Went to the gym yesterday, did a 5k, got off the tm, stretched and my PT told me to get back on and do intervals!
Got back on, started at 13kph and throughout the km went up 0.6kph every 100m! When I reached 1k, slowed down to a jog and kept it slow for 500m and did it all over again until I got to 5k... It was the hardest I've ever run in my life... But worth it!