The snapping chain you are referring to, where is the break? In the side-plates? Or in a pin? I've never seen a chain, either 3/32" or 1/8" that has been through so much force that it actually breaks. I've seen them badly mangled by chain-suck between the granny-ring and chainstay. Or twisted and chewed up when the RD goes into the spokes. But I seriously doubt a human riding a fixed-gear bike can break any chain.