There are a lot of factors that go into understanding how long your longest training run should be.

It’s fall marathon season and many runners are ramping up their mileage to its peak. But not everyone is running the same distance for their longest training runs. How long should your longest long run be when training for a marathon?

These long efforts are some of the most important runs of your entire buildup. They carry extra importance because they’re not just about mileage; they’re about preparing your body and mind for race day.

But what thing you’ll find is that few runners are running the same distances for their marathon build-up long runs. Some runners push their long runs out to 20–22 miles, while others stop at 14–16. For some, the limit is 2 hours; for others, it’s 4 hours.

There are a lot of variables that go into understanding what’s best for you. Here are my thoughts as a general guide, broken down by approximate pace goals for runners, plus several key notes to consider. Remember, that a training plan should be fluid, and several current factors

Longest Training Run for +/- 3-Hour Marathoners

If you plan to run 3 hours or faster for your marathon, then my recommendation for your maximum long run is:

Maximum long run = [your marathon time] up to [marathon time + 30-45 minutes]

For example: A 2:45 marathoner’s longest long run would be in the 2:45-3:30 range; 2:45 is the approximate marathon time and 3:30 is the marathon time + 45 minutes.

Just a quick note that is represents the longest long run in the training plan. It does not suggest every long run in your plan must be this long.

Longest Training Run for +/- 4-Hour Marathoners

If you plan to run around 4 hours for your marathon, then my recommendation for your maximum long run is:

Maximum long run = [your marathon time-15-30 minutes] up to [marathon time + 15-30 minutes]

Example: A 4:00 marathoner’s longest long run would be in the 3:30-4:30 range; 3:30 is the approximate marathon time (4:00) minus 30 minutes and the 4:30 is the marathon time plus 30 minutes.

Another note: The runner should build slowly and gradually to this longest long run over 2-3 months.

Longest Training Run for +/- 5- to 6-Hour Marathoners

If you plan to run around 5 hours or longer for your marathon, then my recommendation for your maximum long run is:

Maximum long run = < Your marathon time (4:00-4:30)

Unlike faster marathoners, five-hour marathoners (or longer) can’t follow the same advice. The main reason is that the long run will take so long to complete and will result in so much additional recovery time that it interferes with the upcoming training.

Things to Consider About Your Longest Training Run

• This article if focused on your longest training run during your marathon build-up. It is not saying you have to do this every weekend. You would build up to this level near the end of your plan. Most runners find that running their longest training run 3-5 weeks before the marathon is best.
  
• Necessarily, the pace is slow. This type of super long run isn’t about speed. It’s about time on your feet so make sure to run within the long run pace range (and often toward the slower end) and just let the time roll by. This is not a run to push the pace and try to run fast.
  
• You can’t rely on mileage when discussing long run distance because of the different in pace (and thus duration) of the runner. So if someone says, “You should never run 20 miles.” or “You must run 20 miles.” Ask them how long that will take. My pro runners would do 20 miles all the time but that only took them just over 2 hours to complete. So telling me that running 2 to 2.5 hours on a regular basis is wrong makes no sense. Likewise, having a 5-hour marathoner listen to a pro and try to run 20 miles frequently (and thus taking several hours to complete) makes no sense either. The recover would take so long that it would interfere with the upcoming training. Therefore, we must make it relative so I think talking in time is best.
  
• A range should be provided for each long run so the runner can run the longer or shorter end based on how he/she is feeling. Feeling great? Shoot for the longer end of the range. Feeling bad? Stop at the short end. Be your own coach and adjust on the fly based on how you are feeling.
  
• Endurance Monster runners typically do well with these really long long runs. Speedsters sometimes struggle so adjust your expectations based on your runner type.
  
• New marathoners should use a process of gradually building to the longest training run. This is typical in most new marathoner programs where the long runs gradually increase week to week with some “down” weeks for recovery.
  
• Experienced marathoners should run more long runs that are longer. I call it decreasing the delta and there is an article that discusses this. As your body and mind get used to longer long runs then you can include more longer long runs in your training plan. Again, not necessarily the maximum long run distance as described above but simply longer than was used in the first few marathon plans.
  
• Injury history and how quickly the runner recovers plays a role in the long run strategy. For example, I’ve run 2:31 for the marathon but could never do same long runs as others I’ve coached that ran the same time. I was too injury prone and long runs really beat me up. So, the individual recovery rate and injury rate of the runner plays a role in the long run sequencing as well. Runner know thyself! If you are frequently injured, then be cautious of the really long end of the maximum long run range.
  And, make sure to add in extra recovery days after your longer long runs.The goal of the long run plays a role as well in your longer long runs. Two long run goals in particular change the sequencing. If you are working on low glycogen long runs (low/no carb) to improve fat burning (again, there is an article on the marathon long run) then the long runs will be shorter than if you are fueled.
  
• Second, if muscular durability is your limitation (your legs fail you late in the marathon), then you may want to extend long runs to provide a deeper stimulus for the legs to get used to the stress of running long. Again, it’s somewhat individual so whenever you read about long run guidance, it often requires more info on what the situation is for that runner.
• Final Thoughts

The marathon may be 26.2 miles for all runners, but I suggest that the event is very different from runner to runner. Training to run as fast as you can for 2 to 3 hours is much different than training to run as fast as you can for 4 to 6 hours. So, when you read training advice, don’t just think about the race distance, but think about how long that race will take you.

This way of thinking allows you to better evaluate the training advice. There will still be lots of conflicting information but I find it provides an easier way to decipher the advice and see if it is relevant for a runner like yourself.

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About Greg McMillan

Called one of the best and smartest distance running coaches in America by Runner’s World, Greg McMillan is renowned for his ability to combine the science of endurance performance with the art of real-world coaching. While getting his graduate degree in Exercise Science he created the ever-popular McMillan Running Calculator–called “The Best Running Calculator” by Outside Magazine. A National Champion runner himself, Greg coaches runners from beginners to Boston Qualifiers (15,000+ and counting!) to Olympians.

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