In 1976 a drafting chair kicked out on me, injuring my back.I was unable to walk, stand , or do much of anything except lie in bed. I missed work for a couple of weeks. Dr Clark was my neighbor (and a good one) and treated me with ultrasound treatments for about 3 months. I moved back to Idaho in 1978 and have had no problems with my back since. His treatment also took care of a 1955 disc issue to another adjacent disc/vertebrae that was a probleml at times, but not since '76. Thanks George.