The first thing to keep in mind is that it is a fun run. It is a special type of fun run, but a fun run all the same. Down N Dirty Mud Run in Semora, NC will be about 3.2 miles (5K) through the woods, up and down hills, and of course, through mud. So if you can’t run that far you need to start getting in some runs.
While you may be able to lift more weight in a two-legged exercise, in my experience you’ll be better off using single leg exercises. My current leg plan for endurance people is a mix of single leg deadlifts, step-ups, single leg curls with a physio ball, and calf work. I keep the reps to 5 per set allowing me to use a decent load, although the focus here is getting everything balanced so that your single leg stance is stable while running on uneven ground.
Finally you need to add some extra conditioning work. A simple circuit of heavy two-hand kettlebell swings, crawling, and push ups done non-stop for around 10 minutes will be all the extra work you need.
The key, as always, for event preparation is to start early. If you haven’t run in a long time then allow adequate build up time for the run break-in plan. Don’t take the event lightly – it’s still a 5K trail run with the added difficulty of the obstacles to overcome. So make sure to commit to fitness and make sure to hit those three sessions each week as they are all vital for your mud run success.