Prevalence of Indicators of Low Energy Availability in Elite Female Sprinters Jennifer Sygo Athletics Canada Alexandra M. Coates University of Guelph Erik Sesbreno Canadian Sport Institute Ontario Margo L. Mountjoy Fédération Internationale de Natation (FINA) and McMaster University Jamie F. Burr University of Guelph Low energy availability (LEA), and subsequent relative energy deficiency in sport, has been observed in endurance, aesthetic, and team sport athletes, with limited data on prevalence in athletes in short-burst activities such as sprinting. We examined prevalence of signs and symptoms of LEA in elite female sprinters at the start of the training season (PRE), and at the end of a 5-month indoor training period (POST). Four of 13 female sprinters (31%) presented at PRE testing with at least one primary (amenorrhea, low bone mineral density, low follicle-stimulating hormone, luteinizing hormone, or estradiol, resting metabolic rate ≤29 kcal/kg fat-free mass, Low Energy Availability in Females Questionnaire score ≥8) and one secondary indicator of LEA (fasting blood glucose <4 mmol/L, free triiodothyronine <3.5 pmol/L, ferritin <25 μg/L, low-density lipoprotein cholesterol > 3.0 mmol/L, fasting insulin <20 pmol/L, low insulin-like growth factor-1, systolic blood pressure <90 mmHg, and/or diastolic blood pressure <60 mmHg). At POST, seven out of 13 athletes (54%) presented with at least one primary and one secondary indicator of LEA, three of whom had also presented with indicators of LEA at PRE. Five out of 13 (39%) athletes had previous stress fracture history, though this was not associated with current indicators of LEA (PRE: r = .52, p = .07; POST: r = -.07, p = .82). In conclusion, elite female sprinters may present with signs and symptoms of LEA, even after off-season rest. Medical and coaching staff should be aware of the signs and symptoms of LEA and relative energy deficiency in sport and should include appropriate screening and intervention strategies when working with sprinters. Keywords: amenorrhea, bone density, RED-S, sprint athletes Relative energy deficiency in sport (RED-S) is a term used to describe the wide-ranging physiological, health, and performance- related effects associated with inadequate energy intake in athletes or active individuals (Mountjoy et al., 2014). RED-S is a syndrome that can affect numerous body systems, including, but not limited to, the endocrine, cardiovascular, immune, and gastrointestinal systems, as well as menstrual function and bone health. The underlying cause of RED-S is low energy availability (LEA), defined as the amount of energy relative to fat-free mass remaining for physiological functioning after accounting for the energy expenditure of exercise (Mountjoy et al., 2014). LEA may occur with or without disordered eating or an eating disorder. Acute and prolonged LEA has been shown to disrupt the pulsatility of hypothalamic-pituitary axis hormones, including luteinizing hormone (LH) and triiodothyronine, and is associated with menstrual dysfunction and secondary functional hypotha- lamic amenorrhea in women (Loucks & Thuma, 2003; Nattiv et al., 2007). LEA suppresses other hormones and substrates, including insulin, insulin-like growth factor-1 (IGF-1), glucose, growth hormone, and leptin, and can lead to an increase in cortisol and ghrelin (Hulmi et al., 2017; Loucks, 2007; Loucks & Thuma, 2003; Thong et al., 2000). Low energy availability contributes to reduced bone density and an increased risk of stress fracture and osteoporosis (Keen & Drinkwater, 1997; Lambrinoudaki & Papadimitriou, 2010; Rauh et al., 2006; Wentz et al., 2012), even independent of the effect of Sygo is with Athletics Canada, Ottawa, Ontario, Canada. Coates and Burr are with Human Performance & Health Research Laboratory, University of Guelph, Guelph, Ontario, Canada. Sesbreno is with Canadian Sport Institute Ontario, Toronto, Ontario, Canada. Mountjoy is with Fédération Internationale de Natation (FINA), Lausanne, Switzerland; and the Dept. of Family Medicine, McMaster University, Hamilton, Ontario, Canada. Address author correspondence to Margo L. Mountjoy at mmsportdoc@mcmaster.ca. 490 International Journal of Sport Nutrition and Exercise Metabolism, 2018, 28, 490-496 https://doi.org/10.1123/ijsnem.2017-0397 © 2018 Human Kinetics, Inc. ORIGINAL RESEARCH