I'm definitely from the same planet as the parent poster (PP). There is a subset of people, like me and PP (I'd say we're probably < 10% of the general population), for which physical exercise really is "repetitive, boring and requires discipline" and sometimes even feels like
pure pain when we force ourselves to do it, because we know it's healthy, even if we'd rather be lazying around, although there is no physical pain involved and we are otherwise in good health.
It would probably make sense to further split the participants of a study like this into two groups: the ones that enjoy physical exercise and the ones that most of the time don't enjoy physical exercise.
If I were to speculate on the physiology of this, I'd say that for people like me and the PP, the brain either fails to secrete enough endorphins - the feel-good chemicals that are usually released during physical exercise that make it "fun" and an "urge" (I've read once about a study liking physical exercise addiction to addiction to hard drugs, so it makes sense to have a similar mechanism) - or we don't have enough receptors for endorphins. Thankfully I also happen to have an auto-burner metabolism (I can eat anything anytime and just never get fat) and and no genetical predisposition for obesity or diabetes, so I can stay reasonably healthy even when I stop doing any kind of exercise for some periods of time, but other people are not as lucky as me...