I’ve been doing speed work of 12 intervals of 400m (0.25 mile) each every other week during this training cycle. I completed my last 400m speed day last week (still have one more 800m day), so I thought I’d compare and see if I’ve improved.

I’m not including the first one that I did back in December because I timed it different, so it’s not quite apples to apples. However, the other three were all measured and timed in the same way on the same treadmill with same shoes. Here are the results:

The most recent is on the left and a month ago is on the right. You can see that I did improve on each speed interval each time I did these.

The problem is, I don’t know whether I really improved or did I just push myself faster on the treadmill each time? Is there a difference?

I always start out more cautiously because I don’t want to burn out, having to go through twelve of these things. I didn’t, at any time on any interval, slow down my speed, so I think that has to count for something. Although, my notes for the January 7th run say, “Actually felt like I probably could have either done these faster or with less recovery time.” Because of this I started jogging part of my recoveries on the other runs.

I would be interested in repeating these one more time on an actual track or flat pavement and seeing how they compare. Would I burn out early or would I push myself harder?

Anyone out there do speed work on a treadmill? How can you tell if you’re improving or just pushing yourself harder?