Find a hill (stay local, we don’t want to all meet on our favourite hill) that will take 40/50s to run up. The session is to run hard uphill then jog back down to recover (walk if necessary). Repeat 10 times. You should be sufficiently recovered when you reach the bottom of the hill to accelerate back up. Aim to keep all of your uphill efforts at a consistent pace, ie don’t blast the first few then really struggle by no 10.
These short fast hills will help to develop strength and power. Focus on a tall, strong posture and powerful arm drive.
This can either be incorporated into a longer run (make sure you keep the rest of the run nice and easy) or as one of your 5K runs this week. If the latter, I suggest an easy 10 min warm up run to your hill of choice, do the session then a nice easy pace run home.
Don’t forget to stretch!