The joys of exercise

This morning I went for my first 30 minute walk on my treadmill. I probably tried to do too much for just getting back into the exercise routine because before I was 4 minutes into the walk I had a horrible cramp in my calf, got dizzy, and was sweating so much I could have started my own salt water pond. I think my pulse was the highest that I've ever seen it (got up to 150). My head was so wet from sweat it looked like I had just gotten out of the shower. Tomorrow I'm going to try just walking for 30 minutes at a rather constant pace and work myself back into the rigors of the preprogrammed options that my treadmill has.