Long runs are key to any training program. Here’s how to make them count.

By Ed Eyestone

Question: I never race more than 5-K. Why should I do long runs?

Answer: Long runs are for every runner, not just marathoners. The runners I coach in college run a weekly 13- to 15-mile long run even though some seldom race over a mile. The long run increases aerobic base, improves running economy, and boosts confidence. — E.E.

Shortly after college when I decided to race my first marathon, a friend asked why I’d moved up to the marathon when I’d enjoyed success at the 10,000 meters. “You must enjoy long runs,” he said.

“Not really,” I replied.

“I hate to tell you this,” he said, “but the marathon is a long run.”

Over the years I’ve learned that whether you’re a recreational runner or a hard-core marathoner, the long run is the backbone of any successful training program.

Like any extended aerobic exercise, the long run delivers the predictable physiological benefits: increased max VO2 and blood volume, maximum stroke volume (the amount of blood ejected from the heart with each beat), and new capillaries and red blood cells.

Just as important, the long run teaches your body to spare glycogen and rely more on fat as a fuel source. Translation: You delay glycogen depletion during a long race, so you delay bonking. And let’s not forget the mental angle: To prepare for the psychological challenge of racing for hours, you have to train for hours.

How long? “Long” is a relative term. One person’s long run is another’s easy 8-miler. Most experts agree that 20 to 30 percent of your weekly mileage should be devoted to the long run, depending on your overall mileage. For example, an elite runner logging 100 miles per week might do a 20-mile long run (20 percent of weekly mileage), whereas someone running 40 miles per week might do a 12-mile long run (30 percent of weekly mileage).

Unless you’re an ultra-marathoner, I recommend keeping your long runs to 3 hours or less. Any training benefit beyond 3 hours is just not worth the added fatigue and risk of injury.

How fast? If it feels too hard, it probably is. Tempo runs and interval workouts are for building lactate threshold. Long runs are not. They should be carried out at a comfortable, conversational pace. (Remember that even a “comfortable” pace will feel challenging in the last few miles.) For faster runners that means 1 to 1? minutes per mile slower than your 10-K race pace. For slower runners, 30 seconds to 1 minute per mile slower than 10-K pace.

How often? Weekly long runs are fine, provided you:

1.     Follow your long run with a recovery day of very easy running, cross-training, or rest.

2.     Start your long run well hydrated and consume sports drinks and gels en route. This is excellent practice for the marathon and will keep you from getting overly fatigued.

3.     Limit your long run to 1:45 or less (unless you’re training for a marathon–see number 5, below).

4.     Consume 3 to 4 grams of carbohydrate per pound of body weight daily to make sure carbo stores stay loaded.

5.     Alternate long runs with very long runs when training for a marathon. For example: 2 hours one week, 2:45 the following week, then back down to 2 hours the week after that.

6.     Run with someone of comparable ability. Otherwise your long run may turn into a tempo run or a Sunday stroll.

7.     Ease back into training if you’ve missed a long run due to illness or injury. Going long as soon as you feel better can overtax an already battered immune system. Instead, do half or three-quarters of your scheduled long-run distance, then resume your normal schedule the following week.