Six months ago, the unthinkable happened to Cecelia Tam. A passionate runner, she became bored of pounding the pavement and could no longer face the wear and tear on her joints. Desperate to stay motivated and keep fit, she relocated her workout to the pool.
"I needed something to loosen me up," says Tam, 38. She was apprehensive at first, thinking she would arrive in a class full of geriatrics. She was also worried her swimming skills were not up to scratch.
But her fears were unfounded, and aqua workouts are now a regular part of her exercise regimen and a good way of indulging her love of the water.
Using a variety of modified equipment, such as water dumbbells, webbed resistance gloves and pool noodles, Tam works up more sweat during aqua workouts than she ever did running.
"After a pool workout I am more energetic and refreshed," she says. It makes sense: in water, the body is buoyant and there's much less impact on the joints during exercises. In addition, water is 12 times more resistant than air. The result is the perfect combination of low-impact cardio and strength training.
"Running on pavements places an incredible amount of compressive forces and pressure on your body," explains Ben Lai, osteopath at City Osteopathy in Central. "Being in the water reduces those forces, making it especially beneficial for injury rehabilitation and arthritic conditions."
While water workouts are not new, pool-based fitness and therapy in different formats - from aqua resistance training, aqua jogging to aqua zumba - is enjoying a worldwide renaissance.
"Aqua fitness is becoming increasingly popular [in Hong Kong]," says course coordinator Lychee Lai of ATP Swimming Centre, which offers personalised aqua fitness programmes to individuals and private clubhouses. "More people can enjoy it especially those with joint or back problems, or those who are overweight."
Lilian Chan, from the Asian Academy for Sports & Fitness Professionals, says 70 aqua trainers have been certified since the courses were introduced in 2007, and that number is expected to grow.
"We find clubs want to maximise the use of the pool and lots of life guards and swimming coaches want to expand their scope of services," says Chan. "Working out in water is cooling, particularly in summer, when high intensity exercises like running can expose you to the risk of dehydration or sunstroke."
Marco Ku, director at swim school Sportsmax Hong Kong, added a variety of water-based exercise and therapy programmes to his classes about 18 months ago.
"Not every one in Hong Kong can swim," says Ku. "I noticed parents dropping their children off for swimming training and wanting to get involved, but were not confident in the water or thought swimming was boring."
Although the take up for his hydro exercises classes has been gradual, it's catching on, he says. The sport is addictive because it turns the dreaded idea of a workout into a more positive experience, according to aqua zumba enthusiast Sue Wong. Aqua zumba is the hydro variation of the Latin dance fitness programme that's become a worldwide craze.
Before jumping into the water six months ago, Wong, 29, didn't have any type of fitness regimen. But after long, sedentary hours working as a marriage planner took their toll, she needed a way to release her stress and tone her muscles.
"Aqua zumba is my timeout," she says, before confidently taking to the water to shake her tail feather with Tam, who also recently added zumba to her aqua-based workout regime.
Being in the pool, Wong doesn't have to worry about having two left feet or the lack of a dancer's agility, says aqua zumba instructor Christian Monge, 40.
"In the pool you have resistance, so the speed is different. Your feet can't move as fast," says Monge. But the added resistance has big benefits. "You burn the same amount of calories but your muscles get more of a workout."
Dr Martin Juneau, director of prevention at the Montreal Heart Institute in Canada, says water training can have the same benefits as land training in terms of improving aerobic fitness.
In a study he presented last year at the Canadian Cardiovascular Congress, healthy participants were put through exercise tests on both the land and water cycling machines (with water up to chest level). Maximal oxygen consumption - which indicates how good a workout is - was almost the same using for both.
Juneau also found that participants' heart rate was a little lower in the water. This is because the heart pumps more blood for each beat, as the pressure of the water on the legs and lower body makes the blood return more effectively to the heart.
A lack of pool venues and availability of courses, however, means aqua workouts are still not commonplace in Hong Kong, says Lai. Last summer, her centre ran a promotion on group buying website Groupon to generate more awareness. Around 300 people took up the offer.
Water workouts are also great for therapy and rehabilitation. After suffering a shoulder injury while playing rugby, former Hong Kong national rugby player Li Chin-on took up aqua therapy twice a week to accelerate his recovery.
"I've found my range of movement is much better after aqua therapy," says Li, 23. "It involves similar exercises to what they would do in the physiotherapy clinic, but it's more challenging [and with better results] because of the added resistance."
Physiotherapist Raymond Tsoi believes the pool is the best way to treat clients. "The water helps to relax overused muscles," he says. "It also unloads the joints, especially the weight-bearing joints in the body, such as the hip, knee and spine."
Above all, being in the water is enjoyable. "I get to go in the pool for my sessions," says Li. "That's more fun than being in a physio's office."