Oxygen Uptake Values Research Articles

Signal-morphology impedance cardiography is a non-invasive tool to predict responses to exercise based cardiac rehabilitation in chronic heart failure patients

Abstract Background All the studies and meta-analyses showed beneficial effects of the exercise based cardiac rehabilitation (ExBCR) on peak value of oxygen uptake (VO2peak) in patient with chronic heart failure (CHF). It is widely recognized that changes in VO2peak induced by training (ΔVO2peak) have a prognostic value. A 5.0% increase in ΔVO2peak has been associated with a significant clinical improvement1. However, 20 to 30 % of CHF are non-responders to ExBCR. The Signal-Morphology Impedance Cardiography (SM-ICGTM) technology has allowed previous researchers to show the role of cardiac output (CO) on DVO2peak2. CO responses may be partly attributed to the peak ejection flow velocity that can explain the impaired response to ExBCR. Purpose The study aimed to establish whether SM-ICGTM is an appropriate technology to predict responses to ExBCR in CHF patients. Methods A retrospective study was conducted on 65 CHF patients (LVEF: 29.0±8.3%). All patients performed a cardiopulmonary exercise test (CPET) on bicycle to determine ventilation (VE) and VO2peak before and after 20 ExBCR sessions. In addition, stroke volume (SV), heart rate (HR), and CO were continuously monitored by SM-ICGTM (PhysioFlow® Lab1). The value of peak ejection flow velocity, so called CTi by the manufacturer, was calculated as the peak of the first mathematical derivative over the time of the impedance waveform during the systole and measured by PhysioFlow® throughout the test. For the analysis of training response patients were divided in two groups: the normal CTi profile which was characterized by an initial increase followed by a plateau until CPET exhaustion, and the abnormal CTi response if CTi decreased at the onset of CPET or increased then decreased before exhaustion. Statistical analyses were performed with JASP. The significant level was set at p value < 0.05 for 95% confidence interval. Results Our study population consisted in 32 patients who presented a normal CTi profile and 33 with an abnormal CTi profile. As shown in Table 1, no significant difference was found at baseline between both groups. ExBCR induced significant changes in VO2peak even if 29 % patients were non-responders. Patients with normal CTi profile presented a greater DVO2peak compared to patients with abnormal CTi profile (28 ± 30 vs. 14 ± 19 %, p<0.01). 78% of patients with normal CTi profile versus only 64% of patients with abnormal CTi profile were ExBCR responders. The logistic regression showed that patient with normal CTi profile were 3.3 time more likely to present a ΔVO2peak ≥ 5%. Conclusion Exercise CTi profiles determined by SM-ICGTM prove to be an interesting tool to help predicting ExBCR responses in CHF patients and maybe highlighting the hemodynamic determinants of VO2 responses to exercise training.

Aerobic capacity in swimming, cycling and arm cranking in swimmers aged 11–13 years

BackgroundThis study aimed to compare the aerobic capacity in swimming, cycling and arm cranking in swimmers aged 11–13 years.MethodsEleven swimmers (mean age, 12.1 ± 1.0 years) performed three incremental exercise tests. One of the tests was performed under specific conditions (front crawl swimming), and the other two were under non–specific conditions (cycling and arm cranking). Data on the pulmonary gas exchange were recorded using the portable analyser MetaMax 3B (Cortex, Leipzig, Germany). One-way analysis of variance for repeated measures was employed to test the null hypothesis and determine statistically significant differences between the indicators obtained under specific and non–specific testing conditions. Pearson’s correlation coefficient was calculated to assess the relationships between the indicators of the pulmonary gas exchange.ResultsThe relative peak oxygen uptake (V̇O2peak) value during swimming was 49.3 ± 6.2 mL/kg/min, which was higher than that during arm cranking (39.6 ± 7.3 mL/kg/min; P < 0.01) but lower than that during cycling (54.3 ± 7.8 mL/kg/min; P < 0.01). The peak minute ventilation (V̇Epeak) value during swimming (84.9 ± 12.6 L/min) was higher than that during arm cranking (69.4 ± 18.2 L/min; P < 0.01) but lower than that during cycling (98.4 ± 15.4 L/min; P < 0.01). Strong positive correlations were observed in the absolute and relative V̇O2peak values between swimming and cycling (r = 0.857, P < 0.01; r = 0.657, P < 0.05) and between swimming and arm cranking (r = 0.899, P < 0.01; r = 0.863, P < 0.05). A strong positive correlation was also observed in V̇Epeak values between swimming and arm cranking (r = 0.626, P < 0.05).ConclusionSwimmers aged 11–13 years showed V̇O2peak and V̇Epeak values during the specific swimming test greater than those during arm cranking but lower than those during cycling. However, aerobic capacity parameters measured during specific swimming conditions correlated with those measured during non–specific arm cranking and cycling conditions.

Assessment of Angular and Straight Linear Rowing Ergometers at Different Intensities of Exercise.

We aimed to conduct a biophysical comparison of angular (Biorower) and linear (Concept2) rowing ergometers across a wide spectrum of exercise intensities. Sixteen (eleven male) skilled rowers, aged 29.8 ± 8.6 and 23.6 ± 1.5 years, with international competitive experience, performed 7 × 3 min bouts with 30 W increments and 60 s intervals, plus 1 min of all-out rowing on both machines with 48 h in between. The ventilatory and kinematical variables were measured breath-by-breath using a telemetric portable gas analyzer and determined using a full-body markerless system, respectively. Similar values of oxygen uptake were observed between ergometers across all intensity domains (e.g., 60.36 ± 8.40 vs. 58.14 ± 7.55 mL/min/kg for the Biorower and Concept2 at severe intensity). The rowing rate was higher on the Biorower vs. Concept2 at heavy and severe intensities (27.88 ± 3.22 vs. 25.69 ± 1.99 and 30.63 ± 3.18 vs. 28.94 ± 2.29). Other differences in kinematics were observed across all intensity domains, particularly in the thorax angle at the finish (e.g., 19.44 ± 4.49 vs. 27.51 ± 7.59° for the Biorower compared to Concep2 at heavy intensity), likely due to closer alignment of the Biorower with an on-water rowing technique. The overall perceived effort was lower on the Biorower when compared to the Concept2 (14.38 ± 1.76 vs. 15.88 ± 1.88). Rowers presented similar cardiorespiratory function on both rowing ergometers, while important biomechanical differences were observed, possibly due to the Biorower's closer alignment with an on-water rowing technique.

Does Aerobic Capacity Change According to Position in Football Players?

Aerobic capacity plays an important role in football as it influences players' physical performance and long-lasting endurance levels. The aim of this study was to investigate the aerobic capacity levels of football players playing in different positions according to the positions they play. The study group consisted of 83 football players in super amateur league. Football players playing in 8 different positions voluntarily participated in the study (goalkeeper: n= 8, defender: n=13, left back: n=9, right back: n=7, midfield: n=24, left winger: n=7, right winger: n=7 striker: n=8). Yo-Yo Intermittent Recovery Test (YYIRT1) was applied to determine the aerobic endurance parameters of the players. One-way ANOVA analysis was used to compare the distance travelled, average speed (km/h) and maximum oxygen uptake (VO2max) values. It was determined that there was a significant difference between the test parameters of the players in different playing positions, and this difference was found to be between the left back players, goalkeepers, and stoppers (p&amp;lt;0.05). It was determined that goalkeepers had the lowest average aerobic capacity in the distances travelled by the players by position, while back players and wingers had high aerobic capacity averages. According to these results, we can say that the aerobic capacities of football players vary according to their positions, and the physiological demands of the position played by back players and wingers are effective in the distance travelled and the football players have different aerobic capacities.

The long-term effect of elexacaftor/tezacaftor/ivacaftor on cardiorespiratory fitness in adolescent patients with cystic fibrosis: a pilot observational study

BackgroundPhysical activity is a crucial demand on cystic fibrosis treatment management. The highest value of oxygen uptake (VO2peak) is an appropriate tool to evaluate the physical activity in these patients. However, there are several other valuable CPET parameters describing exercise tolerance (Wpeak, VO2VT1, VO2VT2, VO2/HRpeak, etc.), and helping to better understand the effect of specific treatment (VE, VT, VD/VT etc.). Limited data showed ambiguous results of this improvement after CFTR modulator treatment. Elexacaftor/tezacaftor/ivacaftor medication improves pulmonary function and quality of life, whereas its effect on CPET has yet to be sufficiently demonstrated.MethodsWe performed a single group prospective observational study of 10 adolescent patients with cystic fibrosis who completed two CPET measurements between January 2019 and February 2023. During this period, elexacaftor/tezacaftor/ivacaftor treatment was initiated in all of them. The first CPET at the baseline was followed by controlled CPET at least one year after medication commencement. We focused on interpreting the data on their influence by the novel therapy. We hypothesized improvements in cardiorespiratory fitness following treatment. We applied the Wilcoxon signed-rank test. The data were adjusted for age at the time of CPET to eliminate bias of aging in adolescent patients.ResultsWe observed significant improvement in peak workload, VO2 peak, VO2VT1, VO2VT2, VE/VCO2 slope, VE, VT, RQ, VO2/HR peak and RR peak. The mean change in VO2 peak was 5.7 mL/kg/min, or 15.9% of the reference value (SD ± 16.6; p= 0.014). VO2VT1 improved by 15% of the reference value (SD ± 0.1; p= 0.014), VO2VT2 improved by 0.5 (SD ± 0.4; p= 0.01). There were no differences in other parameters.ConclusionExercise tolerance improved after elexacaftor/tezacaftor/ivacaftor treatment initiation. We suggest that the CFTR modulator alone is not enough for recovering physical decondition, but should be supplemented with physical activity and respiratory physiotherapy. Further studies are needed to examine the effect of CFTR modulators and physical therapy on cardiopulmonary exercise tolerance.

The contribution of energy systems during 30-second lower body Wingate anaerobic test in combat sports athletes: Intermittent versus single forms and gender comparison.

Combat sports, encompassing a range of activities from striking and grappling to mixed and weapon-based disciplines, have witnessed a surge in popularity worldwide. These sports are demanding, requiring athletes to harness energy from different metabolic pathways to perform short, high-intensity activities interspersed with periods of lower intensity. While it is established that the anaerobic alactic (ATP-PC) and anaerobic lactic systems are pivotal for high-intensity training sessions typical in combat sports, the precise contribution of these systems, particularly in varied training modalities such as single (SMT) and intermittent (IST) forms of the 30-second Wingate test, remains inadequately explored. This study aims at comparing performance outputs, physiological responses and gender differences during the SMT and IST forms of the 30-second Wingate test. Thirty-three highly trained combat sports athletes (17 women, 16 men; 10 boxing, 8 wrestling, 8 taekwondo and 7 karate) randomly performed SMT and IST. The IST consisted of three 10-second all-out attempts separated by 30 seconds of passive recovery, whereas the SMT was a single 30-second maximal effort. Resting, exercise and post-exercise oxygen uptake and peak blood lactate value were used to determine the metabolic energy demands via the PCr-LA-O2 method. The findings showed that total metabolic energy expenditure (TEE), ATP-PCr system contribution and the output of mechanical variables were higher in the IST than in the SMT form (all p<0.001). In contrast, the contribution of glycolytic and oxidative systems was higher in the SMT form (all p<0.001). However, exercise form and gender interaction were not significant (p>0.05). In combat sports, performance is not only determined by physiological and technical skills but also by metabolic energy input and efficiency. Therefore, our results can provide a comparison regarding the effects of exercise type and gender on metabolic energy metabolism to design the training of combat sports athletes.

Steep uphill cycling using repeated transitions between seated and standing positions results in a lower blood-lactate concentration than continuous use of either seated or standing position.

This study investigated whether repeated transitions between seated and standing positions has a different physiological response compared to continuous use of either seated position or standing position during steep uphill cycling among elite cyclists. Ten elite male cyclists completed three 5-min treadmill cycling tests at an inclination of 6.8° with constant individual-based speed resulting in a work intensity close to the aerobic threshold. During the first and third test, the participants used standing position (ST test) and seated position (SE test) or vice versa, whereas in the second test, they made repeated transitions between standing and seated positions every 10 s (RT test). The last 2 min of each test was used to measure the mean values of oxygen uptake (V̇O2) and respiratory exchange ratio, which were used to calculate the metabolic rate (MR) and gross efficiency (GE). Additionally, the blood-lactate concentration before and after (Lapost) each test was determined. One-way repeated measures ANOVA was used to determine the effect of cycling position on the physiological response. No significant differences between tests were observed for the variables related to aerobic energy expenditure (i.e., V̇O2, MR and GE), whereas the RT test was associated with a significantly lower Lapost compared to the ST and SE tests. Steep uphill cycling, at an intensity close to the aerobic threshold, with repeated transitions between standing and seated positions, did not have a higher oxygen consumption; instead, the blood-lactate concentration was lower during the RT test compared to that under continuous use of either seated or standing position.

Effects of 10-Week Online Moderate- to High-Intensity Interval Training on Body Composition, and Aerobic and Anaerobic Performance during the COVID-19 Lockdown.

The present study aimed to investigate the effects of a 10-week online high-intensity interval training (HIIT) program on body composition and aerobic and aerobic performance in physically sedentary women. A parallel, two-group, longitudinal (pre, post) design was used with physical tests performed before (preintervention) and after (postintervention) the 10-week intervention period. A total of forty-eight healthy and physically sedentary women (defined as an individual who lacks regular exercise or a structured fitness routine) were recruited to participate in this study. The participants were distributed in two groups: the experimental group (EG) with 24 women (mean ± SD: age 21.21 ± 2.15 years; weight: 61.16 ± 8.94 kg; height: 163.96 ± 4.87 cm; body mass index (BMI): 22.69 ± 2.49 kg/m2) and the control group (CG) with another 24 women (mean ± SD: age 20.50 ± 1.29 years; weight: 62.0 ± 6.65 kg; height: 163.92 ± 4.89 cm; body mass index: 23.04 ± 1.74 kg/m2). The EG performed an online HIIT program for 10 weeks, while the CG continued with their daily life routines. The repeated measures ANCOVA indicated a significant effect in the within-group analysis for weight (p = 0.001; d = -0.96) and for BMI (p = 0.001; d = 0.24), with a significant decrease in the experimental group (EG). The control group (CG) did not show any significant decrease in either body weight or BMI. Regarding the maximal oxygen uptake (VO2 max) values, the EG exhibited a significant improvement (p = 0.001; d = -1.07), whereas the CG did not demonstrate a significant improvement (p = 0.08; d = -0.37). The EG's power output (W) (p = 0.001; d = -0.50) and power output standardized by body weight (W/kg) (p = 0.001; d = -0.96) were significantly improved. The CG did not show a significant improvement in either power output (W/kg) or power output. Lastly, the within-group analysis with load revealed that the EG significantly improved (p = 0.001; d = -0.50), while CG did not show a significant improvement in load (p = 0.10.; d = -0.10). The present study showed that 10 weeks of HIIT in an online environment during the COVID-19 lockdown significantly improved maximum oxygen consumption and caused weight loss and a significant decrease in body mass index in physically sedentary women. These results suggest that HIIT may be used as a time-efficient strategy to improve body composition and cardio-respiratory fitness in sedentary women.

Attenuation of the increase of heart rate and oxygen consumption during progressive exercise in professional rugby players.

The response of oxygen uptake (VO<inf>2</inf>) and heart rate (HR) to continuous progressive large muscle mass exercise is not always linear. This study aimed to compare the patterns of the Speed/VO<inf>2</inf> (S/VO<inf>2</inf>) and speed/HR (S/HR) relationships during an incremental treadmill-running test in professional rugby players. Fourteen professional rugby athletes performed a maximal incremental treadmill-running test, following the Conconi test protocol. Speed, heart rate, and gas exchange parameters were recorded. The slope of the S/VO<inf>2</inf> and S/HR relationships were mathematically determined. The S/VO<inf>2</inf> and S/HR relationships were linear up to a submaximal speed and curvilinear thereafter. The speed of locomotion at which the slope of the S/VO<inf>2</inf> and S/HR relationships start to attenuate (VO<inf>2att</inf> and HR<inf>att</inf>) were coincident (12.3±1.0 and 12.4±0.9 km/h), strongly correlated and in good agreement. VO<inf>2</inf> values at VO<inf>2att</inf> (44.9±8.7 mL/kg/min) were significantly correlated with VO<inf>2</inf> values at the ventilatory threshold (43.3±6.0 mL/kg/min) (R2=0.83, P=0.001) and in good agreement. The running speed/VO<inf>2</inf> ratio (ΔS/ΔVO<inf>2</inf>) up to VO<inf>2att</inf> was significantly lower than that beyond VO<inf>2att</inf> (2.98±1.1 vs. 5.16±2.31); P<0,001). The speed/oxygen uptake and S/HR relationships during progressive exercise start to attenuate at a coincident exercise intensity, and at oxygen uptake values strongly correlated with the ventilatory threshold. These findings further support the usefulness of the attenuation of the S/HR relationship as a practical tool for exercise testing and training purposes in professional rugby players.

Effect of Water-Based vs. Land-Based Exercise Intervention (postCOVIDkids) on Exercise Capacity, Fatigue, and Quality of Life in Children with Post COVID-19 Condition: A Randomized Controlled Trial.

Evidence suggests that COVID-19 can cause lasting health consequences called post-COVID-19 condition. We conducted a three-group, randomized controlled trial for children aged 10-12 years with post COVID-19 condition. Participants were randomized to AQUA, LAND, or CONTROL groups. The AQUA and LAND training sessions were conducted twice a week for eight weeks. The primary outcomes were exercise capacity, measured using the modified Balke treadmill protocol, and fatigue, measured using the Cumulative Fatigue Symptoms Questionnaire (CFSQ). The secondary outcome was health-related quality of life (HRQoL), measured with the Pediatric Quality of Life Inventory (PedsQL) for children and parents. A total of 74 of the 86 children completed the intervention and attended the post-intervention assessment. The absolute maximal oxygen uptake (VO2max) values increased after both AQUA (p = 0.001) and LAND (p = 0.004) interventions. No significant differences were found in the degree of total fatigue and individual fatigue symptoms. A significant improvement was found in the PedsQL reported by the parents in the LAND group. In conclusion, the applied eight-week water-based and land-based exercise training programs improved exercise capacity in children aged 10-12 years old with post COVID-19 condition. The parents of the children in the training groups also noted an improvement in HRQoL.

Assessing aerobic physical efficiency through temple surface temperature measurements during light, heavy exercise, and recovery

The study was conducted to determine thecorrelation between the selected measures of aerobic physical efficiency and changes in the temple surface temperature in response to light and heavy exercise. 25 physically active men aged 19–25 were recruited for the study. They performed a graded exercise test on a cycle ergometer to measure maximum power (Pmax) and a test verifying the value of maximum oxygen uptake (VO2max). Then, two 3-min submaximal efforts with constant-intensity of 2.2 W·kgLBM−1 and 5 W·kgLBM−1, respectively were performed. During the constant-intensity efforts, the temperature of the temple surface was measured. Then, the difference between the temperature of the temple measured at the end of the exercise and the temperature measured at the beginning of the exercise was calculated (ΔT1-2.2, ΔT1-5, respectively). It was shown that ΔT1-2.2 correlated statistically significantly with VO2max (ml·min−1·kg−1) (r = 0.49; p = 0.01) and Pmax (W·kg−1) (r = 0.41, p = 0.04). Moreover, ΔT1-5 correlated statistically significantly with VO2max (l·min−1) (r = − 0.41; p = 0.04). Changes in body surface temperature in response to light exercise positively correlate with measurements of aerobic physical efficiency, such as VO2max and Pmax. When the exercise intensity is high (5 W·kgLBM−1), the correlation between exercise body temperature changes and VO2max becomes negative.

Influence of oxygen uptake through the liver surface on the metabolism of ex vivo perfused liver during hypoxia

The low quality of transplants having undergone hypoxic injury can lead to postoperative complications. The aim of the present research is to estimate, by means of mathematical modeling, how the process of oxygen uptake through the liver surface influences the metabolism of ex vivo perfused liver under hypoxia. The value of oxygen uptake through the surface was established to depend on the degree of oxygenation of the perfusion medium. A decrease in the oxygenation of the perfusion medium resulted in a decreased oxygen uptake through the liver surface. Stoichiometric modeling of the liver metabolism shows that upon the decreased oxygenation of the perfusion medium more energy is required for the process of oxygen uptake through the surface even at a lower level as compared to the normal oxygen supply. The application of the Pareto optimality allows estimating the optimum distribution of the energy resources in liver under ex vivo conditions. Both upon the normal and decreased oxygenation of the perfusion medium, the phenomenon of “free competition” for the resource was observed, with the energy being optimally distributed among all the metabolic fluxes. Moreover, this energy is also spent on the accompanying processes, e.g. for the transport of interstitial fluid.

Design of a perceptron model-based physical fitness index monitoring system for sports training

Abstract The purpose of designing a sports training fitness index monitoring system is to grasp better the physical performance data of athletes in the training process to ensure training safety. In this paper, the principle of multilayer perceptron is explained based on the perceptron model, the optimal loss function of multilayer perceptron is solved by using the activation function and forward propagation algorithm, the sensor data collection module is constructed, and the physical fitness index monitoring system for sports training is built by this method. To verify the feasibility of the detection system in this paper, experimental analysis was conducted from three aspects: the distribution of physical fitness index monitoring information density, physical fitness index data and monitoring data accuracy. The index monitoring density distribution was between 0.11 and 2.09 from the monitoring information density. Regarding physical performance indicators, the average values of maximum oxygen uptake, heart rate, relative energy metabolism level, and exercise intensity were 41.02, 121.58, and 11.84, respectively. From the accuracy of indicator monitoring data, the accuracy of the system in this paper was 93.63%, which was 21.57 and 11.03 percentage points higher than that of GAN and MCNN algorithms, respectively. The physical fitness index monitoring system constructed based on the perceptron model can effectively realize the monitoring of physical fitness indexes, help trainers master the training rhythm, and improve the safety of sports training.

#3075 EFFECT OF KIDNEY TRANSPLANTATION ON CARDIORESPIRATORY FITNESS ASSESSED WITH CARDIOPULMONARY EXERCISE TESTING: A SYSTEMATIC REVIEW AND META-ANALYSIS

Abstract Background and Aims Patients with kidney failure often present with reduced functional cardiovascular reserve and exercise intolerance. Kidney transplantation is the optimal treatment for patients with end-stage kidney disease as it is associated with longer survival and improved quality of life compared to hemodialysis or peritoneal dialysis. Method This is a systematic review and meta-analysis of studies using cardiopulmonary-exercise-testing (CPET) to examine the cardiorespiratory fitness of patients with kidney failure before and after kidney transplantation. The primary outcome was differences in pre- and post-transplantation values of peak oxygen uptake (VO2peak). Literature search involved PubMed, Web of Science and Scopus databases, manual search of article references and grey literature. Quality assessment was undertaken with Newcastle-Ottawa-Scale. Results From 379 literature records initially retrieved, 6 studies (207 participants) were included in final meta-analysis. A marginal, but not significant, improvement was observed in oxygen consumption during peak exercise compared to pre-transplantation values (standardized mean difference [SMD]: 0.32, 95%CI −0.02; 0.67). Oxygen consumption at anaerobic threshold (VO2AT) was significantly improved after kidney transplantation (weighted MD [WMD]: 2.30 ml/kg/min, 95%CI 0.50; 4.09), whereas no significant changes were observed in maximum heart rate (WMD: 10.45 bpm, 95%CI −3.97; 24.86). In subgroup analysis, consistent results were shown between patients having undergone transplantation preemptively and those after dialysis initiation (p-value for subgroup differences = 0.95). Of note, a trend for improvement in VO2peak was observed when pooling data reported from follow-up assessments undertaken at least 3 months post-transplantation surgery (SMD: 0.17, 95%CI −0.03; 0.38), but not earlier (WMD: −0.03 ml/kg/min, 95%CI −4.28; 4.23). Conclusion Several major indices of cardiorespiratory fitness tend to improve after kidney transplantation compared to pre-transplantation values. This finding may represent another modifiable factor contributing to better survival rates of kidney transplant recipients compared to patients undergoing dialysis.

#6919 CARDIORESPIRATORY FITNESS AND MORTALITY RISK IN PATIENTS RECEIVING HEMODIALYSIS: A PROSPECTIVE COHORT

Abstract Background and Aims Kidney failure reduces life expectancy by one-third compared with the general population, and cardiovascular complications and poor cardiorespiratory fitness (CRF) are the main causes. We aimed to evaluate the association between severe CRF and all-cause mortality risk in HD patients. Method This observational prospective cohort study followed-up patients receiving HD from August 2015 until March 2022. Cardiorespiratory fitness was evaluated through the cardiopulmonary exercise test and the peak of oxygen uptake (VO2peak) value was used to determine severe CRF (&amp;lt;15 mL·kg−1·min−1). Cox regression and Univariate Kaplan-Meier evaluated its association with mortality risk and survival rate. Results Forty-eight patients were followed-up for a median of 33.0 [14.3 – 49.3] months. A total of 26 patients had severe CRF. During the follow-up period, 11 patients (22.92%) experienced all-cause mortality. From these, eight (30.8%) had severe CRF. Even so, severe CRF was not associated with crude death rates for patients stratified by CRF levels (p = 0.189), neither in unadjusted (HR 2.35; CI 95% 0.61−9.15) and adjusted (HR 1.29; CI 95% 0.30−5.56) Cox proportional hazard models. As a continuous variable, each mL·kg−1·min−1 increase in VO2peak was not associated with mortality risk (HR 0.94; CI 95% 0.79−1.11). Univariate Kaplan-Meier analysis showed that severe CRF patients did not have significantly worse survival rates than those with mild-moderate CRF (p = 0.186). Conclusion Our findings indicated that severe CRF was not associated with all-cause mortality in patients receiving HD. Despite severe CRF being prevalent, larger cohort studies are needed to establish strong conclusions on its association with all-cause mortality.

Acute Cardiopulmonary Response of High-Intensity Interval Training with Elastic Resistance vs. High-Intensity Interval Training on a Treadmill in Healthy Adults.

This study aims to describe and compare cardiopulmonary and subjective responses during high-intensity interval training with elastic resistance (EL-HIIT) and traditional high-intensity interval training (HIIT) sessions. Twenty-two healthy adults (27.6 ± 4.4 years) performed an EL-HIIT and a HIIT protocol consisting of 10 × 1 min at ~85% V·O2max prescribed by cardiopulmonary-specific tests. Pulmonary parameters, heart rate (HR), blood lactate, and rate of perceived exertion (RPE) were measured during exercise. Paired t-test and Cohen's d effect size were used to compare peak and average values. Two-way repeated measures ANOVA and mixed model with Bonferroni's post hoc test were used to compare each bout during the session. The EL-HIIT session showed higher peak and average values of HR, ventilation (V·E), relative and absolute oxygen uptake (V·O2), carbon dioxide production (V·CO2), and RPE than HIIT (p < 0.05). The effect size (ES) comparing HIIT and EL-HIIT was large for HR, V·E, and lactate (≥0.8) in peak values. Comparing each bout between HIIT and EL-HIIT, no difference was found in peak values (p > 0.05) during the session (excluding baseline, warm-up, and recovery). EL-HIIT presented a more pronounced cardiopulmonary and subjective response than HIIT.

EFFECT OF KIDNEY TRANSPLANTATION ON INDICES OF CARDIORESPIRATORY FITNESS ASSESSED WITH CARDIOPULMONARY EXERCISE TESTING: A SYSTEMATIC REVIEW AND META-ANALYSIS

Objective: Patients with kidney failure often present with reduced functional cardiovascular reserve and exercise intolerance. Kidney transplantation is the optimal treatment for patients with end-stage kidney disease as it is associated with longer survival and improved quality of life compared to hemodialysis or peritoneal dialysis. Design and method: This is a systematic review and meta-analysis of studies using cardiopulmonary-exercise-testing (CPET) to examine the cardiorespiratory fitness of patients with kidney failure before and after kidney transplantation. The primary outcome was differences in pre- and post-transplantation values of peak oxygen uptake (VO2peak). Literature search involved PubMed, Web of Science and Scopus databases, manual search of article references and grey literature. Quality assessment was undertaken with Newcastle-Ottawa-Scale. Results: From 379 literature records initially retrieved, 6 studies (207 participants) were included in final meta-analysis. A marginal, but not significant, improvement was observed in oxygen consumption during peak exercise compared to pre-transplantation values (standardized mean difference [SMD]: 0.32, 95%CI -0.02; 0.67). Oxygen consumption at anaerobic threshold (VO2AT) was significantly improved after kidney transplantation (weighted MD [WMD]: 2.30 ml/kg/min, 95%CI 0.50; 4.09), whereas no significant changes were observed in maximum heart rate (WMD: 10.45 bpm, 95%CI -3.97; 24.86). In subgroup analysis, consistent results were shown between patients having undergone transplantation preemptively and those after dialysis initiation (p-value for subgroup differences = 0.95). Of note, a trend for improvement in VO2peak was observed when pooling data reported from follow-up assessments undertaken at least 3 months post-transplantation surgery (SMD: 0.17, 95%CI -0.03; 0.38), but not earlier (WMD: -0.03 ml/kg/min, 95%CI -4.28; 4.23). Conclusions: Several major indices of cardiorespiratory fitness tend to improve after kidney transplantation compared to pre-transplantation values. This finding may represent another modifiable factor contributing to better survival rates of kidney transplant recipients compared to patients undergoing dialysis.

Oxygen uptake efficiency slope measured by cardiopulmonary exercise testing: applicability analysis of the available prediction equations in a Brazilian healthy sample

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). Background Oxygen uptake efficiency slope (OUES) measured by cardiopulmonary exercise testing (CPET) is a measure derived from submaximal oxygen uptake values and has prognostic significance in heart failure patients. Measured values are compared to reference standards for an adequate individual assessment. However, current reference values prediction equations have applicability limitations due to differences in ergometer and sample characteristics (age range and nationatilies), which may impact external validation, as international heterogeneities in peak oxygen uptake values have already been demonstrated by Milani et al. and Peterman et al. Purpose To analyze the applicability of the available prediction equations for OUES in a healthy Brazilian sample from the Midwest region. Methods Cross-sectional study of subjects assessed by treadmill CPET in the Brazilian Midwest region between January/2011 to March/2020. The inclusion criteria were CPET performed on a treadmill in healthy subjects aged 20 years or older, and with respiratory exchange ratio ≥ 1.0. The exclusion criteria were any history of cardiovascular or pulmonary disease, presence of cardiovascular risk factors (such as hypertension, diabetes mellitus, current smoking, and obesity) and abnormalities on CPET. The following available prediction equations were used for comparisons with the measured OUES: 1) Buys et al. from Belgium/Netherlands; 2) Hollemberg et al. from United States; 3) Sun et al. from United States; 4) Brazilian prediction equations calculated in our same sample using sex, age and anthropometric variables. Statistical comparisons between measured and predicted OUES were performed using Spearman correlation test and Bland-Altman agreement analysis. Results During the study period, 7,843 CPETs were performed and included for eligibility. After applying the inclusion and exclusion criteria, 3,544 assessments of healthy individuals were included (1,574 women; 1,970 men; age 20 to 80 years). All correlations between measured and predicted values were significant, with rho ranging from 0.325 to 0.396 in females and from 0.391 to 0.450 in males (Figure 1). The mean errors by the Bland-Altman agreement analysis were heterogeneous between the OUES predition equations, with better results in our Brazilian equation. Greater bias were observed in the equation by Sun et al. for both sexes, in the equation from Buys et al. for females and in the equation by Hollemberg et al. for males (Figure 2). Conclusions The applicability analysis of the international prediction equations for OUES revealed great heterogeneity, limiting the external validation of the available equations, and highlighting the importance of using country-specific reference values for OUES to ensure a correct individual evaluation.

Heel riser height and slope gradient influence the physiology of ski mountaineering-A laboratory study.

In ski mountaineering it is the goal to reach the top of a mountain by sheer muscle force. The specific equipment (flexible boot, only toe fixated binding, and a skin on the ski to prevent from slipping backwards) enables the skier to move up the hill ergonomically, where the heel part of the binding offers a special adaptation possibility. The so-called riser height supports the heel standing height and can be adjusted to individually preferred settings. General recommendations suggest using lower heel support in flat ascents and higher heel support in steep ascents to maintain upright posture and lower the strain. Still, it remains unclear whether the application of riser height affects the physiological response during ski mountaineering. This study was designed to investigate the effects of riser height on physiological response during indoor ski mountaineering. Nineteen participants took part in the study and walked on a treadmill with ski mountaineering equipment. The three available riser heights (low, medium, and high) were applied randomized at 8%, 16%, and 24% gradient. Results show that global physiological measurements like heart rate (p = 0.34), oxygen uptake (p = 0.26) or blood lactate (p = 0.38) values were not affected by changes in riser height. But local measurements of muscle oxygen saturation were affected by the riser height. Additionally comfort and rating of perceived exertion were also prone to changes in riser height. These results suggest differences on local measurements and perceived parameters, while global physiological measurements did not change. The results are in line with the existing recommendations but need to be confirmed in an outdoor setting as well.

Is the Verification Phase a Suitable Criterion for the Determination of Maximum Oxygen Uptake in Patients with Heart Failure and Reduced Ejection Fraction? A Validation Study

The verification phase (VP) has been proposed as an alternative to the traditional criteria used for the determination of the maximum oxygen uptake (VO2 max) in several populations. Nonetheless, its validity in patients with heart failure with reduced ejection fraction (HFrEF) remains unclear. Therefore, the aim of this study was to analyse whether the VP is a safe and suitable method to determine the VO2 max in patients with HFrEF. Adult male and female patients with HFrEF performed a ramp-incremental phase (IP), followed by a submaximal constant VP (i.e., 95% of the maximal workload during the IP) on a cycle ergometer. A 5-min active recovery period (i.e., 10 W) was performed between the two exercise phases. Group (i.e., median values) and individual comparisons were performed. VO2 max was confirmed when there was a difference of ≤ 3% in peak oxygen uptake (VO2 peak) values between the two exercise phases. Twenty-one patients (13 males) were finally included. There were no adverse events during the VP. Group comparisons showed no differences in the absolute and relative VO2 peak values between both exercise phases (p = 0.557 and p = 0.400, respectively). The results did not change when only male or female patients were included. In contrast, individual comparisons showed that the VO2 max was confirmed in 11 patients (52.4%) and not confirmed in 10 (47.6%). The submaximal VP is a safe and suitable method for the determination of the VO2 max in patients with HFrEF. In addition, an individual approach should be used because group comparisons could mask individual differences.