Day 6: 

In one hour, max reps push-ups and sit-ups. Every time you break from a set of push-ups and sit-ups, that’s at failure, complete 400m Run. You can alternate push-ups and sit-ups. 

E.g., I complete 80 push-ups and then 100x Sit-ups; next, I run 400m. When I complete the run, I get 40-push-ups and 80-sit ups: run 400m. Eventually your sets will get drastically smaller and you’ll be running more.