It also adds a streamlined tech layer on top of gyms, which often have various third-party technologies that don't always talk to the fitness wearables people have.

It's Apple's latest fitness expansion, helping it to build an entire ecosystem around the Apple Watch and providing owners with more places to use it to improve their fitness tracking. It creates yet another reason for people to buy Apple Watches: If you're trying to work out, why not get a watch that works seamlessly with the gym you're joining? And it helps gyms keep customers through rewards-based initiatives.

Apple on Thursday announced its new "Apple Watch Connected" gym initiative, a new series of partnerships with fitness facilities that makes it easier for people who own Apple Watches to track workouts, buy stuff and earn rewards for working out.

Four gyms are part of the program with select locations going live on Thursday. Additional fitness facilities will also join the program in the future, Apple said. Launch partners are Basecamp Fitness, Orange Theory, YMCA and Crunch Fitness. It's free for gyms to participate, so long as they meet Apple's criteria.

If you own an Apple Watch, you'll probably want to join an "Apple Watch Connected" gym if there's one nearby and you can afford it, since you'll receive benefits for owning one and working out. The Apple Watch Connected platform includes four tiers that must be supported by a gym that participates in the program.

An Apple Watch Connected gym has to have an iPhone and Apple Watch app that lets people track their fitness, see classes and login at the gym.

Gyms have to offer some sort of option for Apple Watch owners to "earn with Apple Watch." For example, Crunch will give you a $3 to $4 in weekly credit if you meet certain goals, like working out a certain amount of time per month. The credits apply to the following month's bill. You can hit those goals either by working out inside or outside of the gym. Orange Theory will offer gift cards to Apple and Nike for hitting certain goals. Basecamp Fitness will give you an Apple Watch Series 5 GPS model that you can pay off by participating in three classes a week for an entire year. At the YMCA, your workouts will go toward providing free classes for children, like swim lessons.

The gym has to accept Apple Pay. That means you can leave your phone in the car and just use your Apple Watch to buy stuff like water, food or other goods only using your wrist.

A fourth tier requires GymKit on cardio machines, unless it's a studio like Orange Theory where people exclusively get on and off equipment frequently during a studio-style workout class. These are special machines that will automatically sync your workouts to your Apple Watch, providing more information than the Apple Watch might be able to get on its own. For example, a stair climber will give you a more accurate representation on floors you've climbed, since the sensors inside the Apple Watch can only track actual flights of stairs as you change altitude.

There's a benefit to gyms for adding Apple Watch Connected. Gyms see it as a way to help keep customer turnover low.

"I'm confident this will help member retention and keep members active and engaged," Crunch Signature CEO Keith Worts said during a press briefing at a Crunch Fitness gym Wednesday.

Worts also addressed privacy concerns. He said that members will "opt-in" to the program and that the gym "complies with every privacy law there is." Crunch Fitness won't use the data from Apple Watches to see which machines people use most, for example. There are different sensors already built into the machines that already do that, though. None of the data is shared with Apple either, Apple said.

Basecamp will launch Apple Watch Connected to all of its clubs over the next year. The YMCA will start with its greater Twin Cities locations this week followed by 22 additional YMCA branches in the coming weeks before expanding further. Crunch Fitness is launching Apple Watch Connected in two Manhattan gyms this week with more coming. Finally, Orange Theory will deploy it in all U.S. facilities in 2020, starting with two Manhattan locations on Thursday.

Correction: This story has been updated to reflect Crunch Fitness members can earn $3 to $4 per week for reaching certain fitness goals with their Apple Watch. There are four requirements for fitness facilities: Gyms must also support GymKit unless they exclusively offer studio-style workouts where people get on and off different equipment and use the floor, like Orange Theory, or if they don't have cardio machines at all.