Suppose I'm in my peak training week for the marathon. 110 miles, 20 @ 6:XX and 6 @ 5:XX. One day for a 10 mile easy run my muscles are so sore I can only manage 10:00 min/mile pace until mile 10 when my legs loosen up enough to run 8:00 min/mile pace.
Did I get any aerobic or training benefits from the 9 miles at 10:00 min/mile pace or would I have been better off not running at all?
In my second run of the day it went better, 4 miles @ 8:15 min/mile pace.