Exhaustive Cycling Research Articles

The study on the performance of air-cooled open-cathode PEMFC with dead-ended anode

ABSTRACT In order to be able to improve the hydrogen utilization as much as possible while ensuring the performance of the air-cooled open-cathode proton exchange membrane fuel cell (AO-PEMFC), the performance of the AO-PEMFC with dead-ended anode (DEA) was studied in this paper. First, the transient voltage model was established and the possible causes of voltage loss were analyzed. Then, the effects of anode inlet pressure, cyclic exhaust, and exhaust duration on the PEMFC performance were investigated by combining the experimental methods of transient voltage monitoring and EIS measurement. The results showed that the effect of anode inlet pressure is not positively correlated with PEMFC performance with DEA and also influenced by the load current. Cyclic exhaust can effectively reduces the voltage degradation, and the optimal exhaust cycle is different for different load current. The exhaust duration has little effect on the PEMFC performance at various load currents. However, the PEMFC performance showed a tendency to be increased and then stabilized with the increase of exhaust duration at higher current density.

Investigation into the impact of acetylene on performance and emission characteristics of a compression ignition engine using a blended biodiesel of ethanol and tamanu oil.

Due to the significant increase in transportation, traditional fossil fuels utilised in internal combustion engines will only be accessible for a limited duration. Additionally, the harmful pollutants produced by these fuels, including CO, NOx, unburned hydrocarbons, smoke, and a small amount of particulate matter, have a severe negative impact on the environment. Although biodiesel proves efficient without necessitating engine modifications, its performance is hindered by its higher viscosity. Consequently, this research aims to enhance performance by introducing acetylene alongside tamanu methyl ester (biodiesel); however, this approach results in elevated NOx levels. To mitigate NOx emissions, a combination of ethanol and biodiesel is employed. This study investigates the performance and emission attributes of Acetylene + TME90E10 as the fuel. The combustion pressure and heat release rate of TME90E10 with 6 lpm, improved by 5.41% and 9.1% than diesel. When compared to regular diesel fuel, the introduction of 6l per minute of acetylene with TME90E10 yields a substantial 24.4% decrease in hydrocarbon (HC) emissions. Furthermore, employing TME90E10 at the same acetylene flow rate demonstrates the lowest carbon monoxide (CO) emissions, registering at 0.07%, in contrast to the 0.13% emissions observed throughout the exhaust cycle when using pure diesel fuel.

The Impact of Carbohydrate, Protein, and Combined Carbohydrate-Protein Supplementation on Muscle Damage and Oxidative Stress Markers During Prolonged Cycling Performance in the Heat

Background: The impact of oxidative stress (OS) on exercise performance and recovery depends on the mode, intensity, and duration of physical activity, which can lead to inflammation, fatigue, and muscle dysfunction. The effects of carbohydrate (CHO) and protein (PRO) supplementation, as well as their combination (CHO-PRO), on exercise performance remain controversial, particularly under normal and hot environmental conditions. Objectives: The present study examined the influence of locally based isocaloric carbohydrate (CHO) and protein (PRO) supplements on muscle damage and oxidative stress (OS) biomarkers during cycling in the heat (31°C, 70% relative humidity), compared to a placebo (PL). Methods: Sago (Sa), Soy (So), and Sago+Soy (SS) were used as the carbohydrate (CHO), protein (PRO), and CHO-PRO supplements, respectively. The Sa, So, and SS supplements contained 7.5% Sa, 7.5% So, and 6.0% Sa+1.5% So, respectively. Twelve well-trained male cyclists (age: 19.0 ± 5.6 years, height: 170.8 ± 7.6 cm, body weight: 60.1 ± 11.2 kg, and VO2max: 56.5 ± 6.5 mL·kg⁻¹·min⁻¹) participated in four experimental trials. Each trial involved 90 minutes of steady-state cycling on an ergometer at 60% VO2max, followed by a 20-km exhaustive cycling time-trial performance. During the steady-state cycling, participants received supplements five times at 0, 20, 40, 60, and 80 minutes. Results: Plasma concentrations of creatine kinase and F2-isoprostanes, which are biomarkers of muscle damage and oxidative stress (OS), significantly decreased after the trials (P < 0.05). The reduction in these biomarkers in the placebo group indicated that Sa, So, and SS supplementation did not provide additional benefits, as the placebo exhibited similar effects. Conclusions: In conclusion, despite the unexpected results, endurance athletes exercising in hot and humid conditions may potentially reduce symptoms of muscle damage and oxidative stress by consuming greater amounts of carbohydrate and protein supplements.

Electrochemical/computational analysis and the derivation of Pourbaix diagrams of redox-active structural and adsorbed species in uranyl peroxide clusters (U60)

Electrochemical analysis of U60 nanoclusters (Li40K20[UO2(O2)(OH)]60(H2O)214) and their natural analog, the mineral studtite (UO2)O2(H2O)2·(H2O)2, was carried out using cyclic voltammetry with a powder microelectrode setup. Voltammetric analysis was supplemented by ab initio quantum mechanical modeling to understand the mechanism, thermodynamics, and structural changes during redox transition (with a semi-quantitative kinetics evaluation). This research aims to better understand the redox behavior and transport of dissolved and structural (incorporated) uranyl units in the environment. Further analysis is performed to determine if redox switching of actinyl ions in clusters can be performed while leaving the cluster intact or at what redox transition it disintegrates. Quantum-mechanical calculations were applied to approximate electrochemical peak potential shifts and add them to standard reduction potentials to more accurately assign peaks to specific redox transitions between different species. These peak potentials are calculated from oxidation state-dependent binding energies between different uranyl species either within or adsorbed to U60. This theoretical approach incorporates extensive error cancellation and serves to predict electrochemical redox potentials and identify the reaction taking place. Voltammograms of U60 in electrolyte solutions exhibit kinetically-inhibited coupled redox peaks assigned to the U(VI)/U(V) transition of cluster structural uranyl units at −0.34 V (vs. standard hydrogen electrode), indicative of U60 reduction from UO22+ to UO2+. The U(V)/U(IV) transition at −0.71 V is assigned to the subsequent U60 reduction of UO2+ to UO20. A method of observing these transitions in situ using synchrotron x-ray absorption spectroscopy was explored. Voltammetry, modeling, and peak analysis indicate a kinetically-inhibited two-step, one-e- (per step) reduction of U60 from U(VI) to U(V) to U(IV). Voltammetry and x-ray absorption spectroscopy measurements performed before and after exhaustive cycling and the highly stable nature of U60 provide evidence that clusters typically do not break apart upon reduction. Voltammograms of U60 collected in varied uranyl solutions are indicative of UO22+ adsorption to the cluster surface and its subsequent reduction at +0.24 V (U(VI)/U(V)) and −0.05 V (U(V)/U(IV)). For uranyl solutions in electrolyte, the two-step, one-e- (per step) reduction of U60 is superseded by uranyl adsorption from solution to the electrode surface with subsequent reduction via U(V) disproportionation. This study represents the sole electrochemical investigation of U60 in the literature and only the second of any uranyl peroxide nanocluster. It is also one of the first to use quantum–mechanical approaches in combination with existing solution-based standard reduction potentials to calculate Pourbaix (EH-pH) diagrams for adsorbed and structural species.

Sense of time is slower following exhaustive cycling exercise.

Subjective perception of time is altered during vigorous exercise. This could be due in part to the fatigue associated with physical activity at high intensities. The aim of this study was to determine the effect of fatigue, specifically, on subjective time perception. Twenty-six healthy, untrained subjects (17 men/9 women; age = 26.0 ± 4.3years; peak = 38.13 ± 5.62mL/kg/min) completed a maximal aerobic exercise test on a cycle ergometer. Time perception was assessed before (PRE) and after (POST) the exercise test using a time production task wherein subjects started a stopwatch and stopped it once they believed a designated time period had passed. This time produced with the stopwatch was the estimate of the target time that was compared to the target time interval. Relative error of the timing task was significantly higher for POST (0.112 ± 0.260) than for PRE (0.028 ± 0.173), p = .032, η2 = .178. Subjects produced ~ 8.4% more time than the target intervals when fatigued, which is indicative of a slower sense of time perception. A shift in attentional focus from timing to the sensations associated with fatigue is a possible factor to explain this result. Future studies which investigate the effects of exercise on time perception should consider the impact of fatigue experienced during exercise.

Numerical modeling and evaluation of solid-liquid extraction with pressurized hot water extraction applied to Robinia Pseudoacacia wood

Computational Fluid Dynamics (CFD) simulation was used to study the solid-liquid extraction of Robinia Pseudoacacia wood by pressurized hot water extraction (PHWE). The proposed model couples momentum and mass transfer, including the extraction kinetics. The model is based on transport species and flow in a porous medium. The results show that the extraction of the two main flavonoids, Dihydrorobinetin (DHR) and Robinetin (Rob), increased with increasing temperature up to 120 °C, with values of 46.85±1.44 and 6.84±0.42 mg/gdB, respectively. However, at higher temperatures, these flavonoids degraded. Additionally, the exhaustive extraction cycle, ranging from 80 to 160 °C, was found to be less effective when compared to extraction at 120 °C.The kinetic parameters were included in the CFD simulation. As a result, a good agreement between the results of CFD simulation and experimental data was found with R2 > 0.97. The model predicts the temperature distribution inside the reactor during the pre-heating period, the evolution of the DHR and Rob concentrations at the reactor outlet, and the effect of degradation at high extraction temperatures.

Exhaustive Intermittent Cycling Preferentially Decreases Explosive Over Maximal Voluntary Torque in the Knee Extensors, With No Difference Between Normoxia and Moderate to Severe Hypoxia.

To compare the effects of graded hypoxia during exhaustive intermittent cycling on subsequent rapid and maximal torque-production capacity. Fifteen well-trained cyclists repeated intermittent cycling bouts (15s at 30% of anaerobic power reserve; rest = 45s) until exhaustion at sea level (FiO2 ∼0.21/end-exercise arterial oxygen saturation ∼96%), moderate hypoxia (FiO2 ∼0.16/∼90%), and severe hypoxia (FiO2 ∼0.12/∼79%). Rapid (rate of torque development [RTD]) and maximal isometric torque-production capacities of the knee extensors were assessed at baseline (visit 1) and exhaustion (visits 2-4). Exercise capacity decreased with hypoxia severity (39 [30], 22 [13], and 13 [6] cycle efforts in sea level, moderate hypoxia, and severe hypoxia, respectively; P = .002). Changes in maximal-voluntary-contraction torque between baseline and postexercise in all conditions were not statistically significant (pooled values: -2.6% [5.7%]; P = .162). Peak RTD measured postexercise was reduced below baseline in all conditions (-21.5% [5.1%]; P ≤ .015). Compared with baseline, absolute RTD values were lower at 0- to 30-millisecond (-35.1% [5.3%], P ≤ .020), 0- to 50-millisecond (-40.0% [3.9%], P ≤ .002), 0- to 100-millisecond (-30.7% [3.7%], P ≤ .001), and 0- to 200-millisecond (-18.1% [2.4%], P ≤ .004) time intervals in all conditions. Exhaustive intermittent cycling induces substantial yet comparable impairments in RTD of knee extensors between normoxia and moderate to severe hypoxia.

Effects of exhaustive whole-body exercise and caffeine ingestion on muscle contractile properties in healthy men.

The influence of exhaustive whole-body exercise and caffeine ingestion on electromechanical delay (EMD) has been underexplored. This study investigated the effect of exhaustive cycling exercise on EMD and other parameters of muscle contractile properties and the potential ability of caffeine to attenuate the exercise-induced impairments in EMD and muscle contractile properties. Ten healthy men cycled until exhaustion (88±2% of V̇O<inf>2max</inf>) on two separate days after ingesting caffeine (5 mg.kg-1 of body mass) or cellulose (placebo). Parameters of muscle contractile properties of the quadriceps muscles were assessed via volitional and electrically evoked isometric contractions, performed before and 50 minutes after ingestion of the capsules, and after exercise. Muscle recruitment during volitional contractions was determined via surface electromyography. Exhaustive cycling exercise did not affect volitional and relaxation EMD (P>0.05) but increased evoked EMD. In addition, the exhaustive cycling exercise also increased muscle recruitment at the beginning of volitional isometric muscle contraction (P<0.05). The peak twitch force, maximal rate of twitch force development, and twitch contraction time were all compromised after exhaustive cycling exercise (P<0.05). Acute caffeine ingestion had no effect on muscle contractile properties (P>0.05), except that caffeine increased twitch contraction time at postexercise (P<0.05). Exercise-induced decline in peripheral components of the EMD might be compensated by an increase in the muscle recruitment. In addition, acute caffeine ingestion had minimal influence on exercise-induced changes in muscle contractile proprieties.

Vocal Problems and Burnout Syndrome in Nonuniversity Teachers in Galicia, Spain

Introduction: Voice disorders and burnout syndrome are common among teachers. This study aimed to explore the relationship among vocal problems, burnout syndrome, and some personal work factors. Methods: This cross-sectional descriptive study enrolled 90 nonuniversity teachers who completed the Multidimensional Vocal Scale for Teachers (EVM-D) to evaluate vocal problems and an adapted Spanish version of the Maslach Burnout Inventory-Educators Survey (MBI-ES) to detect burnout syndrome. Results: Overall, 16% of teachers expressed symptoms compatible with burnout, and 60% of them were in the interval above the 75th percentile of the EVM-D, i.e., they had a high risk of vocal problems. An association between burnout and more vocal problems was established among teachers, particularly between the vocal symptoms and vocal abuse dimensions with the emotional exhaustion subscale of the MBI-ES. A history of anxiety/depression and fewer years of professional experience were associated with more vocal problems. The burnout group perceived more “loss of vocal power,” “vocal fatigue,” “vocal effort,” and “hoarseness.” Vocal abuse items received the highest scores of EVM-D. However, only “shouting” in the classroom was significantly different between the groups with and without burnout. Conclusion: Emotional exhaustion of burnout syndrome, history of anxiety/depression, and a shorter professional experience were associated with vocal problems, which could limit the performance of teachers. Reducing classroom noise, establishing strategies to avoid shouting, or strengthening personal accomplishments in teachers could be useful in breaking the cycle of vocal problems and emotional exhaustion, particularly at the beginning of their professional experience.

Redirected Attention and Impaired Recognition Memory during Exhaustive Cycling Has Implications for Information Processing Models of Effort-Regulation.

Twenty male participants performed two laboratory ramped cycling tests beginning at 50 W and increasing by 0.25 W/s until volitional exhaustion. Ratings of perceived exertion, heart rate and respiratory gas exchange measures were recorded during the first test. During the second test, participants listened to a list of spoken words presented through headphones at a rate of one word every 4 s. Afterwards, their recognition memory for the word pool was measured. Recognition memory performance was found to have strong negative correlations with perceived exertion (p < 0.0001), percentage of peak power output (p < 0.0001), percentage of heart rate reserve (p < 0.0001), and percentage of peak oxygen uptake (p < 0.0001). The results show that, as the physiological and psychophysiological stress of cycling intensified, recognition memory performance deteriorated. This might be due to impairment of memory encoding of the spoken words as they were presented, or because of a diversion of attention away from the headphones, perhaps towards internal physiological sensations as interoceptive sources of attentional load increase with exercise intensity. Information processing models of pacing and performance need to recognise that an athlete's capacity to attend to and process external information is not constant, but changes with exercise intensity.

Examining regulatory focus in the acceleration and deceleration of engagement and exhaustion cycles among nurses.

Given that emotional exhaustion and nurse engagement have significant implications for nurse well-being and organizational performance, determining how to increase nurse engagement while reducing nurse exhaustion is of value. Resource loss and gain cycles, as theorized in conservation of resources theory, are examined using the experience of emotional exhaustion to evaluate loss cycles and work engagement to evaluate gain cycles. Furthermore, we integrate conservation of resources theory with regulatory focus theory to examine how the ways in which individuals approach work goals serves as a facilitator to the acceleration and deceleration of both of these cycles. Using data from nurses working in a hospital in the Midwest United States at six time points spanning over 2 years, we demonstrate the accumulation effects of the cycles over time using latent change score modeling. We found that prevention focus was associated with the accelerated accumulation effects of emotional exhaustion and that promotion focus was associated with the accelerated accumulation effects of work engagement. Furthermore, prevention focus attenuated the acceleration of engagement, but promotion did not influence the acceleration of exhaustion. Our findings suggest that individual factors such as regulatory focus are key to helping nurses to better control their resource gain and loss cycles. We provide implications for nurse managers and health care administrators to help encourage promotion focus and suppress prevention focus in the workplace.

Bioregeneration of sulfate-laden anion exchange resin

Ion exchange technology removes ionic compounds from waters effectively but treatment of the spent regenerant is expensive. The bioregeneration of sulfate-laden strong base anion exchange resin was successfully tested using both pure and mixed sulfate-reducing bacterial cultures. The resin was first used for removal of sulfate from neutral (pH 6.7 ± 0.5) synthetic sodium sulfate solutions, after which the spent resin was regenerated by incubating with a viable sulfate-reducing bacterial culture in batch and column modes. In the batch bioregeneration tests, the achieved bioregeneration was 36–95% of the original capacity of the fresh resin (112 mg SO42−/g) and it increased with regeneration time (1–14 days). The capacity achieved in the column tests during 24 hours of bioregeneration was 107 mg SO42−/g after the first regeneration cycle. During the bioregeneration, sulfate was mainly reduced by the sulfate-reducing bacteria (approx. 60%), but part of it was only detached from the resins (approx. 30%). The resin-attached sulfate was most likely replaced with ions present in the liquid sulfate-reducing bacterial culture (e.g., HCO3−, HS−, and Cl−). During the subsequent exhaustion cycles with the bioregenerated resin, the pH of the treated sodium sulfate solution increased from the original 6.7 ± 0.5 to around 9. The study showed that biological sulfate reduction could be used for sulfate removal in combination with ion exchange, and that the exhausted ion exchange resins could be regenerated using a liquid sulfate-reducing bacterial culture without producing any brine.

Post-translational dysregulation of glucose uptake during exhaustive cycling exercise in vastus lateralis muscle of healthy homozygous carriers of the ACE deletion allele.

Homozygous carriers of the deletion allele in the gene for angiotensin-converting enzyme (ACE-DD) demonstrate an elevated risk to develop inactivity-related type II diabetes and show an overshoot of blood glucose concentration with enduring exercise compared to insertion allele carriers. We hypothesized that ACE-DD genotypes exhibit a perturbed activity of signaling processes governing capillary-dependent glucose uptake in vastus lateralis muscle during exhaustive cycling exercise, which is associated with the aerobic fitness state. 27 healthy, male white Caucasian subjects (26.8 ± 1.1 years; BMI 23.6 +/− 0.6 kg m−2) were characterized for their aerobic fitness based on a threshold of 50 ml O2 min−1 kg−1 and the ACE-I/D genotype. Subjects completed a session of exhaustive one-legged exercise in the fasted state under concomitant measurement of cardiorespiratory function. Capillary blood and biopsies were collected before, and ½ and 8 h after exercise to quantify glucose and lipid metabolism-related compounds (lipoproteins, total cholesterol, ketones) in blood, the phosphorylation of 45 signaling proteins, muscle glycogen and capillaries. Effects of aerobic fitness, ACE-I/D genotype, and exercise were assessed with analysis of variance (ANOVA) under the hypothesis of a dominant effect of the insertion allele. Exertion with one-legged exercise manifested in a reduction of glycogen concentration ½ h after exercise (−0.046 mg glycogen mg−1 protein). Blood glucose concentration rose immediately after exercise in association with the ACE-I/D genotype (ACE-DD: +26%, ACE-ID/II: +6%) and independent of the fitness state (p = 0.452). Variability in total cholesterol was associated with exercise and fitness. In fit subjects, the phosphorylation levels of glucose uptake-regulating kinases [AKT-pT308 (+156%), SRC-pY419, p38α-pT180/T182, HCK-pY411], as well as cytokine/angiotensin 1-7 signaling factors [(STAT5A-pY694, STAT5B-pY699, FYN-pY420, EGFR-pY1086] were higher in angiotensin converting enzyme I-allele carriers than ACE-DD genotypes after exercise. Conversely, the AKT-S473 phosphorylation level (+117%) and angiotensin 2’s blood concentration (+191%) were higher in ACE-DD genotypes. AKT-S473 phosphorylation levels post-exercise correlated to anatomical parameters of muscle performance and metabolic parameters (p < 0.05 and │r│>0.70). The observations identify reciprocal alterations of S473 and T308 phosphorylation of AKT as gatekeeper of a post-translational dysregulation of transcapillary glucose uptake in ACE-DD genotypes which may be targeted in personalized approaches to mitigate type II diabetes.

Does The Countermovement Jump Accurately Assess Lower-limb Neuromuscular Fatigue?

Neuromuscular fatigue is monitored in athletes following intense exercise to inform future training prescription and to improve performance. Temporal analysis of the countermovement jump (CMJ) is frequently used to assess fatigue in athletes but is infrequently compared directly to low-frequency fatigue (LFF), a long-lasting fatigue typically assessed in the laboratory. LFF may be present in athletes. PURPOSE: To determine the time-course of changes in CMJ and lower limb LFF following an exhaustive cycling test and the relationship between LFF and temporal CMJ variables. METHODS: LFF and CMJ were assessed in seven active adults (24±2 years, 78±14 kg) prior to and following (0, 8, 15, 30, 60 mins and 24 and 48 hours) an incremental cycling test to exhaustion. Cycling began at 100 W and increased 25 W every 2 min until exhaustion. Temporal analysis of CMJ for peak power (PP), jump height (JH), and concentric contraction duration (CCD) were calculated from bilateral force plates. Low-frequency (10 Hz) force (F10) was elicited from transcutaneous femoral nerve stimulation prior to a maximal voluntary contraction (MVC). LFF was quantified as the F10:MVC ratio. The order of CMJ or LFF was randomized across time points. Changes in LFF and CMJ variables were assessed from two-way repeated measures analysis of variance (measure x time). RESULTS: Maximal aerobic power was 234±67 W (96±4% HRmax). A significant measure x time interaction (p<0.0001) and significant main effects of time (p=0.05) and method (p=0.02) were found. Compared to baseline, significant reductions in LFF (i.e., greater fatigue) were seen at 0-, 8-, 15- and 30-mins post-exercise (all p<0.02). No significant changes in any of the CMJ variables were observed post-exercise (p = 1.0). Furthermore, changes in LFF during exercise recovery was not correlated to changes in any of CMJ variables (r2<0.04, p>0.20), whereas all CMJ variables were significantly correlated with each other (0.22<r2<0.42, p<0.001). CONCLUSION: These results show that following exhaustive exercise, LFF persists for at least 30 mins whereas no change in CMJ performance variables were seen. These results call into question the practical utility of interpreting neuromuscular fatigue in athletes using the CMJ, even within 30 minutes of exhaustive exercise.

Validity of the Polar H10 Sensor for Heart Rate Variability Analysis during Resting State and Incremental Exercise in Recreational Men and Women.

Heart rate variability (HRV) is frequently applied in sport-specific settings. The rising use of freely accessible applications for its recording requires validation processes to ensure accurate data. It is the aim of this study to compare the HRV data obtained by the Polar H10 sensor chest strap device and an electrocardiogram (ECG) with the focus on RR intervals and short-term scaling exponent alpha 1 of Detrended Fluctuation Analysis (DFA a1) as non-linear metric of HRV analysis. A group of 25 participants performed an exhaustive cycling ramp with measurements of HRV with both recording systems. Average time between heartbeats (RR), heart rate (HR) and DFA a1 were recorded before (PRE), during, and after (POST) the exercise test. High correlations were found for the resting conditions (PRE: r = 0.95, rc = 0.95, ICC3,1 = 0.95, POST: r = 0.86, rc = 0.84, ICC3,1 = 0.85) and for the incremental exercise (r > 0.93, rc > 0.93, ICC3,1 > 0.93). While PRE and POST comparisons revealed no differences, significant bias could be found during the exercise test for all variables (p < 0.001). For RR and HR, bias and limits of agreement (LoA) in the Bland–Altman analysis were minimal (RR: bias of 0.7 to 0.4 ms with LoA of 4.3 to −2.8 ms during low intensity and 1.3 to −0.5 ms during high intensity, HR: bias of −0.1 to −0.2 ms with LoA of 0.3 to −0.5 ms during low intensity and 0.4 to −0.7 ms during high intensity). DFA a1 showed wider bias and LoAs (bias of 0.9 to 8.6% with LoA of 11.6 to −9.9% during low intensity and 58.1 to −40.9% during high intensity). Linear HRV measurements derived from the Polar H10 chest strap device show strong agreement and small bias compared with ECG recordings and can be recommended for practitioners. However, with respect to DFA a1, values in the uncorrelated range and during higher exercise intensities tend to elicit higher bias and wider LoA.

Lipotoxicity in a Vicious Cycle of Pancreatic Beta Cell Exhaustion.

Hyperlipidemia is a common metabolic disorder in modern society and may precede hyperglycemia and diabetes by several years. Exactly how disorders of lipid and glucose metabolism are related is still a mystery in many respects. We analyze the effects of hyperlipidemia, particularly free fatty acids, on pancreatic beta cells and insulin secretion. We have developed a computational model to quantitatively estimate the effects of specific metabolic pathways on insulin secretion and to assess the effects of short- and long-term exposure of beta cells to elevated concentrations of free fatty acids. We show that the major trigger for insulin secretion is the anaplerotic pathway via the phosphoenolpyruvate cycle, which is affected by free fatty acids via uncoupling protein 2 and proton leak and is particularly destructive in long-term chronic exposure to free fatty acids, leading to increased insulin secretion at low blood glucose and inadequate insulin secretion at high blood glucose. This results in beta cells remaining highly active in the “resting” state at low glucose and being unable to respond to anaplerotic signals at high pyruvate levels, as is the case with high blood glucose. The observed fatty-acid-induced disruption of anaplerotic pathways makes sense in the context of the physiological role of insulin as one of the major anabolic hormones.

Prenatal Exercise and Cardiovascular Health (PEACH) Study: impact of pregnancy and exercise on rating of perceived exertion during non-weight-bearing exercise.

The purpose of this study was to determine if rating of perceived exertion (RPE) during non-weight-bearing exercise is influenced by gestational age and exercise training. We conducted a randomized controlled trial to examine the influence of gestational age and exercise training (three to fourtimes per week for 25-40 minutes at 50%-70% of heart rate reserve) on RPE during an exhaustive cycling exercise test. We observed no influence of gestational age, or exercise training status on RPE responses to non-weight-bearing exercise during pregnancy. Trial registration number: NCT02948439. Novelty: Gestational age and/or exercise training does not influence rate of perceived exertion during non-weight-bearing exercise.

Exercise-induced cardiac troponin release in middle-aged and older athletes with different degrees of coronary atherosclerosis

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Radboud University Medical CenterAcademic Alliance Fund Maastricht - Nijmegen Background Current sports medical examinations do not appropriately detect occult coronary atherosclerosis in athletes, whereas coronary atherosclerosis is more prevalent in middle-aged and older athletes compared to physically active controls. Therefore, new diagnostic approaches need to be developed to identify individuals at risk. Cardiac troponin (cTn) is the standard biomarker to assess myocardial injury. Exercise is known to increase cTn concentrations and a delayed recovery of cTn concentrations after exercise cessation is suggested to be indicative of occult obstructive coronary artery disease. We hypothesized that the magnitude of exercise-induced cTn elevations may be associated with the degree of coronary atherosclerosis. Purpose To compare serial measures of exercise-induced cTnT elevations across middle-aged and older athletes with different degrees of coronary atherosclerosis. Methods A subgroup of 59 men from the Measuring Athlete’s Risk of Coronary events-2 study (MARC-2, n=291) were invited for this add-on study. All participants had undergone a cardiac computed tomography (CT) scan and coronary CT angiography to determine the prevalence and magnitude of coronary atherosclerosis. Athletes were stratified based on the degree of coronary atherosclerosis: I) n=20 with a coronary artery calcium score (CACS) of 0, II) n=20 with CACS ≥300 or ≥75th MESA-percentile, and III) n=19 with a &amp;gt;50% stenosis in any coronary artery, but without ischemia on a stress imaging tests. Participants performed an individualized exercise test (&amp;gt;1 hour, cycling) until volitional exhaustion. High-sensitivity cTnT concentrations were measured at baseline, after 30 minutes of exercise and at 0, 30, 60, 120, and 180 minutes post-exercise. Results Participants (age 60.8 [57.9-72.6] years, BMI 24.5 [23.9-27.3]) exercised for 76±14 minutes, up to 97.6 [94.4-101.8] % of their expected maximum heart rate. Exercise duration and workload did not differ across groups. Baseline hs-cTnT was detectable in everyone. Exercise induced a 1.98±1.63 fold increase in hs-cTnT concentrations. Peak hs-cTnT concentrations occurred at 180 minutes post-exercise (13.9 [9.4-17.0] ng/L versus 12.1 [10.0-21.5] ng/L versus 13.8 [9.1-19.9] ng/L, for group I, II and III, respectively) and the incidence of hs-cTnT concentrations above the URL (n=9 (45%) vs n=7 (35.0%) vs n=9 (47.4%)) was comparable across groups (p=0.92 and p=0.71, respectively). Patterns of time-dependent changes in hs-cTnT concentrations did not differ across groups (p=.49). Conclusion Exercise-induced elevations in hs-cTnT concentrations did not differ among middle-aged and older athletes with different degrees of coronary atherosclerosis. Our findings suggest that hs-cTnT sampled before, during or within 180 minutes following an exhaustive endurance cycling exercise test is not suitable to detect occult coronary atherosclerosis in athletes.

Sleep loss, mood state, and performance of extreme intensity cycling exercise

ABSTRACT The purpose of this study was to investigate the effects of one night’s sleep loss on mood state and exercise performance, for the purpose of identifying relationships between mood state and performance. A within-subjects repeated-measures design was used. Seven women (21 ± 2 y, 164 ± 9 cm, 62 ± 14 kg) participated. They completed Profile of Mood States questionnaires and performed exhaustive extreme intensity cycle ergometer tests (310 ± 70 W) before, and on three consecutive days following, one night’s sleep loss. Mean time to exhaustion was not affected by sleep loss. Mean total mood state disturbance was elevated on days 1 and 2 after sleep loss compared to baseline. There were strong correlations (r > 0.82) between individual changes (day 1 minus baseline, day 2 minus baseline, day 3 minus baseline) in time to exhaustion and individual changes in mood state: changes in time to exhaustion were associated with changes in the fatigue subscore on day 1; with changes in the vigour subscore on day 2, and with changes in the fatigue subscore on day 3. These results demonstrate a relationship, which may or may not reflect causality, between mood state and performance.

Polyprenol Liposomes Improve the Efficiency of Oxygen Usage in Well-Trained Amateur Athletes

Abstract Polyprenols are natural substances that are known for their role as cell membrane protectors from peroxidation. However, there is a lack of information about their effect on the performance of athletes. Therefore, we studied the effects of polyprenol on athlete performance. A total of 30 male floorball players participated in this study, 16 of whom were taking 30 mg polyprenol liposome caps and 14 of whom were not. All of the participants underwent VO2max exhaustive incremental cycling testing, before and after the use of polyprenols. VO2peak and other cardiorespiratory variables were measured to evaluate cardiorespiratory adaptation. For the polyprenol users (PU) the oxygen pulse (O2/HR) increased by 0.9 ml/beat, while in the control group (C) decreased by 0.4 ml/beat from before to after the use of polyprenols (p &lt; 0.05). The diastolic pressure (Pdia) decreased by 4 mmHg for the PU, while it increased by 10 mmHg in the C (p &lt; 0.05). The stroke volume (SVc) in the PU increased by 2.9 ml, while that in the C decreased by 7.4 ml (p &lt; 0.05). In conclusion, polyprenols improved oxygen consumption efficiency by increasing SVc and O2/HR.