Technology is shaking up the fitness industry and making established gym chains work up a sweat.
New apps are challenging traditional membership structures and introducing more flexibility into the market.
For example, ClassPass is an app that allows you to book into fitness classes in over 30 cities around the world - including New York, London and Sydney.
One monthly fee - currently set at £79 - gives you access to around 8,000 studios across the world. And you can book classes up to four times a month at each participating gym.
"Our platform makes fitting fitness into your schedule really easy and flexible, as opposed to making a big commitment with little variety," says Payal Kadakia, ClassPass founder and chief executive.
"I feel we've inspired people to be more active by removing many of the barriers to working out and encouraging discovery."
Ms Kadakia, who launched the service two years ago in New York, saw a gap in the market for a gym app which gave you flexibility, and value for money.
"I was looking for a ballet class one day, and it was impossible to find something," she tells the BBC.
"I realised that other people might be experiencing similar issues, so I wanted to create a service that removed as many friction points as possible."
Similar services are cropping up around the world as start-ups see opportunities to challenge the perceived inflexibility of established fitness club memberships - most of which involve compulsory annual contracts.
In India, Devi Prasad Biswal and Avijeet Alagathi recently set up Book Your Game (BYG), an app that lets users book fitness classes on a per session basis, rather than having to sign up for full membership.
London-based Somuchmore offers access to 40,000 classes at 280 participating studios, gyms and spas, and demands a monthly membership that can be paused or cancelled at any time.
And MoveGB is a fitness service and app that partners with bigger chain gyms allowing you to visit them - without a monthly contract with the gyms themselves.
But what's in it for the established studios?
"It allows studios to build up a new client base, especially if they're relatively small, have no budget for PR, and want people to start talking about them," says fitness industry marketing consultant, Natasha Richardson.
Studio Lagree, a pilates concept studio, founded in California, has attracted new customers after linking up with these fitness apps.
"Once clients in California experienced the transformation from the three classes a month, via ClassPass, they tended to buy more, through us, to fill out their fitness requirements," says Robert Lepone, Studio Lagree director.
This influx of customers allowed them to expand their concept and studios into different US cities, as well as the UK, opening their first London studio last October.
But while some studios benefit from the new clients ClassPass can bring in, others are unhappy with the revenue-sharing arrangements and have been leaving the platform, particularly some studios in London.
The danger is that if the offering becomes too narrow, ClassPass, and apps like it, may lose their appeal.
But established gyms and fitness studios are having to respond to the app generation.
"It's making chain gyms fight for their customers," says Ms Richardson. "A couple of years ago there was no alternative, but now that the boutique gyms are more accessible it's made them up their game."
Virgin Active is one of those gyms to do so. As well as adding a number of new classes in the last year, they have introduced Discovery Lab, where experts share their own experiences and ideas to bring new perspectives to classes.
For example, mountaineer Kenton Cool recently launched the Apex Altitude studio with Virgin Active, sharing his knowledge of altitude training.
Fitness First has followed suit with new freestyle training classes, as well as working closely with UK athletes to create classes around their training techniques.
Virgin Active's app allows you to book onto their classes, while Fitness First's CustomFit app gives gym-goers the opportunity to create personalised workouts, set goals and access exercises and videos from their mobile.
And it's not just gyms that are seeing the benefits of using technology to give customers a better experience.
James Crossley, a personal trainer and owner of Chelsea Fitness, has created the app PTN1, which allows personal trainers the ability to share workouts with clients.
"Gone are the days of scribbling down workouts on a piece of card," he says.
"The app helps with motivation, consistency and allows both you and the client to see development in your workouts."
And dedicated workout apps are flooding the market. Fit Gurus, for example, guides you through your workout, offering videos and an in-app chat facility in case you need to ask any questions.
Fitness expert and personal trainer Laura Williams says such apps mean that even the diehard gym hater can get a great workout without leaving their front room."
But there's nothing like a human trainer barking out orders and encouragement, she maintains.
"I've yet to find an app that closely scrutinises the exerciser," Ms Williams says, "or one that employs every last trick in the book during those last painful minutes of a workout.
"The people I train want human contact. They want to tell me about their day before we warm up, or have someone to hug when their jeans fit again."
Follow Technology of Business editor @matthew_wall on Twitter.