I’m in training for a 5K. I’m very nervous about it, because A) it’s the first one I’ve ever done and B) it’s not just a 5K it’s a “mud run”. (It’s this one). Also B and 1/2) it’s summer, it’s humid, and I have no tolerance for extreme temperatures or bright lights. I saw my wife run a 5K once. She has exercise-induced asthma, spring allergies, but she jogged the whole way (good for her!). But she was in a sorry state when she was done, and she was in better shape than me (at the time). I agreed to go with my sister as doing some kind of…