Pole Length Influences Performance During On-Snow Skating in Female Cross-Country Skiers

Purpose The purpose of this study was to examine the effect of pole length on performance and technique selection during a simulated skating cross-country(XC)skiing competition on snow in female XC skiers.Methods Nine female XC skiers and biathletes(VO2max 63.6±6.2 mL/min/kg,age 22.9±3.5 years,body height 1.69±0.1 m and body mass 60.8±4.6 kg)completed two 5-km skating time-trail with maximal effort.The athletes had a minimum 4.5 h of rest between the two races,which were performed in a random order:one with self-selected poles(89.0%±0.6%of body height)and one with 7.5 cm increased pole length(94.0%±0.5%of body height).Speed in set terrain sections was determined and the selection of sub-technique was self-reported immediately after each race based on a detailed review of the entire track.Results Skiers performed on average 7.1±7.1 s(P=0.029)faster with the long poles,with this difference occurring during the first 200 m and in the uphill parts of the track,in which~5% more G3 and~5% fewer G2 sub-techniques were chosen(both P<0.05).The rating of perceived exertion was 1±0.9 point lower(P=0.04)and skiing technique was perceived to be~1.2±1.5 points better with long poles(P=0.038),while the physiological responses(i.e.,peak and average heart rate,and blood lactate concentration)did not differ between trials.Conclusion In conclusion,poles 7.5 cm longer than self-selected ones improved performance in skating,by enhancing speed in the initial phase(first 200 m)and in the uphill section of the track.In addition,the longer poles induced more use of the G3 skating sub-technique.

Force Generation Profiles of Para-Nordic Sit-Skiers Representing Different Physical Impairments

Purpose To biomechanically profile force generation connected to the complex role of the trunk in double poling in a rep-resentative sample of Para-Nordic sit-skiers.Methods Twelve male World Cup Para-Nordic sit-skiers(sport classes:LW10-12)were skiing on flat snow terrain at submaximal speed of 4.5 m/s(~73% max imum speed).2D video(50 Hz)and pole force analyses(1000 Hz)were performed synchronously,examining angle,force and cycle characteristics to analyse the role of the trunk in generating propulsion.Results LW10-11.5 skiers lost between 21%and 4%propulsive force versus LW12 athletes only due to different geomet-rics of the trunk and pole angle at an equal axial pole force.While LW10-11 skiers indicated trunk extension or position maintenance during pole thrust,LW11.5-12 skiers showed strong trunk flexion combined with smaller pole angles to the ground.Hence,LW11.5-12 skiers could create larger propulsive forces and therefore greater cycle lengths at lower cycle rates at the same speed.Maximum speed increased from LW10 to LW12 and was significantly correlated to trunk flexion range of motion(r=0.63)and cycle length(r=0.59).Trunk flexion ROM showed a significant relationship to the impulse of propulsive force(r=0.63)and pole angle to the ground(r=−0.76)(all P<0.05).Conclusion The impact of impairment on the force production profiles and its physiological-biomechanical consequences need further investigation also in other terrains and at wider spectrums of skiing speeds.The evident problem of low numbers of LW10-11 skiers in World Cup needs creative future solutions for research.