The Rev. Jesse Jackson speaks to inmates at Cook County Jail in Chicago during a Christmas Day sermon on Monday. Standing behind the civil rights leader is Rep. Bobby L. Rush (D-Ill.), who also addressed inmates. (Sophia Tareen/AP)

The Rev. Jesse Jackson said he's relying on daily physical therapy, medication and prayer to manage Parkinson's disease, but he showed few signs of slowing down Monday as he carried on a decades-old Christmas tradition with a sermon to inmates at one of the nation's largest jails.

Jackson, 76, publicly disclosed a 2015 diagnosis last month, saying he would make lifestyle changes to slow progression of the chronic neurological disorder that causes difficulties with movement.

The civil rights leader said during the services that he's scaled back his travels a bit, although he still described a busy itinerary in the coming months.

"My time is used more strategically," he told the Associated Press. "I'm traveling a little less and focusing more."

Jackson appeared lively during the services, which featured gospel music and opportunities for eligible Cook County Jail inmates to register to vote. Reps. Danny K. Davis and Bobby L. Rush, both Chicago Democrats, also addressed inmates.

Jackson said the disease is a "physical challenge" but he is following a strict treatment regimen as he continues to lead the Rainbow/PUSH Coalition, the Chicago-based civil rights organization he founded more than two decades ago.

Parkinson's isn't fatal, but people can die of complications. It can start with tremors, and symptoms generally worsen over time. The exact cause is unknown. Treatments include medications, surgery and physical therapy.

During the services, Jackson offered wide-ranging comments on the right to vote and prison reform, among other topics. He asked inmates to pledge to make changes in their lives.

Many knelt on the floor to pray. Some broke into tears.

"Our mission is to get you out of here and not return," Jackson told the crowd of about 200 men and women. "Jail is not a hotel."