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. 2025 Apr 28;11(2):e002496.
doi: 10.1136/bmjsem-2025-002496. eCollection 2025.

Is fetal well-being jeopardised during high-intensity interval training?

Emilie Mass Dalhaug  1 , Birgitte Sanda  1   2 , Kari Bø  1   3 , Wendy J Brown  4   5 , Kaia Øvstedal  1 , Sofia Brevik-Persson  1 , Lene A H Haakstad  1
Affiliations

Is fetal well-being jeopardised during high-intensity interval training?

Emilie Mass Dalhaug et al. BMJ Open Sport Exerc Med. .

Abstract

Objectives: To explore the acute effects of high-intensity interval training on fetal heart rate (FHR) and uteroplacental blood flow.

Method: Elite (n=10) and recreational athletes (n=50) participated in an experimental laboratory study involving 5×5 min intervals of high-intensity exercise on both a treadmill and cycle ergometer, with a 4 min pause between intervals for measurement of FHR and uteroplacental blood flow. Target intensity was 17 on Borg's rating of perceived exertion (RPE) scale and 90% of estimated maximal maternal heart rate (MHRmax).

Results: Mean exercise intensity was 16.4 (SD 1.0) RPE and 89.4 (SD 3.8) % of MHRmax during running and 16.0 (SD 1.0) RPE and 84.6 (SD 5.0) % of MHRmax 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 (<100 bpm for >3 min) occurred during running, leading to the termination of exercise. The mothers exercised at 17-18 on Borg's RPE scale and 86.4%-92.6% of MHRmax in these cases. All cases were normalised within 8 min 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 (≥180 bpm for >4 min during rest).

Conclusion: 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.

Keywords: Athlete; Exercise; Pregnancy.

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Conflict of interest statement

None declared.

Figures

Figure 1
Figure 1. A and B: plot of percentage of estimated maximal maternal heart rate (%MHRmax) versus fetal heart rate (FHR) during running (A) and cycling (B). The grey area represents the normal FHR range (110-160 bpm). The large circles show cases of prolonged fetal bradycardia, and the squares show cases of prolonged fetal tachycardia.
See this image and copyright information in PMC

References

    1. Brown WJ, Hayman M, Haakstad LAH, et al. Australian guidelines for physical activity in pregnancy and postpartum. J Sci Med Sport. 2022;25:511–9. doi: 10.1016/j.jsams.2022.03.008. - DOI - PubMed
    1. American College of Obstetricians and Gynecologists Physical Activity and Exercise During Pregnancy and the Postpartum Period. Obstet Gynecol. 2020;135:e178–88. doi: 10.1097/AOG.0000000000003772. - DOI - PubMed
    1. Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54:1451–62. doi: 10.1136/bjsports-2020-102955. - DOI - PMC - PubMed
    1. Hayman M, Brown WJ, Brinson A, et al. Public health guidelines for physical activity during pregnancy from around the world: a scoping review. Br J Sports Med. 2023;57:940–7. doi: 10.1136/bjsports-2022-105777. - DOI - PubMed
    1. Mottola MF, Davenport MH, Ruchat S-M, et al. 2019 Canadian guideline for physical activity throughout pregnancy. Br J Sports Med. 2018;52:1339–46. doi: 10.1136/bjsports-2018-100056. - DOI - PubMed

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