getting the hang of intervals

This morning was the first day for real intervals.  It is going to take a while to get use to these on the treadmill.  I did 6 intervals (1m/30s).  My heart rate didn't really elevate that high, but I think it is because with a 30 sec run the heart rate monitor doesn't keep up.  Ran at a 4.5 (little over a 13 minute mile).  My legs complained a bit...a little bit of pain on the front of the legs.  I think it is my legs getting use to it.  Other than that I felt good...especially after a rest day yesterday.