Ski mountaineering (SkiMo) is a new Olympic sport with extreme endurance demands and altitude exposure. Previous studies have focused on traditional cardiorespiratory variables, such as maximal oxygen consumption (Vo2max) or ventilatory thresholds, but, to our knowledge, did not report haemoglobin mass (Hbmass). The aim of this study was to investigate the relationship between Hbmass and Vo2max in elite SkiMo athletes and compare physiological differences across performance levels. Twenty-nine Swiss national team SkiMo athletes (10 females and 19 males) were classified into Tier 3-5. Participants performed a treadmill graded exercise test (25% slope) to determine Vo2max and ventilatory thresholds. The Hbmass and blood volumes were assessed using a CO-rebreathing technique. Sex and tier-based comparisons were made, and correlations between haematological parameters and aerobic performance metrics were analysed. The Hbmass normalized to body mass (HbmassBM) was significantly correlated with Vo2max in the pooled group (r = 0.80, P < 0.001), females (r = 0.82, P = 0.007) and males (r = 0.53, P = 0.024). The Hbmass and related haematological parameters were significantly higher in males (P < 0.05). Males in Tier 5 had higher oxygen consumption at the second ventilatory threshold (63.0 ± 4.3 vs. 58.9 ± 2.8 mL min-1 kg-1; P = 0.022) and Vo2max (72.0 ± 4.4 vs. 67.4 ± 3.1 mL min-1 kg-1; P = 0.015) than those in Tier 3-4. The significant correlation between HbmassBM and Vo2max confirms the key role of Hbmass in oxygen transport and aerobic capacity. However, Tier 5 athletes achieved superior aerobic performance without higher HbmassBM, indicating that additional physiological factors underpin elite-level performance. Highlights - What is the central question of this study? What is the relationship between haemoglobin mass and maximal oxygen consumption or performance metrics in male and female elite ski mountaineers? Data were previously lacking on athletes who train and compete at altitude. We questioned whether haemoglobin mass is higher in this population compared with other elite endurance athletes. - What is the main finding and its importance? Values of haemoglobin mass in ski mountaineers were consistent with those in other endurance athletes. Significant correlations between relative haemoglobin mass and maximal oxygen consumption were observed. Overall, this study confirms haemoglobin mass as a key determinant of aerobic performance in ski mountaineers, highlighting its relevance in this altitude-based sport.
© Copyright 2026 Experimental Physiology. The Physiological Society. All rights reserved.