Americans keep getting heavier, but the backs of ambulance workers aren’t getting stronger. Over the past five decades, the percentage of American obese people rose from about 14 percent to 40 percent. The American Obesity Association estimates that by 2030, 60 percent of Americans will be obese. This change means the average American weighs 30 pounds more than the average American in 1960. According to a study by Dr. Audrey Reichard, about half of emergency medical services (EMS) personnel injured while lifting patients, between 2010 and 2014, were lifting someone obese. “It’s definitely a pain in the back,” said David Williams, an emergency medical technician (EMT) with Care Med Ambulance in Chattanooga, Tennessee. At Care Med Ambulance, nearly 90 percent of ambulance riders are obese, said Williams. Care Med transports people who can’t drive to medical checkups. It doesn’t respond to emergencies. “We’ve been having to do a lot more …