Drenched in perspiration, Megan Miller Yoo and about a dozen other students were pushing themselves to new limits during a special Sunday yoga session at a Manhattan studio.

Stretching their muscles and testing their flexibility, they intently followed the instructor moving through 26 prescribed poses at Bikram Yoga Grand Central in a humid, 40-degree room.

From the outside it looked like an ordinary 90-minute Bikram class, but it wasn't.