The ultra-short-term outcomes in performance, aerobic endur-ance, blood-related parameters, and anthropometrics following prolonged low-intensity ski trekking across Spitsbergen: A case study

This study aimed to evaluate changes in endurance capacity, blood-related variables, and anthropometrics following ultra-short-term, prolonged low-intensity ski trekking (LIST). One female (38 years) and one male (52 years) participated in the study in connection with a self-selected ski expedition (hauling ~40-kg sledges each) across Spitsbergen (~126 km), the largest island in Svalbard, Norway. Results revealed that the two moderately aerobically fit participants performed LIST at a mean velocity of ~3.4 km·h-1, corresponding to ~54–63% of maximal heart rate, ~5 hours·day-1, for eight days during this unsupported event. The mean daily energy intake during the expedition was ~7.8 MJ· day-1 (~1 850 kcal·day-1), of which ~49–61%, ~25–36%, and ~14–15% was derived from carbohydrates, fat, and protein, respectively. Body mass, absolute fat mass, and relative fat mass decreased by 2.2%, 10%, and 8%. In the male participant, time to exhaustion increased by 10% and 3.8% during a ~5 min and ~40 min incremental ski trek-simulated treadmill test. The number of leukocytes declined by 30–41%, as did low-density lipoprotein cholesterol levels. Free triiodothyronine level increased by 19% in the female, whereas thyroid-stimulating hormone concentration increased by 23% in the male. In this category of ski trekkers, one can conclude that ultra-short-term, prolonged LIST can cause slimmer body composition without loss of lean mass, improve performance, reduce low-density lipoprotein cholesterol level, and affect metabolic hormones associated with the pituitary-thyroid axis. However, such an event may impair the immune system.