As a Tae Kwon Do student in the 80's I could do nearly 400 sit-ups in a session. Pushups though? Probably only around 30 or 40 at best. I was pretty thin but not scrawny. I was 165 when I graduated High School. Later while working in a construction job I ate alot of he-man breakfasts and lunches and was just about 200lbs at one point. I reverted back into the meat business where I still am today in my 50's. This work is really hard on your ligaments, joints, tendons, etc....especially since we work in 52F on a hard floor all day along and it's more like 34F in our cooler. We've had many people come and go. Many of them comment how "you guys really deal with some rough work. It's very hard on the body!"
In spite of the "exercise" get at work, my body is getting really stiff and sore these days. I've already had several cortisone shots in some joints. At this point in my life I think something like Pilates or Tai Chi would be good for me, and in fact I practice similar moves at home just to stretch out after work. If I didn't I'd hardly be able to do much.