Hartsdale, April 15 -- A 100-year-old yoga instructor has no plans to stop practicing and teaching.

On a spring day in Hartsdale, a northern suburb of New York City where she leads her classes, Tao Porchon-Lynch said she first encountered the ancient practice at age 7 in her native India. Strolling along a beach, she was transfixed by a group of boys doing yoga poses. When her aunt told her the movements were "not ladylike," she responded, "If boys can do it, I can do it."

By the time Porchon-Lynch was a teenager, already teaching yoga, she was able to explain how to breathe in a healthy way - especially to people in awkward sitting positions.

"I said, 'You're squashing your lungs. Your lungs are not down in the navel, they are above,'...