While training for a marathon, many runners want to know the best distance for their weekly long run. What this question really means is: "How far do I need to run in training to be ready on race day?" This isn't about being lazy; it's a function of reality—most people only have so much time each week to train.
So when you reduce your training to a minimum, what's the shortest distance you need to run in order to be ready? Here are a few ways to determine the ideal distance for your long runs.
The Difference Isn't in the Distance
While the long run is an essential component of marathon training, it's not the difference maker. The long run is the product of all of the work you've done up to this point. If you think of marathon training as a pyramid, the countless shorter runs create the foundation of fitness that allows you to run more miles. Being prepared for a marathon is less about the distance and more about running frequently and consistently.
The first 6 to 8 weeks of your marathon training are about building the fitness and durability you need to complete a long run.
Focus on your total weekly mileage rather than worrying about each individual run. You can run a 36-mile week by doing three, 6-mile runs and one 18-miler, but you can also run 36 miles in a week by doing six, 6-mile runs. The second option requires less recovery time and presents a less demanding schedule.
One Run Doesn't Make a Marathon
The second half of the distance question comes down to understanding the fitness and experience required to complete a marathon. Focusing solely on mileage can cause a runner to neglect other important training factors such as pacing, nutrition, technique and form. In other words, the long run is equal parts physical and mental.
No runner has finished a marathon and said, "The only reason I finished today was because of that one long run I did four weeks ago." The secret to making it to the finish line is the 12 to 16 weeks of consistent training. Logging 4 to 5 runs a week, running through the weather, and managing your training despite schedule conflicts.
A 20-mile long run is equal parts good and bad for your marathon training. It needs to be approached with respect and preparation. You earn the right to run that long by compiling several weeks of consistent, quality training. If you aren't ready for the distance, split up the long run and make it more manageable.