Myth 2: Your Marathon Long Run Needs To Be 20 Miles — Or More!
When training for the marathon, a long run of 20 miles seems to be the magic number for many runners. Psychologically, most runners feel that once they are able to run 20 miles for their long run, they’ll be able to handle 26.2 on race day. However, while hitting the 20-mile mark might feel like it’s an essential component of marathon training, is it really any better physiologically than 19 miles, or even 16 or 17 miles? The scientific research suggests that it’s not.
In terms of aerobic development, which is one of the main benefits of the long run, research demonstrates that 90 minutes to two hours of running seems to elicit the greatest amount of mitochondrial growth. Research has yet to show that running longer than two hours provides any greater stimulus to aerobic development.
So, even if there isn’t any real physiological benefit to running more than 2 hours (which for most sub-elites, is less than 20 miles), why not run 20 miles anyway if it makes you feel more confident?
1. The longer you run, the more tired you become. As a result, your form will begin to break down after 2 hours of running. Major muscles become weak and susceptible to injury while overuse injuries, like tendinitis, begin to take their toll.
2. Recovery time after a very long run is significantly longer than following a moderate long run. This means you can’t complete more marathon-specific workouts, like tempo runs, throughout the week.
What you can do:
Make sure your long run is a complimentary piece to the marathon training puzzle rather than a slow, 3-4 hour run that make up 50 percent or more of your weekly mileage.
As Luke Humphrey, Olympic Trials marathoner and author of The Hansons Marathon Method explains, you should you downplay the role of the long run and focus instead on increasing your overall weekly training volume and hitting your marathon-specific workouts throughout the week. To simulate the fatigue of the marathon distance, utilize the principle of accumulated fatigue to get your legs prepared to handle the full distress of 26.2 miles.
One way to do this is by buttressing the long run back-to-back with a medium length run at a steady pace. Using this idea, your weekend workouts might entail 8 miles of running at just slower than goal marathon pace on Saturday followed by 16 to 18 miles, with the last 3-6 miles of that run completed at goal marathon pace, on Sunday. At the end of the weekend, you’ll have run a total of 24 to 26 miles (with many of them hovering around marathon pace), yet you’ll actually reduce the risk of injury and recover faster than if you had tried to hammer out a 20 or 22 miler.