Author: SAMANTHA BRESNAHAN, CNN

South Africa's 'boxing grannies' juke and jab their way to healthier lives

The women range in age from the mid-60s to the early 80s. They love to dance and sing. And twice a week, they come to a gym in Cosmo City, on the outskirts of Johannesburg, to box. They are affectionately known as South Africa's "boxing grannies," and these women are juking and jabbing their way to healthier lives.

You have two ages, chronological and biological

Reminiscent of a scene from "The Social Network," the whiteboard in researcher and professor Morgan Levine's Yale Medical School office is covered in a series of letters and numbers. She clicks the red cap back onto the dry erase marker and steps back to admire her work.