In practice, a distinction can be made between four types of fatigue:

After eating a big meal, we often feel the need to fall asleep. It may suggest that the liver and the immune system are working hard! (Metabolic fatigue)

1. Muscle fatigue - (Muscles) Often due to the muscles' exertion (not necessarily aerobic). Such as holding a child in your arms and standing still.
   • Muscle fatigue is a result of lactic acid formation. Usually, within a few minutes, the pain will go away.
2. Aerobic fatigue - (Heart & Lungs) Fatigue results from physical exertion, sports activities, climbing stairs, carrying loads, etc. Its manifestation is often associated with high heart rate, rapid breathing, muscle aches, and sweating.
   • Aerobic exertion activates the heart and lungs; therefore, the pulse and respiration rate increase. Sweating is a mechanism designed to cool the body.
3. Metabolic fatigue - (Liver, kidney, Immune system) Is often due to a heavy meal or chronic inflammatory diseases. The manifestation of metabolic fatigue is a desire to take a nap.
   • Metabolic fatigue is fatigue of the liver and kidneys that work very hard, usually after large meals. The liver is the most energetic organ in the human body! The need for drowsiness reflects the direct connection between the liver and the eyes. (According to Chinese medicine)
   • A weak immune system accompanied by prolonged inflammations can impair alertness, memory, and mood.
4. Spiritual and mental fatigue - (Brain & Subconscious) Usually, after unpleasant or traumatic events. The manifestation of mental fatigue is a poor mood, a tendency to outbursts, closure, and social distance.
   • The brain is energetic; unpleasant and traumatic events are often stored subconsciously. (As part of the defense mechanism of the mind) These processes impair the mood and the general energy level of the body.

Continue reading: Immune system boost and rehabilitation.