Why Run Long?

Including a few 18- to 22-mile runs in your marathon training is important because long runs:

Improve the body's capacity to utilize fat as fuel, therefore sparing glycogen, i.e., energy stores in your muscles. (If your body uses only glycogen, you'll eventually run low and "hit the wall" somewhere after 1 ½ hours of running.)

Improve the nervous system's ability to recruit muscle fibers not normally used for running long distances.

Strengthen the heart muscle and oxygen delivery system.

Condition the body to stay relaxed and run with efficient form for long periods despite fatigue.

Allow you to test your body's reaction to water, sports drinks, food, racing shoes, and clothing—under marathonlike conditions.

Teach patience and discipline. Most marathoners succeed in direct proportion to how well they can hold back and run wisely. Your reward for forcing yourself to run for three or four hours in all kinds of weather is increased confidence and mental toughness. Long runs teach you to finish despite your mind and body's objections.

How Far and How Often?

If you're a novice marathoner, you should gradually build up the long runs and complete at least three runs of 18 to 20 miles prior to the marathon. Plan your long runs well in advance so you can fit them into you schedule. Do not, however, attempt to run long every weekend. If you're a veteran marathoner, run long every other weekend, or two out of three weekends during the three months prior to the race. Try to get in at least five or six runs of 20 to 22 miles. No marathon runner should attempt a long run that will take longer than four hours; the result would be severe fatigue and vulnerability to injury. Save the "tearing down" that comes with runs longer than 22 miles for the marathon itself. Your last long run should be done two to three weeks prior to the marathon.

Long Run Tips

1. Control the pace. Start long runs at a slower pace than you run for short and medium distance runs. To avoid fatiguing too soon, your pace should be approximately one and a half to two minutes per mile slower than your 10K race pace.

2. Find training partners. If your partner can't run the whole distance with you, at least meet up for the last few miles of your run to give you a boost.

3. Use races to get in your long runs. For example, run easy for five miles and then run a half-marathon race at your training pace to total an 18-mile run. You'll have plenty of company, get time splits along the way to judge your pacing, and can practice getting cups of water or sports drinks just like you would on marathon day.

4. Avoid heat and hills. Whenever possible, try to start long runs early in the morning or late in the day to avoid the heat, and seek courses that provide shade. If the weather is very bad, consider postponing. As for hills, incorporate a few to toughen you up, but don't overdo—they will tax you.

5. Seek a soft surface. If possible, do long runs on dirt trails, which absorb pounding much more than pavement does. Also, beware of running long distances on slanted surfaces (such as the road), as it leaves you prone to injury.

6. Walk if you have to. Slow down if you need to, especially when it's hot—even take brief walk breaks as necessary, but keep moving. It's okay to stop running for a few minutes to drink fluids or use the toilet, but if you stop running for too long and stand around or sit down, you will stiffen up.

7. Know when to stay home. Don't run long if you are not fully recovered from illness or injury. Favoring an injury over the course of a long run will likely cause additional injury.

8. Dress properly. Wear well-cushioned, well-broken-in (but not broken-down) shoes. And don't overdress, which will contribute to heat buildup and dehydration.

9. Don't get burned. Protect yourself by wearing a hat, a shirt that covers the shoulders, and sunglasses—and use sunscreen.

10. Drink often. Drink fluids at least every 30 minutes, but ideally every 15 to 20 minutes. Sports drinks are a better choice than water; they're absorbed faster and give your energy supply a boost.

11. Refill the tank. Replenish your body with fluids and carbohydrates immediately after running; you will be dehydrated and low on stored glycogen. Drink at least 16 ounces of fluid for every 30 minutes of running. Sports drinks are a good choice, because the body absorbs them more quickly, plus they contain carbs. Keep drinking until your urine is clear or a pale yellow. Carbohydrates are also key: You should consume 50 to 100 grams within 15 minutes of completing your run, then an additional 50 grams every two hours until you eat a regular meal.

12. Be flexible. If you have properly built up your mileage and long runs well in advance, you can skip a long run here and there and not lose out. Don't panic if you miss a long run due to unforeseen circumstances. If you run when you're too tired or hot, it may lead to discouragement instead of building confidence. One run won't make a difference if you have several other long runs under your belt prior to marathon day.

Distance running isn't all about discomfort; many runners look forward to their long runs. It's a time to relax and just run slow and easy. You can do plenty of deep thinking on solitary runs, or you can enjoy the company of others. If you look at the long run as something to savor rather than as a dreaded task, it'll be easier to do.