A) 1 mile warm up (if completing within 30 minutes of a regular training session, only do 800m).
B) 5 x 400m run, rest 1:1
C) 800m cool down jog
400s are sprints, time each sprint. Time for each should be :15 faster per mile (:04 faster per 400) than 5k PR pace. Rest as long as the most recent 400 took. (if your 1st 400 was 1:32, rest 1:32; if 2nd 400 was 1:20, 2nd rest is 1:20…)