The instructor puts on a new tune, and starts tapping her foot along with the beat. "Nice dance posture," she calls out to her students, about twenty dancers that have gathered at the Abington YMCA, outside Philadelphia. On her command, they straighten their backs, and lift their heads. "Groove a little here," she yells, and they start moving their torsos and arms from side to side.

This isn't just any class, it's designed for people with Parkinson's disease, which is often described as a thief that steals people's ability to control their bodies.

Instructor Judith Sachs is a petite woman in her 60s who moves with the precision and grace of a trained dancer.  The other dancers follow her lead, but, everybody is sitting on chairs. Sachs explains that in dance, every move is made with intent — something her students here can relate to.

"People who have a movement disorder, which is Parkinson's, actually think about the body in a very similar way that a dancer does," she said. "So, if you're lifting your arm, you have to really think about it, 'how do I lift it if it's shaking,' or, 'if I'm rigid, how do I open myself up?'"

Parkinson's typically means tremors, stiffness, trouble with balance and the class accommodates those symptoms. The choreography is created in a way that it can be done seated, at a ballet bar, holding on to the back of the chair, or moving across the floor.

Sachs trained for several weeks in New York City at Mark Morris Dance Group, where "Dance for PD" as the program is called, was developed.

Most of the people with Parkinson's are accompanied by their partner or spouse. Connie MacNeil of Doylestown comes with her husband, Dan MacNeil, who has had a diagnosis of Parkinson's for a year. "We're looking into different things that we can do to deal with the disease," he said.

Dan MacNeil says he can replicate most of the dance moves, but like many people with Parkinson's, he has trouble starting — and stopping. "Some activities like turning quickly, I may to catch myself so that I don't keep going," he said.

The MacNeils hope that physical activity will keep Dan active and mobile longer, but the class serves another purpose as well. It's a way to reclaim bits of normalcy, while dealing with a devastating diagnosis.

"We enjoy doing things together," said Connie. "One of the things that I thought we'd have to give up is dancing, because we love "Dancing with the Stars," and we wanted to do ballroom dancing, and I thought that was going to be out."

And then there is the "joy" component. Parkinson's disease has a big impact on mental health, and often leads to depression and anxiety, but during this hour, the mood is decidedly bright. In one dance routine, the participants hold hands and move in a circle. "Don't hang like a meat hook on the person next to you" joked Judith Sachs, her comment is met with a big laugh.

That's what this group is all about, said Wendy Lewis, executive director of the Parkinson's Council - which helped organize these classes.

"You see the smiles on their faces, and the energy level, and just the whole camaraderie of them being around in the circle."

Lewis says there are currently classes in three locations: Abington, West Chester and Philadelphia's Northern Liberties neighborhood.

"This is a great way to connect, and keep people connected with each other," added Lewis.

Research has shown that those participating in dancing classes can walk more quickly and maintain better balance. But University of Pennsylvania neurologist Nabila Dahodwala agrees with Wendy Lewis — the social benefits outweigh all that.

"That's been the biggest feedback we've gotten," she explained. "Not that they're moving more, which we know that through studies, that movement improves, but that they feel better, that they have so much fun going." she said. Dahodwala is a researcher and also treats people with Parkinson's, and says exercise is important in treatment. "That is probably the hardest thing with any exercise, to make it something that you want to go to!"

Friendships have formed at the Abington Y class, caregiver spouses go out for lunch and support each other. At the end of class, the dancers form a circle, and thank each other for dancing with a slight bow.

The gratitude goes beyond a dance. It speaks to how a burden can seem lighter when shared.