An employee climbed a fiberglass ladder to trim a tree. The employee told his coworkers below that he was not feeling well and was getting cramps. He had a rope and a strap along with his climbing belt. He had already put the rope around the limb of the tree. His coworkers told him to stop and come down. He stated that he could not move. One of his coworkers ascended the ladder to secure him from falling. They got him down and gave him some water. He got sick and was hospitalized.