Intervals are tough on your body. If performed too often they increase the risk of overtraining. Overtraining is uncomfortable and a setback so it's important to prevent it by allowing time for recovery and growth between sessions. Consider taking at least two days of rest between sessions and even more if you suspect you are overtrained. Symptoms of overtraining are:

• Loss of strength, speed, endurance, or other elements of performance.



• Loss of appetite.



• Inability to sleep well.



• Chronic aches and pains or soreness.



• Chronic colds or respiratory infections.



• Overuse injuries like tendinitis.



• Unusual fatigue.



• Occasional increase in resting heart rate.



• Irritability.



• Malaise and you don't feel like exercising anymore.

If you have any of these symptoms and it's from overtraining and not a medical condition (for which you should see your doctor), then you will need to either take a break from working out (generally seven to 10 days) or experiment with fewer intervals. Don't worry about losing your fitness if you take a break. Virtually everyone comes back stronger after a break.

NOTE 1: If you have trouble with your knees, then speeding up for work intervals of walking, jogging, or running, might be too tough. You don't want to irritate your joints, so stop the exercise that hurts and modify your workout to make it pain-free (or as close to pain-free as you can). You never want to work through pain, and especially pain that gets worse during your workout. See your doctor if pain persists.

NOTE 2: Check with your doctor before starting interval training if you have any questions about the health of your heart or other medical conditions that might be affected by high-intensity workouts.

This answer should not be considered medical advice...This answer should not be considered medical advice and should not take the place of a doctor’s visit. Please see the bottom of the page for more information or visit our Terms and Conditions.