Driver unloaded product hose to start unloading crushed lime, he was connecting 4 inch cam lock fitting to silo and his back started hurting. He was able to stand up with help holding on to silo leg. Mine EMT checked him out and sent to ER. The e.r. doctor said it was muscle spasms and gave him a muscle relaxer and 24hrs bed rest with a follow up visit on the 24th.