Long Runs: The Definitive Guide

Long runs are one of the most potent workouts in your training toolbox. But contrary to popular belief, long runs don’t merely add to your endurance. They also make you a faster runner. 

“Long runs put the tiger in the cat.”

For that reason, the world’s best runners make sure their long runs are more than just an extension of their easy runs. 

The Benefits of Long Runs

There are numerous physiological adaptations that enhance performance in response to long runs. 

First, let’s look at the cardiovascular system. Long runs put prolonged pressure on the heart and are therefore an excellent means to increase your heart’s stroke volume.  That’s further enhanced by the cardiac drift, which means your heart continues to rise at the same running pace. The duration of long runs also ensures most available slow-twitch fibers will be recruited at some point—meaning comprehensive capillary building. That, too, improves the oxygen supply to your working muscles.

Second, long runs strengthen muscles and connective tissues (bones, ligaments, and tendons). As some of the slow-twitch muscles fatigue, others get called into action to take over. Eventually, even fast-twitch fibers are recruited despite the low intensity of long runs.

Connective tissues are much slower to adapt than your muscles and respiratory system. For that reason, it’s sensible to increase the duration of your long runs gradually. Ultimately, long runs shield you from injury as regular easy runs become a cakewalk. 

Third, long runs deplete your glycogen stores and train your fat metabolism. You may have noticed that when you’re returning to training after some time off, your muscles are fine but you run low on energy after as little as 40 minutes of easy running. That’s because your body has reduced its glycogen stores in your muscles and liver. Regular long runs dramatically increase your glycogen stores, and—to a lesser extent—the ability to rely on a higher percentage of fat to power your working muscles. 

Of course, there are also psychological benefits that come with regular long runs. Everything that challenges us physically fortifies us mentally. Discomfort towards the end of a long run is expected and over time our pain tolerance increases. 

How Long is Long?

While the term “long run” is self-explanatory, we need a more precise definition of what constitutes a long run. After all, a 6-mile run may be a long run for a beginner, but a recovery run for an advanced runner. But even when we measure the long run by time instead of distance we need some guidelines for the duration of long runs. 

One of the cardinal rules for long runs is that they don’t exceed 25 – 30 percent of your weekly mileage. The only exception would be the occasional extended long in preparation for a marathon. But certainly not on a weekly basis. That means if you run 40 miles per week, your long run should be in the range of 10 – 12 miles. If you go beyond you will significantly heighten your risk for injury.  

In addition, your long run shouldn’t be more than 50% longer than your longest easy run. Again, this is a rule of thumb and exceptions apply. So if your midweek easy run is 8 miles then it’s feasible to run 12 miles for your weekend long run. Don’t run 12 miles on the weekend if you are on a 6-day training week running only 5 – 6 miles, even if that’s within 30% of total mileage. Because that would extend your longest easy run by more than 100 percent and places more stress on your body than it can safely adapt to. 

Pace Variations

A classic long run at an easy pace is a very effective workout as it is. No question about it. A long run once a week has stood the test of time. But as you become fitter, it pays dividends to alter your long run routine. 

One option is alternating a classic long run with a slightly shorter long run at a moderate pace. A moderate pace I define as the intensity between an easy pace and marathon pace. That’s about 20sec/mile faster than your easy pace, or 10 heartbeats higher per minute. For example, if you run 12 miles easy regularly, try 9 – 10 miles at a moderate pace every other week. 

Another effective tool is the fast-finish long run. Here, a marathon to half marathon pace segment is attached to the end of an otherwise easy long run. This trains your muscles to perform in a fatigued state. I don’t recommend this on a weekly basis unless you are an advanced runner. Also note that the easy segment always precedes higher intensities. 

You could also incorporate multiple paces into a long run in the form of a long progression run. An example would be 12 mile progression run with 5 miles at easy pace, 4 miles at moderate pace, and 3 miles at marathon pace. Similarly, you can alternate pace every 1 – 2 miles from start to finish. Be creative and change up your long run routine once in a while. You won’t progress by doing the same long run over and over again. 

Long Runs for Various Events

5K Training: The long run plays a lesser role for 5K events compared to longer distances but that doesn’t mean long runs aren’t crucial for fast 5K times. Long runs impact your aerobic system and therefore increase VO2max. Yet, you don’t need to exceed 12 miles even if you are a competitive runner. What’s more, it’s fine to run your long runs at an easy or moderate pace.

10K Training: For 10K runners the long run increases in importance. You can’t expect your best 10K time if your long run is merely 8 or 9 miles. While you don’t need to ramp up the intensity with progressions or add-ons, you should be able to go 10 miles with ease. Serious runners should approach 12 miles regularly. Slightly shorter long runs at a moderate pace are an alternative.

HM Training: Needless to say that long runs are crucial for the half marathon. You can’t expect a fast performance over 13.1 miles if you don’t approach that distance weekly in training. Once you are comfortable running 9 – 12 miles at an easy pace, it’s time to include some faster segments first at marathon and eventually at HM pace at the end. 

Marathon training: For marathon runners, the long run represents the most important training run of the week. After a long gradual buildup, you should be able to run at least 16 miles a few weeks out from the marathon event. This could be up to 22 miles for competitive runners, with 6 – 8 miles at marathon race pace. 

Should You Fuel Your Long Runs?

I wouldn’t recommend ingesting carbohydrates during your long runs, or any of your training runs for that matter. It defeats – at least in part – the purpose of long runs, which is the depletion of glycogen stores in your muscles and liver. As a result, your body adapts by increasing its glycogen storage capacity. That’s a useful adaptation even for 5K runners as loaded glycogen stores send a strong signal to your central governor (your brain) that it’s safe to continue running fast. 

Though, I advise against “running on empty”. You should have a regular meal 2 – 3 hours prior to your long runs or at the very least ingest 100g of fruit 30 minutes prior to long runs to ensure a stable blood sugar level. If you fail to do so your body will convert the amino acids stored in your muscles and convert them into glucose. That’s ok to some degree, but you wouldn’t want your long run to cannibalize your muscles for the majority of your effort. Pack an energy gel for your long runs just in case but try not to use it. 

Note that even if you run at an easy conversational pace,  your fat metabolism contributes only about 50 percent of the required energy. The remainder has to be supplied by glucose via glycogen or protein breakdown. What’s more, glycogen metabolism requires less oxygen than fat to yield the same amount of energy. That’s why your body forces you to slow the pace when you run low on glycogen despite having stored enough fat calories to complete 10 marathons. 

As far as fluid is concerned, the adaptation of long runs can also be enhanced with strategic dehydration. But here, too, you would want to be sensible about it. Mild dehydration during training is normal and will lead to more blood plasma volume over time, but severe dehydration impairs your training performance and could possibly get you hospitalized. It’s generally ok to run up to 90 minutes without taking in fluids unless you run in the heat. Above that, it’s sensible to ingest some water at regular intervals. 

Periodization & Progression

While it’s good to maintain a relatively high fitness level year-round with your weekly long run exceeding 1 hour in duration, the long run is still subject to the principles of progressive overload. Or in laymen’s terms, making your long runs more challenging week by week during the buildup for your A-race. The two methods of progressing long runs are via duration and/or intensity. 

The minimum goal should be running 90 minutes weekly at an easy pace without having the feeling that you’re at your limit. But even that might take a gradual buildup of mileage over a few weeks, depending on your current training level. Once that is achieved you can add some moderate pace, which I define as the pace between easy pace and marathon pace. That’s only about 10 beats per minute higher than your regular easy pace.  

For half-marathon and marathon runners the long run is also a race-specific workout. Therefore long runs exceeding 120 minutes are common. Though, so-called monster long runs don’t have to happen weekly. Every second or third week is sufficient for such an effort and those can be alternated with shorter long runs at a higher intensity. In any case, you should recover sufficiently within 48 hours to be ready for your next key workout. 

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Sandro Sket, CSCS

Sandro is an NSCA-Certified Strength & Conditioning Specialist. He coaches runners since 2013 to achieve faster race results from the 5K to the marathon.

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