The American aging, overweight population is fueling demand for personal trainers skilled at prodding the out-of-shape of all ages to get fit.

But there's no guarantee those buff trainers know the best workout for a 65-year-old man with heart disease or an obese woman in her 50s with diabetes.

Virtually anyone can become a certified trainer because there are no national educational standards for the field. Numerous web sites offer personal trainer certification after just a few hours of online training — and a few hundred dollars.

That situation galls personal trainers like Ken Baldwin, who has seen people become disillusioned or injured by working with unqualified trainers.

The Purdue University instructor helped create that school's four-year undergraduate personal fitness trainer degree, which he believes is the first of its kind in the nation. The year-old program is built on Purdue's health and fitness major, which already focused on exercise physiology, basic health studies, fitness evaluation and program management, psychology and nutrition.

"Large or medium-sized health club chains can't grow because they don't have good, qualified individuals to manage and oversee growth. There's just a dire need for that," said Baldwin, who oversees the personal fitness training at Purdue's Department of Health and Kinesiology.

The program has enrolled 30 students who learn the nuances of toning muscle groups and proper exercise movements, and get hands-on experience with cardiac rehab patients and people in physical therapy after injuries or surgery.

Students also work with seniors and children in fitness settings and take business and management courses so they can manage fitness clubs.

Purdue's program is part of a push to turn out better-educated personal trainers.

Last year, the International Health, Racquet and Sportsclub Association urged its roughly 5,000 member health clubs in the U.S. to hire personal trainers with a least one certification from a group that has third-party accreditation.