ok...
I say this...
4 miles / 45 minutes = +11 minute miles...
4 miles in 32 minutes = 8 minute miles...
that is a pretty big difference... I run quite a bit and that is a big difference! Ok so how do we get there..
I have no idea how much you run now... so lets say you don't run much at all now...
Monday: Run 3 miles easy (12:00 miles)
Tues: Break
Wed: Run 2 miles pretty fast... try to go around a 10 minute mile for now get a watch and time yourself. If you can find a place that has 1/2 miles marked off that would be awesome...
Thurs: 3 miles easy
Friday: Break
Sat: 4 miles easy
sun: break
Do that for a couple weeks... 2-3... on the 3rd week. Really run the 2 miles as fast as you can... write that time down... Let's say it is 18 minutes... 9:00's... alright... so make your new easy run 11:30's
if you make it a month doing this.. then you can up the sat 4 miles to 6... and change the 2 to a 3 and one of the 3's to a 4... but don't do all those changes in 1 week... spread them out so your total millage doesn't go up by more than 10 %
---------- ok easy method ----------
if you are already running...
every once in a while just run a fast run and go here to calc you new training paces...