I work out at home, and part of my workout involves doing (essentially) lunges with weights on my back. Weight vests are (comparatively) extremely expensive, not very breathable, and generally don't go higher than 30ish pounds, so I've resorted to using a backpack with two 25-pound weight plates in it. As you might imagine, a lot of cheaper bags do not hold up to that kind of dense, concentrated weight.

This bag, however, holds up wonderfully. The straps, which is the point of failure on most backpacks, are attached EXTREMELY well. The straps are sewn on so well, I feel no strain or stretching whatsoever when I pick up the bag by one strap. Not only that, but the straps are comfortable even with that much weight, and for an extended period of time (~50min, every other day. No shoulder pain whatsoever!)

I know it's not really the intended use of the bag, but, man, does it hold up. If you're looking for a bag that can take a lot of weight, this is it. I can't say it enough - this bag is extremely well constructed. I've had much more expensive bags that billed themselves as "durable" break in no time under the same stress. I'm planning on buying a second one of these as a backup, just in case they stop making these. It's hard to beat that price, given the quality of the product.