INTRODUCTION: The total mechanical work (W_tot) performed by an athlete has been assessed in several sports but not in roller skating and cross-country skiing. W_tot consists of external (W*_ext) and internal mechanical work (W_int). W*_ext is the work required to move the subject`s center of mass (COM; W_ext) relative to the surroundings, including the work done on the environment (W_env), while W_int is the work required to move the subject`s segments relative to the COM (Saibene et al., 2003). The work done by the subject`s segments (W_seg) is part of W_tot and consists of W_int and W_ext. METHODS: W_tot was evaluated for one subject who roller-skated on an inclined treadmill (5%) for 5 minutes at 10 km/h using the G3 skating technique. In addition to the whole-body kinematics, the ground reaction forces and kinematics of the roller skis and poles were measured. The subject was simplified as 15 linked rigid bodies. The COM and segmental energies were calculated for 5 consecutive cycles. W_ext was calculated by summation of the absolute differences of the total mechanical energy of the COM (TME_com ), while W_seg was calculated by summation of the absolute differences of the total mechanical energy over all the segments (TME_seg). TME_com and TME_seg were calculated as sum of relevant kinetic (KE) and potential energies (PE). W_tot was obtained by summation of W_seg and the work done against friction (W_env) (Hladnik et al., 2016). RESULTS: TME_seg was 5.6% greater than TME_com. The rotational kinetic energy (RKE_seg) was only 0.44% of TME_seg. The translational kinetic energy of the segments (KE_seg) was 3.5% larger than that of the COM (KE_com). W_ext accounted for 61.3%, W_int 30.7% and W_env 8.0% of W_tot over a cycle. CONCLUSION: Under these conditions, the contribution of W_int to W_tot is similar to walking (Cavagna et al., 1977). The RKE_seg was negligible.
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