Five examples of activities that can be done non-stop, which involves the large muscle groups of the body?
Stretching, push ups, running, yoga. I'd personally go for Yoga because it involves a lot of stretching, relaxing, pulling of muscles. It not only makes you fit but also healthy.
Posture is an example of using your muscles over a long period of time. It involves your shoulders and back.
Swimming uses a your muscles, and you could do it for a very long time if you conserve your energy.