Blow off some steam with the hybrid fitness craze kickboxing aerobics.

In a room full of 30 sweaty people, an enraged-looking woman shouts instructions at her obedient students, who are punching the air with clenched fists like an army preparing for war. The training session is extremely challenging, requiring an hour of kicking, grunting and lunging. The whole scene would be rather intimidating if it weren't for the toe-tapping music. This is cardio kickboxing, a new fusion workout that's the hot gym thang at the moment. Also called kickboxing aerobics, this workout is a great alternative to conventional aerobics, and incorporates martial arts techniques to strengthen and tone the upper and lower body. As a bonus, this workout burns up to 800 calories an hour, compared to the 500 normally burned through conventional aerobics.

Of course, kickboxing is already widely practiced around the world, especially in martial arts or self-defense circles. The sport originated in Thailand, where it is known as muay Thai (or Thai boxing), and is a method of self-defense that emphasizes the use of the knees and elbows, plus punches and kicks. First tested in battle by Thailand's ancient warriors, today the Thai military, U.S. Seal teams and members of the CIA continue to use its effective striking techniques.

Mix 'n' Match 
If you want to try it out, this workout is offered in various gyms, with varying levels of creative choreography. Some gyms even have their own unique names for the sessions, like Cardio Tai Box or Body Combat, and integrate various elements from pilates, yoga, tai chi and conventional aerobics. Cardio Kickboxing requires no previous martial arts experience, though those with severe back and knee problems should proceed with caution, since repetitive punching and kicking can place stress on joints and lead to strains and sprains. "Kickboxing is one of the highest-intensity workouts," explains professional kickboxing coach Reuben Thurley of the Hong Kong Cricket Club. "I tell beginners to take it nice and slow, and keep a check on your heart rate. I make sure kicks are pretty low to prevent injury to the vertebrate—I keep everything very safe." The club runs hourly morning classes twice a week in its multi-purpose room. Classes are open to both members and non-members, and are charged accordingly.

Outside the Box
The upsurge in fusion classes is in large part due to consumer boredom. "Ladies like to try new things; they like jumping around, and they'd love to burn a few more calories, so this workout is perfect," enthuses Jackson Chan, membership consultant at Pure Fitness. "Using machines to strengthen and tone muscles can be dull, and people often prefer dancing to music and interacting with others." The gym plans to initiate daily kickboxing aerobics sessions by the end of February, and classes will be included in the price of membership.

"There was a need to create new exercises to motivate members to do much more," says Eva Ip, senior program officer of fitness and wellness sessions at the YMCA. "Boxercise was a very popular group exercise when it was first introduced, so we decided to integrate the two modalities to make things more interesting. Due to a lack of space, boxercise is impractical, especially because of the equipment it requires. Since a fair majority of clientele prefer a milder intensity, the fusion workout is ideal, combining aerobics with that extra kick to really get your heart pumping." The Y offers a three-month program with classes held throughout the day for both members and non-members at a slightly higher cost.

Girl Power
Kickboxing aerobics is indisputably more popular among women than men. Ip attributes the predominantly female participation to group camaraderie encouraged in the weekly sessions. "I find that women are more eager to sign up for group exercises while men prefer to workout individually, in the gym or in classes like cycling. Men are reluctant to participate in aerobic or group-related workouts because they involve too much dancing and fancy footwork."

Also, major problem areas faced by women like the legs, hips, butt and abs are targeted. Most women aren't interested in learning pure martial arts, but they enjoy fusion classes because they can benefit from a high-impact impact workout without being too serious about achieving perfect movements. Self-defense techniques are an added bonus to women. On the flipside, men who normally shy away from dance-oriented aerobics are usually more excited at the mention of martial arts or kickboxing. Seasons Sports Club also offers kickboxing sessions, which are included in their membership price.

Mind Over Matter
Kickboxing produces relatively quick results in terms of physical fitness, but the sport's capacity to stimulate the mind is often overlooked. Kickboxing demands alertness and coordination, helping to nourish your physical and mental state of being. Thurley, who conducts individual classes in addition to the sessions at the HKCC, has been a professional boxing coach for 12 years. He recalls: "One of my clients actually said to me, 'You're better than a shrink and a lot cheaper!''' You may not be the next Uma Thurman in Kill Bill:  Vol. 1, but you're guaranteed to have fun. "When I do a move, I kick you in the groin—literally," he says. "I try to make it as fun as possible ... I make things interesting by doing my own music according to the age group I'm teaching. It's never the same. You never know what's coming."—Vandana Chatlani.