I did 7 x 1/2 mile on the treadmill this afternoon. Times were 4:00, 3:50, 3:40, 3:30, 3:20, 3:10, 3:00. I wore my heart rate monitor. My heart rate at 8 minute pace was 134 bpm, at 7 minute pace was 146 bpm and at 6 minute pace was 157 bpm.