The answer is to increase the minutes in which he is doing the exercise. He can just increase it by a couple of minutes and he will gradually improve his endurance.
Ride his bike to school, find other exercise that lets him stay inside such as pushups, situps, planks etc.
if his parents have a treadmill he can run on that instead
A.Sarcoma
Sarcoma refers to cancers of two types of tumors: soft tissue tumors and bone tumors.