We had one of our school's mtb team kids get a calf cramp early into our ride. We'd only ridden 2 miles on flat ground. It was not hot out, a very pleasant 70-72 degrees. The cramp subsided with a short rest and stretching. I also added a GU electrolyte tab to his water. Soon after, he got another cramp when he faltered going up a short, slightly steep climb. When he dismounted, his other calf cramped too. I had him drink more of the GU electro mix and stretch. Both cramps subsided and we finished the one hour ride with no other incidences. I asked how much water he drinks during the day and has three 16-20 oz bottles at school. He also mentioned he has (tendon?) pain like shin splints low on the shin, just above the ankle on both legs. He said he doesn't run a lot at school for PE.

What do you think caused these cramps so early into a ride? Is he flushing out his minerals with that amount of water at school? (it doesn't see like too much me) Did the electrolyte only act as a placebo? I'm wondering if it's a saddle height /position issue? (He's on flat pedals and I don't recall seeing him noticeably riding toes down or hips rocking). Thoughts?