{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T05:19:06Z","timestamp":1787548746130,"version":"build-2736575974"},"reference-count":34,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T00:00:00Z","timestamp":1787529600000},"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>Professional Formula racing often requires multiple high-stakes on-track sessions within the same competition day, creating a need to characterize pre-performance physiological state under field constraints. Salivary cortisol is a widely used marker of hypothalamic\u2013pituitary\u2013adrenal axis activity, but field-ready options for its immediate assessment during competition remain limited. Wearable heart-rate monitoring during on-track driving may provide an immediately available field signal reflecting composite cardiovascular load. This multi-season single-case field study examined the within-athlete association between wearable heart-rate data and same-day pre-performance salivary cortisol change in one professional Formula racing driver.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Materials and methods<\/jats:title>\n                    <jats:p>\n                      The primary observational series comprised 23 race-day observations across three competitive seasons. During each morning on-track session, the driver wore a wearable electrocardiogram device, and the peak heart rate (HRpeak) was extracted. Saliva samples were collected approximately 30 and 10\u00a0min before each morning and afternoon session and assayed for cortisol. Within-day cortisol change (\u0394Cortisol) was defined as afternoon minus morning pre-session cortisol, averaged across the two samples. The primary analysis included 18 dry-track observations with complete HRpeak and cortisol data. Five additional observations were examined in an exploratory\n                      <jats:italic>post hoc<\/jats:italic>\n                      analysis.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      In the primary analytical sample, morning HRpeak was positively associated with \u0394Cortisol (\n                      <jats:italic>r<\/jats:italic>\n                      \u00a0=\u00a00.720). The positive direction was retained in sensitivity checks using 5-s and 10-s average heart rates anchored on the HRpeak and addressing serial dependence, season\/session characteristics, and \u221230 min and \u221210 min sample-specific cortisol changes. Including the single wet-track observation reduced the correlation to\n                      <jats:italic>r<\/jats:italic>\n                      \u00a0=\u00a00.316. In the\n                      <jats:italic>post hoc<\/jats:italic>\n                      analysis, standardized \u0394Cortisol residuals were negative for the three planned-timing nap opportunities. No inferential comparison was performed.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Discussion<\/jats:title>\n                    <jats:p>\n                      Wearable on-track HRpeak may provide an immediately available field signal of composite cardiovascular load associated with later same-day endocrine variation in the participating driver. This interpretation is limited to dry-track conditions and does not support the use of HRpeak as a stress-specific marker, prediction method, or decision rule; the association does not establish causality. The\n                      <jats:italic>post hoc<\/jats:italic>\n                      observations provide no evidence regarding nap efficacy. Nevertheless, these descriptive findings may inform future prospective studies.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fphys.2026.1813317","type":"journal-article","created":{"date-parts":[[2026,8,24]],"date-time":"2026-08-24T04:23:35Z","timestamp":1787545415000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Within-athlete association between morning on-track peak heart rate and same-day pre-performance salivary cortisol change under dry-track conditions: a multi-season single-case field study in a professional formula racing driver"],"prefix":"10.3389","volume":"17","author":[{"given":"Seiji","family":"Matsumura","sequence":"first","affiliation":[{"name":"Communication Science Laboratories, NTT, Inc.","place":["Atsugi, Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuuki","family":"Ooishi","sequence":"additional","affiliation":[{"name":"Communication Science Laboratories, NTT, Inc.","place":["Atsugi, Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Makio","family":"Kashino","sequence":"additional","affiliation":[{"name":"Communication Science Laboratories, NTT, Inc.","place":["Atsugi, Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Naoki","family":"Saijo","sequence":"additional","affiliation":[{"name":"Communication Science Laboratories, NTT, Inc.","place":["Atsugi, Japan"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,8,24]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"25","DOI":"10.1016\/j.psyneuen.2017.05.018","article-title":"Diurnal cortisol slopes and mental and physical health outcomes: a systematic review and meta-analysis","volume":"83","author":"Adam","year":"2017","journal-title":"Psychoneuroendocrinology"},{"key":"B2","doi-asserted-by":"publisher","first-page":"8515","DOI":"10.1038\/s41598-023-35717-0","article-title":"Heart rate variability changes with respect to time and exercise intensity during heart-rate-controlled steady-state treadmill running","volume":"13","author":"Brockmann","year":"2023","journal-title":"Sci. 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