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International Journal of Environmental... Sep 2022Uphill running induces a higher physiological demand than level conditions. Although many studies have investigated this locomotion from a psychological point of view,...
Uphill running induces a higher physiological demand than level conditions. Although many studies have investigated this locomotion from a psychological point of view, there is no clear position on the effects of the slope on the physiological variables during an incremental running test performed on a slope condition. The existing studies have heterogeneous designs with different populations or slopes and have reported unclear results. Some studies observed an increase in oxygen consumption, whereas it remained unaffected in others. The aim of this study is to investigate the effect of a slope on the oxygen consumption, breathing frequency, ventilation and heart rate during an incremental test performed on 0, 15, 25 and 40% gradient slopes by specialist trail runners. The values are compared at the first and second ventilatory threshold and exhaustion. A one-way repeated measures ANOVA, with a Bonferroni post-hoc analysis, was used to determine the effects of a slope gradient (0, 15, 25 and 40%) on the physiological variables. Our study shows that all the variables are not affected in same way by the slopes during the incremental test. The heart rate and breathing frequency did not differ from the level condition and all the slope gradients at the ventilatory thresholds or exhaustion. At the same time, the ventilation and oxygen consumption increased concomitantly with the slope ( < 0.001) in all positions. The post-hoc analysis highlighted that the ventilation significantly increased between each successive gradient (0 to 15%, 15% to 25% and 25% to 40%), while the oxygen consumption stopped increasing at the 25% gradient. Our results show that the 25 and 40% gradient slopes allow the specialist trail runners to reach the highest oxygen consumption level.
Topics: Exercise Test; Heart Rate; Oxygen Consumption; Respiration; Running
PubMed: 36231513
DOI: 10.3390/ijerph191912210 -
International Journal of Sports... Nov 2021Since its publication in 2012, the W' balance model has become an important tool in the scientific armamentarium for understanding and predicting human physiology and... (Review)
Review
Since its publication in 2012, the W' balance model has become an important tool in the scientific armamentarium for understanding and predicting human physiology and performance during high-intensity intermittent exercise. Indeed, publications featuring the model are accumulating, and it has been adapted for popular use both in desktop computer software and on wrist-worn devices. Despite the model's intuitive appeal, it has achieved mixed results thus far, in part due to a lack of clarity in its basis and calculation. Purpose: This review examines the theoretical basis, assumptions, calculation methods, and the strengths and limitations of the integral and differential forms of the W' balance model. In particular, the authors emphasize that the formulations are based on distinct assumptions about the depletion and reconstitution of W' during intermittent exercise; understanding the distinctions between the 2 forms will enable practitioners to correctly implement the models and interpret their results. The authors then discuss foundational issues affecting the validity and utility of the model, followed by evaluating potential modifications and suggesting avenues for further research. Conclusions: The W' balance model has served as a valuable conceptual and computational tool. Improved versions may better predict performance and further advance the physiology of high-intensity intermittent exercise.
Topics: Exercise; Exercise Test; High-Intensity Interval Training; Humans; Oxygen Consumption
PubMed: 34686611
DOI: 10.1123/ijspp.2021-0205 -
The Japanese Journal of Physiology Jun 2004Studies on left ventricular mechanical work and energetics in rat and mouse hearts are reviewed. First, left ventricular linear end-systolic pressure-volume relation... (Review)
Review
Studies on left ventricular mechanical work and energetics in rat and mouse hearts are reviewed. First, left ventricular linear end-systolic pressure-volume relation (ESPVR) and curved end-diastolic pressure-volume relation (EDPVR) in canine hearts and left ventricular curved ESPVR and curved EDPVR in rat hearts are reviewed. Second, as an index for total mechanical energy per beat in rat hearts as in canine hearts, a systolic pressure-volume area (PVA) is proposed. By the use of our original system for measuring continuous oxygen consumption for rat left ventricular mechanical work, the linear left ventricular myocardial oxygen consumption per beat (VO2)-PVA relation is obtained as in canine hearts. The slope of VO2-PVA relation (oxygen cost of PVA) indicates a ratio of chemomechanical energy transduction. VO2 intercept (PVA-independent VO2) indicates the summation of oxygen consumption for Ca2+ handling in excitation-contraction coupling and for basal metabolism. An equivalent maximal elastance (eEmax) is proposed as a new left ventricular contractility index based on PVA at the midrange left ventricular volume. The slope of the linear relation between PVA-independent VO2 and eEmax (oxygen cost of eEmax) indicates changes in oxygen consumption for Ca2+ handling in excitation-contraction coupling per unit changes in left ventricular contractility. The key framework of VO2-PVA-eEmax can give us a better understanding for the biology and mechanisms of physiological and various failing rat heart models in terms of mechanical work and energetics.
Topics: Animals; Blood Pressure; Energy Metabolism; Myocardial Contraction; Oxygen Consumption; Rats; Stroke Volume; Ventricular Function; Ventricular Function, Left
PubMed: 15541198
DOI: 10.2170/jjphysiol.54.175 -
Frontiers in Bioscience (Scholar... Jan 2011Low temperatures provoke increased production of heat accompanied by increased respiration, oxygen consumption and the production of partially reduced oxygen species... (Review)
Review
Low temperatures provoke increased production of heat accompanied by increased respiration, oxygen consumption and the production of partially reduced oxygen species called ROS. ROS induce different forms of cellular oxidative damage, disturb the redox state and can change the activity of several metabolic enzymes. Organisms have developed a functionally connected set of anti-oxidant enzymes and low molecular mass compounds (together termed the ADS) that metabolise primary ROS. If ROS production within cells overwhelms the ADS, oxidative damage arises and oxidative stress can occur. Short-term cold exposure in endotherms leads to oxidative stress. As cold exposure persists organisms develop adaptive changes toward reducing ROS production and increasing the ADS. In contrast, heterotherms and ectotherms as a normal part of their over-wintering strategy slow down metabolism, oxygen consumption and subsequently cause ROS production. Increased baseline activity of key anti-oxidant enzymes as well as 'secondary' enzymatic defence and/or glutathione levels in preparation for a putative oxidative stressful situation arising from tissue re-oxygenation seems to be the preferred evolutionary adaptation of such animals exposed to low environmental temperatures.
Topics: Acclimatization; Cold Temperature; Humans; Models, Biological; Oxidation-Reduction; Oxidative Stress; Oxygen Consumption; Reactive Oxygen Species; Thermogenesis
PubMed: 21196386
DOI: 10.2741/s161 -
American Journal of Physiology. Renal... Dec 2016The goal of this study was to investigate water and solute transport, with a focus on sodium transport (T) and metabolism along individual nephron segments under...
The goal of this study was to investigate water and solute transport, with a focus on sodium transport (T) and metabolism along individual nephron segments under differing physiological and pathophysiological conditions. To accomplish this goal, we developed a computational model of solute transport and oxygen consumption (Q ) along different nephron populations of a rat kidney. The model represents detailed epithelial and paracellular transport processes along both the superficial and juxtamedullary nephrons, with the loop of Henle of each model nephron extending to differing depths of the inner medulla. We used the model to assess how changes in T may alter Q in different nephron segments and how shifting the T sites alters overall kidney Q Under baseline conditions, the model predicted a whole kidney T/Q , which denotes the number of moles of Na reabsorbed per moles of O consumed, of ∼15, with T efficiency predicted to be significantly greater in cortical nephron segments than in medullary segments. The T/Q ratio was generally similar among the superficial and juxtamedullary nephron segments, except for the proximal tubule, where T/Q was ∼20% higher in superficial nephrons, due to the larger luminal flow along the juxtamedullary proximal tubules and the resulting higher, flow-induced transcellular transport. Moreover, the model predicted that an increase in single-nephron glomerular filtration rate does not significantly affect T/Q in the proximal tubules but generally increases T/Q along downstream segments. The latter result can be attributed to the generally higher luminal [Na], which raises paracellular T Consequently, vulnerable medullary segments, such as the S3 segment and medullary thick ascending limb, may be relatively protected from flow-induced increases in Q under pathophysiological conditions.
Topics: Animals; Biological Transport; Computer Simulation; Kidney; Models, Biological; Nephrons; Oxygen Consumption; Rats
PubMed: 27707705
DOI: 10.1152/ajprenal.00293.2016 -
Journal of the International Society of... Dec 2023Rectal distension increases regulatory burden to autonomic nervous system in the brain.
BACKGROUND
Rectal distension increases regulatory burden to autonomic nervous system in the brain.
PURPOSE
To determine the effect of rectal defecation on endurance performance and blood supply to the prefrontal brain and sub-navel regions of elite triathletes.
METHODS
Thirteen elite triathletes completed a cycling time trial (80% VO) under defecated and non-defecated conditions, using a counterbalanced crossover design. Oxygenation and blood distribution in prefrontal brain and sub-navel regions were monitored by near-infrared spectroscopy (NIRS) during cycling.
RESULTS
Defecation moderately decreased systolic blood pressure (-4 mmHg, < 0.05, d = 0.71), suggesting an alleviation of autonomic nervous activity. During the exercise trials, fatigue (cycling time to exhaustion) occurred when cerebral oxygenation decreased to ~ 5 % below baseline regardless of treatment conditions, suggesting a critical deoxygenation point for sustaining voluntary exertions. Cerebral blood (estimated by total hemoglobin) increased progressively throughout the entire exercise period. Defecation decreased sub-navel oxygenation levels below the non-defecated level, suggesting an increased sub-navel oxygen consumption. Exercise also decreased sub-navel blood distribution, with minimal difference between non-defecated and defecated conditions. Defecation improved blood pooling in the prefrontal brain during exercise ( < 0.05) and enhanced cycling performance in triathletes (Non-defecated: 1624 ± 138 s vs. defecated: 1902 ± 163 s, d = 0.51, < 0.05).
CONCLUSION
Our results suggest that improved exercise performance after defecation is associated with greater blood availability to compensate deoxygenation in the prefrontal brain region during exercise. Further investigation is needed to examine the role of increasing sub-navel oxygen consumption in the performance improvement after defecation.
Topics: Humans; Defecation; Exercise; Oxygen Consumption; Fatigue; Cerebrovascular Circulation
PubMed: 37102434
DOI: 10.1080/15502783.2023.2206380 -
Molecules (Basel, Switzerland) Oct 2020In the wine industry, in addition to condensed tannins of grape origin, other commercial tannins are commonly used. However, the influence of oxygen uptake related to...
BACKGROUND
In the wine industry, in addition to condensed tannins of grape origin, other commercial tannins are commonly used. However, the influence of oxygen uptake related to different tannin additions during the post fermentative phase in wine has not been completely investigated. In this study, we evaluated the influence of four different commercial tannins (namely, condensed tannins, gallotannins, ellagitannins and tea tannins) during four saturation cycles.
METHOD
Wine samples were added with four different tannin classes (30 g/hL) as to have 5 different experimental samples: control, gallotannins (GT), condensed tannins (CT), ellagitannins (ET), and tea tannins (TT). The chemical composition of the four commercially available tannin mixtures was defined by means of NMR and high-resolution mass spectrometry. After the addition of tannins, each wine sample was oxidized by air over four cycles of saturation. During the experiment oxygen consumption rate (OCR), sulfur dioxide consumption, acetaldehyde production, phenolic compounds, chromatic characteristics, astringency measured by the reactivity towards saliva proteins and astringency subqualities were evaluated.
RESULTS
The experiment lasted 52 days. The addition of tannins influenced the oxygen consumption on the 1st day of the saturation cycles and, in the case of TT, a higher total consumption of oxygen was also detected. Acetaldehyde increased during the experiment while the native anthocyanins decreased throughout the oxidation process.
CONCLUSION
Wines added with tannins featured improved color intensities with respect to the control; the addition of TT, GT and ET slightly promoted the formation of short polymeric pigments; the astringency, determined before and at the end of the experiment, decreased in all the samples, including the control wine, and mostly in the ET and GT samples.
Topics: Astringents; Magnetic Resonance Spectroscopy; Mass Spectrometry; Oxygen Consumption; Phenols; Tannins; Wine
PubMed: 33050381
DOI: 10.3390/molecules25204607 -
Journal of Sports Science & Medicine Sep 2022To propose a new Cardiopulmonary Exercise Test with Elastic Resistance (CPxEL) and compare the physiological responses to conventional cardiopulmonary exercise test...
To propose a new Cardiopulmonary Exercise Test with Elastic Resistance (CPxEL) and compare the physiological responses to conventional cardiopulmonary exercise test (CPx) performed on a treadmill. In addition, we tested the reproducibility of the CPxEL. Twenty-four physically active participants completed the CPx (first session) and CPxEL twice (second and third sessions) interspersed by seven days. A treadmill protocol with increments of 1km·h every minute until exhaustion was used in CPx. The CPxEL consisted of performing alternating steps back-and-forth against an elastic resistance attached to a belt and an incremental protocol with 1 stage (S) per minute following a cadence of 200 bpm controlled by a metronome in an 8-stage rubber mat. First analysis: first ventilatory threshold (VT1) occurred at 69.7% and 75.3% of maximal heart rate (HR) and 53.5% and 65.7% of maximal oxygen consumption (V̇O). Second VT (VT2) occurred at 93.3% and 96.8% of the HR and 87.0% and 96.9% of V̇O for CPx and CPxEL, respectively. At exhaustion, V̇O, perceived exertion (BORG-CR10 and OMNI-RES EB), and test duration presented lower values for CPxEL (P < 0.05). Second analysis: VT1 occurred at warm-up (S0) (P = 0.731), VT2 occurred at S5 (P = 0.912), and the exhaustion occurred at S6 and S7 (P = 0.271) for CPxEL and retest, respectively. The intraclass correlation coefficient (ICC) for V̇O was 0.921 and for HR was 0.930. The CPxEL has good test-retest reproducibility and represents a possible and interesting add-on to determine maximal oxygen consumption, maximal heart rate, and second ventilatory threshold without using traditional ergometers.
Topics: Exercise Test; Heart Rate; Humans; Oxygen Consumption; Reproducibility of Results; Rubber
PubMed: 36157388
DOI: 10.52082/jssm.2022.426 -
Archives of Disease in Childhood. Fetal... Jul 2001To determine the effect of phototherapy on the oxygen consumption and resting energy expenditure of term and preterm newborn infants. (Clinical Trial)
Clinical Trial Randomized Controlled Trial
OBJECTIVES
To determine the effect of phototherapy on the oxygen consumption and resting energy expenditure of term and preterm newborn infants.
METHODS
A total of 202 infants (gestation 30-42 weeks; body weight 1270-4100 g) requiring phototherapy for the treatment of neonatal hyperbilirubinaemia were enrolled in a randomised crossover study. In random sequence, the oxygen consumption and resting energy expenditure were measured twice in each infant by indirect calorimetry, once at the end of six hours of continuous phototherapy and once after a control period of at least six hours without phototherapy. Anterior abdominal wall temperature was servocontrolled at 36.5 degrees C throughout the study.
RESULTS
At the end of six hours of continuous phototherapy, oxygen consumption (mean (SD): 6.21 (1.35) v 6.26 (1.51) ml/kg, p = 0.555) and resting energy expenditure (178.11 (37.62) v 180.37 (43.14) kJ/kg/24 h, p = 0.382) did not differ significantly from those measured after the control period. There were also no significant differences in heart rate, respiratory rate, or rectal temperature. Subgroup analysis of those of gestation < 37 weeks or < 34 weeks also showed no effect of phototherapy on either oxygen consumption or resting energy expenditure.
CONCLUSION
Phototherapy has no effect on the metabolic rate of thermally stable term or preterm infants.
Topics: Basal Metabolism; Calorimetry, Indirect; Cross-Over Studies; Humans; Hyperbilirubinemia; Infant, Newborn; Infant, Premature; Infant, Premature, Diseases; Oxygen Consumption; Phototherapy
PubMed: 11420323
DOI: 10.1136/fn.85.1.f49 -
The Journal of Physiology Aug 2019Haemoglobin affinity is an integral concept in exercise physiology that impacts oxygen uptake, delivery and consumption. How chronic alterations in haemoglobin affinity...
KEY POINTS
Haemoglobin affinity is an integral concept in exercise physiology that impacts oxygen uptake, delivery and consumption. How chronic alterations in haemoglobin affinity impact physiology is unknown. Using human haemoglobin variants, we demonstrate that the affinity of haemoglobin for oxygen is highly correlated with haemoglobin concentration. Using the Fick equation, we model how altered haemoglobin affinity and the associated haemoglobin concentration influences oxygen consumption at rest and during exercise via alterations in cardiac output and mixed-venous . The combination of low oxygen affinity haemoglobin and reduced haemoglobin concentration seen in vivo may be unable to support oxygen uptake during moderate or heavy exercise.
ABSTRACT
The physiological implications, with regard to exercise, of altered haemoglobin affinity for oxygen are not fully understood. Data from the Mayo Clinic Laboratories database of rare human haemoglobin variants reveal a strong inverse correlation (r = -0.82) between blood haemoglobin concentration and P , an index of oxygen affinity [Hb = -0.3135(P ) + 23.636]. In the present study, observed P values for high, normal and low oxygen-affinity haemoglobin variants (13, 26 and 39 mmHg) and corresponding haemoglobin concentrations (19.5, 15.5 and 11.4 g dL respectively) are used to model oxygen consumption as a fraction of delivery at rest ( = 0.25 L min , cardiac output = 5.70 L min ) and during exercise ( = 2.75 L min , cardiac output = 18.9 l min ). With high-affinity haemoglobin, the model shows that normal levels of oxygen consumption can be achieved at rest and during exercise at the assumed cardiac output levels, with reduced oxygen extraction both at rest (16.8% high affinity vs. 21.7% normal) and during exercise (55.8% high affinity vs. 72.2% normal). With low-affinity haemoglobin, which predicts low haemoglobin concentration, oxygen consumption at rest can be sustained with the assumed cardiac output, with increased oxygen extraction (31.1% low affinity vs. 21.7% normal). However, exercise at 2.75 l min cannot be achieved with the assumed cardiac output, even with 100% oxygen extraction. In conclusion, the model indicates chronic alterations in P associate directly with Hb concentration, highlighting that human Hb variants can serve as 'experiments of nature' to address fundamental hypotheses on oxygen transport and exercise.
Topics: Hemoglobins; Humans; Models, Biological; Oxygen; Oxygen Consumption
PubMed: 31290158
DOI: 10.1113/JP277591