Laura Baker realized there's no substitute for Cardio Tennis while ... practicing tennis.

"When you practice with a team, you're sitting on the side, and I kept thinking, 'I could have been at Cardio Tennis getting a good workout,' " she said. "You get soaking wet, but it feels so good."

As its name suggests, Cardio Tennis is a combination of cardio work and tennis, an hour-long program that includes a five- to 10-minute warm-up, a 30- to 50-minute cardio segment and a 5- to 10-minute cool down, according to cardiotennis.com.

Baker, 52, a special services director for Macy's West in Hawai'i, enjoys Cardio Tennis because of the improvement in her conditioning and footwork since she began taking the clinics in the late '90s.

Baker's instructor, Kyle Kaneshiro, said "the most important thing is you have to make it fun for everybody. You have to be very enthusiastic as an instructor.

"It's something different. There's music going on and a lot of different drills. It's a fun environment for people to get their exercise."

To aid in the workout, participants usually wear a heart-rate monitor that looks like a wrist watch, allowing them to gauge their work rate and adjust accordingly.

"It's really neat; it shows progression and improvement," said Sheila Kurosu, the director of schools and recreational tennis for the USTA/Hawai'i Pacific Section and a Cardio Tennis instructor.

Baker participates in the clinic once a week at Moanalua High School, one of several locations offering the clinic around O'ahu.

"It's fun, and it really improves your footwork, reaction time, strokes, strategy," Baker said. "You just learn a lot. You don't get a lot of instruction; it's not meant to be a lesson, but you learn from a lot of people when Kyle gives you tips."

Baker noticed the difference in her fitness level after taking off from classes during the heavy rains in March and April.

"When we came back, the first class was so hard, you realize how out of shape you've gotten," she said. "But it comes back pretty quickly. It felt so good to come back, be outside, be with all your friends."

Cardio Tennis is designed to help people of all levels of tennis and fitness ability. Instructors tailor drills to maximize the workout and alter them based on the skill level of the participants.

"The older people, it's good to keep them in shape," Kaneshiro said. "The tournament players, it helps them with their court quickness and anticipation. For the recreational player, it helps them run around and exercise. Some people aren't as good skill-wise, but they still get to hit the ball.

"We make it more fun for the beginners, make sure they have a good time."

Kurosu said a lot of people are hesitant to join because they are afraid they need to be in better shape. She said instead, use the clinics to get into better shape.

"We want to get their heart rate pumping and blood flowing," said Kurosu, who runs a class at Kane'ohe District Park. "I just tell them to make sure you don't hit anybody or yourself."

Reach Leila Wai at lwai@honoluluadvertiser.com.