{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T13:48:19Z","timestamp":1790948899562,"version":"4.1.0"},"reference-count":34,"publisher":"BMJ","issue":"2","license":[{"start":{"date-parts":[[2025,4,28]],"date-time":"2025-04-28T00:00:00Z","timestamp":1745798400000},"content-version":"unspecified","delay-in-days":27,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100008568","name":"Norwegian Women\u2019s Public Health Association","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100008568","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open Sport Exerc Med"],"accepted":{"date-parts":[[2025,4,3]]},"published-print":{"date-parts":[[2025,4]]},"abstract":"<jats:sec>\n                  <jats:title>Objectives<\/jats:title>\n                  <jats:p>To explore the acute effects of high-intensity interval training on fetal heart rate (FHR) and uteroplacental blood flow.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Method<\/jats:title>\n                  <jats:p>Elite (n=10) and recreational athletes (n=50) participated in an experimental laboratory study involving 5\u00d75\u2009min intervals of high-intensity exercise on both a treadmill and cycle ergometer, with a 4\u2009min pause between intervals for measurement of FHR and uteroplacental blood flow. Target intensity was 17 on Borg\u2019s rating of perceived exertion (RPE) scale and 90% of estimated maximal maternal heart rate (MHR<jats:sub>max<\/jats:sub>).<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>Mean exercise intensity was 16.4 (SD 1.0) RPE and 89.4 (SD 3.8) % of MHR<jats:sub>max<\/jats:sub> during running and 16.0 (SD 1.0) RPE and 84.6 (SD 5.0) % of MHR<jats:sub>max<\/jats:sub> during cycling. Mean FHR was 140.9 (SD 27.4) beats per minute (bpm) during pauses between running bouts and 148.9 (SD 16.0) bpm during pauses between cycling bouts. Six cases of prolonged fetal bradycardia (&lt;100\u2009bpm for &gt;3\u2009min) occurred during running, leading to the termination of exercise. The mothers exercised at 17\u201318 on Borg\u2019s RPE scale and 86.4%\u201392.6% of MHR<jats:sub>max<\/jats:sub> in these cases. All cases were normalised within 8\u2009min of ending the protocol. There were no cases of prolonged fetal bradycardia during cycling. Exercise was terminated for three women during running and two women during cycling due to fetal tachycardia (\u2265180\u2009bpm for &gt;4\u2009min during rest).<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Conclusion<\/jats:title>\n                  <jats:p>Despite cases of fetal bradycardia and tachycardia, our results indicate that highly active women can engage in multiple intervals of high-intensity interval training without apparent harm to fetal well-being.<\/jats:p>\n               <\/jats:sec>","DOI":"10.1136\/bmjsem-2025-002496","type":"journal-article","created":{"date-parts":[[2025,4,28]],"date-time":"2025-04-28T20:00:13Z","timestamp":1745870413000},"page":"e002496","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":8,"title":["Is fetal well-being jeopardised during high-intensity interval 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