While the marathon is held as the ultimate goal of running in many circles, the challenge of covering 26.2 miles in one go is no small feat. Even with the rising popularity of distance running, still only a fraction active people have reached a marathon finish line.
There is another path to marathon success. It's not some crazy supplement or short cut—you still have to train and race, but the good news is that the marathon finish line might not be as far off as you originally thought. Instead of just focusing on the miles, build year-round running fitness through regularly scheduled 10K races, then use that fitness as a launching pad to reach your marathon goal.
More: Start With a 10K to Reach Your Endurance Goals
Road Race as Fitness Test
A 10K, or 6.2 mile-race, is a fantastic distance for runners of all ability levels; it's short enough to encourage beginners and just long enough that even the most hardcore runner can still get a great workout. Better yet, there's probably a 10K held in your area at least once a month and most likely year-round.
What makes the 10K relevant to your marathon goals, however, is the distance. At 6.2 miles, it takes the "average" runner just under 50 minutes to complete, with some of the speediest age groupers finishing in the mid-30-minute range. Regardless of your finish time, know that a well run 10K is essentially the equivalent of doing a functional fitness test.
The minute you hit the finish line, you'll have a hard number (finish time), an average speed (pace per mile/kilometer), and maybe even some heart-rate data (not required). Use this information to determine proper training paces and even extrapolate an approximate marathon performance.
More: When Do I Run at Race Pace?
Running Fitness Is Your Speed at Threshold
Benchmarking your running fitness is a critical step in measuring your progress in training as well as ensuring that you aren't over (or under) achieving in your workouts. The best benchmark is a functional test, a measure of the work your body is doing—in our case, a 10K. Your pace at this threshold level is your personal gold standard of fitness.
For a long time, fitness was measured in terms of aerobic capacity (VO2); but having the biggest VO2 isn't necessarily a predictor of performance. The actual work your body can do—and by work we mean running—over the course of a 10K is a much better metric. If you can do run a practice 10K on a measured course in your neighborhood, you can retest and be confident in your results all year.
More: Maximize Your VO2 Max
Rising Tide Lifts All Boats
"But going fast doesn't help me run longer, does it?"
To be clear, running longer in training is most certainly a prerequisite for any marathon. However, even the high-intensity training of a 10K is still aerobic (as defined by being under your functional threshold). The training of high-intensity track mile repeats in Zone 4 (where 1 is easy and 5 is super-threshold), for example, will still improve your aerobic capacity in all the zones below it.