Actually “catch dogs” are lean and look nothing like these aberrant oversized pits which wadle. They need stamina and long necks.
They look like these dogs:
http://www.workingpitbull.com/activities2.html
“This breed combines strength and athleticism with grace and agility and should never appear bulky or muscle-bound or fine-boned and rangy. Above all else, the APBT must have the functional capability to be a catch dog that can hold, wrestle (push and pull) and breathe easily while doing its job. Balance and harmony of all parts are critical components of breed type.
Very Serious Fault: Any disproportionate overdone characteristic (such as short legs, excessive bone or massive head or body) that would interfere with working ability. “
http://www.ukcdogs.com/WebSite.nsf/Breeds/AmericanPitBullTerrierRevisedNovember12008
The catch dogs I worked with were as far as I could tell were average in proportion, with the bulldog a little on the lean side IIRC.