LEAGUE legend Andrew Johns is already anticipating the after-effects the Blackmores Sydney Running Festival will have on his 39-year old body, but he knows the pain is worth it.

The father of two is running in the event for the second year in a row, to raise money for the Shake It Up Australia Foundation, which supports research to identify a cure for Parkinson’s disease.

‘‘ I know my body will probably never let me forget it,’’ he said. ‘‘ I won’t be able to walk for a week after it.’’

The Channel 9 commentator is participating in the shorter 3.5km The Sunday Telegraph Family Fun Run because he’s working later the same day, but, he added, he won’t be completing the full marathon because ‘‘ my knees wouldn’t allow it.’’

Joining Johns is fellow former footy star Brad Fittler.

‘‘ I think myself and Brad Fittler are going to run together, and I don’t know, I might bring my little boy along,’’ Johns said.

‘‘ If you have little kids, you can jog and walk it, I think it’s a big buzz going across the Sydney Harbour Bridge, especially for the little kids and you can do it as a family.

‘‘ And as family it’s something you’ll never forget, doing this sort of thing.’’