Energy Balance and Energy Availability during a Selection Course for Belgian Paratroopers

Introduction: Adequate energy supply is a prerequisite for optimal performances and recovery. The aims of the present study were to estimate energy balance and energy availability during a selection course for Belgian paratroopers. Methods: Energy expenditure by physical activity was measured with accelerometer (ActiGraph GT3X+, ActiGraph LLC, Pensacola, FL, USA) and rest metabolic rate in Cal.d-1 with Tinsley et al.'s equation based on fat-free mass = 25.9 × fat-free mass in kg + 284. Participants had only access to the French individual combat rations of 3,600 Cal.d-1, and body fat mass was measured with quadripolar impedance (Omron BF508, Omron, Osaka, Japan). Energy availability was calculated by the formula: ([energy intake in foods and beverages] - [energy expenditure physical activity])/kg FFM-1.d-1, with FFM = fat-free mass. Results: Mean (SD) age of the 35 participants was 25.1 (4.18) years, and mean (SD) percentage fat mass was 12.0% (3.82). Mean (SD) total energy expenditure, i.e., the sum of rest metabolic rate, dietary-induced thermogenesis, and physical activity, was 5,262 Cal.d-1 (621.2), with percentile 25 at 4,791 Cal.d-1 and percentile 75 at 5,647 Cal.d-1, a difference of 856 Cal.d-1. Mean daily energy intake was 3,600 Cal.d-1, giving a negative energy balance of 1,662 (621.2) Cal.d-1. Mean energy availability was 9.3 Cal.kg FFM-1.d-1. Eleven of the 35 participants performed with a negative energy balance of 2,000 Cal.d-1, and only five participants out of 35 participants performed at a less than 1,000 Cal.d-1 negative energy balance level. Conclusions: Energy intake is not optimal as indicated by the negative energy balance and the low energy availability, which means that the participants to this selection course had to perform in suboptimal conditions.