With tranquil ambient music playing in a studio room at the Windward YMCA, one would hardly imagine students participating in grueling exercise — until you sit through one of Sundae Merrick's yoga sessions.

Students made impressive attempts to follow Merrick's gentle guidance, as the 53-year-old led her class with a smile and encouraging spirit.

The testing nature of yoga soon becomes evident with an occasional groan coming from some of Merrick's disciples, as she reminds her students to stay within their comfort level.

"In the beginning, many people are very tight and contracted, with limited flexibility," Merrick said. "I recommend taking the stretch just to the edge of where it can be felt, but not to the point of pain ... don't make your body scream."

Merrick, a Chicago native and 13-year Windward O'ahu resident, first undertook yoga when she went on a spiritual journey to India and Nepal. Now, she has been sharing her knowledge for the past 23 years.

Geoffrey Chung, 40, of Ho-nolulu, has been practicing yoga since he was 23, and has been Merrick's student since 2002.

Chung said he "was first introduced to yoga by (his) grandmother as a youth ... and after a long break (I) returned to yoga during (my) college years, looking for a means to center (myself)."

"When I first met Sundae, she was very relaxing," he said. "She has a very calming and encouraging manner, adding a bit of spiritual focus with her yoga, yet she is not preachy."

Chung said yoga has not only helped his emotional well-being, but it has also helped him as a triathlete.

"Yoga (helps) me keep my muscles limber and well stretched," he said. "At 23, I developed knee problems due to a lot of running, as well as doing track and field in high school. Yoga helped increase my athletic longevity. It's not to say that my knee problems have gone away entirely; however, they have improved immensely."

Chung practices yoga three to five hours per week to balance out his triathlon training.

"Geoffrey has deepened in his awareness of himself, as his body became more flexible so did the rest of him," Merrick said. "He seems more in tune with people as it's also part of his work as a psychologist."

Kailua resident Steven Trecker, 60, tried yoga in his mid-20s, but it wasn't until nearly four years ago that he recommitted to the practice.

The New Jersey native and retired attorney practices yoga two to three times a week.

"I do much shorter sessions of yoga positions at home almost daily," Trecker said. Trecker uses yoga to reduce tension.

"I was having a lot of personal stress, including the death of my parents and a close friend," he said, "and started yoga to be better able to handle the stress."

Trecker said yoga also has helped him become more limber and better able to participate in other activities, such as weight training, aerobics and golf.

"I find (yoga) provides a meditative and stress-reducing experience, while at the same time being a good workout," he said. "I feel strongly that the vast majority of people would greatly benefit from regularly practicing yoga, and it would noticeably enhance their lives.

"When I first went to Sundae, my flexibility was very limited," Trecker said. "I appreciated her patience and guidance, as she worked to help me improve."