The Iditarod is 1,150 miles, and the best musher and go team will run the course in 10 days - or less. That means the teams of 10 to 12 dogs – many of them Siberian huskies – would run about 115 miles a day.

Poor, Denali. He's born to do that but he can only run 2 to 3 miles a day, 4 at the most. At least for another 9 months, according to the vet.

You see, my husband had this bright idea that we should train for and run a half marathon (13.1 miles). With the race less than two months away, our longest runs are starting to increase. This past Sunday was 7 miles and in another week, we'll be up 8. From there, it goes to 9, 10, 11 ... well, you get the picture.

Denali has accompanied me on nearly ever training run (I don't take him on hill repeats). After all, he's the reason I'm running to begin with. As the mileage increased, I began to wonder how far is too far for him. So I called the vet. I was told, at first, that Denali would let me know when he'd had enough, and I should look out for him limping or sleeping a lot the next day. Then, she asked his age.

"Fifteen months," I said

"Oh."

It seems that it can take up to two years for the growth plates of a puppy to fully close. http://life.familyeducation.com/dogs/exercise/45655.html Exercise, like running, can cause damage to the growth plates and keep them from closing.

Oops.

It scares me a bit to think that an activity that we thought was helping Denali could actually be hurting him. My husband and I are now working on trying to cut back Denali's mileage, switching training schedules and reconfiguring routes to include a drop-off.

The only thing we haven't worked out is what do with the energy of a dog used to running 7 miles in a day.