I read about something once and even tried it, called the 100 reps challenge.
Bascially a 44lb, (20kg), Olympic Bar, curled for as many reps as possible.
I managed about 36 reps. The guy who posted it, claimed to have achieved about 130 reps. Reckoned it also had something to do with Bone density as well as strength and power. Made my Biceps feel like they'd been stabbed with a sharp stick for about 5 minutes
Fun to do once every 3 weeks or so, now and again as part of a workout, but haven't done it for years. Think I did it twice.