State Sen. Rob Calderon of Montebello, who introduced the bill, said personal training has no oversight in California.
Calderon's communications director, Bob Jimenez, says some Internet companies are offering certification without requiring any class time.
Legislation similar to State Bill 374 in several states has prompted a fitness group association to lobby against new rules.
Many in the fitness industry say the state bill is unnecessary since the industry is self-regulating.
The fitness group International Health, Racquet and Sports Club Association says state licenses would be costly and a burden to trainers and gyms.
So far, Louisiana is the only state to pass a bill requiring licensing of exercise physiologists.
California's bill stops short of requiring state licensing.
According to the National Academy of Sports Medicine, fitness trainers charge fees ranging from $40 to $100 per hour.
Senate Bill 374 would require the certifying agency to be accredited by the Council for Higher Education or the U.S. Department of Education.
The bill passed the Senate on April 24 and the Assembly is now considering the bill.