Four out of five people suffer from back pain at some time in their working lives. In the United States, it is the most expensive health problem in the workplace. In all, it costs people up to $60 billion in medical expenses and lost working time. Back pain is bad for business as well-it is the cause of 40 percent of all lost work days. That means a total of about 93 million sick days a year in the United States. Doctors now believe that exercise is the best treatment for many kinds of back pain. For this reason, some companies ●●●●.