My current running pace is around 12 - 13kph, depending on how I am feeling, distance and hills. I'd like to be able to run a 10k in 40mins. What's the best way of increasing my pace? I feel atm that my legs lack some power to go faster, but my endurance/fitness is fine. I've been doing a few sprint intervals, but they are pretty evil, and I'm usually nearly sick at some point - plus it takes me ages to warm up, and usually get better the more I do/longer I'm out for.
So I'm thinking I need to be able to run a negative split, given I feel better the more I do. But I struggle to hold 15kph for more than a few mins without slowing down the pace to recover.
My other issue is hr - my average hr for running is 181. I can sit at 180 (give or take a few beats) for almost all of a steady run (around an hour). However, as this is pretty high, I do struggle when I want to sprint as my hr is already high - it pushes it up to my max pretty easily. Do I just run more sprints/intervals and get used to the faster pace that way (and hope my hr adapts?)
I don't want to get too caught up in the "training" aspect i.e have planned intervals/long runs etc, as i still want to maintain an element of fun/change from riding, so don't want to follow a set programme, just have an idea of what i should be trying to include when i feel like it. (and yes, i have looked on runners world for programme, but i'm keen to hear how other bikers find running/experiences etc)

