Ok for this workout I ran each lap for 2.5 minutes with a 1 minute walk break. I was supposed to run slightly faster than marathon pace. I think I got a tad carried away and ran too fast (for me) again considering that my current marathon pace is 11:30 (explained here). It looks like I am averaging 9:20- 9: 40 pace with one interval actually 8:20. Why do I think I ran too fast? Because my heart rate was hitting 172 on each interval. Now interestingly it was only on the 8:20 pace interval that I actually got winded. Also, according to the charts I ran the majority of the 5 miles in the aerobic threshhold zone, which would not be sustainable in a marathon. Well the idea of the workout was that it will help train my body to run faster. Hopefully these speed workouts will be helpful there. I think it is encouraging that I was running the 9:40 pace without much issue. It makes me wonder if that if a 10:00 pace could be sustainable and keep my heart rate under 165 and in the aerobic zone. I think more experimention is needed.