Scientists have been studying the internal clock for about 40 years. Their goal is to find out the reasons for the observed regularity of daily highs and lows, which in extreme cases can fluctuate between top fit to totally exhausted. For hundreds of years, the phenomenon of internal rhythm has been considered by traditional Chinese medicine. The Chinese divide 12 organs into day and night organs and attribute to each of the organs a functional high over two hours a day. Regularly occurring complaints at certain times of the day are attributed to problems with the organ active at that time.
The day has 24 hours – does our internal clock, too?
Experiments have corroborated the assumption that our internal 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 arrange their life rhythm 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. If these people then come back to a normal environment with day and night, their inner clock approaches a 24-hour cycle again.
How does the body organize its daily workload?
Throughout the day, fluctuations in the blood concentration of various substances produced by the body have long been known. For example, the concentration of the adrenal hormones, adrenaline and cortisol, in the blood increases as early as 5 a.m. in the morning. Metabolic processes, digestion and energy production, run at full speed in the morning. Heart activity increases – the body prepares itself for the active phase of the day.
Experience shows that concentration, memory and speech function particularly well between 10 a.m. and 12 noon. Around midday, mental and physical performance declines. The siesta, which is particularly popular with southerners, is a habit that is perfectly in line with the break that the body takes at midday. However, the midday nap should not last longer than 20 minutes if you want to master the afternoon with verve and vigor. Sumptuous meals can increase tiredness at midday.
Around 2 p.m., the blood level of the body’s endorphins probably rises, which experience has shown to increase general well-being. Around 4 p.m., physical and mental performance levels really pick up. It is believed that the greatest training and learning successes can be achieved around this time. In the evening, the body adjusts to its recovery phase. Blood pressure and body temperature drop. During the night, the organs regenerate in order to be fully operational again the next day.
Does lifestyle affect the body clock?
However, the empirical values around the diurnal form fluctuations are strongly dependent on the personal lifestyle. If you turn night into day every day and regularly sleep until noon, you will not have your first performance peak at 10 o’clock. The body is very adaptable and can adjust to a changed rhythm. It just needs a little time to do so. Anyone who has ever spent a vacation in a different time zone has experienced on their own body that it adjusts to the new rhythm of life within a few days.
The rule of thumb when changing time zones is that the body adjusts to the new time by one hour every day. The body of shift workers and frequent flyers must constantly adjust to a new rhythm of life. The bodily functions of these people must regularly readjust their rhythms as soon as they have found a new one.
As a result, recovery phases can be shorter than is good for the body, which in the long term can lead to exhaustion, permanent fatigue and a lack of performance. The habitual person who lives strictly according to his set daily pattern will have fewer problems with this.
