clap skate

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A speed skate that has a blade attached by a hinge at the heel, allowing one to skate more efficiently by keeping the full length of the blade on the ice while the heel is raised.

Wiktionary

1. n. sports, longtrack speedskating a type of speedskate used in longtrack speedskating, where the skate blade is hinged at the front pillar to the skate boot, with the heel pillar being free, and kept in place by a spring mechanism.