How To Train Smarter
If you’re training to run 3:45 or slower I suggest that you downplay the role of the long run and focus instead on improving your aerobic threshold (the fastest pace you can run aerobically and burn fat efficiently) and utilize the theory of accumulated fatigue to get your legs prepared to handle the full 26 miles, without needing to run the full distance.
For example, focus on stringing out your workouts and mileage over the course of the week, rather than having 40 to 50 percent of your weekly mileage come from the long run, which increases the total amount of quality running you can do and decreases the potential for injury.
The million-dollar question still remains, however: How do you get your legs prepared to run for 26 miles? The answer lies in the theory of accumulated fatigue. By shortening your long run to 16 to 18-miles and buttressing it against a shorter, but steady paced run the day before, you’re able to simulate the fatigue you’ll experience at the end of the race.
In addition, when you have shorter long runs, you’re able to increase the total quality and quantity of tempo and aerobic threshold workouts throughout your training week. Instead of needing four to five days to fully recover from a 3-hour plus run, with a shorter long run, you can recover in one or two days and get in more total work at goal marathon pace or faster. Developing your aerobic threshold is the most important training adaptation to get faster at the marathon distance because it lowers the effort level required to run goal pace and teaches your body how to conserve fuel while running at marathon pace. The more work you can do to improve aerobic threshold and your ability to burn fat as a fuel source, the faster you can run the marathon.
Finally, with a focus on shorter, more frequent long runs, you can implement faster training elements, such as fast finish long runs or surges, which allow you to increase the overall quality of your long runs. Running your long runs at a slightly higher intensity level teaches your body how to run marathon pace while tired, and also increases your body’s ability to store energy for the end of the race and use fat as a fuel source more efficiently.
When you balance out the gains from finishing a long run fast and upbeat with the potential drawbacks from an extended 3-hour plus long run, you can see why a shorter, faster long run is the better training option for newer marathoners and those aiming to finish over 3:45.