Biological rhythms in sport and training
Biological rhythms affect every athlete’s performance more than most of us realize. The body is not a machine that runs independently of the clock — it follows an internal schedule that dictates when you are stronger, faster and have more endurance. Knowing that schedule can be the difference between a good result and a very good one.
Why biological rhythms affect athletic performance
Biological rhythms are recurring changes in living organisms. They can play out within a few milliseconds or stretch to 24-hour cycles — like the circadian rhythm — and even longer, like menstrual cycles.
One of the simplest examples: body temperature fluctuates by 0.4–0.5 degrees over the course of a day. It is lowest at around 4 a.m. and highest at around 6 p.m. That may sound like a small difference, but for your muscles it is significant — temperature directly affects muscle elasticity, reaction speed and strength and power output.
Resting heart rate varies by 5–15% over a day, peaking at around 3 p.m. Even your height is not constant: you are tallest at 8 a.m. and shortest at midnight. The variation is roughly 1.1% — the spine compressing over the course of the day.
Hormonal changes are perhaps the best known. Testosterone and growth hormone levels behave differently across the day — and that is exactly what influences how training actually affects the body.
When the body peaks: hours 17–23
World records are set mainly in the late afternoon and evening, between 17 and 23 hours. That is no coincidence.
This is when body temperature is at its highest — muscles work more efficiently, reaction time is shorter and there is more strength available. The effect is especially clear in sports that demand speed and strength: sprinting, weightlifting and jumping.
Studies show that both muscle strength and contraction speed are better in the late afternoon. Peak isometric strength occurs between 14 and 19 hours, varying by up to 6% over the day. Back muscle strength is also greater in the late afternoon, and jumping performance is likewise best at that time.
So what is actually going on? Studies have found significantly higher blood concentrations of growth hormone (somatotropin) and testosterone in athletes who train in the late afternoon. That means a better anabolic environment — muscle grows more from the same workout.
Biological rhythms and training planning
As a rule, it is most beneficial to train and compete between 16 and 20 hours, based on the athlete’s biological clock time. The exception is a change of time zone: when travelling west, your biological time can shift so far that the optimal training time falls in the early morning hours instead.
There is, however, one important nuance: morning sessions are better suited to learning technique. New movements and coordination-heavy exercises come more easily when the central nervous system is fresh. In addition, injuries are less common among those who train in the late afternoon — worth keeping in mind when planning your training time.
You also need to consider whether the athlete is a so-called morning or evening type. Chronotype affects when the body reaches its daily peak — an early riser may hit their best form earlier than a late riser. Researchers have found quite varied results here, so there is no universal recipe.
Some physiological measures — such as heart rate under training load and oxygen consumption — are not as clearly tied to the circadian rhythm. But one rule holds firmly: the better trained an athlete is, the more clearly biological rhythms show up in their performance. For recreational exercisers the effect is less noticeable; in elite sport it can make a real difference to results.
FAQ: biological rhythms in sport
What time of day is best for training?
According to research, the best time to train is between 16 and 20 hours, when body temperature is highest and powerful muscle work is most effective. If your schedule doesn’t allow for that, a morning workout is perfectly fine — and even preferable for practicing technique.
Is morning training worse than evening training?
Not necessarily. Morning training works well for refining technique and coordination work. Maximal strength may be somewhat lower than in the late afternoon, but training regularly matters more than the time of day.
Does changing time zones affect an athlete’s performance?
Yes. When travelling west, the body’s biological clock time shifts, which can mean the competition takes place at a time when your body is not yet at its peak. This needs to be taken into account when planning competition trips, and if necessary the training program should be adjusted several days in advance.
Let’s find your peak form! ArtGym
Author: Toivo Jürimäe (professor)
Source: WHO – physical activity.
