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What is a biorhythm and what is it for?
The biorhythm forms part of a research field called chronobiology, which relates to the science of rhythmical processes in plants, animals and human beings.So far, however, proof thereof could not be furnished scientifically.  The science of the biorhythm deals with the theory, that the human organism in its physical, intellectual and emotional constitution is subject to a strictly periodical and slow oscillation in terms of time. Said oscillations have the form of sine waves, which commonly start at the date of birth. The three oscillations have different time lengths.

Days when you have no power or energy are specifically associated with sensitiveness to changes in the weather or an impending illness or other negative influences. Special vitality and energy, good concentration abilities, sensitiveness and creativity, in contrast, may be the result of a preceding event. Perhaps, however, we have  much less influence on our well-being than we would expect. And exactly this is asserted by the biorhythm, namely that the human being is subject to three rhythms enforced on him.

The physical Rhythm lasts 23 days.
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Power, endurance, vitality - someone who has to rely on his physical constitution during work or leisure time particularly knows and feels his ups and downs during the physical cycle.The ups are accompanied by special endurance, vitality and energy.The downs are shown by fast fatigue, and even after minor works you must have a break. In this case one should relax and recover, if possible.

The emotional Rhythm lasts 28 days.
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Creativity, sensitiveness,  the sensory perception is intensified once said cycle has reached its peak. Those who are exposed to interpersonal performances, e.g. teachers or nurses, should try to pay most attention to this cycle.Optimism and duty are subject to the ups. The day starts slowly, quietly, positively and with a certain extent of creativity. Throwbacks and changes can be processed much more easily.Questions for the meaning of life, despair and depressions are part of the minimal phase in the emotional cycle. Problems can now be coped with only with difficulties. .

The intellectual Rhythm lasts 33 days.
Combinationtalent , The power of deduction, intellect, logic, strategic thinking and the ability to learn are features influenced by the intellectual rhythm.The present text (i.e. new knowledge) should therefore best be dealt with during the maximum of this cycle.The ability to concentrate lasts longer and more easily. A difficult problem or a new field of knowledge should be dealt with during said high phase.In times of depressions mentally difficult tasks are particularly hard to cope with. Someone, who is exposed to long phases of concentration during the intellectual minimum, e.g. during driving, should have more breaks and keep an eye on himself and on his constitution.

It is important to note that during all cycles the transitional time is the most critical one. The change from strong to weak, i.e. from the active to the passive phase, is the hardest. It takes time to adjust oneself to reduced energy, sensitiveness or reduced concentration. If someone does not realize this change may overestimate himself, which may require a great deal of energy, which then lacks during the down phase and is urgently needed. The ups and downs are not positive and negative, not good and bad, they are rather like Yin and Yang or like being awake and being asleep.Important are , that in all cyclen the time of passage, the important critical are. The transposition from strong to weak, from activ to passiv Phase, this is very critical. This take some time to react of the reduced energy, sensibility or concentration. If you not observe the change, you maybe overrate you, which maybe cost very energy, which you have not more in the downphase where you must have it.
The hihg- and lowphase are not positiv and negativ, good and bad, they are near like Yin and Yang or better like weak up and sleep..