Russell said before that the best thing to do is find a decent hill and go up and down it 8 times, keeping a constant pace for each repeat. I think the same applies to running. Easier said than done when it’s cold and dark though. Or is hopping on a turbo better?
Wiggo said in his book that he extended a 450 watt effort from 2 minutes to nearly an hour using a turbo trainer in his shed. If anyone wants the book, let me know as I was going to donate it to a charity shop.