Mud comes in so many varieties. When I try to describe the different types of mud to people, they look at me as if I were a little off center. Normal garden variety mud, clumps to feet, knocks of easily. Similar mud, but with a clay mix. This mud cakes up like jumbo-sized pancakes to your shoes. A big mistake with this mud is walking on grass or leaves after getting a good dose on your shoes. The leaves and grass blend well with it to make adobe, which is a popular building material in the southwest. Once dry, a light duty jack hammer available at any tool rental enter is needed to restore your footwear. For a more durable shoe covering, pure clay is hard to beat. This variety is best used when you want to strengthen your quads, glutes, and calves. No problem loading 20-25 lbs per foot. Just stomp through and begin your workout.
Aww.... good old red dirt. Makes fine colorful mud which will give your shoes a nice color variation. It has a mild caking factor, and actually will cling to some of the sticky clay and clay blends and can actually help to remove a few of the outer layers of build-up. Given clean shoes and a 1/4 mile of red mud to tromp through, you will walk away with no more than a few extra ounces of weight, have shoes that may or may not match your running outfit, and will have a fair amount of grit hell bent on finding it's way into your shoes and between your toes. One of my favorite muds is black mud aka shoe sucking mud. This mud has a good clumping factor, and can be deceptively deep. Baptize your shoes in this, and you had better be careful stepping out of your predicament. This mud will KEEP your shoes, and quickly cover up the crater where you stepped. I believe this is where some of the crazy barefoot runners got their start.
Another variety of black mud is mud made from rotting leaves. It has many of the same characteristics of the above black mud, but is characterised by a foul smell, like old doo doo. Hopefully no black doo doo mud here. This is the good garden variety mud, diluted to a thin slop state. This mud is actually so clean that you could eat a Quik Trip sandwich without even bothering to wash your hands. (I always advise smelling the QT sandwich before biting into it.) A good mix of 2 or 3 of the above mentioned muds. This runner made it through a marathon through some of the worst mud that Kansas has to offer. Even some rain and hosing had not been able to wash all of it away. Notice the mud that was able to make it's way through the shoes and socks and between the toes. Finally, proof that the battle with the mud in trail races is sometimes lost. Mud that will take away a shoe will also take all it can get. That foul smell in some of that mud may be more than rotting leaves!