I wonder if the status in the gym is the same as the status out of the gym, as far as hierarchy of the group.
Motivation to be in the gym is incredibly overlooked in the social sciences, especially for men. There are assumed motivations but very little work. This ritual before ritual is interesting. Why do you think it exists?
Why the activity needs, for some, to be social is approaching individual psychology and group dynamics. I am sure there are all sorts of theories out there that could sound really interesting. I am sure has something to do with support but I would guess in these groups it is feats of strength for hierarchy + bonding. I think this is different, though related, to your question of what makes gym interactions unique. This short of a paper needs to be well focused if you are going to say anything in the space allowed.
I worked out in college in a hardcore, rusty weights, non-air conditioning in South Texas, where bodybuilders made up 80% of the roughly dozen or so regulars in a campus of over 45,000. The person I saw get the most respect, where the big guys stopped their squat workout to let this person use the lifting platform, was a women who was 5' tall at best and a hell of an Olympic lifter. Much of literature would say this would never happen or it was because of her sexual nature that she was accepted in a male dominated weight room i.e, strange. I would not call it strange as I have often seen women who are lifting hard get respect from the guys in the gym - and guys who are not getting no repsect. (That is not to say the there are not sexist attitudes at play at times but I think it is not gym specific as a 'outdated' way of structuring society and not place specific.) The gender theories are wrong, it was because she could lift some damn heavy weight and that was/is respected. Effort, not gender, to me, is more important in a gym setting. By the way, she was professor at the college as well. This is just one of the reasons I think the gym gender theories are way underdeveloped and overly simplistic.
Well, it seems you have yourself a three page paper.
Do you need any academic theories/perspectives? If you have the time I would suggest a short book, Culture and the Human Body http://www.amazon.com/Culture-Human-Body-Anthropological-Perspective/dp/157766180X/ref=sr_1_1?ie=UTF8&qid=1291586489&sr=8-1 that should ground you pretty well in anthropology and its concerns.