Electrician was doing prev. maint. checks on cont miner, when he bent over to check the traction breaker, a piece of rib rock measuring 6' L, 15"" W and 1-4"" T, struck him on the right hip and upper leg. He was taken to hospital where X-ray was normal. He was referred to follow up w/specialist and MRI. Contacted Safey Dept 9/4/09. MRI on 9/2 showed ruptured discs/1 bulging disc.