While the Apple Watch is seen by many as the ultimate wearable fitness tool, it's somewhat out of place in the gym. The native Workout app has a number of exercise profiles to choose from, including activities that can only be done in the gym. But, in many ways, the Watch is best suited for outdoor activities.

But with the introduction of GymKit, Apple hopes to make the in-gym cardio experience better. Apple's system to connect the Apple Watch to compatible gym equipment started rolling out across the globe earlier this fall, and it just hit the US this week. Below is everything you need to know about GymKit as an Apple Watch user, how you can use it, and what it means for your workouts in the future.

What is GymKit?

Apple announced GymKit at this year's WWDC in June as part of the watchOS 4 update. GymKit is a protocol that allows Apple Watches to use NFC and Bluetooth to connect to various pieces of gym equipment. This allows the wearable and the machine to share information so you can glean more information when working out with the Apple Watch.

The idea behind GymKit is to accumulate the most accurate workout data by using the technology that is best for that specific workout. Apple Watches know a lot about you, including your height and weight, and can accurately measure heart rate over time. However, the Watch won't be nearly as accurate in determining distance and pace as the machine you're using indoors while working out. With GymKit, the Apple Watch can see and collect information registered by a treadmill, elliptical, stationary bike, or stairstepper, and those machines can display accurate heart rate and calorie data during a working out.

A convenient side effect of the Apple Watch sharing information with a treadmill is that you'll see your real-time heart rate and caloric expenditure on the treadmill's display. That means you'll spend less time flipping your wrist upward to check heart-rate zones and how many calories you're burning during a workout.

How does GymKit work?

The real-world implementation of GymKit is painfully simple—just tap and go. Apple Watch users who want to exercise on a GymKit-compatible machine only need to hold their watch near the NFC label on the machine and wait for the Watch's haptic feedback.

During the very first time you pair your Watch to a GymKit machine, it'll show a short paragraph explaining what GymKit does and that all your workout information won't be stored on the exercise equipment at all. At the end of the workout, all exercise data is stored only on your Apple Watch and in Apple's Activity app. Machines don't remember your Apple Watch either—if you walk away after a workout, you'll need to re-pair the Watch to that machine to use GymKit again.

After confirming that you want to pair with a GymKit machine, you can start working out. Starting a workout from the machine will prompt the Apple Watch to plunge into workout mode and track your data. Since GymKit only works with treadmills, ellipticals, stationary bikes, and stair steppers, you don't even need to choose a workout profile because the Watch will recognize the type of cardio machine you're paired with. You'll only have to choose "indoor walk" or "indoor run" when pairing with a treadmill—otherwise, the workout profile recorded by the Watch will automatically match the machine you used.

You don't need to do anything special while exercising, as the Watch and the machine will continue to share information until the workout is finished. Instead of turning to the Watch to see some information, data points like active calories, total calories, and real-time heart rate will show up on the machine's display.

I got the chance to test this out on a Technogym treadmill, and the experience was seamless. Data calculated by my Apple Watch Series 3 transferred to the treadmill via Bluetooth nearly instantaneously. I didn't have to look to the Watch's smaller screen when I had a huge touchscreen in front of me. On the flip side, the treadmill's distance and pace information beamed to the Watch.

Valentina Palladino

Valentina Palladino

Valentina Palladino

Valentina Palladino

Valentina Palladino

Valentina Palladino

Valentina Palladino

Valentina Palladino

When you're finished, you can end the workout either on the Watch or on the machine, and no matter which you choose to use, the other machine will stop. For example, if you end a run by using the treadmill's controls, your Apple Watch will automatically end the workout and you'll receive a summary on both devices that have matching exercise information.

Most of us have forgotten to start a workout on our Apple Watches only to realize half-way through the session. Apple designed GymKit to help in this situation, allowing you to tap the NFC reader at any point during the workout to connect to a machine and sync data. The Watch will not only start tracking the remainder of your workout, but it'll also use the timer on the machine to retroactively account for the exercise time that you forgot to record. That way the 20 minutes you spent on the elliptical before "starting" a workout on the Apple Watch will be recorded, along with all your past movement and heart-rate information.

An Apple Watch has access to all kinds of workout information using GymKit that it never had before. That data shows up in the native Activity app on your iDevice. Information including incline of the treadmill, average RPMs on the stationary bike, and floors climbed on a stairstepper are included in Activity app workout summaries.

Not only will seeing those data points after a workout make some users happy, but they also inform caloric expenditure to a certain extent. Previously, the Apple Watch didn't know if you were walking on a flat treadmill or a steeply inclined treadmill, but that's an important factor of your workout that changes the amount of energy exerted. GymKit gives that information to the Apple Watch so the wearable can more accurately estimate calories burned and the intensity of your workout as a whole.

Who can use GymKit?

I only had a short time to test GymKit, but the feature worked as promised, and it's clearly influenced by Apple Pay. Apple Watches already use NFC to complete Apple Pay transactions when you tap your wrist near an NFC payment reader. People who use GymKit interact with gym equipment in the same way that they would interact with a payment reader for Apple Pay.

While the information sharing is neat, it's not a groundbreaking feature. Other fitness devices like chest strap heart-rate monitors have been communicating with gym equipment using Bluetooth for a while now, albeit without two-way data synchronization. When I use a chest strap, I don't even need to pair it with the machine I'm using—my real-time heart rate information immediately shows up on the machine's screen when I'm within range.

But the Apple Watch is a more complicated device that requires more security and privacy measures, which is why Apple requires all compatible machines to have a GymKit module in them. You can't pair an Apple Watch with a machine that already has NFC and Bluetooth capabilities if it doesn't have the GymKit protocol built in.

That being said, equipment manufacturers and fitness clubs currently decide who has access to GymKit. Any Apple Watch running watchOS 4.1 or higher can connect to a GymKit machine, but currently those machines are limited. GymKit launched in North America this week, but only the Life Time Athletic at Sky club in New York City has GymKit machines. The feature already launched in Australia and the UK, but only one fitness center in each country has compatible machines so far.

Life Time Athletic is one of the first club partners for GymKit and has promised to include GymKit machines, made by Technogym, in all of the 14 new clubs it will build in 2018. The club will also retrofit its cardio equipment in the clubs that opened in 2017 with GymKit, while retrofitting of equipment in older clubs will come later. Technogym is one of GymKit's first manufacturer partners and claims that only a couple of hours are needed to retrofit machines in one club. Technogym will also be building GymKit into all of its treadmills, ellipticals, stationary bikes, and stairsteppers in the future.

The other two current partners are Equinox and Life Fitness—Equinox will outfit all its new clubs opening in 2018 with GymKit machines made by Life Fitness. The first Equinox location to have GymKit machines will open in Q1 2018 on Orchard Street in Manhattan.

The biggest pain point I have (and likely that many others will have) is the initially limited rollout of GymKit. If you don't live in or around New York City, you can't use GymKit at all right now. Life Time Athletic and Equinox are also expensive clubs, so if you don't want to increase your monthly gym payment, there isn't a road map for GymKit to come to your club yet. While manufacturers need to get on board with GymKit and either make new equipment or retrofit old machines, there's no guarantee your gym will get GymKit equipment within the next year. We'll likely see Apple announce more partners in the months to come, and hopefully those will include more affordable fitness clubs that reach customers in various North American regions.