Answer: Usually age unless its level of fitness but that's kind of vague
Explanation:
So I would say age in moderation because if you have like a 20 year old and a 17 year old doing exercise I don't think there will be a big heat exertion illness getting them down but if your health teachers annoying and is talking about a 18 year old exercising with an 87 year old than its definitely level of fitness
Its just got to be Robert Lewendowski and Bayern Munich currently.
You have not given us any options to pick from @Kristina986
