Your body requires a certain amount of stressful stimulus to grow stronger. In fact, that damage- recovery cycle is the whole basis of fitness training: You break your body down, and it responds by building itself back up better than before.

But if you?ve been putting your body through its paces without opportunity for full recovery, or if you?ve been under additional stresses (physical, mental or emotional), you may not be giving your body a chance to restore itself. To do so, you may need to change your routine, pare down your training load or, in some cases, walk away from training altogether ? at least for a little while.

Knowing when and how to moderate your training plan is critical to your weight and fitness success, as well as your health. Here are some of the most common indicators that suggest you need to take a step back, along with strategies for when and how to step it up again.

Symptom No. 1: You?re feeling tired, strung out and crabby.

What your body is trying to tell you: It may be maxed out. Generally, exercise should make you feel better, not worse. But when you?re clocking 80-hour weeks, intense exercise can become one more strain in your already-stressed-out life. A lot of busy people find time to exercise by cutting back on sleep, but it?s during sleep that your body repairs and restores itself.

What to do: Focus on quality rather than quantity. Instead of training six days a week, switch to an every-other-day schedule. Sleep in on your days off. The rest and recuperation will reduce cortisol levels. It?s better to have three good workouts during the week than to have five or six so-so workouts.

Symptom No. 2: You?re sick ? again.

What your body is trying to tell you: If you?re getting sick a lot, it?s a sign that your immune system is struggling and that it may need more attention than your workouts for a while. Regular, moderate exercise usually boosts immunity, but intense sessions, particularly those that last two hours or more, can lower it ? especially if you don?t rest adequately between sessions or you aren?t getting adequate nutrients.

What to do: Take stock of your illness. Go to your doctor and rest.

How to come back: The effects of flu or other illness may linger long after your fever subsides. During your first week back, train at no more than three-quarters of your normal intensity and duration. After a week, if you feel energetic during and after your workouts, resume your normal training load. During longer sessions, consume some carbohydrate in the form of a sports drink, energy bar or energy gel.

Click to the next page to read more about getting your training back on track