APEX, N.C.

On a Tuesday evening under the roof of a public picnic shelter, a group of women ages 20 to 55 groaned through a series of high-intensity exercises in the 88-degree heat and humidity.

Cheered on by their leader, who yelled, “You’re getting stronger,” and “You’re going to feel like Popeye,” the women press on with  jumping jacks, burpee box jumps and a set of other cardio exercises with inventive names: “Dying cockroach,” “Ski moguls” and “Sparky crabs.”

But the intensity of the boot camp-like drill ended on a quieter, more reflective note 45-minutes later as the women came into a circle, their faces still flush from working out, to close with a prayer:

“Lord, thank you for the time we’ve been able to be together and just exercise,” said Julie Swift, one of the women. “Please bless all these ladies and sustain them through their week. In Jesus’ name we pray.”

After a unison “Amen,” they roll up their mats, give each other a hug and head home — until the next workout.

A host of modern exercise groups have sprung up in the last decade that aim to create fitter bodies, minds and hearts: CrossFit, SoulCycle, Pure Barre, Orangetheory.

All promise to empower, strengthen and transform while creating a sense of community.

The latest is Females in Action, a Southern-style fitness program designed to make women stronger and develop friendships. The FiA brand is the female equivalent to F3  —  its larger male counterpart, which aims to build men up through fitness, fellowship and faith.

But unlike the for-profit studios that cater to urban millennials willing and able to pay $40 a class, Females in Action (like F3) is free. Workout sessions are peer-led. They most often take place outdoors, in public parks or school fields. And they typically end with a spiritual high five.

“We are focused on fitness, but it goes beyond that,” explained Catherine Butler, who leads one of three FiA groups in Charlotte, N.C. “We are a community of women that lifts each other up.”

Started six years ago, FiA has grown to 53 regional workout groups spread across multiple states but heavily concentrated in North and South Carolina. Many are located in the suburbs and appeal to church-going working women whose husbands oftentimes participate in the male counterpart.

FiA estimates 5,700 women work out at its exercise sessions, and many say the biggest draw is the camaraderie and support the women offer one another.

“There’s nothing ever negative here,” said Caroline Uenking, 20, who accompanied her mother, Heather, to a recent workout. “It’s all positive.”

Ms. Uenking, who has some problems with her calves, and her mother, who has a hard time touching her toes, are never singled out, they said. Instead, they’re  encouraged to do what they can, altering a particular exercise to meet their abilities.

Like the F3 male-only version from which it borrows extensively, the workouts have a certain military style that stems from one of its founders, David Redding, a former member of the Green Berets. Although some workouts incorporate yoga and others running, the typical session features aerobic exercise sets in which participants push themselves as hard as they can, rest and repeat.

In keeping with military nomenclature, participants are required to have nicknames, too. Stephanie Walton, the leader of the Apex, N.C., group, is known as Peachtree; Janice Azeveda, who leads a group that meets in Cary, N.C., is known as Van Gogh.

But although the exercises are hard-core, the female-only environment makes it more inviting for some women.

Ms. Swift, 55, said she felt overwhelmed attending gym classes alongside men.

“I would prefer women who can influence each other,” she said.

The gender restriction may be part of FiA’s more traditional appeal. If some of the newer fitness center brands draw millennials with no particular faith, FiA draws people who tend to be more religiously conventional.

Though not explicitly Christian, FiA promotes the idea of a belief in a higher being, whatever that might be called. It’s a formula that also echoes the second Alcoholics Anonymous step, “We came to be aware that a Power greater than ourselves could restore us to sanity.”

Ms. Walton, a mom now studying for a degree in health and fitness science, said FiA made her a better person.

“Since I’ve been doing FiA I’ve been going to church more,” she said. “I’ve been doing more soul-searching. It’s just part of it. You start caring about people. You see their children being born. You do things for their husbands when their husbands are sick.”

Not everyone in F3 is religiously devout, and not all sessions end in prayer.

But the group leader, called a “Q,” is expected to end each workout with what’s called a “Circle of Trust,” intended as a short time to reflect.

Ms. Azeveda, who leads a 5:30 a.m. workout in Cary, tends to keep things strictly nonsectarian. She concluded a recent session by reading a quote from personal coach Cheryl Richardson about the importance of self care.

A 58-year-old preschool teacher, Ms. Azeveda said she nearly fainted the first time she attended a FiA workout. She was never very athletic, she said, and gyms did nothing for her.

“If you decide not to go, nobody at the gym is going to say, ‘Hey, I missed you. Where were you?’ ” she said. “With this particular group, if you’re not there, somebody checks in with you and asks, ‘Are you OK?’ That’s a beautiful thing, having relationships of support. That’s really important.”

Through FiA, she’s lost weight and gained muscle. Best of all, FiA empowers women and cheers them on.

“It’s a life-changing group,” she said. “Physically you change because you’re taking care of your body. Mentally you change because you’re meeting new people and establishing new relationships and spiritually you change because you’re taking time out to reflect on your life. It’s a good thing.”