Two ways to manage who you interact with.
Blocking an athlete removes any follow relationship between you in both directions, prevents them from following you again, and stops them from seeing your activities or interacting with them.
You can block someone from the menu next to the Follow button on their profile, or from the Connections page. Manage everyone you've blocked in Settings → Privacy, where you can also unblock them.
Muting is lighter than blocking. When you mute an athlete, their activities stop appearing in your Feed, but you stay connected — they aren't notified, they can still see your activities per your visibility settings, and you can still visit their profile. Unmute anytime from Settings → Privacy.
Use mute when you simply want a quieter feed, and block when you want to cut off contact entirely.