todd williams did something similar (i think) almost every week. when you see WHEEL in his logs it is continous hill running, harder on the uphill. so hard ~30[s] up, float 35[s] down. i could be wrong but its my theory.
also he would often go to the track after and do a 3200 of pace-changing, either alternating the 200m or 400m segments.
below is a sample from his logs at
http://www.pushthepace.com/logs.html
p.m. - 4 mile warm - up 4 x wheel(HARD hill running non-stop on grass) (9:53) then run 1 mile back to track for 3200m of alternatin pace. I ran 69-64's for a 8:51 3200m felt like I was walking
he is a little behind in updating the logs but when he does it is always great stuff.
also i think he progressed through the years. he started in college with say 800m of pace changing after a wheel segment.