Some newer training devices include the ability to connect to Apple Watch to sync data automatically. If you do not want this pairing process to happen automatically, you can disable gym equipment detection on your iPhone. Here's how to do it.
Open the "Watch" app on your iPhone.
In the main menu, tap the "Exercise" option, which is halfway down the list.
Scroll to the bottom of the list and turn off “Detect Gym Equipment.”
 If you ever want to reset the setting, you can return to the “Workout” menu and turn on “Detect Gym Equipment” again.
And that's it. Apple Watch will no longer automatically detect and connect GymKit-compatible exercise equipment.
If you still want to sync data from smart training equipment to the Apple Watch, you can even turn off the automatic detection feature. All you need to do is open the Workout app on your watch and then keep your watch close to your device.