kettlebell swings (2 pood / 1.5 pood)
AbMat butterfly situps
AbMat back extensions / Supermans*
Results: 7:29 Rx
After doing the set of 21 swings unbroken, I was really surprised by how much harder the second set of swings felt after the back extensions.
* The AbMat peeps call it an "erector crunch". We did what is demonstrated in this video, except we raised the feet too, the same as a Superman. These were very effective, plus more comfortable than doing Supermans flat on the floor -- they usually make my hip bones dig into the ground, not pleasant.