“Can I split up my long run?” – the Ultramarathon Edition

Last Updated on January 27, 2022 by Heather Hart, ACSM EP, CSCS

Let’s face it: most of us are not elite runners, and running is not our full time job.  Instead, we have endless other responsibilities – a 9 to 5 job, family, appointments, housework, walking the dog, you name it – that can often put our training much lower on the list of priorities.  Therefore, a common question running coaches often hear from clients is “can I split up my long run?”.  The idea being that a runner can hit their desired long run mileage by breaking the training run into two (or more) shorter distance intervals spread throughout the day, typically to accommodate a busy schedule.

The practice of splitting up a long run may sound convenient, but is it ideal for training?  And what about applying it to ultramarathon training – the black sheep of the running world where seemingly so many other running rules go out the window?  Let’s break it down.

Splitting Long Runs for Beginner Endurance Athletes

For those new to the endurance world, or new to a given distance (training for a first marathon, for example) splitting your long run is not recommended.   There is a lot to be gained, not just physically, but mentally, from each new long run distance.

The benefits of long runs from a physiological standpoint include:

• Strengthening the heart and lungs (building “endurance”).
• Conditioning muscles, tendons, and ligaments to cover more distance.
• Stimulating the development of the capillary system (more capillary beds = more oxygen to the muscles).
• Recruiting different muscle fibers as you fatigue.
• Improving the body’s ability to burn fat as fuel as glycogen stores are depleted over longer distances.

Physical adaptations for distance running occur, you guessed it, over distance.  It’s the principle of specificity: in order to train for long distance running, you’ve got to log long distances all at once.

The benefits of a long run from a mental standpoint are equally as important.  

A long run teaches you how to push through fatigue and physical discomfort.  Let’s face it: the way your legs feel after 18 miles at once simply isn’t the same feeling that you experience if you break that up into two shorter nine mile runs.   Further, simply covering a new, long distance training run gives you the mental confidence that you CAN do hard things, and you ARE capable of going the distance of your race.  Who doesn’t remember the thrill of finishing your first ever 20 mile training run?  If you’re like me, you probably spent the rest of that day feeling pretty damn proud of yourself.   The confidence of tackling new distances goes a long way.

Lastly, during the long run you learn what works – and doesn’t work – for you over long distances, as far as fueling, hydration strategies, shoe choices, and even clothing.

Splitting Long Runs for Ultramarathon Training 

When it comes to training for an ultramarathon, a lot of the traditional endurance training methods go out the window.  Avoid runs longer than 3 hours?  That’s not going to help you finish a 100 miler.  Using pizza or potatoes as fuel instead of endurance gels? Not at all unheard of.  And of course, training methods tend to be unorthodox as well.

Now, in this discussion we’re going to assume that runners training for an ultramarathon are already experienced runners, and have already completed shorter (definitely a relative term) distances such as a full marathon.   Therefore running distances of 20+ miles, whether in training or in a race, is not a new experience.

Though not recommended for every run, there certainly can be benefits of splitting long runs during ultramarathon training.  I like to incorporate split long runs occasionally into client’s ultramarathon training plans, for the following reasons:

Learn to run on fatigued legs.

This is a similar concept to the back to back long run training method often utilized in the ultra world.  When you put in a portion of your long run earlier in the day, then allow your body to begin the recovery process, muscle soreness and feelings of fatigue may begin to set in.   This can mimic the soreness and heavy leg feeling that accompanies the later miles of ultramarathons.  While there may be no avoiding that soreness, you can mentally learn how to push through the discomfort, so it is not a surprise on race day.

Injury prevention: quality over quantity.

Splitting your long runs can help you increase the amount of time you spend on your feet, while minimizing the risk of injury.  There is no denying that training for an ultramarathon requires a very high volume of training miles.  Occasionally splitting your long run can help you achieve that volume, while reducing the damage and impact of a standard long run.

You’ll be running day…and night…so you should get used to it. 

So many runners like to knock out their training runs first thing in the morning.  Which is perfect – if your race is first thing in the morning.  But if you’re running an ultramarathon, especially longer distances such as 50 miles or more, you’ll be running in the morning, and in the afternoon, and maybe into the evening or even overnight.  Do you know how your body reacts to a run at the end of the day?  Have you practiced running in the mid day heat, and the tricky lighting of dusk?  Does your body prefer “real” food over processed gels and drinks at different times of day?

Splitting up your long run gives you an opportunity to run at different times of day on the same day, and can be great practice for the varying conditions you may experience on race day.

Mental toughness.

Sometimes mustering up the motivation to get one training run can be rough, never mind two runs in one day. But the mental toughness of stopping and starting again can absolutely be applicable to ultras.   Unlike a traditional half or full marathon, in an ultra, especially the longer distances, there may come times where you stop for awhile mid race.  It may be 2-3 minute stop to change shoes and socks, or it may be a 30 minute stop to refuel and put your feet up during an overnight stop.  Either way, I can assure you that the stopping – and then starting again – can be tough.

How to split up your long run: 

If you plan on splitting up your long run, ideally you will complete about 60-70% of your long run in the first session, and the remaining 40-30% during the second session.  During the rest period, focus on hydration, nutrition, and resting as best as possible (though, if you are breaking up your long run due to scheduling conflicts, this might be difficult).   Try to keep the effort similar for both runs, and pay extra attention to your form and gait on the second run, when you are feeling more fatigued.

In summary, the need to split your long run up may arise occasionally during training.  But as an ultramarathoner, a split long run can actually be beneficial, and should be incorporated into your training routine from time to time.   Remember, this training method should only be used occasionally, and is not a substitute for traditional long runs, completed all at once.