A Case Study of the Short-Term Development of Body Composition and Substrate Utilization Following Prolonged Low-Intensity Ski Trekking with Inadequate Energy Intake in Svalbard

This case study aimed to examine the short-term development of body composition and substrate utilization (i.e., contribution of fat and carbohydrates to energy supply) following prolonged low-intensity ski trekking (LIST) with inadequate energy intake in an Arctic region. For 23 days, two highly aerobically fit, male recreational athletes (24 and 26 years) performed similar to 2 - 11 hours of LIST each day, while pulling supply sledges (initially similar to 80 kg) across the length of Svalbard's largest island, Spitsbergen (similar to 640 km). We estimated body composition using bioelectrical impedance analysis (BIA). For evaluation of substrate utilization, we analyzed pulmonary respiratory gas-exchange ratio (RER) using an ergospirometry system during treadmill trekking (ski trekking simulation). Results indicated that the energy intake of each participant during this unsupported expedition was similar to 21.4 MJ center dot day(-1) (similar to 5107 kcal center dot day(-1)), of which similar to 33% (similar to 5.0 g center dot kg(-1)center dot day(-1)), similar to 51% (similar to 3.4 g center dot kg(-1)center dot day(-1)), and similar to 16% (similar to 2.4 g center dot kg(-1)center dot day(-1)) came from carbohydrates, fat, and proteins, respectively. Body mass decreased by 7.2 kg (8.4%) in Subject A, and 4.4 kg (5.2%) in Subject B. Absolute fat mass decreased by 5.4 kg (37%) and 4.7 kg (30%) in Subject A and Subject B, respectively, whereas the changes in fat-free mass (-1.8 kg in Subject A, and +0.3 kg in Subject B) were within the random measurement error of the BIA analyser. Changes in RER in Subject A (-0.01 to -0.02 units) were within the random measurement error, whereas the RER data in Subject B were not interpretable due to excessive fluctuations in ventilatory equivalent for oxygen. In conclusion, this study indicates that short-term, prolonged LIST, performed with an energy deficit corresponding to a weight loss of similar to 2 kg center dot week-1, can lead to leaner body composition without notable changes in fat-free mass in well-trained, male recreational athletes. Furthermore, substrate utilization does not appear to be affected by short-term, prolonged LIST in this subgroup of athletes.