Jo has a top sports physiotherapist with her, Professor Greg Whyte, OBE, the same guy who got Davina McCall through her 500 miles in 7 days triathlon challenge for Sport Relief in 2014.
Jo also trained for it, walking a marathon's distance as her final preparation.
Jo isn't Davina McCall but she isn't doing 500 miles of swimming, biking or riding either.
She's doing 20+ miles a day walking, which in terms of achievement for her is up there with Davina's.
Yes, she probably will be doing something else next year to support Comic Relief as she has done in previous years. Walking is a lot kinder on the joints than running. A friend was irreperably damaged when she damaged her back doing gardening. I'd rather walk, if I could.