There's a new exercise program in town called TRX.

Designed by a former Navy SEAL, it stands for Total-Body Resistance Exercise and is based on suspension training. It builds strength, balance, flexibility and core stability by using body weight and gravity for resistance.

The device — a pair of sturdy straps with handles, joined by a metal clasp ring — can be anchored from a stable location within a gym or at home. It costs about $150.

At the Nu'uanu YMCA, where two fitness professionals have adopted the method, it's making an impact.

Allison Beale teaches yoga and Pilates; she's into mind-body exercise and wants to increase core strength, flexibility and balance.

J.J. Bush is senior program director for healthy lifestyles and aquatics; he's all about dynamic exercise, training for triathlons and surfing, building endurance and muscle strength.

Both of them use TRX to take their workouts up a notch.

The equipment can be used to increase resistance during traditional Pilates and yoga — as Beale does — or incorporated into other basic exercises, such as push-ups, bridges, lunges and squats — as Bush does.

Because the straps used in TRX aren't fixed, it constantly challenges balance, creating an instability that causes core muscles to engage with each move, accelerating strength development.

The challenge can be tough, but it's also flexible. You can move from a simple version of an exercise to an extremely difficult version simply by moving your body a few inches.

Bush finds the TRX ideal for sports-specific training, because of its flexibility in moving through space. It's being used to train golfers, tennis players, surfers, triathletes and others who take fitness seriously.

The TRX is not for everyone, because it uses one's entire body weight to work against gravity. It's not recommended for people with shoulder, back and joint injuries or those who lack core strength or have balance issues.

Trudy Couillard of Punchbowl is taking Beale's TRX class.

"It totally does work all the muscles in the body," she said. "It has alleviated all the pressure to my shoulders. And, hey, you're sweating like you're in a cardio class!"

Pilates enthusiast Sonia Franzel of Punchbowl, a skier, says the system made a difference in her endurance. "The results are amazing," she said.

But she cautions, "TRX is not easy to master. It is hard work and total concentration. During the class you cannot allow your mind to wander, not even for a second."