In some cases of the hand anatomy (I’m the unlucky one), the bulge on the back of the apple watch is perfect shape to pressure/tap a branch of the ulnar nerve, causing symptoms similar to ulnar nerve entrapment at the wrist such as:

• Wrist pain
• Tingling in the 4th and 5th finger
• Weaker grabbing force in the arm
• Mild to strong pain when lifting things, with your palms up - this kind of motion:

https://preview.redd.it/hpyxiikh4o1c1.png?width=640&format=png&auto=webp&s=e2a0dfae651ad86787cd3f7da572e1f1ef4ae4d3

It is caused, unintuitively when the watch is worn looser, compared to tighter, as in this case it tends to slip over and under the carpal bones, and find its way to touch the nerve continuously.

I know this is one of many of these posts but I wanted to clear some bad advices given in previous posts, and share if someone searches for the info:

• If you feel the wrist pain, change your watch arm. Regardless if it’s an apple watch or anything else. Things are not symmetrical, and it will most probably not cause you pain in the other arm.
• Tighten the watch, don’t loosen it. Especially during the exercise, or wrist movements. It should stay above the carpal bones.
• If nothing works, reduce the time you wear the watch, try a different brand, or stop. Continuous pressure on this nerve can mess up your hand.