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      Enhanced Metabolic Stress Augments Ischemic Preconditioning for Exercise Performance

      research-article
      , *
      Frontiers in Physiology
      Frontiers Media S.A.
      exercise, hypoxia, occlusion, cycling, metabolites

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          Abstract

          Purpose: To identify the combined effect of increasing tissue level oxygen consumption and metabolite accumulation on the ergogenic efficacy of ischemic preconditioning (IPC) during both maximal aerobic and maximal anaerobic exercise.

          Methods: Twelve healthy males (22 ± 2 years, 179 ± 2 cm, 80 ± 10 kg, 48 ± 4 ml.kg −1.min −1) underwent four experimental conditions: (i) no IPC control, (ii) traditional IPC, (iii) IPC with EMS, and (iv) IPC with treadmill walking. IPC involved bilateral leg occlusion at 220 mmHg for 5 min, repeated three times, separated by 5 min of reperfusion. Within 10 min following the IPC procedures, a 30 s Wingate test and subsequent (after 25 min rest) incremental maximal aerobic test were performed on a cycle ergometer.

          Results: There was no statistical difference in anaerobic peak power between the no IPC control (1211 ± 290 W), traditional IPC (1209 ± 300 W), IPC + EMS (1206 ± 311 W), and IPC + Walk (1220 ± 288 W; P = 0.7); nor did VO 2max change between no IPC control (48 ± 2 ml.kg −1.min −1), traditional IPC (48 ± 6 ml.kg −1.min −1), IPC + EMS (49 ± 4 ml.kg −1.min −1) and IPC + Walk (48 ± 6 ml.kg −1.min −1; P = 0.3). However, the maximal watts during the VO 2max increased when IPC was combined with both EMS (304 ± 38 W) and walking (308 ± 40 W) compared to traditional IPC (296 ± 39 W) and no IPC control (293 ± 48 W; P = 0.02).

          Conclusion: This study shows that in a group of participants for whom a traditional IPC stimulus was not effective, the magnification of the IPC stress through muscle contractions while under occlusion led to a subsequent exercise performance response. These findings support that amplification of the ischemic preconditioning stimulus augments the effect for exercise capacity.

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          Most cited references23

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          Hypoxia-inducible factor-1 is central to cardioprotection: a new paradigm for ischemic preconditioning.

          Ischemic preconditioning provides strong cardioprotection from ischemia, but its molecular mechanisms remain unknown. Convincing evidence confirms a central role of hypoxia-inducible factor (HIF)-1 in mammalian oxygen homeostasis. Thus, we pursued HIF-1 as a central component of cardioprotection by ischemic preconditioning. Murine studies of in situ preconditioning revealed a robust activation of cardiac HIF-1. Moreover, in vivo small interfering RNA repression of cardiac HIF-1 resulted in abolished cardioprotection by ischemic preconditioning. In contrast, pretreatment with the HIF activator dimethyloxalylglycine was associated with cardioprotection similar to that of ischemic preconditioning itself. Finally, selective small interfering RNA repression of prolylhydroxylase 2 resulted in significant activation of HIF-1 alpha and attenuated myocardial infarct sizes (0.44+/-0.09-fold). As an end point of HIF-dependent cardioprotection, we defined the role of A2B adenosine receptor (A2BAR) signaling. Although the cardiac A2BAR was induced with HIF activation, HIF-dependent cardioprotection was abolished in A2BAR-/- mice. Taken together, these studies provide evidence for a critical role of HIF-1 in ischemic preconditioning via enhancing purinergic signaling pathways.
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            Separate Effects of Intensity and Amount of Exercise on Interindividual Cardiorespiratory Fitness Response.

            To determine the separate effects of exercise intensity and amount on interindividual cardiorespiratory fitness (CRF) response.
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              Observations in man upon a blood pressure raising reflex arising from the voluntary muscles.

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                Author and article information

                Contributors
                Journal
                Front Physiol
                Front Physiol
                Front. Physiol.
                Frontiers in Physiology
                Frontiers Media S.A.
                1664-042X
                15 November 2018
                2018
                : 9
                : 1621
                Affiliations
                Department of Human Health and Nutritional Sciences, University of Guelph , Guelph, ON, Canada
                Author notes

                Edited by: François Billaut, Laval University, Canada

                Reviewed by: Oliver R. Gibson, Brunel University London, United Kingdom; Martin Burtscher, Universität Innsbruck, Austria

                *Correspondence: Jamie F. Burr, burrj@ 123456uoguelph.ca

                This article was submitted to Exercise Physiology, a section of the journal Frontiers in Physiology

                Article
                10.3389/fphys.2018.01621
                6249303
                30498458
                8b5ac7ff-9932-4a34-88cb-6eb2beee1dd4
                Copyright © 2018 Slysz and Burr.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 11 September 2018
                : 26 October 2018
                Page count
                Figures: 3, Tables: 1, Equations: 0, References: 31, Pages: 8, Words: 0
                Funding
                Funded by: Natural Sciences and Engineering Research Council of Canada 10.13039/501100000038
                Funded by: Canada Foundation for Innovation 10.13039/501100000196
                Funded by: Mitacs 10.13039/501100004489
                Categories
                Physiology
                Original Research

                Anatomy & Physiology
                exercise,hypoxia,occlusion,cycling,metabolites
                Anatomy & Physiology
                exercise, hypoxia, occlusion, cycling, metabolites

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