The sledge hammer workout got very famous when vidoes of Fedor Emelianenko hit the internet. When I was training in Eastern Europe this was something very popular among combat athletes and when I used to visit the United Stated I would not see folks training like this in nineties. I used to see bowflex types of tools in home gyms and there was a huge body building era. Since then there has been a huge changes in the fitness community in US and many of the training methods from Eastern Europe was adopted. Video below is Ilias performing sledge hammer slams. Ilias is one of the greatest Judokas Europe produced.