Exercise Breathing Reserve in Cross-Country Skiers: Ventilatory Capacity vs. Ventilatory Demand

Breathing reserve (BR), defined as the difference between ventilatory capacity and ventilatory demand during exercise, is an indicator of respiratory limitations. However, it is unclear which of the two factors has the greatest impact on BR in cross-country skiers during cardiopulmonary exercise testing on a bicycle ergometer (CPET). The purpose of this study is to investigate how ventilatory capacity and ventilatory demand influence BR during CPET in highly-trained cross-country skiers. Materials and methods. Current members of the Komi Republic national cross-country skiing team (n = 46; aged 22.6 ± 4.7) underwent spirometry and CPET at the beginning of the preparatory training period. BR was calculated at rest and during CPET – at the anaerobic threshold and at peak exercise. The athletes were divided into two groups with low BR (≤20%) and normal BR (>20%) at peak exercise. Results. The two groups showed no lung function differences. However, at peak exercise, the low BR group demonstrated statistically significant higher breathing frequency, minute ventilation, ventilatory equivalent for carbon dioxide, respiratory exchange ratio, and lower end-tidal carbon dioxide partial pressure. BR directly correlated with forced vital capacity, forced expiratory volume in the first second and the Tiffeneau index at peak exercise. BR demonstrated an inverse correlation with breathing frequency and minute ventilation throughout the test, as well as with oxygen consumption (except at peak exercise). Thus, in cross-country skiers, exercise intensity significantly influences the relationship between ventilatory capacity and BR, while the relationship between ventilatory demand and BR remains constant. Importantly, low BR at peak exercise, even with comparable exercise capacity in the groups of skiers, is associated with increased ventilatory demand.