-
Journal of Applied Physiology... Jun 1998Thoroughbred (TB) and draft horses (DH) have long been selected for tasks of very different intensities and force-speed relationships. To study their adaptations, we... (Comparative Study)
Comparative Study
Thoroughbred (TB) and draft horses (DH) have long been selected for tasks of very different intensities and force-speed relationships. To study their adaptations, we measured O2 consumption and related variables in three TB and four DH during progressive exercise tests on a level treadmill. The horses exerted a draft force of 0, 5, 10, 15, or 20% of their body weight at speeds that increased by 2 m/s every 3 min until they could not maintain that speed. We found that TB could exert the same draft forces as DH and, at each force, TB achieved about twice the speed, twice the external power, and twice the O2 consumption as DH; thus the two breeds had the same gross efficiencies. We also found maximal O2 consumption of TB to be about twice that of DH (134 vs. 72 ml . kg-1 . min-1, respectively), suggesting adaptations to high-intensity exercise. Peak efficiency was reached at lower speeds in DH than in TB, suggesting adaptations to high-force, low-speed exercise. These differences between TB and DH in force-speed and aerobic capacities and in speed for peak efficiency likely reflect different contraction velocities in locomotor muscles.
Topics: Aerobiosis; Anaerobic Threshold; Animals; Biomechanical Phenomena; Energy Metabolism; Horses; Male; Oxygen Consumption; Physical Exertion; Running; Species Specificity
PubMed: 9609800
DOI: 10.1152/jappl.1998.84.6.2052 -
Experimental Physiology Mar 2010Ascent to altitude is associated with a fall in barometric pressure, and with it a decline in the partial pressure of atmospheric (and thus alveolar) oxygen. As a... (Review)
Review
Ascent to altitude is associated with a fall in barometric pressure, and with it a decline in the partial pressure of atmospheric (and thus alveolar) oxygen. As a result, a variety of adaptive physiological processes are engaged to mitigate the fall in tissue convective oxygen delivery which might otherwise occur. The magnitude and nature of such changes is also modified with time, a process known as acclimatization. However, other phenomena are at work; the ability to perform physical work at altitude falls in a manner which is not wholly related to changes in arterial oxygen content. Indeed, alterations in local skeletal muscle blood flow and metabolism may play an axial role. Thus, for those who are not native to high altitude, the ability to compete at altitude is likely to be impaired. The magnitude of such impairment in performance, however, differs greatly between individuals, and it seems that genetic variation underpins much of this difference. The identification of the relevant genetic elements is in its infancy in humans, but ongoing work is likely to help us gain an increasing understanding of how humans adapt to altitude and to develop mitigating interventions.
Topics: Adaptation, Physiological; Altitude; Athletic Performance; Humans; Hypoxia; Oxygen Consumption
PubMed: 19946029
DOI: 10.1113/expphysiol.2009.047589 -
American Journal of Physiology. Heart... Dec 2001To maintain tissue oxygenation, normal aortic valves contain a vascular bed where tissue thickness is greatest. Avascular "living" tissue-engineered heart valves have...
To maintain tissue oxygenation, normal aortic valves contain a vascular bed where tissue thickness is greatest. Avascular "living" tissue-engineered heart valves have been proposed, yet little information exists regarding the magnitude of valve tissue metabolic activity or oxygen requirements. We therefore set out to measure the oxygen diffusivity (DO(2)) and oxygen consumption (VO(2)) of seven porcine aortic valve cusps in vitro at 37 degrees C using a chamber with a Clark oxygen sensor. Mean DO(2) and VO(2) were 1.06 x 10(-5) cm(2)/s and 3.05 x 10(-5) x ml O(2). ml tissue(-1) x s(-1), respectively. When modeled as a three-layered structure by using these values and a boundary condition of 100 mmHg at both surfaces, the average aortic cusp predicted a central mean PO(2) of 27 mmHg (range of 0-50 mmHg). The DO(2) value obtained was similar to that found for other vascular structures, but because our studies were carried out in vitro, the VO(2) measurements may be lower than that required by the functioning valves. These values provide an initial understanding of the oxygen supply possible from the cusp surfaces and the oxygen needs of the tissue.
Topics: Animals; Aortic Valve; Diffusion; Energy Metabolism; Heart Valve Prosthesis; Humans; Oxygen; Oxygen Consumption; Swine; Tissue Engineering
PubMed: 11709429
DOI: 10.1152/ajpheart.2001.281.6.H2604 -
Journal of Biomedical Materials... Mar 2023We perform a novel 3D study to quantify the corneal oxygen consumption and diffusion in each part of the cornea with different contact lens materials. The oxygen profile...
We perform a novel 3D study to quantify the corneal oxygen consumption and diffusion in each part of the cornea with different contact lens materials. The oxygen profile is calculated as a function of oxygen tension at the cornea-tear interface and the oxygen transmissibility of the lens, with values used in previous studies. We aim to determine the influence of a detailed geometry of the cornea in their modeling compared to previous low dimensional models used in the literature. To this end, a 3-D study based on an axisymmetric volume element analysis model was applied to different contact lenses currently on the market. We have obtained that the model provides a valuable tool for understanding the flux and cornea oxygen profiles through the epithelium, stroma, and endothelium. The most important results are related to the dependence of the oxygen flux through the cornea-lens system on the contact lens thickness and geometry. Both parameters play an important role in the corneal flux and oxygen tension distribution. The decline in oxygen consumption experienced by the cornea takes place just inside the epithelium, where the oxygen tension falls to between 95 and 16 mmHg under open eye conditions, and 30 to 0.3 mmHg under closed eye conditions, depending on the contact lens worn. This helps to understand the physiological response of the corneal tissue under conditions of daily and overnight contact lens wear, and the importance of detailed geometry of the cornea in the modeling of diffusion for oxygen and other species.
Topics: Humans; Contact Lenses; Cornea; Oxygen; Eyelids; Oxygen Consumption; Contact Lenses, Hydrophilic
PubMed: 36214217
DOI: 10.1002/jbm.b.35180 -
PloS One 2022Measurement of oxygen consumption of cultured cells is widely used for diagnosis of mitochondrial diseases, drug testing, biotechnology, and toxicology. Fibroblasts are...
Measurement of oxygen consumption of cultured cells is widely used for diagnosis of mitochondrial diseases, drug testing, biotechnology, and toxicology. Fibroblasts are cultured in monolayers, but physiological measurements are carried out in suspended or attached cells. We address the question whether respiration differs in attached versus suspended cells using multiwell respirometry (Agilent Seahorse XF24) and high-resolution respirometry (Oroboros O2k), respectively. Respiration of human dermal fibroblasts measured in culture medium was baseline-corrected for residual oxygen consumption and expressed as oxygen flow per cell. No differences were observed between attached and suspended cells in ROUTINE respiration of living cells and LEAK respiration obtained after inhibition of ATP synthase by oligomycin. The electron transfer capacity was higher in the O2k than in the XF24. This could be explained by a limitation to two uncoupler titrations in the XF24 which led to an underestimation compared to multiple titration steps in the O2k. A quantitative evaluation of respiration measured via different platforms revealed that short-term suspension of fibroblasts did not affect respiratory activity and coupling control. Evaluation of results obtained by different platforms provides a test for reproducibility beyond repeatability. Repeatability and reproducibility are required for building a validated respirometric database.
Topics: Cell Respiration; Fibroblasts; Humans; Oxidative Phosphorylation; Oxygen Consumption; Reproducibility of Results
PubMed: 35239701
DOI: 10.1371/journal.pone.0264496 -
American Journal of Physiology. Renal... Jun 2015The objective of this study was to investigate how physiological, pharmacological, and pathological conditions that alter sodium reabsorption (TNa) in the proximal...
The objective of this study was to investigate how physiological, pharmacological, and pathological conditions that alter sodium reabsorption (TNa) in the proximal tubule affect oxygen consumption (QO2 ) and Na(+) transport efficiency (TNa/QO2 ). To do so, we expanded a mathematical model of solute transport in the proximal tubule of the rat kidney. The model represents compliant S1, S2, and S3 segments and accounts for their specific apical and basolateral transporters. Sodium is reabsorbed transcellularly, via apical Na(+)/H(+) exchangers (NHE) and Na(+)-glucose (SGLT) cotransporters, and paracellularly. Our results suggest that TNa/QO2 is 80% higher in S3 than in S1-S2 segments, due to the greater contribution of the passive paracellular pathway to TNa in the former segment. Inhibition of NHE or Na-K-ATPase reduced TNa and QO2 , as well as Na(+) transport efficiency. SGLT2 inhibition also reduced proximal tubular TNa but increased QO2 ; these effects were relatively more pronounced in the S3 vs. the S1-S2 segments. Diabetes increased TNa and QO2 and reduced TNa/QO2 , owing mostly to hyperfiltration. Since SGLT2 inhibition lowers diabetic hyperfiltration, the net effect on TNa, QO2 , and Na(+) transport efficiency in the proximal tubule will largely depend on the individual extent to which glomerular filtration rate is lowered.
Topics: Animals; Biological Transport; Diabetes Mellitus; Glomerular Filtration Rate; Hypoglycemic Agents; Kidney Tubules, Proximal; Oxygen Consumption; Rats; Sodium; Sodium-Glucose Transporter 2; Sodium-Glucose Transporter 2 Inhibitors; Sodium-Hydrogen Exchangers
PubMed: 25855513
DOI: 10.1152/ajprenal.00007.2015 -
International Journal of Environmental... Nov 2022A decrease in physical activity levels among university students during the COVID-19 pandemic is well-documented in the literature. However, the effect of lockdown...
BACKGROUND
A decrease in physical activity levels among university students during the COVID-19 pandemic is well-documented in the literature. However, the effect of lockdown restrictions on cardiovascular fitness has not been thoroughly investigated.
METHODS
The aim of the study was to assess the possible changes in cardiovascular fitness among university students during a 14-week period of the COVID-19 pandemic. Thirteen female and seven male tourism and recreation students participated in the study. Examinations were conducted in November 2020 and in February/March 2021. Students performed the PWC170 test on a cycling ergometer. Maximal oxygen consumption was calculated based on the PWC170 test results. Blood pressure and heart rate were measured at rest, as well as in the 1st and 5th minute of post-exercise recovery.
RESULTS
No substantial changes were observed in maximal oxygen consumption level when comparing autumn and winter indices. Male students presented elevated blood pressure whereas female students presented normal blood pressure. Heart-rate and blood-pressure indices did not show substantial alternations in examined students during analyzed period.
CONCLUSIONS
Fourteen weeks of lockdown had little effect on the cardiovascular health of tourism and recreation students.
Topics: Humans; Male; Female; Pandemics; COVID-19; Communicable Disease Control; Oxygen Consumption; Exercise
PubMed: 36497556
DOI: 10.3390/ijerph192315483 -
Anaesthesia Aug 2013
Topics: Anaerobic Threshold; Colon; Exercise Test; Female; Humans; Male; Oxygen Consumption; Postoperative Complications; Rectum; Walking
PubMed: 23789846
DOI: 10.1111/anae.12343 -
PeerJ 2022Maximal aerobic speed (MAS) is a useful parameter to assess aerobic capacity and estimate training intensity in middle- and long-distance runners. However, whether...
Maximum aerobic speed, maximum oxygen consumption, and running spatiotemporal parameters during an incremental test among middle- and long-distance runners and endurance non-running athletes.
BACKGROUND
Maximal aerobic speed (MAS) is a useful parameter to assess aerobic capacity and estimate training intensity in middle- and long-distance runners. However, whether middle- and long-distance runners reach different levels of MAS compared to other endurance athletes with similar V̇O has not been previously studied. Therefore, we aimed to compare V̇O, MAS and spatiotemporal parameters between sub-elite middle- and long-distance runners ( = 6) and endurance non-runners ( = 6). In addition, we aimed to compare the maximal blood lactate concentration [BLa] experienced by participants after conducting these tests.
METHODS
Telemetric portable respiratory gas analysis, contact and flight time, and stride length and rate were measured using a 5-m contact platform during an incremental test at a synthetic athletics track. V̇O, heart rate, respiratory quotient values in any 15 s average period during the test were measured. [BLa] was analyzed after the test . Running spatiotemporal parameters were recorded at the last two steps of each 400 m lap. A coefficient of variation (%CV) was calculated for each spatiotemporal variable in each participant from 8 km h onwards.
RESULTS
Whereas runners reported faster MAS (21.0 vs. 18.2 km h) than non-runners ( = 0.0001, ES = 3.0), no differences were found for V̇O and maximum blood lactate concentration during the running tests (p > 0.05). While significant increases in flight time and stride length and frequency (p < 0.001, 0.52 ≤ ≤ 0.8) were observed throughout the tests, decreases in contact time (p < 0.001, ) were reported. Runners displayed a greater %CV ( = 0.015) in stride length than non-runners. We conclude that middle- and long-distance runners can achieve a faster MAS compared to non-running endurance athletes despite exhibiting a similar V̇O. This superior performance may be associated to a greater mechanical efficiency. Overall, runners displayed a greater ability to modify stride length to achieve fast speeds, which may be related to a more mechanically efficient pattern of spatiotemporal parameters than non-runners.
Topics: Humans; Physical Endurance; Oxygen Consumption; Respiratory Function Tests; Athletes; Lactates
PubMed: 36217384
DOI: 10.7717/peerj.14035 -
Developmental Cognitive Neuroscience Jul 2011BOLD fMRI (blood oxygenation level dependent functional magnetic resonance imaging) is increasingly used to detect developmental changes of human brain function that are... (Review)
Review
BOLD fMRI (blood oxygenation level dependent functional magnetic resonance imaging) is increasingly used to detect developmental changes of human brain function that are hypothesized to underlie the maturation of cognitive processes. BOLD signals depend on neuronal activity increasing cerebral blood flow, and are reduced by neural oxygen consumption. Thus, developmental changes of BOLD signals may not reflect altered information processing if there are concomitant changes in neurovascular coupling (the mechanism by which neuronal activity increases blood flow) or neural energy use (and hence oxygen consumption). We review how BOLD signals are generated, and explain the signalling pathways which convert neuronal activity into increased blood flow. We then summarize in broad terms the developmental changes that the brain's neural circuitry undergoes during growth from childhood through adolescence to adulthood, and present the changes in neurovascular coupling mechanisms and energy use which occur over the same period. This information provides a framework for assessing whether the BOLD changes observed during human development reflect altered cognitive processing or changes in neurovascular coupling and energy use.
Topics: Animals; Brain; Cerebrovascular Circulation; Humans; Magnetic Resonance Imaging; Neuronal Plasticity; Oxygen Consumption; Signal Processing, Computer-Assisted
PubMed: 22436508
DOI: 10.1016/j.dcn.2011.04.001