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100 Mile Run Ultramarathon Training Program

Training for a one hundred mile ultramarathon is a seemingly impossible feat for most runners to get their head wrapped around.  Admittedly, these races tend to attract a fringe group of runners, widely considered to be a little off their rockers.  But those runners that are willing to train hard and put in the work to prepare intelligently will find an accepting, helpful, laid-back group of people with which to develop new friendships.  Many an ultramarathon has been saved by the supportive words or helpful advice of a stranger when all hope appeared to be lost.  But beware, those who cross over to the dark side rarely go back to “regular” running.


It goes without saying that these races are not for the faint-of-heart.  Ideally, runners should have completed shorter ultramarathons in the past, such as fifty milers or 100k races before attempting this one hundred mile ultramarathon training program.  While previous ultramarathon experience is not required for some races, the key to a successful 100 mile ultramarathon is race strategy.  Those with zero race experience at shorter ultras are at a very real disadvantage when it comes to spending 24 hours, or more, in a trail ultra. This training program is for those attempting a 100 mile ultramarathon for the first time and starts out with long runs in the 16 to 18 mile range.   Find a 100 mile race about 24 weeks out.  If your current long run is more than 18 miles, simply start the training program at the point that corresponds with your current long run and find a race at the appropriate time.

Race Terrain

There is no such thing as an “easy” 100 mile ultramarathon, but the terrain varies greatly from one race to the next, and some are less brutal than others.  The Leadville 100 is a race across the sky, run over high mountain passes at altitudes higher than 13,000 feet, while Lean Horse is run on relatively flat rail beds in the hills of South Dakota. The number one rule of training for a 100 mile ultramarathon is to train in similar conditions and on similar terrain as the race will be run.  If that is not possible, it is going to be very difficult to train properly for the race.  Some gifted runners with cardiovascular mojo to spare may be able to compensate, but the majority of runners will not succeed at completing a race under these circumstances.   Shift the odds of completion in your favor by selecting a race for which you are able train appropriately.

Weekly Mileage

Weekly mileage among ultra-runners also varies dramatically.  Those capable of 100+ mile weeks run them, but most ultra-runners cannot handle that much weekly running without causing injuries.  The trick is to use recovery strategies during training to build up to a long series of back-to-back runs rather than constant, back-breaking weekly mileage.  A peak training week for a 100 mile race might include 3 days of back-to-back-to-back runs of 15 miles, 25 miles, and 30 miles for 70 miles run in those 3 days.  All previous weeks of training build up to this level of mileage for the long run. Additional runs during the week are included in this training program and these should be considered a minimum.  Additional running during the week can be at whatever mileage levels can be tolerated while allowing for sufficient recovery for the long runs.  In this training program, the weekly runs are used to manage the total weekly mileage in such a way as to not increase more than 10% per week.  Success in the 100 mile ultramarathon will depend on the long runs, not the other short runs during the week.


Very few can run the whole 100 mile distance.  Of course, there are exceptions, and most of those exceptions can be seen holding the hardware at the end of the race.  For everyone else, walking is a necessity and a large part of the strategy involved in these races.  Most ultra runners walk the uphill sections and run the downhill sections.  Long flat stretches of the course are where choices must be made regarding how much walking is needed. Most use a run/walk strategy and it is better to walk often in the beginning of the race, even though it is possible to run more.  Every ounce of energy must be conserved so that you can continue to run as long as possible.  Alternating between running and walking uses different muscles and lets you go further than either one alone will.  Continue short bouts of running throughout the entirety of the race, even if you are only able to run for a few yards at a time, or you will be forced to walk exclusively.  If you have not trained to walk 40 or 50 miles…you won’t make it.


Hydration is vital, particularly in warmer climates.  The potential for being out in the heat for many hours adds to the potential for dangerous levels of dehydration.  Drink lots of water and check the color of your urine to make sure that it is not too dark.  The other significant hydration-related issue is hyponatremia, or an electrolyte imbalance caused by low electrolyte levels.  Drinking only water all day without replenishing electrolytes can lead to a type of “water intoxication”, and possibly death.  Use electrolyte capsules, such as S-Caps, Endurolytes, or Salt Sticks and follow the directions carefully.


Assuming an average calorie burn of 100 calories per mile, a conservative estimate, a 100 mile ultramarathon will burn 10,000 calories in a 24 to 30 hour period, in addition to the calories you would have burned anyway in a normal day.  That equates to several days worth of food that needs to be consumed in a short period of time.  Practice eating real food with high calorie densities on long training runs and find out what foods work for you. From a race strategy standpoint, no decision that you make will be as important as what you choose to eat during the race.  One mistake, eating something disagreeable, will turn an already difficult situation into a DNF.  Find out what works for you and what does not during training so that you have an eating plan during the race.

Long Runs

Long runs for ultra-marathons are divided up into shorter back-to-back runs commonly known as sandwich runs.  Long runs are sandwiched together over several days to get in the high mileage while allowing for some recovery and reducing the chances of injury.  For 100 mile ultras, 3 days totaling 60 to 80 miles is common.  The distances vary, but these sandwich runs train you to run with tired legs and force you to use a run/walk strategy, which will be important in the actual race.  Don’t make the mistake of attempting runs longer than 30 miles, as the recovery time for these distances is too long.

100 Mile Ultramarathon Training Program for First-Timers

This plan is developed for those running their first 100 mile ultramarathon with the goal of finishing the race.  These mileages should be considered a minimum for completing the race and running should take place on terrain that is similar to that of the chosen race.  The mileages do not need to be exact. You can convert them to hours of running at your pace, if you prefer.  Days of the week can also be changed; just be sure to do the back-to-back runs on consecutive days. 


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Supplements for Runners

There are a variety of supplements that can help enhance your training and running performance. Caffeine can keep your energy up during your long or early-morning runs. Creatine can boost the effectiveness of your training leading up to the big race. Beta-alanine can increase your endurance and delay fatigue.