The 39th president, born in 1924 and raised during the Great Depression, has slowed physically in recent years, acknowledging recently that he has trouble walking after hip replacement surgery in May. But he remains active with programs at the post-presidency center he and Rosalynn Carter opened in Atlanta in 1982. He still teaches Sunday School at Maranatha Baptist Church in Plains. The Carters plan to travel later this week to Nashville, Tennessee, where they will help build houses for Habitat for Humanity.