Bell Wealth ManagementBuilding endurance from weekly mileage is the most important part of distance running, but the long run with its endurance boost is the most important part of weekly mileage. Most marathoners are acutely aware of the import of the long run, but either don’t know how far or fast it should be.

Just like the majority of the weekly mileage, a long run should be done easily and at conversational pace. You get endurance gains by going long for increasing longer periods of time—longer than your daily weekday runs. That’s why it is best to focus on running easy, but farther on long-run days than the rest of the week’s runs. You can always work on speed and strength on other days, just not the long run day.

Generally speaking, the length of the long run should be approximately 25-30 percent of your weekly mileage. For example, if your weekly mileage is 60, the weekly long run should be between 15 and 20 miles. The reason the long run is important comes from the endurance you will gain in running for a longer period of time.

Having a mileage goal for the long run is fine, but you should also have an elapsed time goal for it as well. By establishing a time goal, it gives you something to shoot for and also means you can’t run it too fast and miss out on the endurance effect.

One way you can make sure you are not running the long run too fast is to place a time limit on it. Add a minute per mile to your MGP (marathon goal pace). (If you don’t know what that is, add a couple of minutes per mile to a recent 5-K race pace.) Then, figure out based on that time how long it should take you to complete the long run. That gives you a minimum time that you need to be running. Going faster defeats the purpose because the entire idea of the long run is to build stamina.

“Three hours slow is better than two hours fast,” said Peter Gavuzzi, who coached Gerard Cote of Canada to four Boston Marathon titles in the 1940s.

Let’s take this weekend’s 15-20 mile long run as an example. Your MGP is eight minutes per mile so your long-run pace is approximately nine minutes per mile which means it should take you three hours to cover 20 miles. That should be your game plan.

But on long-run morning, you meet up with your group and are so pumped up, you decide to push the pace. You start out at 8:15 per mile pace and feel so good, especially in the beginning, you push the pace to the point of running faster than MGP. After about 10 miles, you begin to feel like you’ve been running a little too hard, yet are in such a good groove you don’t want to slow down. At this point, you decide to hold the pace, but cut the long run from the planned 20 to 15. When you finish, you’re proud of holding onto the eight-minute per mile pace for the 15 which you finished in two hours.

Mission accomplished? Not really. The long run would have been more beneficial to you if you had stuck with the original plan to run 20 miles in three hours, rather than pushing the pace and going five miles shorter in two hours.

Using this same example, you could even have gone slower than three hours for the 20 and gained the same endurance benefit. Our tough heat and humidity, lack of rest, stress, and other factors all add up to make some long runs slower than others. But again, that’s OK.

It’s certainly better than doing the long run too fast. While you may be able to run the long run faster, it is risky in the short term and can be devastating in the long term. In the short term, you can train too hard on the long runs and ruin your goal race because the long run—in essence—became your race. Do that too often and you will have blown the race you are training so hard for.

The riskier damage comes in the long term. Continually running long runs at too fast a pace relative to your ability, will result in a series of poor races and can shorten your racing career.

Speed is the killer on long runs, not the distance. As a marathoner, you should build up to several long runs of 20-22 miles during your training cycle. But build up slowly, increasing the weekly mileage by about 10 percent. Some weeks you will actually decrease the mileage of the long run to half of a recent max long run to a minimum long run of 10 miles.

If you are on a three-week cycle of two weeks of increasing weekly mileage and one week backing off, then you can have the same cycle for increasing and decreasing the long run. Or, if that cycle is one-week increase and two weeks of lower mileage, the same can be said for the long runs.

The peak long run—your longest–should be four weeks away from the goal race. Then taper back each week to 50-75 percent of the previous long run to a final distance effort of 10-12 miles one week before the race.

Don’t try to squeeze one more long run in a week or two before the big race. It won’t help add to your endurance and can only add to a fatigued feeling you don’t want going into the big race.

If you stay consistent with your weekly mileage and nail your long runs at the proper pace and distance, you will make substantial endurance gains. This hard-won endurance, gained from training many miles of weekly training, including the all-important long run, will give you the strength and mental fortitude that you will need for the tough miles in the marathon and half marathon.

Mac Allen coaches Team Mac ( for racing in distances from 800 meters through the marathon. A top-flight masters competitor, Mac has over 15 years of coaching experience.