Day 31 adds the third set: 6 minutes running, 2 minutes walking, 3 sets in total. Twenty-four minutes, 18 of them running. That is more running than any three-set session so far, in three even pieces.
Eighteen minutes of running across three sets is the week's volume day. The 2-minute walks provide real recovery, so each run should start close to fresh, but the third set will tell you whether your pace was sustainable - it always does. Holding three identical 6-minute runs is a bigger pacing challenge than holding three 4-minute ones, simply because there is more time for a pace to prove itself wrong. Run each piece at the effort you would use for a long continuous run, not faster.
Start easy, settle fast, hold steady. Keep the upper body tall and relaxed, the elbows bent and swinging straight, and the feet landing lightly under the hips. Walk the 2 minutes briskly with deep breathing, and begin each run promptly.
Eighteen minutes of running - three pieces, one pace, no surprises.
Make it Harder: Push the third set noticeably faster than the first two and finish with a strong last minute.
Make it Easier: Split the third 6-minute run into 3 running, 1 walking, 2 running, and take the walks as written.
