All of us experience occasional tiredness and sleepiness. But if you feel tired and sleepy day in and day out, something else may be in play.

Physical exhaustion may be accompanied by many symptoms. According to a New York Times article published online in February 2008, fatigue or exhaustion is one of the most common health problems and can signal the presence of various medical problems.

Heavy lifting, poor sleep or a particularly tough workout can lead to aching joints, generalized body pain and fatigue. But these common symptoms may actually reflect a medical condition when they are severe and persist.

Fatigue is best described as a lack of energy, tiredness or weariness, according to MedlinePlus. Fatigue can result from taking certain medications or from underlying medical conditions.

Exhaustion—also referred to as extreme fatigue—is a severe lack of energy that affects a person’s ability to perform mental or physical tasks. While the possible causes of exhaustion are virtually endless, the most common include excessive stress and lack of quality sleep.

The fatigue index is a concept used in the study of the development of fatigue during anaerobic exercise. Anaerobic exercise consists of activities -- such as sprinting -- that rely on glycogen rather than oxygen for fuel.

Children experience tiredness from time to time, especially during their developmental years when they have growth spurts. Generally a nap and some rest will help to cure fatigue. If your child has an overwhelming need to sleep even after adequate rest, it could become problematic.

Menstruation can be an unpleasant part of life for women. For most, however, it is no more than an inconvenience. For some, however, the symptoms can take over your life and make it difficult to function, especially if you suffer from fatigue.

Your gut is filled with both friendly and unfriendly bacteria. Probiotics are supplements that help to increase the balance of friendly bacteria in your gut. Adding probiotics to your diet can improve immune health, help you synthesize vitamins and alleviate diarrhea.

Throughout pregnancy, many women complain of fatigue. In early pregnancy, this is due primarily to hormones and the many changes your body is dealing with. In late pregnancy, the reasons are often more complicated and sometimes unique to each woman.

Everyone gets tired from time to time. Prolonged tiredness can cause someone to become exhausted. Long periods of exhaustion can cause or exacerbate additional conditions because it decreases the effect of the immune system in fighting off diseases.