As group fitness fads come and go, one class has stayed popular for years - Spin.
Also known as RPM (rotations per minute) classes, Spin is an indoor cycling class where the groups, perched on fixed exercise bikes, follow an instructor in sprints, hill and interval training.
Next Generation Kings Park health and fitness manager Renee Tuke said Spin was designed to give a hard cardio workout.
"My motto at the end of the class is 'You and I should have a love/hate relationship - you love me at the start and you hate me at the end'," she said.
"I have never had a member ask for a refund yet. Not only does it work your legs, hamstrings, butt (glutes), calves, triceps (arms) and core, it is also good for the mind."
Goodlife Health Club group fitness manager Sharon Briggs said in an average 45 to 50-minute class, a participant could burn 500 to 700 calories and cycle anywhere from 20km to 27km.
And many participants found Spin addictive.
"It is extremely fun, fantastic and leaves you with a huge smile on your face," Ms Briggs said. "It is low impact and does not discriminate against age, ability or fitness level. Basically, all that is needed is for you to be able to sit on a seat and move your legs."
Ms Briggs said the class worked out the body both aerobically and anaerobically through fast, short sprints, long endurance hills, high-intensity intervals and recoveries.
"This improves health and lung fitness, increases strength and endurance and leaves you with an endorphin high," she said.
Ms Tuke said Spin classes were continually popular as it was a class you could never master.
"For example, you could never turn your legs at more than 130 RPM, at the max gear level for a whole hour," she said."And if the weather is too cold, too wet or too hot, the temperature in the Spin room is just right. It is a class that requires no co-ordination. Many men do not join in group fitness as they feel out of their comfort zone. But Spin would generally have the most males, more than any other group exercise class."