Talkback: Q+A: How can I calm my nervous pre-race stomach?

I am a 48 year old male and have played sport most of my adult life, having played football for 20 years I have now turned to triathlons and swimming. I have found that over alls these years when it came to a big game such as a grand final I would always cramp in the legs badly meaning i would need to come from the ground. Everyone says its dehydration and at the time i got so frustrated I had blood test to see if i was lacking in something however nothing came back. I am now doing triathlons and I am cramping again when it comes to events that I am building myself up to usually I am alright if I can get to the day of the event with out thinking about it to much. I hydrate well in the days  before I take magnesium supplements but am convinced I am losing something vital through nerves. It is frustrating and with all the training put in to get half way through an event  and have an onset of muscle cramps that wreck the day.

Any Ideas that could help or has anyone else suffer from the same?