Find a steep hill run at a good hard pace close to 400 meters walk back down. Repeat this until you have reached RPE-9.
If you don’t run then try a high resistance bike. Bike for 2 min at hard effort, repeat until the same effort becomes an RPE-9 effort. \
What do I mean by RPE-9 effort? Well, try to reproduce the effort with plenty of rest, but once you struggle to hold the same pace then you are done!