I am having a problem with my legs for the past year. It has become such an issue that I can no long do a full triathlon by myself, but need to get someone to do the running for me. First off I run on my toes without stretching. This is the only way for me to run because if I run heel toe or stretch before I run I get shin splint like pains. After I run for a while and slow down my calves lock up because I didn't stretch them and I have to walk off the pain and boing there comes the shin splints. I am clueless what to do, I can't stretch so that I don't lock up my calves during the run because of it causing almost immediate shin splint as I start the run.
Running on your toes puts most of the stress on the calf muscles. That's probably why the shins don't bother you and it is certainly why the calves do, rather than the lack of stretching. Do you have the same problem on your training runs? Here is a good site with exercises for shin splints.
http://www.sportsinjurybulletin.com/archive/0161.htm
I have been doing the "Wall Shin Raises" with great success. Try the exercises for several weeks. If they work, you're golden. But . . . you may not have shin splints. The almost instant shin pain sounds more like compartment syndrome. If the exercises don't help, see a doctor.
Len