Measuring time or distance will allow you to set a measurable goal.My goal is 10min mile or this was my goal! This year may VO2 or "horsepower" has improved ( see post on VO2) and my time has increase to 8min miles.

I measure time due to running a distance of  2 miles and 6 miles several different times a week. The distance ran depends on the time available for running that day.

The Olympic running team may not be calling me anytime soon but seeing my time improve was a great incentive to train harder!!