4x4

Who it's for

Boulderers with a base already built who need to hold on longer at the end of a hard problem. It's the classic power endurance session for a reason: no equipment, no board, just four problems and a timer.

Common mistakes

• Picking boulders that are too hard. Go 3 or 4 grades below your max, easy enough to climb four times in a row. If you fail the fourth lap of the first boulder, the other three sets are wasted.
• Picking boulders that are too short. Four moves repeated four times isn't power endurance. You want something that takes real time to climb.
• Skimping on the four minutes of rest. The rest is prescribed, not suggested. Cutting it turns a power endurance session into a capacity grind.
• Choosing vertical problems. Overhanging. On slab you'll run out of skin and patience before you run out of forearm.
• Running it as a weekly staple. Two to four weeks, twice a week, then move on.

How to progress

Harder problems, not more sets. Once four sets feel controlled, step up a grade and expect the first week to feel bad again. If you want more out of it, shorten the rest to three minutes before you add a fifth boulder.