View source for A brief guide to ultramarathon distances


There are a variety of ultramarathon distances, each with its own 'flavor'.
 
== 50K ==
In many ways, the 50K is an odd distance. It is only about 5 miles longer than a marathon, rather than part of the usual doubling that occurs in the progression of '5K-10K-half marathon-marathon-50 miles-100 miles'. Some runners can run a 50K like a marathon - continuous running at an intense pace, where every second counts. For most runners however, this approach does not work, and the 50K needs be treated as an ultramarathon, with varying the intensity, eating, etc.
 
The 50K can be used as "over distance training" for a marathon. Running a 50K at a slow and easy pace builds endurance and confidence for a marathon. There is a psychological barrier for many marathon runners about the marathon distance. Going further can help overcome this barrier and promote better marathon performance.
 
A 50K can be a good choice as a first ultramarathon as long as it is treated like an ultramarathon, not a marathon. I believe that a sub 4:30 marathon runner can complete a 50K using a run/walk pattern without excessive training. A run/walk pattern of 15 minutes running with 3 minutes walking seems to work well.
 
== 50 Miles ==
This is a sweet distance. It is far enough to be a serious challenge, but is achievable with suitable training. In many ways it reminds me of the half marathon; The half marathon is an endurance race without the difficulty and long training require for the marathon. Likewise, the 50 miles is an ultramarathon, but without the problems of the 100 mile races. A 50 mile race requires respect, but a runner with the dedication to focus on the training required can finish the 50 mile distance.
 
A 50 mile race requires significant adaptation from the marathon distance. Very few runners can complete a 50 mile race without some walking and eating solid food. The 50 mile distance also generally requires significantly more training time than the marathon.
 
Races of 40 miles are broadly similar to the 50 mile distance. Some of them have some extra challenges to make them a very similar level of difficulty to the 50 miles. Likewise, the 100K (62 miles) is similar enough to the 50 mile to be considered in the same broad category.
 
== 100 Miles ==
Just as the marathon is more than twice as hard as the half marathon, so the 100 mile race is more than twice as hard as the 50 mile race. For many runners, the 100 mile race is summed up in the saying "You won't die, but you might wish you had." Just look at the DNF (Did Not Finish) rate for 100 mile races and you will get a sense of how difficult this distance is. I know of good, dedicated runners who failed many times at the 100 mile distance before succeeding. Finishing a 100 mile race is in some ways similar to qualifying for the Boston Marathon; while there are a few runners who can do it relatively easily, for most it is a herculean effort requiring multiple attempts.
 
The 100 mile distance brings new challenges to runners that are not seen at shorter distances. For instance, sleep deprivation becomes an issue for most runners, as they are running over night, sometime for more than 30 hours. Running at night can be a psychological challenge as well as a practical one.
 
== 24 Hours ==
A timed race, like 24 hours, is obviously different to a distance race. With a distance race, the slower you go, the longer it takes. This tends to punish slower runners even more, as they are on their feet for longer. With a timed race, the slower you go, the easier it is. If you reduce your pace, the lower the intensity AND the shorter the distance. Of course, the opposite is true - when you push things hard, the race becomes disproportionately harder.
 
Timed races are normally run on a small loop course, which make them sociable events. You get to see, and often run with, the fastest and slowest runners. This type of loop course also makes logistics simple; your gear is never far away. The opportunity to take a break is always available, which is a two edged sword. A few runners will keep going continually, but most will take some rests. This might be 5-10 minutes here and there, or it might be an 8 hour sleep. I have even known people go off to a wedding and come back!
 
Overall, a 24 hour race is a wonderful opportunity, regardless of if you are a complete beginner, or an elite ultrarunner.
 
== Multiday ==
I have not participated in multi day events, so I cannot provide any useful advice. One day I hope to update this section with some personal experience ;}