D, I split this off of the glutamine and thread and moved it to the BFL forum

I suspect that training for a marthon is more than enough cardio for you. I would not recommend adding in the 20 MAS on top of that, just in case you were wondering about that aspect.

Too much cardio can lead to wasting of muscle if you do not consume adequate protein - particularly if the cardio is of the high intensity interval type (hence, no added 20 MAS). I would suggest ensuring you get a minimum 1g of protein per lb of body weight to keep this from happening.

Cheers,
Nat