At 74 years old grandmother is the Guinness World Records' oldest female bodybuilder.Ernestine Shepherd is in better shape than most people, decades her junior. She spends her days running, lifting and follows a strict diet to keep her health.Ms Shepherd with impeccably toned 'six-pack' abs also teaches fitness classes at Baltimore fitness centre.The world's oldest female bodybuilder wakes up every day at 02:30 to fit in a 10 mile (16km) run before hitting the gym.But 75-year-old Ernestine Shepherd insists that "age is nothing but a number"."Miss Ernie", as she is known in the world of competitive bodybuilding, began training at the tender age of 17.She says her true calling in life, however, is helping others to follow a healthier lifestyle.The BBC caught up with her at an exercise class at her church in the US city of Baltimore, Maryland, to find out why she started bodybuilding.