In the muscle growth stories that Oldshep, Darknevoir, MysteriousMist (Ruduen), HRRB and I co-write, readers know we like our numbers - height, bicep circumference, weight, lifts, and so on.

The first story that Shep, Ruduen and I did (the fox arc) had somewhat realistic numbers - the final lifts at the very end are near 1,100 pounds, which if one is a 7', bodybuilder-sized muscle beast, isn't as much of a stretch as later arcs (but still superhuman - the record unassisted bench press is something like 730 offhand, and those belong to really meaty powerlifters).

Then in the second story (the dalmatian arc), we definitely took it well out of the realm of what's natural - Jared Kuznetsov, whose weight is never explicitly stated at the time, can lift a 4000-lb. car. A couple of "reasons" have been worked in over time - statements in the raccoon arc note that anthros/furs are stronger than humans pound-for-pound, and that they have denser muscle fibers. Other arcs have mentioned other weights and feats of strength, and this evening, I decided to break down bench press ratios based on size and weights we've already used. This doesn't account for things like height and type of body build (physique/classic bodybuilder/powerlifter), but here are some examples:

George (multiple arcs) - 5000 lb lift, 600 lbs weight, ratio 8.33:1
Buck (badger arc, kangaroo arc) - 4000, 550, 7.27:1
Colin (collie arc) - 585, 275, 2.13:1
Human Male in 20s, 90th percentile (i.e. pretty buff) - 1.48:1 - 296 lbs. for a 200 lb. male (source: http://www.livestrong.com/article/4.....-body-weight/)

Apparently, somewhere between 275 and 550, the body decides it can get a whole lot stronger. The conclusion is, we have some logic quirks; but I doubt people were worried about that in their gay muscle furry hyper-cock porn :P