Improvement in running never follows a linear upward path. Don’t look for or expect straight lines. Instead, you’ll go through peaks and valleys. The goal isn’t to avoid the valleys, which are inevitable, and also highly valuable when you have planned for them. Rather, you want your peaks to keep getting higher.

To achieve this you must vary your training in at least two ways. You need to switch up the types of workout you are focusing on, and the duration (length of time) of each.

I first recognized how type and duration function together while covering races for Runner’s World. I would go to a major road race wherein one runner would place higher than expected. Naturally I would ask him or her what had caused the big improvement. “I just changed to a new coach,” the runner would say. “The results are amazing. I can’t wait to see what I’ll be running in six months.”

Six months later, I’d see the same runner at another big race. Only this time he or she would have finished far down the results list. The expected improvement hadn’t happened. I asked why. All I got in return was a shoulder shrug and a long, sad face.

I decided to experiment on myself. I subjected myself to various training systems, as if I had just changed from one coach to a new one with a different workout program. I tried long runs, hill sprints, interval 400s, tempo runs, and so forth. I did that system’s specific hard workout—and no other hard workout—at least once a week, and monitored how I felt and performed.

No matter what workout I tried, I felt great for three weeks. On the fourth week, however, I could feel the air coming out of my tires. Clearly I was overtrained and headed in a bad direction.

That’s when I developed the “Magic of Three” strategy. It states that you should do only three weeks of a particular kind of hard workout. After three weeks it’s time to recover and change things up.

  

Do less (at times) to achieve more: To improve, all runners need to gradually add more stress to their training. This is the way we apply Hans Selye’s famous general adaptation syndrome. We train harder. We rest, recover, and adapt. And then we train harder again, beginning the next cycle.

Selye observed that without the rest and adaptation, the body gets weaker instead of stronger. The resulting crash used to be called overtraining. Today physiologists use the term overreaching, which is wonderfully apt, but essentially the same. If you reach too high in your training because you are always trying to do more, you will too soon hit a wall.

It’s far smarter to plan regular recovery periods than to have them batter your training progress. In my experience the recovery should come every fourth or fifth week. Keep running, but take a break from hard workouts. Go easy every day for a full week.

  

Switch gears: I’ve noted that there are many fantastic workouts. However, no single type of workout is superior to all others. All are capable of producing great results. The “magic” of the Magic of Three system comes from the way you weave workouts together.

Don’t repeat any particular hard-day workout more than three weeks in a row. Then take a recovery week. The system produces optimal results if you change the focus of your key workout every month. Switch from hills to tempo runs to intervals. Try long runs and fartlek workouts. Include 30-20-10 workouts and out-and-back speed runs.

Whenever you begin to feel a little stale, stop the hard workouts you’ve been doing and swap in something else. You’ll notice both mental and physical benefits.

  

Cycle your training—hard and easy, hard and easy: To reach your fitness and performance goals, you need to train hard. You need to train consistently hard. However, you can’t train hard all the time, and you shouldn’t try.

Exercise scientists call this approach “periodization.” There are times to do a little speed work and a lot of slow distance (early in your racing season), and times to reverse the emphasis (when you approach your key races).

You will reach your potential only when you recognize that your fitness and performance follow an undulating slope. They curve up and down and up again. It’s your job to bend your training to match these slopes. Because they will not bend to you. They will break you.