Oxygen Cost Research Articles

Quantification of aerobic determinants of performance in post-pubertal adolescent middle-distance runners

PurposeThe use of oxygen cost (dot{O}aero) parameters to predict endurance performance has recently been criticized. Instead, it is suggested that aerobic energy cost (dot{E}_{text{aero}}) provides greater validity; however, a comparison of these quantification methods has not previously been made.MethodsFifty-six male (n = 34) and female (n = 22) competitive adolescent (17 ± 1 years) middle-distance runners participated in a sub-maximal and maximal incremental treadmill test. Running economy (RE) was measured at the speed corresponding to lactate turnpoint, and the three speeds prior. Maximal oxygen uptake (dot{V}O2max), speed at dot{V}O2max and fraction of dot{V}O2max utilized across a range of intensities, and speeds from 0.8, 1.5 and 3 km races were also quantified. RE and fractional utilization were calculated in units of dot{O}aero and dot{E}aero.ResultsMultiple linear regression models demonstrated no discernible difference in the predictive capability of RE, fractional utilization and dot{V}O2max when expressed as dot{O}aero or dot{E}aero in both sexes. When plotted as a function of running speed, dot{O}aero displayed a stepwise decrease (F = 11.59, p < 0.001) whereas dot{E}aero exhibited a curvilinear response (F = 4.74, p = 0.015). Differences were also evident in the slopes plotted for %dot{V}O2max and %dot{E}aeromax against running speed (F = 5.38, p = 0.021).ConclusionsQuantifying aerobic determinants of performance in units of dot{E}aero provides no greater validity compared to dot{O}aero-based measurement. Although both dot{E}aero and dot{O}aero are sensitive to changes in speed, dot{E}aero provides the more valid reflection of the underlying metabolic cost of running. Physiologists should also be aware of the potential differences between expression of aerobic running intensity based upon %dot{V}O2max compared to %dot{E}aeromax.

Predictors of Walking Efficiency in Children With Cerebral Palsy: Lower-Body Joint Angles, Moments, and Power.

People with cerebral palsy (CP) experience increased muscle stiffness, muscle weakness, and reduced joint range of motion. This can lead to an abnormal pattern of gait, which can increase the energy cost of walking and contribute to reduced participation in physical activity. The aim of the study was to examine associations between lower-body joint angles, moments, power, and walking efficiency in adolescents with CP. This was a cross-sectional study. Sixty-four adolescents aged 10 to 19 years with CP were recruited. Walking efficiency was measured as the net nondimensional oxygen cost (NNcost) during 6 minutes of overground walking at self-selected speed. Lower-body kinematics and kinetics during walking were collected with 3-dimensional motion analysis, synchronized with a treadmill with integrated force plates. The associations between the kinematics, kinetics, and NNcost were examined with multivariable linear regression. After adjusting for age, sex, and Gross Motor Function Classification System level, maximum knee extension angle (β=-0.006), hip angle at midstance (β=-0.007), and maximum hip extension (β=-0.008) were associated with NNcost. Age was a significant modifier of the association between the NNcost and a number of kinematic variables. This study examined kinetic and kinematic variables in the sagittal plane only. A high interindividual variation in gait pattern could have influenced the results. Reduced knee and hip joint extension are associated with gait inefficiency in adolescents with CP. Age is a significant factor influencing associations between ankle, knee, and hip joint kinematics and gait efficiency. Therapeutic interventions should investigate ways to increase knee and hip joint extension in adolescents with CP.

Validity and Reliability of an On-Court Fitness Test for Assessing and Monitoring Aerobic Fitness in Squash.

James, C, Tenllado Vallejo, F, Kantebeen, M, and Farra, S. Validity and reliability of an on-court fitness test for assessing and monitoring aerobic fitness in squash. J Strength Cond Res 33(5): 1400-1407, 2019-Current on-court assessments of aerobic fitness in squash are not designed to yield a wealth of physiological data. Moreover, tests may require complex computer equipment or involve simulated racket strokes, which are difficult to standardize at high intensities. This study investigated the validity and reliability of a squash-specific fitness test which can yield both a standalone performance score, as well as pertinent physiological markers such as V[Combining Dot Above]O2max, the lactate turnpoint and oxygen cost, in a sport-specific environment. Eight national squash players completed 3 tests in a counterbalanced order: an incremental laboratory treadmill test (LAB) and 2 on-court fitness tests (STs) that involved repeated shuttle runs at increasing speeds. V[Combining Dot Above]O2max during ST was agreeable with LAB (typical error [TE] = 3.3 ml·kg·min, r = 0.79). The mean bias between LAB and ST was 2.5 ml·kg·min. There were no differences in maximum heart rate, postexercise blood lactate concentration, or end of test rating of perceived exertion between LAB and ST (p > 0.05). The ST was highly reliable, with 74 (10) laps completed in ST1 and 75 (12) laps in ST2 (mean bias = 1 lap, TE = 3 laps, r = 0.97). Physiological markers were also reliable, including V[Combining Dot Above]O2max, (TE = 1.5 ml·kg·min, r = 0.95), the lap number at 4 mMol (TE = 4 laps, r = 0.77), and average V[Combining Dot Above]O2 across the first 4 stages (TE = 0.94 ml·kg·min, r = 0.95). We observed good agreement between LAB and ST for assessing V[Combining Dot Above]O2max and between both on-court trials for assessing test performance and selected physiological markers. Consequently, we recommend this test for monitoring training adaptations and prescribing individualized training in elite squash players.

Oxygen Cost During Mobility Tasks and Its Relationship to Fatigue in Progressive Multiple Sclerosis

ObjectiveTo compare the oxygen costs of mobility tasks between individuals with progressive multiple sclerosis (MS) using walking aids and matched controls and to determine whether oxygen cost predicted fatigue. DesignCross-sectional descriptive. SettingA rehabilitation research laboratory. ParticipantsA total of 14 adults with progressive MS (mean age ± SD [y], 54.07±8.46) using walking aids and 8 age- and sex-matched controls without MS (N=22). InterventionsParticipants performed 5 mobility tasks (rolling in bed, lying to sitting, sitting to standing, walking, climbing steps) wearing a portable metabolic cart. Main Outcome MeasuresOxygen consumption (V˙o2) during mobility tasks, maximal V˙o2 during graded maximal exercise test, perceived exertion, and task-induced fatigue were measured on a visual analog scale before and after mobility tasks. ResultsPeople with progressive MS had significantly higher oxygen cost in all tasks compared to controls (P<.05): climbing steps (3.60 times more in MS), rolling in bed (3.53), walking (3.10), lying to sitting (2.50), and sitting to standing (1.82). There was a strong, positive correlation between task-induced fatigue and oxygen cost of walking, (ρ [13]=0.626, P=.022). ConclusionsPeople with progressive MS used 2.81 times more energy on average for mobility tasks compared to controls. People with progressive MS experienced accumulation of oxygen cost, fatigue, and exertion when repeating tasks and higher oxygen cost during walking was related to greater perception of fatigue. Our findings suggest that rehabilitation interventions that increase endurance during functional tasks could help reduce fatigue in people with progressive MS who use walking aids.

The clinical- and cost-effectiveness of functional electrical stimulation and ankle-foot orthoses for foot drop in Multiple Sclerosis: a multicentre randomized trial

Objective: To compare the clinical- and cost-effectiveness of ankle-foot orthoses (AFOs) and functional electrical stimulation (FES) over 12 months in people with Multiple Sclerosis with foot drop. Design: Multicentre, powered, non-blinded, randomized trial. Setting: Seven Multiple Sclerosis outpatient centres across Scotland. Subjects: Eighty-five treatment-naïve people with Multiple Sclerosis with persistent (>three months) foot drop. Interventions: Participants randomized to receive a custom-made, AFO (n = 43) or FES device (n = 42). Outcome measures: Assessed at 0, 3, 6 and 12 months; 5-minute self-selected walk test (primary), Timed 25 Foot Walk, oxygen cost of walking, Multiple Sclerosis Impact Scale-29, Multiple Sclerosis Walking Scale-12, Modified Fatigue Impact Scale, Euroqol five-dimension five-level questionnaire, Activities-specific Balance and Confidence Scale, Psychological Impact of Assistive Devices Score, and equipment and National Health Service staff time costs of interventions. Results: Groups were similar for age (AFO, 51.4 (11.2); FES, 50.4(10.4) years) and baseline walking speed (AFO, 0.62 (0.21); FES 0.73 (0.27) m/s). In all, 38% dropped out by 12 months (AFO, n = 21; FES, n = 11). Both groups walked faster at 12 months with device (P < 0.001; AFO, 0.73 (0.24); FES, 0.79 (0.24) m/s) but no difference between groups. Significantly higher Psychological Impact of Assistive Devices Scores were found for FES for Competence (P = 0.016; AFO, 0.85(1.05); FES, 1.53(1.05)), Adaptability (P = 0.001; AFO, 0.38(0.97); FES 1.53 (0.98)) and Self-Esteem (P = 0.006; AFO, 0.45 (0.67); FES 1 (0.68)). Effects were comparable for other measures. FES may offer value for money alternative to usual care. Conclusion: AFOs and FES have comparable effects on walking performance and patient-reported outcomes; however, high drop-outs introduces uncertainty.

A dynamometer for nature's engines

Muscle is an amazing natural thermodynamic engine that converts chemical energy into mechanical work. Each muscle twitch is ‘sparked’ by an electrically-released pulse of calcium ions, which trigger force-development and cell shortening, at the cost of energy and oxygen, and the dissipation of heat. Like other engines, muscle is inefficient at converting chemical energy to mechanical energy; at least 80% of the energy consumed by the muscle is released as heat. When we want to measure or enhance the performance of a human-made engine, such as an internal combustion engine, we typically attach it to a dynamometer—a device that can apply a controlled load to the engine, and measure its fuel consumption and work output. Imagine that we had a similar tool that allowed us to inspect nature's engine—muscle tissue—and thereby measure its energetic performance. Such a tool would allow us to better understand the muscle's work output and energy consumption, diagnose problems with the engine, tune its performance, and observe its response to changes in load, or to additives in its fuel. In this article, we report on our construction of a dynamometer for heart muscle.

Developing a multi-criteria decision support system based on fuzzy analytical hierarchical process (AHP) method for selection of appropriate high-strength wastewater treatment plant

The selection of an optimum treatment process for high-strength wastewater is complicated. Familiarity with wastewater treatment methods is not enough to design a plant and requires a multidisciplinary knowledge base. In this research, five alternative wastewater treatment methods for high-strength wastewater were investigated and ranked based on the analytic hierarchy process (AHP) fuzzy method: upflow anaerobic sludge blanket (UASB) + membrane bioreactor (MBR), UASB + extended aeration (EA), anaerobic baffled reactor (ABR), anaerobic lagoon (ANL) + aerated lagoon (AL), and sequencing batch reactor (SBR) + ABR. These treatment methods were ranked based on five criteria, namely energy consumption, effluent total suspended solids (TSS), effluent chemical oxygen demand (COD), cost, and level of technology. The different options of the wastewater treatment plant were rated by expert decision-makers in this field. The results show that for typical high-strength wastewater, the use of an UASB reactor followed by a MBR is the most appropriate alternative for treating the wastewater.

The relationships between age and running performance variables in master runners.

Peak aerobic capacity (V̇O2peak) declines with age, but running economy (RE) may not. We evaluated VO2peak and RE in master runners and determined whether age is associated with these measures. In a cross-sectional study, runners completed two running tests within four weeks of a goal race of 10-26.2 miles. Subjects ran for five min at 88% of predicted maximum heart rate, approximating a marathon-intensity effort (MIE), then performed a V̇O2peak test. Running economy in the MIE was measured using oxygen cost with body mass scaled allometrically (alloV̇O2); energy cost (EC), determined using caloric equivalents; and percent of V̇O2peak (%V̇O2peak). Pearson's correlations were used to determine relationships between age and running performance variables. Runners (n = 31, 13 females; mean age 54.9 ± 8.4 years) had a mean VO2peak of 52.5 ± 7.9 ml O2 kg-1 min-1. Age was significantly correlated with V̇O2peak (r = - 0.580, p = 0.001) and alloV̇O2 (r = - 0.454, p = 0.034). Age was related to EC in females (r = 0.649, p = 0.042) and MIE V̇O2 in males (r = - 0.600, p = 0.039). In this population, age was negatively associated with V̇O2peak and alloV̇O2. Females showed a positive relationship between age and EC, while males had a negative correlation between age and MIE V̇O2. Aerobic capacity declines with age, but there may be sex differences in age-related alterations to submaximal running.

An alternative to oxygen deficit as a way to quantify anaerobic contributions in running

The purpose of this study was to determine if the sum of estimates of the phosphocreatine contribution and the glycolytic contribution (we refer to this sum as PCr+glycolysis ) provides an alternative to oxygen deficit as a way to quantify the anaerobic contribution in running. Thirty university students performed three treadmill tests, each test at one speed individually selected for each participant; one test was terminated after 3 min, one after 7 min, and one at exhaustion (mean ± SD, 10.3 ± 0.4 min). Oxygen deficit was calculated by subtraction of the accumulated oxygen uptake from the total oxygen cost. Phosphocreatine and glycolysis contributions were determined from post-exercise VO 2 responses and blood lactate concentrations, respectively. The mean values for PCr+glycolysis was ~3 mL·kg –1 lower (p < .05) than oxygen deficit across three exercise durations, but well correlated ( r ≥ .80, p < .05) at each. These results confirm the validity of PCr+glycolysis as an alternative to oxygen deficit to quantify the anaerobic contribution in running exercise.

Changes in Running Economy During a 65-km Ultramarathon.

Purpose: Running economy (RE), expressed as oxygen cost (O2 cost) and energy cost of running (Cr) is important in ultramarathon (UM) running as it can help predict race performance. Controversy remains if RE increases, decreases, or remains stable in UM running. We examined RE before, during, and after a 65-km UM.Methods: 15 male UM runners (mean age 45 ± 5.7 years) completed a standard exercise test (mean VO2max 48.8 ± 3.4 ml⋅kg-1⋅min-1) for determination of the individual testing speed (60% VO2max: mean speed 9.4 ± 0.7 km/h). This was followed by a 65-km UM (elevation ± 1093 m) consisting of three laps (each 21.7 km). Pre and post indirect calorimetry measurements at individual running speed on the treadmill at UM-specific slopes (average percentage of positive and negative elevation) at -3, +3%, and level grade were performed in randomized order on a motorized treadmill in the laboratory for calculation of RE. Additionally after each lap, testing at +3% took place.Results: The O2 cost, Cr, and RER increased significantly pre to post UM (p < 0.01). During the uphill running, a main effect of distance indicated a gradual, linear increase in O2 cost, F(2,28) = 5.81, p < 0.01, = 0.29, and Cr, F(2,28) = 5.96, p = 0.01, = 0.30.Conclusion: O2 cost and Cr increased significantly pre to post UM in all testing conditions as well as during the uphill testing throughout the UM. This is the first study to demonstrate a consistent increase in O2 cost and Cr among a range of different slopes, at individual running speeds and race-specific slopes giving further evidence that these measures of RE increase in UM running.

Physiological, kinematic, and electromyographic responses to kinesiology-type patella tape in elite cyclists

Kinesiology-type tape (KTT) has become popular in sports for injury prevention, rehabilitation, and performance enhancement. Many cyclists use patella KTT; however, its benefits remain unclear, especially in uninjured elite cyclists. We used an integrated approach to investigate acute physiological, kinematic, and electromyographic responses to patella KTT in twelve national-level male cyclists. Cyclists completed four, 4-minute submaximal efforts on an ergometer at 100 and 200 W with and without patella KTT. Economy, energy cost, oxygen cost, heart rate, efficiency, 3D kinematics, and lower-body electromyography signals were collected over the last minute of each effort. Comfort levels and perceived change in knee stability and performance with KTT were recorded.The effects of KTT were either unclear, non-significant, or clearly trivial on all collected physiological and kinematic measures. KTT significantly, clearly, and meaningfully enhanced vastus medialis peak, mean, and integrated electromyographic signals, and vastus medialis-to-lateralis activation. Electromyographic measures from biceps femoris and biceps-to-rectus femoris activation ratio decreased in either a significant or clinically meaningful manner. Despite most cyclists perceiving KTT as comfortable, increasing stability, and improving performance, the intervention exerted no considerable effects on all physiological and kinematic measures. KTT did alter neuromuscular recruitment, which has potential implications for injury prevention.

Energy Consumption and Economic Analyses of a Supercritical Water Oxidation System with Oxygen Recovery

Oxygen consumption is one of the factors that contributes to the high treatment cost of a supercritical water oxidation (SCWO) system. In this work, we proposed an oxygen recovery (OR) process for an SCWO system based on the solubility difference between oxygen and CO2 in high-pressure water. A two-stage gas–liquid separation process was established using Aspen Plus software to obtain the optimized separation parameters. Accordingly, energy consumption and economic analyses were conducted for the SCWO process with and without OR. Electricity, depreciation, and oxygen costs contribute to the major cost of the SCWO system without OR, accounting for 46.18, 30.24, and 18.01 $·t−1, respectively. When OR was introduced, the total treatment cost decreased from 56.80 $·t−1 to 46.17 $·t−1, with a reduction of 18.82%. Operating cost can be significantly reduced at higher values of the stoichiometric oxygen excess for the SCWO system with OR. Moreover, the treatment cost for the SCWO system with OR decreases with increasing feed concentration for more reaction heat and oxygen recovery.

The Relationship between Running Power and Running Economy in Well-Trained Distance Runners.

A novel running wearable called the Stryd Summit footpod fastens to a runner’s shoe and estimates running power. The footpod separates power output into two components, Stryd power and form power. The purpose of this study was to measure the correlations between running economy and power and form power at lactate threshold pace. Seventeen well-trained distance runners, 9 male and 8 female, completed a running protocol. Participants ran two four-minute trials: one with a self-selected cadence, and one with a target cadence lowered by 10%. The mean running economy expressed in terms of oxygen cost at self-selected cadence was 201.6 ± 12.8 mL·kg−1·km−1, and at lowered cadence was 204.5 ± 11.5 mL·kg−1·km−1. Ventilation rate and rating of perceived exertion (RPE) were not significantly different between cadence conditions with one-tailed paired t-test analysis (ventilation, p = 0.77, RPE, p = 0.07). Respiratory exchange ratio and caloric unit cost were significantly greater with lower cadence condition (respiratory exchange ratio, p = 0.03, caloric unit cost, p = 0.03). Mean power at self-selected cadence was 4.4 ± 0.5 W·kg−1, and at lowered cadence was 4.4 ± 0.5 W·kg−1. Mean form power at self-selected cadence was 1.1 ± 0.1 W·kg−1, and at lowered cadence was 1.1 ± 0.1 W·kg−1. There were positive, linear correlations between running economy and power (self-selected cadence and lower cadence, r = 0.6; the 90% confidence interval was 0.2 to 0.8); running economy and form power (self-selected cadence and lower cadence r = 0.5; the 90% confidence interval was 0.1 to 0.8). The findings suggest running economy is positively correlated with Stryd’s power and form power measures yet the footpod may not be sufficiently accurate to estimate differences in the running economy of competitive runners.

Relationship between oxygen cost and C-reactive protein response to marathon running in college recreational runners.

PurposeIndividual variations in response of C-reactive protein (CRP) to acute strenuous exercise are less well known. The purpose of this study was to investigate the relationship between running economy and systemic inflammation following a marathon.Materials and methodsSixteen college recreational runners participated in this study. To measure maximal oxygen uptake and running economy, the treadmill running test was performed 1–2 weeks before the marathon race. Running economy was defined as oxygen cost (mL/kg/km) at submaximal running. CRP and muscle damage markers (creatine kinase and lactate dehydrogenase) were measured before and 1, 2, and 3 days after the race.ResultsAll subjects completed the race in 4 hours 7 minutes 43 seconds±44 minute 29 seconds [mean±SD]. The marathon running significantly increased CRP and muscle damage markers. The levels of inflammation and muscle damage peaked after 1 day and remained high throughout the 3-day recovery period compared to that before the race. Spearman correlation analysis showed that the change in CRP level was significantly positively correlated with oxygen cost (r=0.619, P=0.011) but not maximal oxygen uptake. There was no significant relationship in responses between muscle damage markers and CRP.ConclusionThese findings suggest that running economy is related to postmarathon race CRP response. Further study to clarify the cause of the relationship and clinical significance of transient increase in CRP is necessary.

Postural and Metabolic Benefits of Using a Forearm Support Walker in Older Adults With Impairments

ObjectiveTo investigate the postural and metabolic benefits a walker with adjustable elbow support (LifeWalker [LW]) can provide for ambulation in population with impairment. The clinical outcomes from the elbow support walker will be compared with standard rollator (SR) and participants predicate device (PD). DesignCase-crossover study design. SettingClinical laboratory. ParticipantsIndividuals aged between 18 and 85 years using a rollator walker as primary mode of assistance and certified as medically stable by their primary physician. Participants (N=30; 80% women [n=24]) recruited from a convenient sample provided voluntary consent and completed the study. InterventionNot applicable. Main Outcome MeasuresThe trunk anterior-posterior (AP) sway (during the 10-meter walk test), oxygen consumption (during the 6-minute walk test), the mean forearm load offloaded to the elbow support as percentage of body weight, and mean peak hand grip load (during the 25-meter walk test) were measured. ResultsAmbulating with a LW led to (1) reduced trunk sway in the AP direction [(ZLW vs PD= −2.34, P=.018); (ZLW vs SR= −3.461, P=.001)]; (2) reduced erector spinae muscle activation at the left lumbar L3 level [(ZLW vs PD= −2.71, P=.007); (ZLW vs SR= −1.71, P=.09)]; and (3) improved gait efficiency [(ZLW vs PD= −2.66, P=.008) Oxygen cost; (ZLW Vs. SR= −2.66, P=.008) Oxygen cost]. Participants offloaded between 39% and 46% of their body weight through the elbow support armrest while ambulating with the LW. Irrespective of the walker used, participants exerted ∼5%-6% of their body weight in gripping the walker handles during walking. ConclusionsUsing the forearm support-based LW led to upright body posture, offloaded portions of body weight from the lower extremity, and improved gait efficiency during ambulation in comparison to the SR and the participants’ own PD. Further studies focusing on population-specific benefits are recommended.

PRS56 - COST-EFFECTIVENESS OF AMBULATORY OXYGEN IN IMPROVING QUALITY OF LIFE IN FIBROTIC LUNG DISEASE: A TALE OF TWO OUTCOMES

Ambulatory oxygen may allow patients with fibrotic lung diseases to lead an active and independent life for longer. This economic analysis compares the health service costs and health-related benefits of ambulatory oxygen with those of usual care from a NHS perspective. Data on costs of ambulatory oxygen and condition-specific health-related quality of life outcomes (measured using the KBILD and SGRQ instruments) were collected alongside a UK prospective, multicentre randomised controlled crossover trial in which participants received ambulatory oxygen or no oxygen for a 2 week period each. The primary outcome measure was change in K-BILD scores. Benefits were also estimated as QALYs derived by translating SGRQ scores to EQ-5D-3L utility weights using a published mapping algorithm. The incremental costs were £90.16 per person treated with a 3.47 increase in K-BILD score, leading to an incremental cost-effectiveness of £25.96 per unit increase in K-BILD. However, the estimates were highly uncertain. When the QALY was used as an outcome, ambulatory oxygen was dominated by usual care as it was both more costly than usual care and produced fewer QALYs (although the difference in QALYs was not statistically significant). There was a 0.059 probability that ambulatory oxygen would be considered cost-effective at a threshold of £20,000 per QALY. The cost-effectiveness of ambulatory oxygen in ILD may depend on the outcome measure used. When evaluated using the K-BILD, its cost-effectiveness will depend on willingness to pay for an improvement in K-BILD score. When evaluated using the QALY (converted from SGRQ), ambulatory oxygen is unlikely to be cost-effective for managing interstitial lung disease. Findings are limited by the short duration of the trial and the lack of data supporting conversion of the trial’s primary outcome (KBILD) to QALYs.

Nitrite lowers the oxygen cost of ATP supply in skeletal muscle cells by stimulating the rate of glycolytic ATP synthesis

Nitrite lowers the oxygen cost of ATP supply in skeletal muscle cells by stimulating the rate of glycolytic ATP synthesis

Crystal-plane-dependent metal oxide-support interaction in CeO2/g-C3N4 for photocatalytic hydrogen evolution

CeO2 and its derivatives are potential photocatalysts due to their superior redox ability, abundant oxygen defects and cost effectiveness. However, little attention has been paid to the crystal-plane-dependent interactions in CeO2-based nanocomposites for photocatalytic hydrogen evolution. In this work, CeO2/g-C3N4 were synthesized with tunable CeO2 crystal planes ({110}, {100}, and {111}). Photoelectrochemical, XPS, Raman, ESR results suggested that the electron-separation efficiency, oxygen defects and Ce3+/Ce4+ reversibility pairs were greatly dependent on the crystal-faceted CeO2 and g-C3N4 interaction, and the photocatalytic performances of hydrogen evolution under visible light irradiation were in the order: CeO2{110}/g-C3N4>CeO2{100}/g-C3N4>CeO2{111}/g-C3N4>g-C3N4. Furthermore, the FT-IR, XPS and density functional theory (DFT) calculations shown that the different properties of CeO2/g-C3N4 were resulted from the built-in electric field at the interface, and more intensive electronic interaction was found on CeO2{110}/g-C3N4, leading to the efficient separation and transfer of photo-generated electrons under light illumination.

Prediction of the oxygen cost of walking in hemiparetic stroke patients

The energy cost of walking is a marker of metabolic solicitation and allows energy quantification of walking. It is strongly correlated to the patient's walking speed with post-stroke sequelae. We wanted to develop a model for predicting the energy cost of walking to create of walking distance recommendations aimed at achieving recommended energy expenditure levels to ensure health benefits (> 1000 kcal/week during physical activities). To verify the close relationship between spontaneous walking speed (S free ) and energy cost of walking at S free (Cw free ) in subjects with post-stroke hemiparetic patients sequelea and to test the validity of a prediction model to estimate Cw free based on S free . Twenty-six mild to moderately disabled chronic participants with stroke aged 65 yrs (± 15.7yrs) walked at S free using mobility aids if necessary, for 6 minutes. The Cw free was measured at a stabilized metabolic rate by indirect calorimetry using the Metamax3B device. The relationship between S free and Cw free was analyzed using the correlation coefficient, coefficient of determination. The Cw free prediction model was developed from a regression equation and then tested on a new population with the same inclusion/exclusion criteria ( n = 29). S free and Cw free had a correlation coefficient of −0.94 and a R 2 of 0.97 enabling to formulate a regression equation and develop the Cw free prediction model based on S free . The prediction model tests yielded accurate results with a mean bias of −0.02 mL.kg −1 .m −1 –MD% = 4%. The limits of agreement were −0.31; 0.26 mL.kg −1 .m −1 MD% = 30.9% of the mean measured Cw free . Cw free can be estimated precisely by a simple measurement of the walking speed. In this way, we can easily define the distance the subject must travel according to his Cw to reach the recommended energy expenditure targets. It is a great help for the practitioner for recommendations in the field of physical activity after stroke.

Renal Blood Flow, Glomerular Filtration Rate, and Renal Oxygenation in Early Clinical Septic Shock.

Data on renal hemodynamics, function, and oxygenation in early clinical septic shock are lacking. We therefore measured renal blood flow, glomerular filtration rate, renal oxygen consumption, and oxygenation in patients with early septic shock. Prospective comparative study. General and cardiothoracic ICUs. Patients with norepinephrine-dependent early septic shock (n = 8) were studied within 24 hours after arrival in the ICU and compared with postcardiac surgery patients without acute kidney injury (comparator group, n = 58). None. Data on systemic hemodynamics and renal variables were obtained during two 30-minute periods. Renal blood flow was measured by the infusion clearance of para-aminohippuric acid, corrected for renal extraction of para-aminohippuric acid. Renal filtration fraction was measured by renal extraction of chromium-51 labeled EDTA. Renal oxygenation was estimated from renal oxygen extraction. Renal oxygen delivery (-24%; p = 0.037) and the renal blood flow-to-cardiac index ratio (-21%; p = 0.018) were lower, renal vascular resistance was higher (26%; p = 0.027), whereas renal blood flow tended to be lower (-19%; p = 0.068) in the septic group. Glomerular filtration rate (-32%; p = 0.006) and renal sodium reabsorption (-29%; p = 0.014) were both lower in the septic group. Neither renal filtration fraction nor renal oxygen consumption differed significantly between groups. Renal oxygen extraction was significantly higher in the septic group (28%; p = 0.022). In the septic group, markers of tubular injury were elevated. In early clinical septic shock, renal function was lower, which was accompanied by renal vasoconstriction, a lower renal oxygen delivery, impaired renal oxygenation, and tubular sodium reabsorption at a high oxygen cost compared with controls.