For many marathoners, the long run is a physical and mental test to make sure they are on track with their race day goals. Most chase an arbitrary mileage benchmark in their quest to confirm their preparation: for some it's 20 miles, for others it's 22.
Instead of just plodding along to rack up miles, the long run is a chance to put the finishing touches on your race execution strategy and build some final critical fitness. Here are a few pointers to make sure you get it right.
Your Body Doesn't Think In Terms of Miles
A 2.5-hour run at long run pace is the same effort for Speedy Stan (7:00/miles) and Wandering Wally (12:00/miles). They are both running the same effort for the same time, it's just that Stan can rack up 21+ miles while Wally covers 12.5 miles. They are doing the same work, it's just that Stan's output is much higher.
Inside Marathon Nation, the ultimate distance of our long runs is not built upon a fixed plan -- your mileage is determined by how fast you have proven you can run. If you can run an 18-minute 5K, for example, your long run will be capped at about 2.5 hours. If that same 5K takes you 36 minutes, then your long run will be capped at three hours.
So How Far to Run?
This is the eternal marathon question. Ultimately, the length of your long run is determined by your training program. If you've built up to 18 miles by this point, jumping to anything longer than 21 will be a real challenge. If you've already hit 20 twice, another 20 might not be enough while 22 could be too much.
While there are no set guidelines to how far a long run should be, there are guidelines around how long it shouldn't be. For faster folks like Stan, make sure your longest run is no more than 10 to 15 percent longer than your previous longest effort. If you are more like Wally (athletes who plan to run 10:00/mile or slower on race day), your longest run should be capped at three hours.
Only Three Hours? How Will I Ever Be Ready?
At the end of the day, there really is no physical or aerobic benefit to running beyond three hours. At this point you'll be doing more harm than good to your body. Per the effort example above, remember that at three hours you will have already run an extra 30 minutes longer than Stan -- you are doing much more work!
If a three-hour run will "only" get you 15 miles, revisit your training schedule to incorporate two longer runs a week (e.g. Thursday and Sunday) into your training as soon as possible. This way you'll be able to build up the durability you will need for race day over time without risking injury or burnout.
Read Marathon Training: Re-Thinking the Long Run, Part II
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