I am in about 15:30 5k shape and ran a 2:28 marathon in the Fall...I was thinking of trying to run this workout :
alternate 800 at 5K/800 at MP for 4 miles
So about
2:30/2:50 = 21:40 or 5:20 pace for the whole thing, inefficiently, which is about my half marathon pace.
Is this too ambitious, not hard enough or about right? I am more of a distance type naturally. Training for a half in two months but might try some 3K to 5K on the track soon.