We know, we know, we keep emphasizing on keeping fit by, er, exercising. But not too much, as in overdoing it.

Do you know that too much exercising can be as bad as too little? Here are 4 negative effects of what excessive exercise can do to us:

1. Reproductive Health Issues

Women whose body-fat level falls below 13 to 17% can stop menstruating, a condition known as amenorrhea. This is reversible once the body-fat returns to normal, that is, above 20% but women can experience irreversible bone loss if they are not menstruating.

2. Supressed Immune System

Overexercising without adequate recovery can stress the body, decreasing immune function and increasing the chance of respiratory infection. Research has found that during intense physical exertion, the body produces certain hormones that temporarily lower immunity. Cortisol and adrenaline (also known as the stress hormones) raise blood pressure and cholesterol levels that suppress the immune system.

The effect has been linked to increased susceptibility to infection in endurance athletes after extreme exercise such as marathon running. This can be avoided by including enough rest and recovery days to allow your immunity to recover.

3. Soft Tissue Injuries

Avoiding rest or treatment for injuries sustained during exercising can result in chronic damage to connective tissue. Too much exercise can also destroy muscle mass, especially if the body is not getting enough nutrition, forcing it to break down muscle for energy. In addition, endurance sports such as marathon running can cause stress fractures, fatique and cause menstrual periods to stop in some women.

4. Mood Problems

People who exercise too much can suffer from withdrawal symptoms including sleep disturbances, depression, anxiety, confusion and difficulty concentrating when they miss a day of exercise.