Laughing River Yoga — Om, my. Forget flannel — in Burlington, yoga pants are the go-to clothing choice. People roam the city in stretchy leggings, ready to enter one of the many local studios promising to free the mind and tighten the backside. With so much competition, only the good studios stay in business. Laughing River Yoga is one of them. The bright, airy space in the Chace Mill is known for its skilled instructors and welcoming vibe. Beginners to advanced practitioners hit the mats for rigorous vinyasa classes, AcroYoga and even, weather permitting, outdoor sessions overlooking the neighboring Winooski River. As instructors guide students into the deep hamstring stretch of a downward dog asana, they emphasize the studio’s underlying philosophy that yoga is as much about mental well-being as physical.