Air conditioning is a physically demanding field, so it's important to establish and maintain a regular training routine. Depending on the type of air conditioner you're working with, commercial service and installation can be particularly strenuous. Despite this, I still see many strong people in the industry. It's a lot of ladder yoga, and you'll learn to curse the builders who placed the heat pump too close to the wall, and to bite your tongue when the office worker below you tests your patience.
At first, some tasks may seem physically challenging and frustrating, but you'll soon learn how to use your body to work for you instead of against you. HVAC technicians often have to stretch their arms out in the field, and there may be physical demands that are part of their daily life.