exactly. i ran a 4:30/15:58 5k in high school and during my first year of college (hadnt TRAINED for a few months but had still been running) i ran a 5k with a few friends, one of whom rowed heaviweight crew. this guy was a good 6'4'' and probably weighed around 220. anyway, he killed me and i ran around 17:20. i remember that, having not raced in awhile, i went out pretty hard. i passed the mile in 5:06 and this guy was right with me. he finished in under 17. now rowers do specific AT workouts like runners, but this guy resembled a basketball player more than a runner. in fact, he was recruited to walk on the football team at our pac10 school but chose to row. this somewhat illustrates the point better. he was two years removed from being a high school offensive lineman and here he was running a sub17 5k. take someone like hamilton who has no bodyfat, is lean, and a great athlete and 4:30 is not out of the question.