Jimbone - completely correct, the amount & type of effort involved to recce and eventually complete this challenge has apparently cured the mystery thigh pain in my THR leg, which at 18 months post-op (ie last Xmas) had me back using a stick, and one day even a crutch, to hobble around. My health insurer did not want to pay for an MRI but would offer physiotherapy. Didn't bother with that; after 2 months I found I could manage to run again despite twinges, biking was never really affected so I stayed relatively fit throughout, and I stopped visiting the climbing wall because the type of movement with twisting and pushing off that leg did seem to make things worse.
Some days since then have been fine, others twingy, could never tell which it was to be.
Came back from the first week in Wales with a terrible limp and a load of fluid retention (about 7 pounds of extra weight, lost in two days through excessive peeing). Obviously done significant remodelling of major muscles, and I was completely exhausted.
One month later, with experience and a steadier pace, we not only completed the walking challenge but managed a 40 mile bike ride the next afternoon, and another nearly 3000' mountain the next day - both painless, though neither easy...
Back to racing 5km every Saturday now, but have added longer runs on the Sunday as well, up to 13 miles, in preparation for a 10 mile race in September. The only slight cloud on the horizon is that now my right leg is carrying its fair share of the load my BHR left hip is complaining a bit about the increased mileage, feeling a bit stiff but responding well to resting for a day. Cobalt/chrome ion levels were good last year so not too worried just yet...
And yesterday, raced in the morning 5k and found someone to climb with in the afternoon - three hours on the wall seem to have done no damage, so it really feels like my problem is resolved - touch wood!
I suspect that sitting, which I enjoy and do to excess, is probably the riskiest thing I do as regards health and fitness, walking down steep rocky slopes seems to cure most ills but it does take time to acquire the musculature to tolerate prolonged effort.