In Yaffa Bruckner's "Klee" class, however, the phrase takes on a much more literal translation: It involves an actual combination of physical movements and spirituality.
In the women-only class, held Wednesday evenings at Congregation Kesher Israel in Center City, participants study Torah while lifting weights; they use aerobics to re-enact Jewish life-style and biblical scenes, like dancing under the chupah and wading through the Red Sea; and they do yoga positions, breathing exercises and dance routines to traditional klezmer tunes.
The class, which has been up and running since Purim, was developed by Yaffa Bruckner, who has a background in physical therapy and Pilates.
Bruckner said that the program is actually an extension of her interest in Mussar, a Jewish movement that began in 19th-century Lithuania. Translated as "instruction," Mussar is a set Jewish laws that offers step-by-step guidelines on how to live an ethical Jewish life.
"I think I was drawn to it because I, myself, need a certain amount of discipline," explained Bruckner, sitting in the living room of her Center City home. "If you have specific goals you want to achieve, you have to be very focused."
Before she created her class, she admitted to not being entirely enamored with Mussar; Bruckner said she faulted the teachings for not paying enough attention to the physical self.
"It's all very philosophical, but the problem is, there's nothing that's physical. The point is, in 2007, we can't do that.
"We have an epidemic of diabetes in this country; we have obesity," said the instructor. "We need to deal with the klee" -- Hebrew for the body as a container, as a vessel.
So Bruckner, who is a home-care physical therapist with the University of Pennsylvania's health system, developed a program to address the body within the framework of Judaism.
Last week's class, which was held in the synagogue lobby, allowed six female participants -- some of whom donned modest clothing like long skirts and head coverings -- to act out an Israeli harvest scene, to simulate breaking the glass at a Jewish wedding and to discuss the story of King Balach, while at the same time pumping up their heart rates.
"Okay, we're going into the shuk to try to sell our wheat," shouted Bruckner, instructing the women to pretend to carry baskets while jogging in place.
Ducking to the side for a water break, Linda Joy Goldner, 57, noted that -- at least initially -- she wasn't sold on the idea.
"I started off not knowing what the heck she was going to do," said Goldner, who lives in Center City. "I just knew a tiny bit about Mussar, and I couldn't even conceive of what it would be. I'm somebody that normally doesn't like to think while I exercise."
But after trying a few classes, Goldner, a member of both Society Hill Synagogue and Congregation B'nai Abraham, described herself as a full-fledged devotee.
"Instead of watching CNN while I'm on the treadmill, I'm now listening to the parshah in advance of hearing it at shul," she said. "And I'm transported -- in the context of what I'm doing, and in the context of this place -- to Eretz Yisrael."