δε compared to single-cycle sandwich structures, there have been few systematic studies to find the optimal cycle structure. This paper theoretically discusses the influence of material properties and cyclic structure on SRD performance using Finite-Difference Time-Domain (FDTD) software, which is a rigorous and powerful tool for modeling nano-scale optical devices. An optimal structural model with maximum emissivity tunability is proposed. The BaF2 obtained through optimization is used as the dielectric material to further optimize the cyclic resonator. The results indicate that the tunability of emissivity can reach as high as 0.7917 when the BaF2/VO2 structure is arranged in three periods. Furthermore, to ensure a longer lifespan for SRD under harsh space conditions, the effects of HfO2 and TiO2 protective layers on the optical performance of composite films are investigated. The results show that when TiO2 is used as the protective layer with a thickness of 0.1 µm, the maximum emissivity tunability reaches 0.7932. Finally, electric field analysis is conducted to prove that the physical mechanism of the smart radiator device is the combination of stacked Fabry-Perot resonance and multiple solar reflections. This work not only validates the effectiveness of the proposed structure in enhancing spacecraft thermal control performance but also provides theoretical guidance for the design and optimization of SRDs for space applications.

Switchable Vanadium Dioxide Metasurface for Terahertz Ultra-Broadband Absorption and Reflective Polarization Conversion.

Based on the unique insulator-metal phase transition property of vanadium dioxide (VO2), we propose an integrated metasurface with a switchable mechanism between ultra-broadband absorption and polarization conversion, operating in the terahertz (THz) frequency range. The designed metasurface device is constructed using a stacked structure composed of VO2 quadruple rings, a dielectric layer, copper stripes, VO2 film, a dielectric layer, and a copper reflection layer. Our numerical simulations demonstrate that our proposed design, at high temperatures (above 358 K), exhibits an ultra-broadband absorption ranging from 4.95 to 18.39 THz, maintaining an absorptivity greater than 90%, and achieves a relative absorption bandwidth of up to 115%, significantly exceeding previous research records. At room temperature (298 K), leveraging VO2's insulating state, our proposed structure transitions into an effective polarization converter, without any alteration to its geometry. It enables efficient conversion between orthogonal linear polarizations across 3.51 to 10.26 THz, with cross-polarized reflection exceeding 90% and a polarization conversion ratio over 97%. More importantly, its relative bandwidth reaches up to 98%. These features highlight its wide-angle, extensive bandwidth, and high-efficiency advantages for both switching functionalities. Such an ultra-broadband convertible design offers potential applications in optical switching, temperature dependent optical sensors, and other tunable THz devices in various fields.