Me too actually, it's also lovely to hear him speak so supportively of all the other competitors. I wonder whether doing the commentating bit actually helps him further assess the way the course is riding in preparation from his next ride?
It probably does help him get a good look at how others are riding things and how it's all going. He is really supportive of the other riders, but also honest enough to admit why he was watching Sharon Hunt's time so closely!!
Would assume the shaking leg is muscle fatigue i often get it if i have been running or riding a bike for a long time and pushing myself hard assume ( although i might be wrong ) that horses get the same.