Molecular vital signs: wearable technologies for the real-time measurement of molecular markers of health and human performance

Abstract

Introduction: Warfighters operate in complex and chaotic multi-stressor environments. Soldier interface with the external world on the battlefield impacts health and performance and is reflected through changes in internal physiology. Previous studies of operational stress using either cross-sectional or repeated measures designs have demonstrated substantial alterations in physiology including heightened hypothalamic-pituitary-adrenal axis (HPA) arousal, suppressed function of hypogonadal (HPG) and hypothalamic-pituitary-thyroid (HPT) axes, and increased immune system activation1. Responses of these systems are monitored and measured via biological analytes including, but not limited to, epinephrine, norepinephrine, adrenocorticotrophic hormone, cortisol, insulin-like growth factor-I, testosterone, thyroid hormones, and inflammatory cytokines2. However, interpretation of these results is complicated by pre-analytical factors such as collection timing, sample processing, nutrient intake, and hydration status. Therefore, we propose the implementation of continuous or real-time monitoring of biological fluids (e.g., saliva, blood, sweat) for actionable information regarding hydration, muscle status, inflammation, injury risk, and metabolic health that can be used for individualized recommendations and performance optimization. Application platforms and monitoring technologies for active and passive data collection have evolved to the point where holistic surveillance is becoming feasible. For example, continuous monitoring of hormones related to systemic anabolic/catabolic balance and inflammation can help enhance physical performance and minimize overtraining, respectively3,4. Future directions: Real-time, high-fidelity tracking of biomarkers across multiple biocompartments for the purposes of enhancing health, performance, and career longevity is a next critical step for optimizing soldier readiness, lethality, and survivability in combat. Future technologies will likely enable a wider range and more precise tracking of systemic signalling (e.g., multi-omics), leading to actionable information, at the individual level, for military leaders to use in training and combat. Soldier self-report input, however, will likely remain an important aspect for guiding practices. Real-time tracking may also reorient our perception of what is deemed most physiologically relevant for monitoring soldier performance. References 1Henning PC, Park B-S, Kim J-S. Physiological decrements during sustained military operational stress. Mil Med 2011; 176:991-997. https://doi.org/10.7205/MILMED-D-11-00053 2Lee EC, Fragala MS, Kavouras SA, et al. Biomarkers in sports and exercise: tracking health, performance, and recovery in athletes. J Strength Cond Res 2017; 31:2920-2937. https://doi.org/10.1519/JSC.0000000000002122 3Kraemer WJ, Ratamess NA, Nindl BC. Recovery responses of testosterone, growth hormone, and IGF-1 after resistance exercise. J App Physiol 2017; 122:549-558. https://doi.org/10.1152/japplphysiol.00599.2016 4Smith LL. Cytokine hypothesis of overtraining: a physiological adaptation to excessive stress? Med Sci Sports Exerc 2000; 32:317-331.