Quipy, and dead on about the joints and ligments, but bad advice on the muscles.
Go ahead and tear a muscle and then enjoy either surgery or spending months/years waiting for it to heal, same as a joint or ligament tear.
We are resilient in general, but any sudden "treat them like dirt" action can fuck up either. If you want to "get shit done" you need to build to it, grease the groove until your body adapts to the motion.
That dude was a special kind of stupid. The attack script had his name on it, usee his account status as the trigger, and was running from his laptop. It attacked other peoples profiles and was extremely explicit in being designed to revenge his firing.
There are for sure idiots in infosec, but when your job is working to close holes and gaps, it gets pretty easy to learn what to "forget" about if you want to cause devastation in a deniable way. There are so, so many ways to fuck this job up, doing it on purpose would be a cake walk.