Pete Doherty is wearing his girlfriend's bras to protect his "sore nipples".The troubled Babyshambles rocker, who is in training for this year's Flora London Marathon, complains his T-shirts are chafing his chest and has been borrowing 19-year-old model Portia Freeman's padded underwear to ease the pain.
A source said: "He's doing so well. He's really serious about kicking drugs and this is really testing his will power and giving him a goal.
"All that is putting him off are his amazingly sore nipples, but Portia's underwear is really helping."
Portia - who has reportedly been dating Pete since last December - has also signed up to the punishing 26-mile race in April and the couple even hit the gym together during a recent trip to Paris, where Pete played at the city's Olympia Theatre.
The 28-year-old singer, who entered rehab to tackle his addiction to heroin last year, is so determined to get fit for the marathon his friends say he has become obsessed with reaching his goal.
A source added to Britain's Daily Star newspaper: "Pete is showing the same devotion to marathon now as he did do to drugs.
"It's a much healthier obsession than heroin."
Earlier this week, it was revealed Portia - who has been described as a "clean-living" girl - fell for Pete after watching him perform in London before going back to his Wiltshire home.