5K Ironman Is Dead. Long Live 10K Ironman!

After a year of training, the data is indisputable. One simply cannot train for a half Ironman by only running 5Ks. It was a valiant effort of intense interval training, but it is time to face facts: mileage matters.  So armed with this new knowledge and further advice from the experts we are killing the 5K Ironman idea and replacing it with the far better 10K Ironman!

That’s right, I’m training for an Ironman, but only running 10Ks!exhausted-runner

The basic principals remain: train for a Half Ironman – commonly referred to as a 70.3 (1.2 mi swim, 56 mi bike, 13.1 mi run) with minimal training miles and time.

How is this possible?

HIIT. That’s High Intensity Interval Training. Translated from trendy trainer lingo it means: running hard; really, really hard. HIIT is simply a fancy acronym for the same interval training which has been around for a long time. However, it is rarely applied to endurance race training which is traditionally running lots of miles at a moderate pace (ignoring limited “speed work” done on top of the massive mileage).

The New Plan

  • Run 10K worth of intervals (run/walk/repeat) generally on my treadmill increasing the running speed, incline or ratio (more running or less walking) as I’m able.*
  • Run 10Ks twice a week.
  • If it is nice outside I may optionally substitute 60-90 minutes of cycling or swimming for one of my 10Ks.


I initially got into trisport because I needed a reason to workout and I enjoy both swimming and biking. I first set my sights on a Sprint Tri and then later an Olympic Tri. But I slowly fell out of it because training at long distances was too much of a time commitment. Then I went back to grad school and my free time all but vanished.

I got the idea from Tim Ferris’ book The 4 Hour Body that covers how intense interval training can substitute for moderately paced longer mileage training for marathons or even ultra marathons. His book includes a full training schedule with different intervals for different days (runners do seem to love complicated schedules – just pick up any running magazine), but I wanted something super simple, so I distilled Tim’s two chapters into this:


When I started in December 2013 I was only doing 2 min of 10 min/mi pace runs with 2 min walks, because grad school had gotten me completely out of shape.  Now I’m doing things like running 7 min/mile half mile “sprints”, or 11 min/mile 10% incline “hill” intervals, or 62 minute 10K “races.” My resting heart rate has dropped from the high 90s to the low 50s.


I feel like I should point out the fact that I hate running. It sucks. Unfortunately it is both effective and efficient at preparing my heart and body for an Ironman event.

The longest I’ve ever run is 10 miles. The longest I’ve ever swam continuously is ~55 min and ~1 mile. The longest I’ve ever biked is ~36 miles.

* I do not include my warm up (1 min walk/1 min run walk intervals at 5, 6, & 7 mph) and cool down (3 min walk) in my 10K interval distance. I do include the distance walking between the running portions of the main intervals.