Training according to your internal clock: Why it's worth taking a look at your biorhythm

Jürgen Aschoff could be satisfied with this particular laboratory: no noise, no light. Thick walls, windowless rooms. And the occupants? Completely isolated. For the researcher, the perfect place to search for the "internal clock". The physiologist from the Max Planck Institute of Behavioural Physiology had been searching for this for years. And he actually found it in his famous "Andechs Bunker", which NATO had built especially for his experiments.

Experiments on biorhythms

However, what Aschoff put his test subjects through in the 1960s sounds scary: they spent up to four weeks in the bunker, isolated from the outside world and without any information about the time. They were not aware of sunrise and sunset, and Aschoff had taken away their watches. Because he did not believe what most people thought: that people only live according to a certain rhythm because they react to sunlight and other external circumstances. Hardly anyone believed in an "internal clock" - until Aschoff published his findings.

During the experiment, his test subjects lived approximately to their usual rhythm. They slept regularly, had high and low phases and their body temperature fluctuated throughout the day. Although a day in the bunker lasted 25 hours, slightly longer than outside, Aschoff proved that there is an internal clock.

It sits behind the forehead, the inner clock

Today it is even clear where it is located - behind the forehead, above the point where the optic nerves cross. In medicine, the timer in the head is called the "suprachiasmatic nucleus", or "SCN" for short. The area of the brain the size of a grain of rice activates, among other things, the pineal gland in the diencephalon, which releases the sleep hormone melatonin at night and the wakefulness hormone serotonin during the day.

In addition to hormone levels, the SCN controls heart and respiratory rates, organ activity, the ability to concentrate and even visual acuity - all of which fluctuate within 24 hours and influence performance. For example, most people are at their most productive in the morning and late afternoon - when blood pressure, heart rate and respiratory rate have reached their maximum. Between these two peak phases there is a tough midday low, and from 9 p.m. the systems shut down.

How do you train according to your internal clock?

What does this mean for training? Training works best when the body is particularly alert and ready to perform. Strenuous rides are then easier and the muscles can cope better with high intensities, which makes training more effective. If the release of the sleep hormone melatonin has already started in the evening, you should not exert yourself as much as possible.

That would be tiring and produces stress hormones, which leads to problems falling asleep. "I think everyone recognises high and low phases in the course of the day," says Sebastian Grospitz, personal trainer and Bavaria's U19 national association coach for road and track. "Between 9 and 11 a.m. and between 4 and 7 p.m. we are theoretically at our best."

Of larks and owls

Theoretically. If it weren't for the fact that not everyone's internal clock ticks in the same way. Biorhythm experts such as Jürgen Aschoff distinguish between different chronotypes. In addition to the normal types described above, there are also larks and owls, i.e. early risers and night owls. Their highs and lows are genetically shifted in time. While larks are already in top form before eight o'clock in the morning and then again in the early afternoon, owls only hit top form around midday and experience a second high in the evening.

Because every chronotype is particularly fit at a different time, it is worth knowing your own tendencies (see below) and to take them into account when planning training. "If an athlete could organise their training solely according to their biorhythm, this would definitely have a positive effect on their performance," cycling coach Grospitz is convinced.

On the other hand, those who constantly live and train against their inner clock do not utilise their potential on the bike and even damage their health in the long term. Psychologists such as Prof Dr Till Roenneberg from the Institute of Medical Psychology at the Ludwig Maximilian University of Munich warn that people who constantly go against their inner clock live in a kind of social jet lag, which impairs health and performance. This can result in sleep and digestive disorders, chronic stress and an increased risk of cardiovascular disease and diabetes.

Training according to your internal clock is not always feasible in everyday life

However, training expert Sebastian Grospitz knows that listening to the ticking of your inner clock and always adapting your daily routine to your biorhythm is not that easy: "Most recreational athletes have to organise their training according to their schedule or working hours, at least during the week, and can't train at all when their inner clock opens the optimal time window."

However, those who are flexible will benefit: Austrian psychologists from the University of Salzburg, who have investigated the influence of biorhythms, regeneration and sleep in competitive sport, consider training according to biorhythms to be "one of the underestimated cogwheels that can perhaps be turned to be one or two hundredths of a second faster or to face your opponent with more stamina and concentration". At amateur level, your career doesn't depend on it - but it's worth a lot when it comes to having fun during training: what lark wants to be pedalling at eight in the evening?

Familiarisation is possible

The internal clock cannot be shifted. Only with a lot of discipline can owls get used to training in the morning and larks get used to going out in the evening. The rule is: once a lark, always a lark - once an owl, always an owl. The better solution is therefore not to adapt your biorhythm to your training, but to adapt your training to your biorhythm.

For a long time, it was not clear that it is a question of type when athletes can deliver peak performance. Until recently, scientists believed that most people performed best in the evening. It was not until 2015 that Elise Facer-Childs and Roland Brandstaetter from the School of Biosciences at the University of Birmingham published a widely cited study that changed this view.

After studying 121 competitive athletes, the psychologist and the neuroscientist came to the conclusion that not only are there serious differences between owls and larks, but that owls are at a disadvantage in top-class sport. Compared to larks and normal types, whose performance only varies between 7 and 10 per cent over the course of the day, owls show extreme performance fluctuations of 26 per cent throughout the day. "These enormous differences can have a major influence on talent identification, performance assessment and competitive success and explain why previous studies had identified top international athletes predominantly as early types," the study concludes.

Larks suffer when the starting shot is fired in the evening

The second important finding of the experiment: the ability to achieve peak performance depends primarily on how much time has elapsed since waking up. Larks and normal types reach their peak performance six hours after waking up. Owls, on the other hand, are only at their best eleven hours after the alarm clock rings - a major disadvantage if a race starts in the morning. After all, getting up in the middle of the night or even pulling an all-nighter is not an option either.

U19 coach Sebastian Grospitz only advises his young riders to have breakfast at least three hours before the start of the race - and to take this into account when getting up. According to the cycling coach, it is not necessary to complete every training session in the morning when preparing for a morning race: "In order to get used to the race day schedule, it can make sense for owls to vary the training time and to at least schedule it close to the start time of the race. But if everyman races or cycle marathons start at 6.30 a.m., it makes little sense to always train then." He himself wouldn't find this so difficult: "I've always been a lark and prefer to train in the mornings," says Grospitz.

Larks suffer when the starting signal is given in the evening. They could then benefit from a light shower, a team of researchers from Basel discovered. Top athletes who were exposed to blue light for an hour were then measurably faster than the others in a twelve-minute time trial on the ergometer in the final sprint. The fact that blue light suppresses the production of the sleep hormone melatonin was clearly visible in their lower hormone levels.

>> Muscle cramps when cycling: TOUR gives important tips

When to train what?

Researchers used to believe that certain types of training were only useful at certain times of day and recommended strength training in the morning and endurance training in the evening. This has not been scientifically proven; current data shows that it does not matter when you prioritise your training. One more argument in favour of following your internal clock when planning your day. A team of Chinese researchers who investigated the mood during sport at different times of the day also advise taking the chronotype into account: "To achieve the best emotional state, we recommend that night owls train in the afternoon or evening."

Admittedly, this is often unrealistic in everyday life - bike rides take a few hours; and if you have to pick up the kids or go to a meeting when you're at your physical best, you can't just start cycling. However, if it is possible to take your biorhythm into account, it is worthwhile. Because training against your body clock is neither fun nor fast.

Training according to your inner clock - Which chronotype am I?

Larks

... usually wake up without an alarm clock.

... feel fit and well-rested straight away.

... are hungry for breakfast.

... are on top form again in the early afternoon.

... often get tired after 8 pm.

Owls

... need an alarm clock to wake up.

... are hardly hungry in the morning.

... only feel fit around midday.

... are on top form again in the evening.

... don't get tired until after midnight.

All about light

Red light

... or infrared light improves regeneration after sport, relieves sore muscles and accelerates the healing of muscle injuries, according to a US study.

Light therapy

... has been used successfully for years to combat depression. The light, which physically corresponds to sunlight, influences the internal clock and hormone levels.

Blue light

... from smartphones or televisions is said to cause problems falling asleep because it allegedly disrupts the production of the sleep hormone melatonin. However, there are doubts about this theory.

Jet lag and shift work harbour health risks

How the body suffers from a "wrong" time zone can be felt during jet lag. Symptoms include feeling unwell, fatigue, difficulty falling asleep and sleeping through the night, tiredness, loss of appetite, poor concentration, digestive problems and headaches. For every day that passes, you move another hour closer to the new rhythm. Frequently changing your daily rhythm is anything but healthy. Studies on shift workers have even shown that it increases the risk of cancer. Good for cyclists: regular exercise helps to cope better with changing daily routines such as shift work and jet lag.

Training according to the internal clock - performance highs and lows

Larks are already in top form before 8 a.m., while owls don't hit top form until around midday. Normal types are in between. All three have a second daily peak - at different times.

Interview with sleep physician and psychiatrist Prof Dr Kneginja Richter

The sleep physician and psychiatrist Prof Dr Kneginja Richter heads the CuraMed day clinic in Nuremberg and teaches at the Nuremberg Institute of Technology.

TOUR: Prof Dr Richter, do cyclists train more successfully if they take their chronotype into account?

Prof Dr Richter: Yes, sleep research clearly shows that performance reaches its first peak three hours after getting up, so that larks are particularly fit in the morning and owls only from midday. Exercising then makes a lot of sense. Fatigue also depends on the chronotype. Normal types peak at around 1 p.m., larks earlier and owls later.

The alarm clock should ring three to four hours before the start!

TOUR: So owls are at a disadvantage when races start in the morning?

Prof Dr Richter: Yes, we know that among professional athletes, larks have the better performance. Owls can compensate for their disadvantage a little by temporarily adjusting their internal clock to the start time. This can be done in a similar way to jet lag. On the first day in a new time zone, you are not very fit. However, owls don't always have to train in the morning. It is enough to get up a little earlier each day one to two weeks before an early race to get used to the new "time zone". I recommend a half-hour shift per day, which is slow and gentle. A power nap of 20 to 30 minutes helps owls in tired phases with the changeover. The alarm clock should then ring three to four hours before the start.

TOUR: Good sleep is important for performance. How can athletes optimise it?

Prof Dr Richter: For professional athletes, I recommend a sleep coach who analyses and optimises their sleep quality and accompanies them to races. Otherwise, a smartwatch helps to measure sleep quality. If you race a lot, you often spend the night in unfamiliar surroundings, which reduces the quality of your sleep. At least the first night in a strange bed is often bad; we call this the "first-night effect". Thinking about the upcoming race as you fall asleep is not exactly conducive either. Ruminating releases the stress hormone cortisol, which disrupts sleep and prevents you from waking up refreshed. If you have problems with this, you should learn from a sleep coach how to fall asleep with good thoughts.