When you make a website, you have to think out of the box.

Your audience will not necessarily be a 20 year old in good physical condition. It may be as well a 10 year old that doesn't know what to do with the information you are giving to them. Or someone with a pacemaker, or someone with some medical condition that puts them at risk.

Then... Not only people can get injured by following an exercise routine in good-faith... some people may injure themselves on purpose so they can sue you.

Will people be able to injure themselves anyways if you add a disclaimer to the website? Absolutely. But it won't be your fault anymore.

But that's only the start. If you allow people to write anything they want in a textbox, bad things can happen. People can write ANYTHING, not only exercise routines... And by anything, I mean, very illegal things.

And if you allow people to upload pictures, well... that can go very wrong as well.