Digital phenotyping in transmission constrained, military operational environments

Abstract

Introduction: Stress fracture injuries affect defence forces worldwide. The sudden onset of high-impact exercise, insufficient recovery, and suboptimal conditions (e.g., energy and sleep restriction) elicit injuries in 5 to 10% of military recruits. Women are three times more likely to develop stress fractures than men1, and this risk of injury is projected to increase further in women employed in ground close combat roles2. Oestrogens have two distinct roles in women’s bone biology. 1. Oestrogens influence the size and shape of bone during puberty, promoting endosteal contraction, and resulting in a smaller cross-sectional area than men. A smaller bone size contributes to the increased risk of stress injuries under loading in women. 2. Oestrogens prevent excessive bone resorption by suppressing RANKL expression. Low oestrogen caused by suppression of the hypothalamic-pituitary-ovarian axis—indicated by a loss of menstrual periods—is highly prevalent during arduous exercise3 and demineralises bone. Cessation of menstrual periods, amenorrhoea, is a risk factor for stress fracture injury4. Ovulation is a key event in the menstrual cycle, preceded by a peak in oestrogen concentration, and followed by increased progesterone concentration. Anovulatory cycles are characterised by low, non-cyclical oestrogen and progesterone. Ovulation is a sign of menstrual health and informs women of their reproductive hormonal status. Non-invasive, innovative methods of detecting ovulation are disrupted approaches to mitigating injury risk in women. Methods: This presentation will provide an overview of the epidemiology of stress fracture injuries in military personnel, reporting the prevalence and patterns of injuries observed during basic military training. The role of the sex steroid hormones on bone health will be described, and the utility of wearables to detect ovulation appraised. Primary evidence will be obtained from open-source, peer-reviewed literature, and wearable data will be drawn from both published studies and preliminary data from the British Army’s EMPOWER study. Conclusions: A high proportion of women experience menstrual disturbances during arduous training and suffer a high incidence of stress fractures. The validity of wearable technology for women to detect ovulation during arduous military training, characterised by high physical demands, stress, and restricted energy and sleep, is under investigation. Acknowledgements: This work was funded by the British Army. References 1O’Leary TJ, Wardle SL, Rawcliff AJ, et al. Understanding the musculoskeletal injury risk of women in combat: the effect of infantry training and sex on musculoskeletal injury incidence during British Army basic training. BMJ Mil Health. 2020; 0:1-5. https://doi.org/10.1136/jramc-2019-001347 2Ministry of Defence. Women in Ground Close Combat Roles - Interim Health Report 2016. Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/536381/20160706_ADR006101_Report_Women_in_Combat_WEB-FINAL.PDF Accessed 31 Aug 2021. 3Gifford RM, O’Leary TJ, Wardle SL, et al. Reproductive and metabolic adaptation to multistressor training in women. Am J Physiol Endoc-M 2021; 321(2):E281-E291. https://doi.org/10.1152/ajpendo.00019.2021 4Ackerman KE, Sokoloff NC, Maffazioli GDN, et al. Fractures in relation to menstrual status and bone parameters in young athletes. Med Sci Sports Exerc 2015; 47(8):1577-1586. https://doi.org/10.1249/MSS.0000000000000574