{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T11:05:51Z","timestamp":1777633551094,"version":"3.51.4"},"reference-count":45,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T00:00:00Z","timestamp":1777420800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Physiol."],"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>From a process-oriented perspective of endurance durability, this exploratory study aimed to characterize the dynamic evolution of heart rate\u2013running speed decoupling during a simulated half-marathon in adolescent endurance athletes and to examine phase-specific associations between decoupling characteristics and physiological regulation.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      Thirteen adolescent endurance runners with systematic endurance training completed a 21.1-km simulated half-marathon under self-paced conditions. Heart rate and running speed were recorded continuously and aggregated into consecutive 2-km distance segments. Internal and external loads were normalized to individual maximal heart rate and running speed at VO\n                      <jats:sub>2peak<\/jats:sub>\n                      , respectively, and used to derive a relative heart rate\u2013running speed decoupling index (DM\n                      <jats:sub>i<\/jats:sub>\n                      ). Decoupling characteristics included the distance of decoupling onset (Onset), maximal decoupling magnitude (DM\n                      <jats:sub>max<\/jats:sub>\n                      ), and mean decoupling during the late phase of exercise (15\u201320 km). Core body temperature, interstitial glucose concentration, and sweat-derived estimates of fluid and sodium loss were monitored concurrently. Associations were examined using Spearman correlation analysis.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Heart rate\u2013running speed decoupling increased progressively throughout the run and showed substantial inter-individual variability. The median decoupling onset occurred at 10.0\u00a0km (interquartile range: 7.0\u201312.0 km). An earlier onset was associated with greater concurrent increases in core body temperature (\u03c1 = \u22120.579,\n                      <jats:italic>p<\/jats:italic>\n                      \u00a0=\u00a00.038) and sodium loss per unit distance (\u03c1 = \u22120.605,\n                      <jats:italic>p<\/jats:italic>\n                      \u00a0=\u00a00.037). The maximal decoupling magnitude (DM\n                      <jats:sub>max<\/jats:sub>\n                      ) was positively correlated with changes in core body temperature (\u03c1 = 0.632,\n                      <jats:italic>p<\/jats:italic>\n                      \u00a0=\u00a00.021) and sodium loss per unit distance (\u03c1 = 0.643,\n                      <jats:italic>p<\/jats:italic>\n                      \u00a0=\u00a00.024). In contrast, the change in decoupling during the final stage of the run (15\u201320 km) was not associated with thermoregulatory or fluid\u2013electrolyte indices but was positively correlated with changes in glucose concentration (\u03c1 = 0.599,\n                      <jats:italic>p<\/jats:italic>\n                      \u00a0=\u00a00.031).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Discussion<\/jats:title>\n                    <jats:p>During a simulated half-marathon, heart rate\u2013running speed decoupling evolved progressively in adolescent endurance athletes and demonstrated marked inter-individual variability. Decoupling onset and maximal magnitude were primarily associated with thermoregulatory and electrolyte-related physiological loads during the early to middle stages of exercise, whereas decoupling dynamics in the latter stage were more closely aligned with physiological responses related to energy supply regulation. These findings support heart rate\u2013running speed decoupling as a durability-related indicator with phase-specific physiological characteristics during prolonged endurance exercise.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fphys.2026.1807399","type":"journal-article","created":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T04:42:51Z","timestamp":1777437771000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Physiological associations with heart rate\u2013speed decoupling during a half-marathon in adolescent endurance runners"],"prefix":"10.3389","volume":"17","author":[{"given":"Weiyu","family":"Wang","sequence":"first","affiliation":[{"name":"Sports Training Research Center, China Institute of Sport Science","place":["Beijing, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ruihang","family":"Zhou","sequence":"additional","affiliation":[{"name":"Sports Training Research Center, China Institute of Sport Science","place":["Beijing, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Guangze","family":"He","sequence":"additional","affiliation":[{"name":"Sports Training Research Center, China Institute of Sport Science","place":["Beijing, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yumeng","family":"Si","sequence":"additional","affiliation":[{"name":"Sports Training Research Center, China Institute of Sport Science","place":["Beijing, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yongqin","family":"Cao","sequence":"additional","affiliation":[{"name":"Sports Training Research Center, China Institute of Sport Science","place":["Beijing, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pengxi","family":"Zheng","sequence":"additional","affiliation":[{"name":"Sports Training Research Center, China Institute of Sport Science","place":["Beijing, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wei","family":"Zi","sequence":"additional","affiliation":[{"name":"Sports Training Research Center, China Institute of Sport Science","place":["Beijing, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2026,4,29]]},"reference":[{"key":"B1","first-page":"644","article-title":"Statistical considerations regarding the use of ratios to adjust data","volume":"19","author":"Allison","year":"1995","journal-title":"Int. J. Obes. Related Metab. Disord."},{"key":"B2","doi-asserted-by":"publisher","first-page":"117","DOI":"10.4085\/1062-6050-44.2.117","article-title":"Sodium replacement and plasma sodium drop during exercise in the heat when fluid intake matches fluid loss","volume":"44","author":"Anastasiou","year":"2009","journal-title":"J. Athletic Training"},{"key":"B3","doi-asserted-by":"publisher","first-page":"3345","DOI":"10.1242\/jeb.02340","article-title":"Influence of the muscle-tendon unit\u2019s mechanical and morphological properties on running economy","volume":"209","author":"Arampatzis","year":"2006","journal-title":"J. Exp. Biol."},{"key":"B4","doi-asserted-by":"publisher","first-page":"59","DOI":"10.1159\/000320633","article-title":"Endurance training and elite young athletes","volume":"56","author":"Armstrong","year":"2011","journal-title":"Med. Sport Sci."},{"key":"B5","doi-asserted-by":"publisher","first-page":"111","DOI":"10.1007\/s40279-017-0691-5","article-title":"Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra\/interindividual variability","volume":"47","author":"Baker","year":"2017","journal-title":"Sports Med."},{"key":"B6","doi-asserted-by":"publisher","first-page":"1250","DOI":"10.1152\/japplphysiol.00391.2022","article-title":"Explaining variation in sweat sodium concentration: effect of individual characteristics and exercise, environmental, and dietary factors","volume":"133","author":"Baker","year":"2022","journal-title":"J. Appl. Physiol."},{"key":"B7","doi-asserted-by":"publisher","DOI":"10.3389\/fphys.2025.1717275","article-title":"Sweat sodium composition and sweat loss estimation through wearable sensors and predictive equations in dry and humid hot conditions","volume":"16","author":"Bandiera","year":"2025","journal-title":"Front. Physiol."},{"key":"B8","doi-asserted-by":"publisher","DOI":"10.3389\/fphys.2020.00512","article-title":"Pacing strategy affects the sub-elite marathoner\u2019s cardiac drift and performance","volume":"11","author":"Billat","year":"2020","journal-title":"Front. Physiol."},{"key":"B9","doi-asserted-by":"publisher","first-page":"S17","DOI":"10.1111\/sms.12149","article-title":"Fueling strategies to optimize performance: training and competition","volume":"24","author":"Burke","year":"2014","journal-title":"Scandinavian J. Med. Sci. Sports"},{"key":"B10","doi-asserted-by":"publisher","first-page":"537","DOI":"10.1016\/j.jshs.2020.06.011","article-title":"Pacing profiles and tactical behaviors of elite runners","volume":"10","author":"Casado","year":"2021","journal-title":"J. Sport Health Sci."},{"key":"B11","doi-asserted-by":"publisher","first-page":"743","DOI":"10.2165\/00007256-200131100-00004","article-title":"Thermoregulation and marathon running: biological and environmental influences","volume":"31","author":"Cheuvront","year":"2001","journal-title":"Sports Med."},{"key":"B12","doi-asserted-by":"publisher","first-page":"968S","DOI":"10.1093\/ajcn\/61.4.968S","article-title":"Substrate utilization during exercise in active people","volume":"61","author":"Coyle","year":"1995","journal-title":"Am. J. Clin. Nutr."},{"key":"B13","doi-asserted-by":"publisher","first-page":"S121","DOI":"10.1055\/s-2007-971975","article-title":"Cardiovascular drift during prolonged exercise and the effects of dehydration","volume":"19","author":"Coyle","year":"1998","journal-title":"Int. J. Sports Med."},{"key":"B14","doi-asserted-by":"publisher","first-page":"88","DOI":"10.1097\/00003677-200104000-00009","article-title":"Cardiovascular drift during prolonged exercise: new perspectives","volume":"29","author":"Coyle","year":"2001","journal-title":"Exercise Sport Sci. Rev."},{"key":"B15","doi-asserted-by":"publisher","first-page":"213","DOI":"10.1152\/advan.00053.2013","article-title":"Explorations in statistics: the analysis of ratios and normalized data","volume":"37","author":"Curran-Everett","year":"2013","journal-title":"Adv. Physiol. Educ."},{"key":"B16","doi-asserted-by":"publisher","first-page":"420","DOI":"10.1139\/H07-185","article-title":"Children\u2019s thermoregulation during exercise in the heat: a revisit","volume":"33","author":"Falk","year":"2008","journal-title":"Appl. Physiol. Nutr. Metab."},{"key":"B17","doi-asserted-by":"publisher","first-page":"247","DOI":"10.1007\/s40279-023-01910-4","article-title":"Continuous glucose monitoring in endurance athletes: interpretation and relevance of measurements for improving performance and health","volume":"54","author":"Flockhart","year":"2024","journal-title":"Sports Med."},{"key":"B18","doi-asserted-by":"publisher","first-page":"340","DOI":"10.1113\/expphysiol.2011.058701","article-title":"Human thermoregulation and the cardiovascular system","volume":"97","author":"Gonz\u00e1lez-Alonso","year":"2012","journal-title":"Exp. Physiol."},{"key":"B19","doi-asserted-by":"publisher","first-page":"1032","DOI":"10.1152\/jappl.1999.86.3.1032","article-title":"Influence of body temperature on the development of fatigue during prolonged exercise in the heat","volume":"86","author":"Gonz\u00e1lez-Alonso","year":"1999","journal-title":"J. Appl. Physiol."},{"key":"B20","doi-asserted-by":"publisher","first-page":"1509","DOI":"10.1080\/17461391.2023.2193953","article-title":"Concurrent validity of the CORE wearable sensor with BodyCap temperature pill to assess core body temperature during an elite women\u2019s field hockey heat training camp","volume":"23","author":"Goods","year":"2023","journal-title":"Eur. J. Sport Sci."},{"key":"B21","doi-asserted-by":"publisher","first-page":"728","DOI":"10.1016\/j.clinbiochem.2006.12.014","article-title":"Error propagation in calculated ratios","volume":"40","author":"Holmes","year":"2007","journal-title":"Clin. Biochem."},{"key":"B22","doi-asserted-by":"publisher","first-page":"1292","DOI":"10.1249\/00005768-199509000-00009","article-title":"Criteria for maximal oxygen uptake: review and commentary","volume":"27","author":"Howley","year":"1995","journal-title":"Med. Sci. Sports Exercise"},{"key":"B23","doi-asserted-by":"publisher","first-page":"131","DOI":"10.1080\/02640414.2025.2567780","article-title":"Durability of physiological and biomechanical variables during a marathon","volume":"44","author":"Hunter","year":"2025","journal-title":"J. Sports Sci."},{"key":"B24","doi-asserted-by":"publisher","first-page":"270","DOI":"10.1123\/ijspp.2018-0935","article-title":"Internal and external training load: 15 years on","volume":"14","author":"Impellizzeri","year":"2019","journal-title":"Int. J. Sports Physiol. Perform."},{"key":"B25","doi-asserted-by":"publisher","first-page":"669","DOI":"10.1016\/j.nut.2004.04.017","article-title":"Carbohydrate intake during exercise and performance","volume":"20","author":"Jeukendrup","year":"2004","journal-title":"Nutrition"},{"key":"B26","doi-asserted-by":"publisher","first-page":"101","DOI":"10.1007\/s40279-017-0690-6","article-title":"Training the gut for athletes","volume":"47","author":"Jeukendrup","year":"2017","journal-title":"Sports Med."},{"key":"B27","doi-asserted-by":"publisher","first-page":"321","DOI":"10.1080\/02640419608727717","article-title":"A 1% treadmill grade most accurately reflects the energetic cost of outdoor running","volume":"14","author":"Jones","year":"1996","journal-title":"J. Sports Sci."},{"key":"B28","doi-asserted-by":"publisher","DOI":"10.3389\/fphys.2022.1059221","article-title":"Running economy and lower extremity stiffness in endurance runners: a systematic review and meta-analysis","volume":"13","author":"Liu","year":"2022","journal-title":"Front. Physiol."},{"key":"B29","doi-asserted-by":"publisher","first-page":"276","DOI":"10.1016\/j.jsams.2012.08.003","article-title":"Effect of stage duration on maximal heart rate and post-exercise blood lactate concentration during incremental treadmill tests","volume":"16","author":"Machado","year":"2013","journal-title":"J. Sci. Med. Sport"},{"key":"B30","doi-asserted-by":"publisher","DOI":"10.3389\/fphys.2023.1128111","article-title":"Durability is improved by both low- and high-intensity endurance training","volume":"14","author":"Matom\u00e4ki","year":"2023","journal-title":"Front. Physiol."},{"key":"B31","doi-asserted-by":"publisher","first-page":"1619","DOI":"10.1007\/s40279-021-01459-0","article-title":"The importance of \u201cdurability\u201d in the physiological profiling of endurance athletes","volume":"51","author":"Maunder","year":"2021","journal-title":"Sports Med."},{"key":"B32","doi-asserted-by":"publisher","first-page":"234","DOI":"10.1080\/1091367X.2022.2161820","article-title":"Validation of Garmin and Polar devices for continuous heart rate monitoring during common training movements in tactical populations","volume":"27","author":"Merrigan","year":"2022","journal-title":"Meas. Phys. Educ. Exerc. Sci."},{"key":"B33","doi-asserted-by":"publisher","first-page":"1340","DOI":"10.1152\/jappl.1992.73.4.1340","article-title":"Influence of graded dehydration on hyperthermia and cardiovascular drift during exercise","volume":"73","author":"Montain","year":"1992","journal-title":"J. Appl. Physiol."},{"key":"B34","doi-asserted-by":"publisher","DOI":"10.3390\/medicina55010014","article-title":"Pacing of women and men in half-marathon and marathon races","volume":"55","author":"Nikolaidis","year":"2019","journal-title":"Medicina"},{"key":"B35","doi-asserted-by":"publisher","first-page":"871","DOI":"10.1152\/japplphysiol.00910.2007","article-title":"Hyperthermia and fatigue","volume":"104","author":"Nybo","year":"2008","journal-title":"J. Appl. Physiol."},{"key":"B36","doi-asserted-by":"publisher","first-page":"1873","DOI":"10.1152\/physrev.00038.2020","article-title":"Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies","volume":"101","author":"P\u00e9riard","year":"2021","journal-title":"Physiol. Rev."},{"key":"B37","doi-asserted-by":"publisher","DOI":"10.3389\/fpsyg.2023.1273451","article-title":"The pacing differences in performance levels of marathon and half-marathon runners","volume":"14","author":"Ristanovi\u0107","year":"2023","journal-title":"Front. Psychol."},{"key":"B38","doi-asserted-by":"publisher","first-page":"S39","DOI":"10.1080\/02640414.2011.614269","article-title":"Fluid and electrolyte needs for training, competition, and recovery","volume":"29","author":"Shirreffs","year":"2011","journal-title":"J. Sports Sci."},{"key":"B39","doi-asserted-by":"publisher","first-page":"1151","DOI":"10.1136\/bjsports-2025-109832","article-title":"Thermoregulation and dehydration in children and youth exercising in extreme heat compared with adults","volume":"59","author":"Smallcombe","year":"2025","journal-title":"Br. J. Sports Med."},{"key":"B40","doi-asserted-by":"publisher","first-page":"2283","DOI":"10.1007\/s40279-022-01680-5","article-title":"Decoupling of internal and external workload during a marathon: An analysis of durability in 82,303 recreational runners","volume":"52","author":"Smyth","year":"2022","journal-title":"Sports Med."},{"key":"B41","doi-asserted-by":"publisher","first-page":"1269","DOI":"10.1007\/s40279-024-01997-3","article-title":"The relationship between running biomechanics and running economy: A systematic review and meta-analysis of observational studies","volume":"54","author":"van Hooren","year":"2024","journal-title":"Sports Med."},{"key":"B42","doi-asserted-by":"publisher","DOI":"10.3390\/s21175932","article-title":"Reliability and validity of the CORE sensor to assess core body temperature during cycling exercise","volume":"21","author":"Vedel","year":"2021","journal-title":"Sensors"},{"key":"B43","doi-asserted-by":"publisher","first-page":"88","DOI":"10.1097\/JES.0b013e31824c43af","article-title":"Cardiovascular drift during heat stress: implications for exercise prescription","volume":"40","author":"Wingo","year":"2012","journal-title":"Exercise Sport Sci. Rev."},{"key":"B44","doi-asserted-by":"publisher","first-page":"551","DOI":"10.1007\/s13410-022-01112-0","article-title":"Evaluation of the performance and usability of a novel continuous glucose monitoring system","volume":"43","author":"Yan","year":"2023","journal-title":"Int. J. Diabetes Developing Countries"},{"key":"B45","doi-asserted-by":"publisher","DOI":"10.3389\/fendo.2025.1536292","article-title":"Clinical performance evaluation of the SiJoy GS1 continuous glucose monitor during oral glucose tolerance testing in healthy adults","volume":"16","author":"Zhao","year":"2025","journal-title":"Front. Endocrinol."}],"container-title":["Frontiers in Physiology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fphys.2026.1807399\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T04:42:54Z","timestamp":1777437774000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fphys.2026.1807399\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4,29]]},"references-count":45,"alternative-id":["10.3389\/fphys.2026.1807399"],"URL":"https:\/\/doi.org\/10.3389\/fphys.2026.1807399","relation":{},"ISSN":["1664-042X"],"issn-type":[{"value":"1664-042X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,29]]},"article-number":"1807399"}}