I've had one of my hands lock up whilst hanging off scaffolding (25+ minutes of fully clenched grip) and my legs/calves lock up and refuse to move for about 30 seconds. The legs are painful, but the hands are just scary, because I wrapped my legs around the scaffolding to support myself and tried to use my other hand to move my digits in any direction, but they were frozen in place :O
About a minute later, all was well.