Day 19 is the third climbers-and-planks day, and the holds reach 20 seconds. Part 1 is 30 seconds of climbers, 30 seconds of rest, 5 times. Part 2 is the six-position sequence - elbow plank, side plank each side with the top hand on the hip, elbow plank with each leg lifted in turn, elbow plank - each held for 20 seconds, one pass, no rest between poses. Two full minutes of holding.
From 10 seconds on Day 3 to 15 on Day 11 to 20 today, the sequence has doubled its length without changing a single shape. At 20 seconds a pose, the sixth position stops being a formality: by the time you reach the closing elbow plank, the shoulders have been loaded for 100 seconds and the core has not had a break. That is deliberate - the last plank is where the sequence finds out how much stability you have left. The climbers in Part 1 warm everything up and, by tiring the shoulders early, make the holds count for more.
In the elbow planks, keep the neck long and the eyes on the floor, forearms parallel, elbows under shoulders. In the side planks, keep the top hand on the hip and the hips high; if you feel the shoulder giving out before the core does, check that it is stacked over the elbow. In the single-leg planks, the lifted leg stays straight and low, and the hips stay square. On climbers, drive the knees in fast and keep the hips level with the shoulders.
Two minutes of holds, and the last 20 seconds are the ones the whole sequence was built for.
Make it Harder: Add a second pass through all six poses after a 30-second rest.
Make it Easier: Take the side planks from the knees and keep every other pose as written.
