Your body becomes a dead weight pulling down on your arms and hands and wrists and then add the wind factor whipping your body like a rag doll, it doubles or triples your body weight.
Hard for me to imagine this isn't staged in some way. I've been gliding before and pilots are very cautious about hooking you in before they are connected. In some cases there is a second pilot not flying that assists with connecting the harness. The pilot would have been aware of the problem immediately and could have nosed the glided into a crash before too much altitude was gained. It's possible these guys were not certified and it could be real, but if that is the case they are both idiots! Speaking from experience there are pre-flight instructions and I guarantee you are very aware of the process where you are hooked up.