Off to bed late, so I'll get down the details of today (Saturday)'s exercise.
Phase 1 people (most of us including me):
10 Minute warm up
Run fast 30 secs, rest 2 minutes. 5 times.
10 minute warm down.
Phase 2 people:
10-15 minute warm-up
Run fast for 1 minute, run slowly for 1 minute, run fast for 1 minute, run slowly for 1 minute. Continue for ten minutes.
10 minute cool down
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Warming up and cooling down means doing a few stretches, and shambling about a bit, waving your arms and legs around to serve notice to your body it's about to do work, or can calm down.
Don't let the short length of today's exercise fool you. If you reallly push the speed on the running it will still leave you warmed through. It's the transitions which will get you.