Parenting an ADHD kiddo is hard enough, for sure. But I read that sentence with emphasis on the word, "different" rather than "exercise" -- so they would be say

Parenting an ADHD kiddo is hard enough, for sure. But I read that sentence with emphasis on the word, "different" rather than "exercise" -- so they would be saying that there's such variety in exercise, it's hard to say with enough certainty WHICH exercise. (But I'm also just an interested layperson.)