Please do not worry. Although I confess to having the same initial worries, I have NEVER seen anyone pass out or throw up during a hot yoga class. I am 53 and not the oldest in the class. If you feel that you need to lie down or rest in child’s pose, by all means do so. Tell the instructor that you are a new student and they will keep an eye on you. I am sure that they will tell you to take a break if necessary. Yoga is not a competition. Go at your own pace and don’t worry about what anyone else is doing around you. Namaste!