I also primarily do a lot of weight lifting. Its difficult not having the Apple Watch bumping into things with the weights, but I would suggest you could purchase a bumper that surrounds the Apple Watch casing to help protect it.
“If you sell or give away your Apple device, you can also transfer the ownership of your AppleCare Protection Plan or AppleCare+ in regions that allow it. You can also transfer your AppleCare coverage plan between your own devices that are the same type of product and within 30 days of your original device purchase. “
https://support.apple.com/en-us/HT202712