{"corpus_id":265658716,"paper_sha":"0a9fa0e30f85986a59463ad27f1f85c8ecceaf4e","doi":"10.1113/JP285650","arxiv_id":null,"pmid":38048175,"pmcid":"PMC10841684","mag_id":null,"dblp_id":null,"acl_id":null,"title":"Endurance exercise training changes the limitation on muscle V̇O2max${\\dot{V}}_{{{\\mathrm{O}}}_{\\mathrm{2}}{\\mathrm{max}}}$ in normoxia from the capacity to utilize O2 to the capacity to transport O2","year":2023,"publication_date":"2023-12-04","venue":"Journal of Physiology","journal":{"name":"The Journal of Physiology","pages":null,"volume":"602"},"journal_issn":null,"journal_title":null,"publication_types":["JournalArticle"],"pubmed_pub_types":["Journal Article","Research Support, U.S. Gov't, Non-P.H.S.","Research Support, N.I.H., Extramural"],"s2_fields_of_study":["Medicine"],"reference_count":40,"citation_count":6,"influential_citation_count":0,"is_open_access":false,"arxiv_categories":null,"arxiv_license":null,"arxiv_journal_ref":null,"mesh_headings":[{"d":"Male","mj":false,"ui":"D008297"},{"d":"Humans","mj":false,"ui":"D006801"},{"d":"Muscle, Skeletal","mj":true,"qs":[{"q":"physiology","mj":false,"ui":"Q000502"}],"ui":"D018482"},{"d":"Oxygen Consumption","mj":true,"qs":[{"q":"physiology","mj":false,"ui":"Q000502"}],"ui":"D010101"},{"d":"Oxygen","mj":false,"qs":[{"q":"metabolism","mj":false,"ui":"Q000378"}],"ui":"D010100"},{"d":"Exercise","mj":false,"qs":[{"q":"physiology","mj":false,"ui":"Q000502"}],"ui":"D015444"},{"d":"Hypoxia","mj":false,"ui":"D000860"}],"chemicals":[{"n":"Oxygen","ui":"D010100","reg":"S88TT14065"}],"comments_corrections":null,"source_flags":5,"s2_open_access_pdf_url":null,"s2_open_access_landing_url":null,"s2_open_access_license":null,"s2_open_access_status":null,"pmc_open_access_pdf_url":null,"pmc_open_access_landing_url":null,"pmc_open_access_license":null,"pmc_open_access_status":null,"unpaywall_open_access_pdf_url":null,"unpaywall_open_access_landing_url":null,"unpaywall_open_access_license":null,"unpaywall_open_access_status":null,"abstract":"Maximal oxygen (O2) uptake ( V̇O2max${\\dot{V}}_{{{\\mathrm{O}}}_{\\mathrm{2}}{\\mathrm{max}}}$ ) is an important parameter with utility in health and disease. However, the relative importance of O2 transport and utilization capacities in limiting muscle V̇O2max${\\dot{V}}_{{{\\mathrm{O}}}_{\\mathrm{2}}{\\mathrm{max}}}$ before and after endurance exercise training is not well understood. Therefore, the present study aimed to identify the mechanisms determining muscle V̇O2max${\\dot{V}}_{{{\\mathrm{O}}}_{\\mathrm{2}}{\\mathrm{max}}}$ pre‐ and post‐endurance exercise training in initially sedentary participants. In five initially sedentary young males, radial arterial and femoral venous PO2${P}_{{{\\mathrm{O}}}_{\\mathrm{2}}}$ (blood samples), leg blood flow (thermodilution), and myoglobin (Mb) desaturation (1H nuclear magnetic resonance spectroscopy) were measured during maximal single‐leg knee‐extensor exercise (KE) breathing either 12%, 21% or 100% O2 both pre and post 8 weeks of KE training (1 h, 3 times per week). Mb desaturation was converted to intracellular PO2${P}_{{{\\mathrm{O}}}_{\\mathrm{2}}}$ using an O2 half‐saturation pressure of 3.2 mmHg. Pre‐training muscle V̇O2max${\\dot{V}}_{{{\\mathrm{O}}}_{\\mathrm{2}}{\\mathrm{max}}}$ was not significantly different across inspired O2 conditions (12%: 0.47 ± 0.10; 21%: 0.52 ± 0.13; 100%: 0.54 ± 0.01 L min–1, all q > 0.174), despite significantly greater muscle mean capillary–intracellular PO2${P}_{{{\\mathrm{O}}}_{\\mathrm{2}}}$ gradients in normoxia (34 ± 3 mmHg) and hyperoxia (40 ± 7 mmHg) than hypoxia (29 ± 5 mmHg, both q < 0.024). Post‐training muscle V̇O2max${\\dot{V}}_{{{\\mathrm{O}}}_{\\mathrm{2}}{\\mathrm{max}}}$ was significantly different across all inspired O2 conditions (12%: 0.59 ± 0.11; 21%: 0.68 ± 0.11; 100%: 0.76 ± 0.09 mmHg, all q < 0.035), as were the muscle mean capillary–intracellular PO2${P}_{{{\\mathrm{O}}}_{\\mathrm{2}}}$ gradients (12%: 32 ± 2; 21%: 37 ± 2; 100%: 45 ± 7 mmHg, all q < 0.029). In these initially sedentary participants, endurance exercise training changed the basis of limitation on muscle V̇O2max${\\dot{V}}_{{{\\mathrm{O}}}_{\\mathrm{2}}{\\mathrm{max}}}$ in normoxia from the mitochondrial capacity to utilize O2 to the capacity to transport O2 to the mitochondria.","claims":[{"public_id":"cl_172957445b5bf8fa9e09f3bc01baf23c","status":"active","text":"After 8 weeks of knee-extensor endurance training, muscle V̇O2max differed significantly across all inspired O2 conditions and increased in each condition.","confidence":0.98,"contributors":[{"id":1,"public_id":"12632b8b5f","public_label":"Anonymous (12632b8b5f)","roles":["extraction"],"url":"https://sah.borca.ai/u/12632b8b5f"}],"url":"https://sah.borca.ai/claims/cl_172957445b5bf8fa9e09f3bc01baf23c"},{"public_id":"cl_72d058a9c1d6163e8fb059be5ad43998","status":"active","text":"After training, the muscle mean capillary–intracellular PO2 gradient also differed significantly across all inspired O2 conditions and was greatest in hyperoxia.","confidence":0.95,"contributors":[{"id":1,"public_id":"12632b8b5f","public_label":"Anonymous (12632b8b5f)","roles":["extraction"],"url":"https://sah.borca.ai/u/12632b8b5f"}],"url":"https://sah.borca.ai/claims/cl_72d058a9c1d6163e8fb059be5ad43998"},{"public_id":"cl_f6bd4a88c62e3e5de1093cc7fc7d18ac","status":"active","text":"Before training, muscle V̇O2max did not differ significantly across hypoxic, normoxic, and hyperoxic inspired O2 conditions despite larger capillary–intracellular PO2 gradients in normoxia and hyperoxia than in hypoxia.","confidence":0.97,"contributors":[{"id":1,"public_id":"12632b8b5f","public_label":"Anonymous (12632b8b5f)","roles":["extraction"],"url":"https://sah.borca.ai/u/12632b8b5f"}],"url":"https://sah.borca.ai/claims/cl_f6bd4a88c62e3e5de1093cc7fc7d18ac"},{"public_id":"cl_3eea8de6e0fec0d6a870230d140628f2","status":"active","text":"In initially sedentary young males, endurance exercise training shifted the main limitation on normoxic muscle V̇O2max from mitochondrial O2-utilization capacity to O2-transport capacity to the mitochondria.","confidence":0.99,"contributors":[{"id":1,"public_id":"12632b8b5f","public_label":"Anonymous (12632b8b5f)","roles":["extraction"],"url":"https://sah.borca.ai/u/12632b8b5f"}],"url":"https://sah.borca.ai/claims/cl_3eea8de6e0fec0d6a870230d140628f2"}],"concepts":[{"public_id":"co_2c4b19448ddc82a6f58d2a251467a531","status":"active","name":"knee-extensor training","description":"Single-leg exercise training focused on the knee extensor muscles.","types":["intervention","exercise protocol"],"aliases":["KE training"],"contributors":[{"id":1,"public_id":"12632b8b5f","public_label":"Anonymous (12632b8b5f)","roles":["extraction"],"url":"https://sah.borca.ai/u/12632b8b5f"}],"url":"https://sah.borca.ai/concepts/co_2c4b19448ddc82a6f58d2a251467a531"},{"public_id":"co_3fb43dc54f4107f3a115dde566e6bd9e","status":"active","name":"normoxia","description":"A normal-oxygen breathing condition used during 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