Well, looks like the way I’m thinking has already been expressed by the others on this post.
Just looking at the physique of a marathon runner should be enough to put you in touch with reality- they’re treading a very fine line between being the LIGHTEST and LEANEST BW they can be, whilst still having enough (slow twitch) LEG muscle mass to propel the torso through space quickly (upper body muscle not required at all).
I used to run a lot. Fitone’s right- the only way to train for running (distance) is to RUN.
The body adapts to the running training by improving aerobic capacity, and stimulating slow-twitch fibres. The fast twitch fibres are surplus to requirements, and as such provide unnecessary bodyweight which will hinder your performance. However, they provide a great energy source for the prolongued exertion periods, and soon, as you lose that large muscle mass, your distance times will start to really improve, with less bodyweight to support!
Is your friend doing this marathon too? I bet he’s already a distance runner isn’t he? Well, what does he look like? Is this compatible with a Testosterone physique??
If the run is now inevitable, and if you want to do WELL, start reading “Runner’s World” and working on increasing mileage weekly up to the big day(probably >70 miles/wk), whilst your body starts to morph into the necessary “look”:-).
(However, for me, I guess I would train and compete in a “minimal damage” mode- training as infrequently as possible to support completing the final day, and ensure I stepped up the calorie intake SUBSTANTIALLY, using short intense weight sessions to try to hold onto any of that muscle size.)
Sorry to hear of this inconvenience dude. Good luck. SRS