Start no lower than 65% and go no higher than 80% of 1rm.
30 Double Unders
10 Toes to Bar
Since there is a :60 rest after every round this is an opportunity to empty the tank a bit more than usual each round. I wouldn't suggest max effort but work at an uncomfortable pace starting in round 1 and see if you can hold your times from one round to the next. You must take the full :60 every round.