This is how our biological rhythm ticks
Scientists have been studying the internal clock for around 40 years. Her goal is to find out the causes of the observed regularity of daily highs and lows, which in extreme cases can fluctuate between top fit and totally exhausted. The phenomenon of internal rhythm has been taken into account by traditional Chinese medicine for hundreds of years. The Chinese divide 12 organs into day and night organs and ascribe each of the organs a functional high over two hours a day. Complaints that occur regularly at certain times of the day are attributed to problems with the organ that is active at that time.
The day has 24 hours – also our internal clock?
Experiments have confirmed the assumption that our inner clock  is based on daylight. If people stay in a room without daylight for more than four weeks, they can no longer distinguish between day and night and organize their rhythm of life in accordance with their inner clock.
Most people then live in a cycle of 25 hours, but some people even have a rhythm of 30 hours. When these people return to a normal environment of day and night, their internal clocks revert to a 24-hour cycle.
How does the body organize its daily workload?
Fluctuations in the blood concentration of various substances produced by the body throughout the day have been known for a long time. For example, the concentration of the adrenal hormones, adrenaline  and cortisol, in the blood already rises at 5 a.m. in the morning. Metabolic processes, digestion and energy generation, run at full speed in the morning. Heart activity increases – the body adapts to the active phase of the day.
Experience has shown that the ability to concentrate, memory and language skills work particularly well between 10 a.m. and 12 p.m. Around noon, mental and physical performance initially decreases. The siesta, which is particularly popular with southerners, is a habit that is entirely consistent with the break that the organism takes around midday. However, the midday nap should by no means last longer than 20 minutes if you also want to master the afternoon with drive and vigour. Heavy meals can increase tiredness  at midday.
Around 2 p.m., the blood level of the body’s endorphins probably increases, which experience has shown increases general well-being. Around 4 p.m., physical and mental performance increase again. It is believed that the greatest training and learning success can be achieved around this time. In the evening, the body adjusts to its recovery phase. Blood pressure and body temperature drop. The organs regenerate during the night in order to be fully operational again the next day.
Does lifestyle affect the internal clock?
However, the empirical values ​​relating to the daily shape fluctuations are strongly dependent on the personal lifestyle. If you turn night into day every day and regularly sleep until 12 noon, you will not have your first performance peak at 10 a.m. The body is very adaptable and can adapt to a changed rhythm. All he needs is some time. Anyone who has ever spent their vacation in a different time zone has experienced first-hand that they adapt to the new rhythm of life within a few days.
The rule of thumb when changing time zones is that the body adapts to the new time by one hour every day. The body of shift workers and frequent flyers must constantly adapt to a new rhythm of life. The bodily functions of these people regularly have to change their rhythm again as soon as they have found a new rhythm.
Recovery phases can therefore be shorter than is good for the body, which can lead to exhaustion, permanent tiredness and poor performance in the long term. The habitual person who lives strictly according to his daily schedule will have fewer problems with this.
