Equation needed to balance distance/speed training
My theory is that I need to be able to go fast if I am to go further. So I am mixing up my distances and occasionally going a few kilometers further. The aim is to do the London 100 next summer, or some other sportive. The furthest I have gone so far is 89km and I am wrecked but go just 70 and I am bashing it out. So I want to be able to compare mathematically my performances. I've got 45 times from the summer on a chart already.
So is it better to do 50km at 30kph or 100km at 20kph? Both are good training; and further and faster is the aim but if I did 60km at 28kph next week would that be better or worse? At the moment I have a spreadsheet plotting (Square root of distance)*speed against distance. I am calling this an audax number, just in my mind. And it does produce a nice wee graph that curves up and to the right but it still favors larger distances so that a swift 50kph 10km wouldn't show very well.
Does anyone else know a better way of comparing data or a better equation?
Sorry, maths, I know.