Mechanical Energy and Propulsion in Ergometer Double Poling by Cross-country Skiers

Purpose This study aims to investigate fluctuations in total mechanical energy of the body (E-body) in relation to external ergometer work (W-erg) during the poling and recovery phases of simulated double-poling cross-country skiing. Methods Nine male cross-country skiers (mean SD age, 24 5 yr; mean +/- SD body mass, 81.7 +/- 6.5 kg) performed 4-min submaximal tests at low-intensity, moderate-intensity, and high-intensity levels and a 3-min all-out test on a ski ergometer. Motion capture analysis and load cell recordings were used to measure body kinematics and dynamics. From these, W-erg, E-body (sum of the translational, rotational, and gravitational potential energies of all segments), and their time differentials (power P) were calculated. P(tot)the rate of energy absorption or generation by muscles-tendonswas defined as the sum of P-body and P-erg. ResultsE(body) showed large fluctuations over the movement cycle, decreasing during poling and increasing during the recovery phase. The fluctuation in P-body was almost perfectly out of phase with P-erg. Some muscle-tendon energy absorption was observed at the onset of poling. For the rest of poling and throughout the recovery phase, muscles-tendons generated energy to do W-erg and to increase E-body. Approximately 50% of cycle P-tot occurred during recovery for all intensity levels. Conclusions In double poling, the extensive contribution of the lower extremities and trunk to whole-body muscle-tendon work during recovery facilitates a direct transfer of E-body to W-erg during the poling phase. This observation reveals that double poling involves a unique movement pattern different from most other forms of legged terrestrial locomotion, which are characterized primarily by inverted pendulum or spring-mass types of movement.