Kylie N. Sears, Tony R. Montgomery, Colin W. Kipper, Petra Kis, Taylor K. Dinyer-McNeely, Shane M. Hammer
{"title":"Muscle microvascular oxygen delivery limitations during the contraction phase of intermittent maximal effort contractions","authors":"Kylie N. Sears, Tony R. Montgomery, Colin W. Kipper, Petra Kis, Taylor K. Dinyer-McNeely, Shane M. Hammer","doi":"10.1007/s00421-024-05605-0","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Purpose</h3><p>The end-test torque (ETT) during intermittent maximal effort contractions reflects the highest contraction intensity at which a muscle metabolic steady-state can be attained. This study determined if ETT is the highest intensity at which the contraction phase of intermittent exercise does not limit the matching of microvascular oxygen delivery to muscle oxygen demand.</p><h3 data-test=\"abstract-sub-heading\">Methods</h3><p>Microvascular oxygenation characteristics of the biceps brachii muscle were measured in sixteen young, healthy individuals (8M/8F, 22 ± 3 years, 80.9 ± 20.3 kg) by near-infrared spectroscopy during maximal effort elbow flexion under control conditions (CON) and with complete circulatory occlusion (OCC).</p><h3 data-test=\"abstract-sub-heading\">Results</h3><p>Increases in total-[heme] were blunted during OCC compared to CON (225 ± 87 vs. 264 ± 88 μM, <i>p</i> < 0.001) but OCC did not elicit a compensatory increase in deoxygenated-[heme] at any timepoint (108 ± 62 vs. 101 ± 61 μM, <i>p</i> > 0.05). Deoxygenated-[heme] was significantly elevated during contraction, relative to relaxation, above ETT (107 ± 60 vs. 98.8 ± 60.5 μM, <i>p</i> < 0.001), but not at ETT (91.7 ± 54.1 vs. 98.4 ± 62.2 μM, <i>p</i> = 0.174). Total-[heme] was significantly reduced during contraction, relative to relaxation, at all contraction intensities during CON (<i>p</i> < 0.05) and OCC (<i>p</i> < 0.05).</p><h3 data-test=\"abstract-sub-heading\">Conclusion</h3><p>These data suggest that ETT may reflect the highest contraction intensity at which contraction-induced increases in intramuscular pressures do not limit muscle perfusion to a degree that requires further increases in fractional oxygen extraction (i.e., deoxygenated-[heme]) despite limited microvascular diffusive conductance (i.e., total-[heme]).</p>","PeriodicalId":12005,"journal":{"name":"European Journal of Applied Physiology","volume":null,"pages":null},"PeriodicalIF":2.8000,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"European Journal of Applied Physiology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1007/s00421-024-05605-0","RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Purpose
The end-test torque (ETT) during intermittent maximal effort contractions reflects the highest contraction intensity at which a muscle metabolic steady-state can be attained. This study determined if ETT is the highest intensity at which the contraction phase of intermittent exercise does not limit the matching of microvascular oxygen delivery to muscle oxygen demand.
Methods
Microvascular oxygenation characteristics of the biceps brachii muscle were measured in sixteen young, healthy individuals (8M/8F, 22 ± 3 years, 80.9 ± 20.3 kg) by near-infrared spectroscopy during maximal effort elbow flexion under control conditions (CON) and with complete circulatory occlusion (OCC).
Results
Increases in total-[heme] were blunted during OCC compared to CON (225 ± 87 vs. 264 ± 88 μM, p < 0.001) but OCC did not elicit a compensatory increase in deoxygenated-[heme] at any timepoint (108 ± 62 vs. 101 ± 61 μM, p > 0.05). Deoxygenated-[heme] was significantly elevated during contraction, relative to relaxation, above ETT (107 ± 60 vs. 98.8 ± 60.5 μM, p < 0.001), but not at ETT (91.7 ± 54.1 vs. 98.4 ± 62.2 μM, p = 0.174). Total-[heme] was significantly reduced during contraction, relative to relaxation, at all contraction intensities during CON (p < 0.05) and OCC (p < 0.05).
Conclusion
These data suggest that ETT may reflect the highest contraction intensity at which contraction-induced increases in intramuscular pressures do not limit muscle perfusion to a degree that requires further increases in fractional oxygen extraction (i.e., deoxygenated-[heme]) despite limited microvascular diffusive conductance (i.e., total-[heme]).
期刊介绍:
The European Journal of Applied Physiology (EJAP) aims to promote mechanistic advances in human integrative and translational physiology. Physiology is viewed broadly, having overlapping context with related disciplines such as biomechanics, biochemistry, endocrinology, ergonomics, immunology, motor control, and nutrition. EJAP welcomes studies dealing with physical exercise, training and performance. Studies addressing physiological mechanisms are preferred over descriptive studies. Papers dealing with animal models or pathophysiological conditions are not excluded from consideration, but must be clearly relevant to human physiology.