PALESTINE — Quiet is hard to find in prison. But in the Powledge Unit gym on Tuesday afternoon, the silence was interrupted only by the sounds of breathing, toes on sticky yoga mats and occasional moans from nine men in white uniforms as they sank deeper into pigeon pose.

“It hurts in a good way,” said Stephen Vinez, who is serving a 20-year sentence for a manslaughter conviction.

The class was the fourth that Jim Freeman, a lawyer turned yogi and the founder of Conviction Yoga, has led at the Texas Department of Criminal Justice’s Powledge Unit in East Texas. For the inmates, the weekly two-hour sessions offer a reprieve from their cells and the boredom of prison life, along with physical and mental health benefits. And the Powledge chaplain said corrections officers saw better behavior from inmates who took part in spiritual programs that gave them a chance to exercise.

Mr. Freeman, 48, who started the volunteer yoga classes this summer, hopes to expand the program to all 109 Texas prison units. But there are financial and administrative challenges. Mr. Freeman spends about $300 a week driving to four rural prisons from his Austin home. And the criminal justice department classifies yoga as a religious offering, he said, so at some prison units, only inmates who identify themselves as practitioners of Eastern religions like Buddhism, Taoism and Hinduism are allowed to attend .