I think this is a very good way of encouraging people to learn to like exercise without them having to do it because it is obligatory.

obligatory 是形容词，来自动词 oblige（迫使、使有义务），加上后缀 -tory 构成形容词形式，意思是"强制性的、义务性的"。这个词强调某种行为是必须履行的责任或义务，而非自愿选择。