Mechanical energetics and dynamics of uphill double-poling on roller-skis at different incline-speed combinations

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Date: Feb. 22, 2019
From: PLoS ONE(Vol. 14, Issue 2)
Publisher: Public Library of Science
Document Type: Report
Length: 8,042 words
Lexile Measure: 1520L

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Abstract :

Objectives The purpose of this study was to investigate the effect of different incline-speed combinations, at equal external power outputs, on the mechanics and energetics of the double-poling (DP) technique in cross-country skiing. Methods Fourteen elite male cross-country skiers performed treadmill DP on roller-skis at low, moderate, and high mean external power outputs (P.sub.mean) up a shallow incline (5%, INC5), at which DP is preferred, and up a steep incline (12%, INC12), at which DP is not preferred. Speed was set to produce equal P.sub.mean at both inclines. From recorded kinematics and dynamics, arm power (P.sub.arm) and trunk+leg power (P.sub.T+L) were derived, as were pole propulsion power (P.sub.pole) and body mechanical energy perpendicular to the treadmill surface (E.sub.body[up tack]). Results Over a locomotion cycle, the arms contributed 63% to P.sub.mean at INC5 but surprisingly only 54% at INC12 (P Conclusions The considerable larger amount of negative P.sub.T+L during poling at INC5 than at INC12 indicate that the legs and trunk generate more power than 'necessary' during the swing phase and thus must absorb more energy during the poling phase. This larger surplus of P.sub.T+L at INC5 seems necessary for positioning the body and poles so that high P.sub.arm generation can occur in a short time. At INC12, less P.sub.arm is generated, probably due to less advantageous working conditions for the arms, related to body and pole positioning. These incline differences seem linked to shorter swing and longer poling times during steep uphill DP, which are due to the increased influence of gravity and slower speed at steep inclines.

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Gale Document Number: GALE|A575300507