20 mile long runs appear as much of a staple on many marathon training plans. During the past few years, however, many popular methodologies including the Hansons Marathon Method have proclaimed 20 mile long runs as unnecessary. Many runners will soon begin training for summer and fall marathons, so let’s look at the advantages, drawbacks, and considerations of the 20 mile long run.
Of course, this post will only skim the surface of this debate. Research on the physiology of long runs literally fills volumes. As always, please consult your running coach before making changes to your training plan. Don’t have a coach? Learn more about my coaching services!
Pro 20 Mile Long Runs
Some coaches, including the coach who taught my RRCA seminar and Brad Hudson of Run Faster from the 5K to Marathon advocate that experienced marathoners (NOT new marathoners) extend their long run to last nearly as long as their goal time in order to adapt to that duration of time on their feet. Obviously, these runs are executed at a significantly slower pace than marathon goal pace; a 3:30 marathoner will run for 3 hour and 30 minutes but only cover 22-23 miles. These long runs will teach your body to handle all of the physical demands of the marathon while also mentally strengthening you for your race.
20 mile long runs, for many runners, break a mental barrier. If you can run 20 miles, you can run 26.2! The 20 mile long run has become a staple in most marathon training plans, regardless of overall weekly mileage or training paces. It’s the hallmark of marathon training, the run which many runners consider their peak workout.
Anti 20 Mile Long Runs
The most famous of the no 20 miler marathon training plans is the Hansons Marathon Method. The Hansons Marathon Method (which regular readers will recall I followed for the Portland Marathon last year) advocates a 16 miler cap for their long runs for their standardized training plans.
Hansons cuts all long runs off at 25-30% of total weekly mileage. So if you’re running 60 miles per week (which is high mileage for many recreational runners), 16-18 miles falls within this range. Luke Humphrey, author of Hansons Marathon Method, cites too many high risks as the reason for not running more than 25-30% of your total weekly mileage in a single long run.
“Breaking this cardinal rule risks too much: injury, overtraining, depleted muscle glycogen, and subpar workouts in the following days or even weeks.”
If you’re following the Hansons Marathon Method but increasing your weekly mileage (primarily through extending your easy runs and warm up/cool down miles), you may be able to include 20 mile long runs while still adhering to their guidelines. For most recreational runners, generally speaking, weekly mileage over 70 miles is neither recommended (diminishing returns) nor feasible in the balance of family, work, and running, which means most will not hit the 20 mile point following Hansons plan.
The science behind this limit on the long run is not unique to Hansons. The renowned exercise physiologist Jack Daniels argues the optimal duration of a long run is 90 minutes to 3 hours, which may or may not include 20 mile long runs. In his book Jack Daniel’s Running Formula, he writes:
“I like to limit any single run to 30 percent of weekly mileage for runners who are totaling fewer than 40 miles per week. For those who are accumulating 40 or more miles per week, I suggest [long] runs be the lesser of 25 percent of weekly mileage or 150 minutes, whichever comes first.”
Numerous studies and coaches agree that after 3 hours, you reach the point of diminishing returns. The most physiological gains are made in 1.5 to 2.5 hours of running; once you surpass three hours, you cease to reap any additional physiological benefits and sharply increase your risk of injury.
Yes, a 16 mile long run will sufficiently build your aerobic capacity for the marathon, so long as you are following the other pillars of the Hansons Method: overall high mileage, back to back longer runs, long marathon paced workouts, and cumulative fatigue.
However, as many of us know from experience, there is more to racing the marathon than simply building adequate endurance. Your legs and lungs are not solely responsible for carrying you over 26.2 miles; your stomach, mind, and feet must cooperate as well, especially if you have a goal time in mind.
For example, when I followed Hansons Marathon Method, I completed my 16 mile long runs in under 2:20. These long runs certainly prepared me to cover 26.2 miles, but I was not completely mentally prepared nor was my sensitive stomach trained to handle the pounding of running for well over 3 hours. At my training pace, I could still run 20 miles in training and finish in under 3 hours.
Your pace and race goals factor significantly into the length of your longest marathon training run. The general consensus appears to be that time, not distance, should be the deciding factor in marathon training long runs. 3 hours should serve as the cap, since that’s the point before you incur diminishing returns. Let’s keep in mind that a majority of long runs should be done at your easy pace, which for most runners is 50 seconds to 2 minutes per mile slower than goal marathon pace.
So let’s say you are aiming to run a 4 hour marathon (9:09/mile average), which is a popular goal for many marathoners. Your long run pace is approximately 10:00/mile or slower; running at this pace for 3 hours will cover 18 miles. 18 miles is thus an adviseable cut off for marathon long runs for the 4 hour marathoner, while a 3:30 marathoner can cover 20 miles in 3 hours during training, and a 3 hour marathoner could extend up to 22 miles without incurring detrimental levels of fatigue.
Finally, there’s the issue of quantity: Arthur Lydiard, the great master of long slow distance training, asserted that athletes only needed one 3-hour long run 5-6 weeks before their marathon to reap the benefits. (It is worthwhile to note, however, that many of Lydiard’s athletes were highly skilled distance runners and able to cover the marathon distance or further on a 3 hour run).
On the flip side, an argument can be made for including 2-4 20 milers in your training, particularly if you can complete an easy 20 miler in under 3 hours (so, typically for 3:30 marathoners and faster). You prepare your body for the demands of the distance while also training your mind to handle the mental demands of the marathon distance.
Here’s one final question to consider: what will better prepare you for the marathon, easy 20 mile long runs or a 14-18 mile long run with a large portion at marathon goal pace?
The answer to this question is as individual as each runner. However, specificity is one of the key factors in race training. The more specifically you train for your goal race, the better you can expect to run on race day. Shorter yet hard long runs offer numerous benefits, including improved fat burning and running economy at goal marathon pace, training your body to run at goal marathon pace for a sustained period of time, and adding variety to the weekly long slow distance run.
Runner’s Connect even recommends that marathoners running slower than a 3:30 marathon favor shorter and faster long runs over 20 mile long runs, for the sake of reducing training fatigue and preventing injury.
I would argue there are benefits from both easy 3 hour long runs and from marathon-paced 2 hour long runs (so long as you have the overall weekly mileage and training background to support these workouts). Furthermore, including both in training (with cutback weeks) will stimulate various physiological adaptations while keeping marathon training boredom at bay.
Too many hard long runs will burn you out before race day, while only easy long runs prepares you, well, to run long at that easy pace. For new marathoners, all of your long runs should be performed at an easy pace to adapt your body to the new distances without overtraining or injury. Endurance first, then speed.
Ultimately, the inclusion of 20 mile long runs hinges upon a wide variety of individual factors: injury history, recovery rate, pace and goal time, your experience in marathoning, and your overall weekly mileage. As Pete Pfitzinger says in his book Advanced Marathoning, “No scientific evidence will tell you the best distance for you long runs as you train.” It’s something you have to decide for yourself by taking all of the factors into consideration and weighing the risks and rewards.
Runners of any ability will reduce their risk of injury and prepare themselves better for the marathon by following the 3 hour cut off for marathon training long runs and by safely increasing their weekly mileage so their long run is not 40% or 50% of their total weekly mileage.
As I’ve said before, cookie cutter training plans do not address your specific needs as a runner and therefore do not always optimally prepare you for a race. A good self-assessment or, even better, working with a certified running coach will guide you in planning out your marathon training plan.
Do you run your long runs by distance or time?
How long is your longest run before a marathon?
What other aspects of training do you need to consider (like mental strength, gut, etc)?
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