Peeta is meant to be well built alright but nothing special powerhouse (due to working in bakery and lugging around bags of flour all day, and being well fed unlike others in D12), very strong, kind of guy that makes someone feel safe just by being there.
Yet for some reason in the movie he's shorter than Katniss, and doesn't look like he could fight his way out of a paper bag.
He should have been much bulkier in the movie. Also he's meant to be an excellent speaker, yet they make him mumble his way through the film. Plus his entire attitude, and body language just don't match the character from the book at all. Not to mention the whole Katniss / Peeta dynamic was completely off the mark.
Honestly, read the book, you'll be surprised just how much better it is. It's an easy read as well, you can get through the whole trilogy in a week.