His father was one of the few men in the business who understood that a beam put in an inch or two off would affect the entire structure of the building. David inherited his father's eye. From over a hundred feet away he could tell if a beam was only an inch or two off. The human body is a structure. Almost no-one involved in various aspects of the health field understands this, from medical doctors to strength coaches.
Chiropractors probably come the closest.
Nobody has ever come as close as David Scott Lynn. David was on a job in Minnesota, working outside in the winter, about 15 years ago. The cold was too much for him. He walked off the job and went to Florida. Shortly afterwards he began applying what he knew about structures to the human body.