All living organisms are functioning with certain rhythm. More than, all our organs and body cells have also rhythms of biological functioning. We know this fact since the dawn of civilization. What we learn only recently is when exactly different systems have peaks of maximum and slowest activity, when is a time for records of performance, and when is a time of tendency to get sick.

The main biological rhythm is considered to be about 24 hours. It is called Circadian (circa- means: about; dian –means: day). The reason why it is not exactly 24 hours is that some people have a few hours longer, and others a few hours shorter than 24 hours rhythm of functioning if they are placed in no time clue environment.

Major phenomena of the Circadian rhythms are sleep and alertness.

Rhythms shorter than 24 hours called ultradian. These rhythms are rhythms of our hearts, breathing and minutes and seconds rhythms of our metabolism.

Rhythms that are longer than 24 hours are called supradian (weekly, monthly, yearly etc.). Each and all of these rhythms have some significance in physiology and medicine.

Below are some interesting facts about different biological rhythms.

Time of the Maximum activities of the body organs or systems:
Liver 1-3 am
Gall bladder 11pm – 1 am
Stomach 7-9 am?
Intestinal 13-15 pm
Large intestinal 5-7 am
Spleen and pancreas 9-11 am
Heart 11-13 am
Vascular circulatory system 19-21 pm
Lungs 3-5 am
Kidneys 17-19 pm
Temperature control 21-23 pm
Growth hormone 10-12 pm falling asleep
Thyroid  12-2 am

Circadian Disorders events
Diabetes (sugar drops) 2-3 am
Heart arrhythmias 3-5 am
Heart attacks  4-5 am
Stroke 4-6 am upon awakening

Weekly  Rhythms
Monday Morning Syndrome    

Monthly rhythms
Menstrual cycles 28-31 days
Intellectual cycles 28-31 days
Emotional cycles 26 -28 days
Physical cycles 30-31 days
Monthly cycles of seizures

Seasonal Cycles
Seasonal Affective Disorder Dark days

Yearly Cycles
Birthday Sick Syndrome (getting sick a month prior and getting stronger a month after birthday)..
Holiday/ Anniversary syndrome (Getting more sick at certain days like during holidays, at the expected age; during separation, “programmed” death, etc.

Four years Cycles
A peaks of Physical Activity fluctuate every four years (that is why Olympic Games are every four not five years).

11 years cycles
Disorders associated with the Sun’s storms