50-40-30-20 and 10 rep rounds of:
Double-unders (1 min of practice and the same amount of singles per round: 50-40-30-20-10)
Sit-ups

Want some tips on how to do Double Unders?

WOD Demo with Dave Castro with GHD sit-ups – video [wmv] [mov]

From the Vault: Chris Spealler WOD Demo – video [wmv] [mov]