I just signed up for a walking event in 3 months where we walk 100 kms in max. 26 hours. I am not an athlete, I even haven't reached normal primal fitness yet. I walk daily, but so far only short distances (about 3 kms) and do a longer hike on weekends (but not more than 10 kms).

What can I do to prepare my body for that event? Keep up walking, start sprinting, longer hikes once a week. On which muscles should I focus with my strength training?

Any strategies for the 100 kms? What to eat? They provide bread, fruit, chocolate, sausages and drinks along the way, but I would prefer to carry something primal and only get fruit and drinks at the 4 supply stations.

I don't want to stress my body during the preparations, but I am aware that the event itself will be a high stress situation. So any tipps are welcome!