How can common fitness-related injuries be treated at home? When should medical care be sought?

It really depends on the injury.

Explanation:

If it's a twisted/sparined ankle or wrist you can usally wrap it in an ACE Bandage that you can buy from the convinence store as well as ice it to help with swelling and let it heal. If the swelling or pain has not decreased you should seek medical attention. It may be broken.

I hope this helped!!