Pope John Paul practiced flagellation and flagellated himself to emulate Jesus Christ's suffering, according to "Why A Saint," a book written by Monsignor Slawomir Oder.
Flagellation is defined as the process of driving or punishing someone, typically through whipping.
"In Krakow as in the Vatican, Karol Wojtyla flagellated himself," Oder writes in the book. He cites testimony from people close to the pope and prior bishop.
Monsignor Oder is the Vatican official in charge of leading an investigation that may lead to Roman Catholic sainthood for John Paul, who died in 2005.
Reports in the past, such as one in November 2009, have suggested Pope John Paul "whipped himself" in remorse for sins.