Effects of slight ski boot weight variations on ski mountaineering energy cost and mechanical work at race intensity

Purpose Uphill ski mountaineering performance appears to be related to metabolic cost of locomotion and skiers' weight. The present study aimed to evaluate the effects of slight variations in equipment weight on metabolic and mechanical work (MW) of ski mountaineering, at race pace. Methods Thirteen male ski mountaineers were asked to ski on a treadmill at 25% slope and 80% of their maximal aerobic speed. They completed four 5-min bouts with additional weights of 0 kg (control), 0.2 kg, 0.4 kg, and 0.6 kg added to each ski boot in a blind mode and random order. Ski mountaineering energy cost (EC) was determined by gas exchange measurements, while MW was determined from the changes in the mechanical energy of body centre of mass (COM), body segments and equipment. Results EC and total MW were significantly (all p < 0.001) and largely (eta(2) = 0.712 and eta(2) = 0.704, respectively) increased for every 0.2 kg of mass added, by around 2% and 1%, respectively. The increase in the MW was related to a significant increase in the work needed to lift the weight against gravity and to the increased work done to move the segments of the lower body with respect to COM. Conclusion The present investigation shows that even small increments in racing gear weight are associated with an increase in ski mountaineering EC, possibly leading to a consequent decreased performance on uphill terrains.