Does the application of ground force set the energetic cost of cross-country skiing?.
We tested whether the rate at which force is applied to the ground sets metabolic rates during classical-style roller skiing in four ways: 1) by increasing speed (2.5 to 4.5 ) during skiing with arms only, 2) increasing speed (2.5 to 4.5 ) during skiing with legs only, 3) changing stride rate (25 to 75 ) at each of three speeds (3.0, 3.5 and 4.0 ) during skiing with legs only, and (4) skiing with arms and legs together at three speeds (2.0 to 3.2, 1.5_ incline). We determined net metabolic rates () from rates of oxygen consumption (gross – standing ) and rates of force application from the inverse period of pole-ground contact (1/tparms) for the arms and the inverse period of propulsion (1/tplegs) for the legs. During both arm and leg skiing at different speeds, metabolic rates changed in direct proportion to rates of force application, while the net ground force to counteract friction and gravity () was constant. Consequently, metabolic rates were described by a simple equation () wit
