"I'm still under contract with Sunderland and will train with the club for the rest of this season. Then, presumably, I'll quit," Schwarz told Swedish newspaper Aftonbladet.
"I've had a lot of injuries throughout the years, everything from cruciate ligament to Achilles problems.
"The body has taken a lot of stress and it's time to take care of my health.
"There's a life after football and I'm going to continue in the sport in some way. But at the moment I'm not going to carry on at Sunderland.
"However, I'd like to come back to the club at some point in the future, as I have a good relationship with them."