Easy runs
Top coaches and exercise physiologists believe that most runners should do 80 to 90 percent of their weekly training at the easy run pace (this includes your long runs, done at approximately the same pace). Easy runs build your aerobic fitness, and your muscular and skeletal strength. They also help you burn more calories and recover for harder workouts.

Tempo runs
Tempo runs help you improve your running economy and your running form. They are often described as "hard but controlled" runs, and they will help you prepare for races of 10,000 meters to the marathon. Tempo workouts generally fall into one of two categories: steady runs of 2 to 6 miles; or long intervals with short recoveries. Here's an example of the latter: 4 x 1 mile at tempo run pace with 2 minutes of recovery jogging between repeats. You should do tempo runs no more than once a week, and they should make up no more than 10 to 15 percent of your total training.

Maximum-oxygen runs
Maximum-oxygen workouts help you improve your running economy and your racing sharpness. These workouts are often called "interval workouts," and are most useful when you are preparing for a race of 5000 meters to half-marathon. Here's an example of a good maximum-oxygen workout: 6 x 800 meters at maximum-oxygen pace with 4 to 6 minutes of recovery jogging between repeats. You should do maximum-oxygen workouts no more than once a week, and they should make up no more than 6 to 10 percent of your total training. (When you run these workouts, you are running at or near 100 percent of your maximum oxygen capacity, which scientists call max VO2; hence the name for these runs.)

Speed-form runs
Speed-form workouts help you improve your running economy, form and leg speed. These are also interval workouts tailored to help you prepare for races of 800 meters to 5000 meters. Here's an example of a good speed-form workout: 8 x 400 meters at speed-form pace with 3 to 4 minutes of recovery jogging between repeats. You should do speed-form workouts no more than once a week, and they should make up no more than 4 to 8 percent of your total training.

Yasso 800s
Yasso 800s are an invention of Runner's World staffer Bart Yasso, who has run more than 50 marathons and ultramarathons. Because of their simplicity, Yasso 800s have proven popular and useful for marathoners worldwide. Basically, Bart says that if you want to run a marathon in 2:45, 3:29 or 4:11, you should train to the point where you can run 10 repeats of 800 meters in the same time?2:45, 3:29 or 4:11. The only difference is that your marathon time is hours:minutes and your 800 time is minutes:seconds. Bart suggests doing Yasso 800s once a week as part of your marathon training. Start with perhaps 4 x 800 and build up to 10 x 800. Between the 800s, take a recovery jog that lasts as long as your 800s. (Additional hint: Yasso 800s are a great workout for any runner. Because they are "strong but controlled," they're basically a form of tempo training.) A good Yasso 800 workout: 6 x 800 at Yasso pace with recovery jogs between the 800s.

Long runs
Long runs form the foundation of all marathon training programs. Long runs build everything from your confidence to your discipline to your fat-burning. So, even when you're not training for a specific marathon, it's a good idea to do at least one semi-long run a week. Because long runs are done at a relaxed pace, there's great latitude in how fast you actually run. In general, we believe that slower is better than faster. Let your long runs be your slow runs, and save your legs for other days of the week when you might do tempo runs or maximum-oxygen runs. But there are a thousand theories about how to do long runs, none of which have yet been proven superior to the others. The important thing is building up the distance and training your body to keep going for 3, 4, 5 or however many hours it's going to take you.