The organisers of this Challenge, on behalf of Kidney Research UK, is the very experienced company Global Adventure Challenge. When you sign up, they supply a pack of information and advice. Included is a training guide that addresses the various aspects of the challenge. 
Of course, what you actually can or have to do depends upon baseline fitness and the time you have. In my case, I gave myself a full year in the recognition of my baseline - given all the factors that have impacted my fitness over the past 5 or so  years.

Whenever I am attracted to embarking on something that's, maybe, a little unusual, I think of three key questions:

Can I, realistically? Why not? Who says I can't?

Then I can judge whether I really even want to give it a go, what are the issues I have to address, and to make sure the answer to the last Q doesn't include me!

So here I am: a 74 year old chap who's fundamentally healthy (or I couldn't have donated a kidney) but who's had three reasonably decent operations over recent years leaving me in some sort of shape - if you ignore the injuries and the arthritis that wangles its way into an increasing number of places; which I mostly do.

That aside, I do have to pay attention to the modest but important needs of Kevin - my remaining kidney - who cannot deal with certain medications, foods and especially dehydration as well as he could when sharing the load with his now absent brother.

Finally, I have learned to my cost that, these days, I can only push my muscles and tendons and ligaments so hard. If I am to avoid injury, I can no longer bash and crash, but must proceed in measured steps. That said, exercise has definitely improved my ability to undertake and sustain ....... more exercise!

This has all informed my training plan into phases.

What I can now identify as Phase 1 actually started a month or so after the kidney op, when I joined a 12 week Weight Off Workshop (WOW) to lose the weight I had gained around my knee replacement plus the nephrectomy in 2025. Joining this program proved an epiphany. Not only did I actually achieve the 5% weight loss target but I found myself enjoying the body conditioning classes and feeling definite benefits in all my previously injured places.

In turn, it led to me joining a local Gym to continue those types of class, and gave me the confidence to seriously consider answering Kidney Research UK's call for  Mt Kilimanjaro Challengers.

A discussion with my brilliant GP secured my signature.

This current phase is about gently building on that progress, testing and improving my capabilities and pushing my general fitness. It will last until the end of November, to allow for family summer activities and holidays. It consists mostly of gym based spin bike and body conditioning classes plus longish 'HeartSmart' walks . I want to include more swimming but, for various reasons, this phase  prioritises my legs, core and back. That balance will change as I include more gym based weights and machinery such as the hill climber and rowing. I'm still cautiously testing myself in these areas so as not to aggravate old injuries and known weakness. My objective is to lay solid foundations for the more focused work to follow over the winter and spring.

Of course, walking my dog - Freya - continues to provide a base of regular exercise and the incentive to do more, and more challenging, walks.

The Kilimanjaro challenge features long, back-to-back days at a slow pace (to minimise the impact of altitude sickness) under a 10-15kg backpack load, up a reasonably steep hill in mixed terrain and weather, with diminishing oxygen in the air, having slept in increasingly cold, windy and, I suspect, noisy tented campsites. For me to successfully complete this mission, I need to prepare for each of those elements as best I can.

As a result, I have begun doing a couple of days (back-to-back) of local 7 and over miles 'Heartsmart' walks each week. I'll be wearing my backpack with increasing weight as progress allows. Currently that's a modest 6kgs. I've also joined the Ramblers Association for some serious walking.

In addition, I've put trekking the South Downs Way and the Great Glen Way in my sights. These are 70 -100 miles long, so giving 6+ back-to-back days of backpacking and sleeping in a tent. Since I'd like Freya to come along, I need better temperatures than those of the summer to date, but I'd like to get them done in this current phase, but will have to cope with a bigger and heavier backpack.

Meanwhile, I also want to tackle a couple of Scotland's "Munros" (mountains that are over 3000 feet high) starting with Ben Lomond this coming Saturday, with son Christopher plus Freya.

Achieving these Phase 1 goals will contribute to my fitness and inform my plans for the winter, and Phase 2.
We fly out on my dear departed father's birth date (17th June) so I aim to be fully ready by the end of May.
I'll update this section as my plans unfold. Hopefully on the back of steady progress.