Within-day energy balance and symptoms of Relative Energy Deficiency in Sport (RED-S) in recreational female athletes

Moore, Helen (2024) Within-day energy balance and symptoms of Relative Energy Deficiency in Sport (RED-S) in recreational female athletes. Masters by Research thesis (MSc), Manchester Metropolitan University.

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Abstract

Relative Energy Deficiency in Sport (RED-S) is a syndrome whereby low energy availability (EA) causes downregulation of physiological processes, resulting in health and performance consequences. Energy availability is normally calculated over 24-hours, however this may conceal energy deficient periods in the day. The present study combined questionnaire, lab, and field-based measures to assess low EA prevalence and to establish whether within-day energy balance (WDEB) was associated with RED-S symptoms in recreationally active (4-6 hours per week moderate-vigorous physical activity), premenopausal women. Seven-day food and training diaries alongside accelerometry and heart rate were used to estimate 24-hour energy availability and hourly WDEB. The largest within-day energy surplus and deficit, the number of hours spent in a surplus and deficit, and the maximum number of consecutive hours in each, were calculated daily and averaged across the 7-days. Body composition, quantitative ultrasound of bone, hematocrit, hemoglobin, total cholesterol, maximum voluntary contraction of the knee during flexion and extension, VO2peak and lactate profile were all assessed. Questionnaires assessed menstrual function, psychological, immunological, and gastrointestinal health, disordered eating, and injury history. Of the 16 participants (mean ±SD; age = 27 ±6 yrs., height = 1.67.0 ±0.05 m, mass = 63.5 ±8.2 kg), 88% did not have adequate energy availability (< 45 kcal∙kg-1FFM∙day-1¬). Low energy availability (< 30 kcal∙kg-1FFM∙day-1¬) was seen in 13% of participants, and 75% had subclinical energy availability (30-45 kcal∙kg-1FFM∙day-1¬), typically associated with weight loss. Correlational analysis between WDEB and RED-S symptoms was done accounting for 24-hour energy availability. Menstrual health was negatively correlated with mean largest energy surplus (p = 0.022). Body fat percentage was positively correlated with total time (p = 0.048), time per day (p = 0.003) and consecutive hours per day (p = 0.020), spent in an energy deficit. Relative muscle strength variables were positively correlated to within-day energy surplus variables (p = 0.008-0.050). Bone health at the radius and tibia were positively correlated with energy surplus variables (p = 0.004-0.013). In conclusion, 24-hour low EA is not highly prevalent in recreationally active women, but WDEB may have health and performance implications that are overlooked when assessing low EA alone.