Crawling around on their hands and feet, the group of 30-odd adults imitate the movement of a bear, spurred on by their instructor's shouts.

This is Zuu, a high-intensity group workout that mimics animal movements.

It is part of the increasingly popular trend of group workouts, which the American College of Sports Medicine (ACSM) has identified as one of next year's top fitness trends.

The ACSM's annual survey also picked Exercise is Medicine as one of the top fitness trends for 2017. Exercise is Medicine is a global initiative that encourages healthcare professionals to include exercise in their treatment plans for patients.

Both group training and Exercise is Medicine are new to the Top 10 list since the survey started in 2006, making it to the sixth and seventh spots respectively.

Gyms in Singapore said group training classes are popular here, especially among executives looking for a short, intense workout combined with the opportunity to socialise. These classes are about 30 to 45 minutes long and are held during lunchtime or after work.

The choices for group classes here have increased considerably over the years.

Sport Singapore's 19 ActiveSG sport centres, for instance, have more than doubled their group training programmes to at least 90 since two years ago. More men are now going for such classes, which attract mostly women aged 25 to 60.

At Virgin Active gyms, the number of weekly group training classes has risen to nearly 200 this year, from more than 100 three years ago. About 70 per cent of its members take part in group exercise classes.

Spurred by the demand for such classes, it is making group training the focus of its third club here, which will open at Raffles Holland V Mall next year.

Group high-intensity interval training (HIIT) classes, such as Zuu, and Grit Strength and Core - a combination of weightlifting, running and jumping - are usually fully booked, said its managing director for South-east Asia, Mr Christian Mason. "Such classes help people stay motivated in a group who share the same interest for fitness and exercise."

The sense of camaraderie in group training has kept Virgin Active member Caryn Cheah, 32, hooked since she joined the gym three years ago.

"Group training helps, especially when you're new to something, you don't know anyone there and you feel insecure, especially when you're big in size," said the food and beverage manager at Zouk, who weighs 45kg but used to be a lot heavier.

Managing chronic diseases through regular exercise

"But during group training, you see people of a similar size, while others will encourage you. It helps to build a community," she added.

At Fitness First, its Capital Tower Sports Performance outlet added six group training classes in August.

These classes can be held up to nine times a week to meet demand, mostly from executives in their 30s to 40s, said Mr Andrew Phillips, managing director of Fitness First Singapore.

Undergraduate Jennifer Gwee, 22, who wakeboards and goes to the gym, recently signed up for group training classes.

"I'm deskbound for eight hours during my e-commerce internship, so the classes are a nice break and help to build up my endurance levels for wakeboarding," she said.

The increasing popularity of group exercise classes is also due to the rise in non-dance-based workouts since last year, said Ms Sharifa Norliza, senior manager for programme development at Sport Singapore.

"There are programmes which have elements of body weight, strength and flexibility training, which are rhythm-based or combined with music," she said.

Examples include Pound, a cardio workout with weighted drumsticks, and Piloxing, which combines pilates and boxing.

While more people are going to group classes to socialise and get fit, others have been ordered by their doctors to work out if they want to get well.

A check with Exercise is Medicine Singapore (EIMS) showed that demand for its programmes has picked up significantly in the past year. A spokesman said it had certified 389 doctors and 184 allied health and fitness professionals since its launch in 2011.

EIMS trains doctors on how to prescribe exercise to prevent common chronic diseases such as diabetes and hypertension. It also trains allied health and fitness professionals on how to safely supervise exercise prescribed by the doctor.

EIMS director of research, Dr Lim Ang Tee, said the not-for-profit organisation has limited resources and funding to train larger groups.

However, it is focusing on people who deal with patients with chronic diseases daily, such as general practitioners, he said.

More allied health professionals are being roped in.

For instance, nurses from the National Kidney Foundation are being trained to do exercise prescription specifically for dialysis patients, said Dr Lim.

Scientific research has shown that regular physical activity protects against chronic diseases such as hypertension, Type 2 diabetes, heart disease, obesity, stroke and cognitive decline.

"The importance of exercise in managing chronic disease is even more urgent as Singapore's population is ageing rapidly," Dr Lim said.