Today's Sub-25 Minute 5K!

Today was my first intervals run on the training plan.  Instead of hitting the track, I ran it on the treadmill at the gym while I had my younger son in the babysitting room.  I was originally thinking I would get to the gym later in the afternoon - when my older son was back from day camp - however, I had an hour to spare in the morning and by clearing up my afternoon schedule I was able to take the boys to the pool before dinner.

Back to running...the intervals for today was 8 x 600m with 90 seconds of recovery between intervals.  This seemed really odd to me at first.  I had always run either 400m intervals (once around the track) or 800m intervals (twice around the track) - but one and a half times around the track???  Since I'm shooting to run the 5K around an 8 minute mile, I chose this speed as my interval speed - on the treadmill that's 7.5 mph...if I was running at the track, I'd try to run each 600m interval in as close to 3 minutes as possible.  I also decided that my recovery runs would be at a 12 minute mile or 5.0 mph on the treadmill.  This (a) allowed me to recover fully before the next interval and (b) worked out to 200m in the 90 seconds of recovery time.  Which meant that each interval plus rest was a half mile.

I started with a warm-up mile, starting at a slow 12 min/mile pace and working up to an 11 min/mile pace before the first interval kicked in.  When I started running at 7.5 mph, I was really surprised to see that my heart rate was still in a reasonable area - the low 160s - and it stayed there for the entire 3 minutes.  During my recovery my heart rate got back to the low 140s.  I felt really good for the entire 5 mile run that I logged.  So good, in fact, that I ran the last 600m interval at a 7:30/mile pace - or 8.0 on the treadmill.  OK...so my heart rate jumped into the mid-170s on that one - so perhaps I pushed myself a little too much there.

As I was running, I was trying to figure out - Why 8 intervals of 600m?  Then it dawned on me.  I was running a full 3 miles at my interval pace - and the intervals were long enough to ensure that I couldn't just sprint them out, but short enough to allow my body to still be able to recover in a short time afterwards.

Since I ran all of the intervals in an 8 minute mile pace (or faster), if you string all of those intervals together, I ran a sub-25 minute 5K today.  My 5K PR is 26:21 right now - it looks like I may be on the road to breaking that on August 30!   :-)