There are as many different types of runners as there are people who run. But one misconception that many runners hold in common is a work ethic that too often precludes rest. Some runners have to be held down in order to get the rest the body requires. Sooner or later that will come by way of injury or overtraining syndrome. For those runners, understanding that rest and recovery does not mean doing nothing, can break through the mile-aholic's misconceptions and change training habits for the better.
For starters, we need to differentiate between rest and recovery days and light workout days. They are two different things. Rest and recovery days are just that. They are days primarily designed to rest and recover. Healthy runners need rest maybe once per week, or even just once or twice a month. Obviously injuries, illness, aging, staleness, increases in distance or intensity, and overtraining can create demands for more rest.
More: What Is Overtraining?
Although rest is needed, it is still important to remain active on those days. The body, just like the mind, needs stimulation every day. Even after a grueling marathon many people find it's a good idea to move around, maybe take a walk, as early as the day after to avoid stiffening up. Even people who suffer heart attacks are encouraged to get out of bed and move around as soon as possible. On rest and recovery days it is important to avoid doing the worst thing you can do for your body... nothing.
Examples of rest and recovery activities are walking, static stretch exercises (after a warm up and loosening up period), dynamic stretching, swimming, water running, and riding a bike. Keep in mind that increasing respiration and heart rate to a level just slightly above normal and challenging your range of motion are generally good things to do almost any time. Rest is a variable to apply in response to the feedback your body gives—more, or less, but always some.
Light workout days are days in which you are actually working out. The difference is that your activities are lighter, less demanding and generally performed at a lower level of intensity or the activities are executed at a high level of intensity for a much shorter period of time. Light workout days are just as important as heavy workout days. They allow development to take place without breaking yourself down and acquiring overuse injuries, experiencing training plateaus, and developing a generally stale, flat, bored attitude that can come from doing the same thing day after day.
More: How to Break Through a Training Rut
In short, the light days make the heavy days possible. They should enhance and compliment your more intense workouts. They can and should be equally enjoyable. If your workouts include heavy days and light days in proper sequence, you should not need as many rest and recovery days.
An important guideline for light workout days is variety. Providing a change in the workloads to shock the system is what is important. When changing the emphasis on workouts from heavy to light workout days, there are a number of things that can be accomplished. Some training objectives that are good to consider on light workout days are flexibility, developing range of motion, improving running form, strength training, hill running, and speed interval training.
If you can, schedule the same amount of time to train on light days as heavy days. A good idea is to spend less time on the track on light days and spend the balance of your training time with strength training. Strength training can improve running times right away. Of course there are many other benefits from strength training such as injury prevention, improved bone density, and increased range of motion that research has shown to help people well into their nineties.