Contemplate the coordination and high-kicking ability of the Rockettes combined with some old-school Ice Capades nostalgia and you’ll get an idea of what synchronized skating is about. Synchronized what? Yes skating. Think swimming, but at warp speed and with blades flying precariously close to faces during the numerous spins and lifts. The Lexington, Mass.-based Haydenettes are the nation’s premier synchro team and will be facing off against 19 other crews from 15 countries at the ISU World Synchronized Skating Championships at Boston University on April 5-6. A team is comprised of 16 skaters performing a 2-minute, 50-second short program and a 4:30 free skate to determine the winner. The Haydenettes, who have won 21 national championships and three consecutive world bronze medals, are opening with choreography set to Jay-Z’s “Run This Town.” On April 6, they just might.