Purpose: To compare gross efficiency (GE) before versus after a simulated cross-country skate-skiing race and investigate the association between changes in GE and in kinematic variables. Methods: GE and kinematic variables were measured during submaximal roller ski skating at a standardized speed-incline combination directly before and after a simulated race (~39 min). GE was calculated from power output and respiratory data, while kinematic variables were obtained using 3D kinematics. The roller-ski-skating race simulation consisted of 3 virtual laps, with each lap (virtual distance: 3.4 km) including flat (2%), uphill (5%, 7%, and 12%), and simulated downhill sections. The race concluded with a final section of 1000 m on a 7% incline. Results: GE declined by 0.6% points throughout the race (before: 15.6% [1.0%]; after: 15.0% [1.0%]; P < .001). The drop in GE coincided with an increase in cycle rate, larger ski edging and orientation angles, and a decline in push-off velocity and ski and pole ground-contact times (P < .05). None of the changes in kinematic variables were associated with the change in GE (P > .05). Conclusions: GE in skating cross-country skiing deteriorates following a simulated roller-ski-skating race on undulating terrain. Although kinematic variables changed, no significant association with the change in GE was found.
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