Push-off mechanics in speed skating with conventional skates and klapskates

Purpose: Personal and world records in speed skating improved tremendously after the introduction of the klapskate, which allows the foot to plantar f lex at the and of the push-off while the full blade continues to glide on t he ice. The purpose of this study was to gain insight into the differences in skating technique with conventional versus klapskates and to unveil the source of power enhancement using klapskates. Methods: Ten elite speed skat ers skated four 400-m laps at maximal effort with both conventional and kla pskates. On the straight high-speed film, push-off force and EMG data were collected. An inverse dynamics analysis was performed in the moving referen ce plane through hip, knee, and ankle. Results: Skating velocity increased 5% as a result of an increase in mean power output of 25 W when klapskates were used instead of conventional skates. The increase in mean power output was achieved through an 11-J increase in work per stroke and an increase i n stroke frequency from 1.30 to 1.36 strokes.s(-1). The difference in work per stroke occurs during the final 50 ms of the push-off. This is the resul t of the ineffective way in which push-off forces are generated with conven tional skates when the fool rotates about the long front end of the blade. No differences in muscle coordination were observed from EMG. Conclusion: A hinge under the ball of the foot enhances the effectiveness of plantar fle xion during the final 50 ms of the push off with klapskates and increases w ork per stroke and mean power output.