Conobiology, Hormones and Circadian Rhythms: what time to train?


Homeostasis is the ability to maintain a condition of internal equilibrium, regardless of the changes that take place outside. For example, our body is able to maintain an almost constant temperature despite continuous climatic variations. All these myriad processes require different times, there are some short-term regulation mechanisms that are activated immediately (regulation of the heartbeat following an effort) and others that require longer time periods (female menstrual cycle).

Hormones and circadian rhythms

The plasma concentrations of the main hormones of the human body follow a sinusoidal trend, characterized by the alternation of:

  • Growing phase
  • Peak (Acrophase)
  • Descending phase
  • Minimum peak

The alternation of these stages can be accomplished or studied over one day (circadian rhythms), one week (circasettan rhythms), one month (circatrigintani rhythms), a lunar cycle (circalunar rhythms) of one year ( circular rhythms) and so on.

Even athletic performance follows a circadian rhythm. Some tests have shown that:

  • the highest peaks of body temperature are recorded in the late afternoon and early evening hours (16-18). This temperature increase is associated with an improvement in reactive capacities, explosive strength, maximum strength and maximum oxygen consumption (maximum aerobic capacity). If we consider that bodily hyperthermia improves the speed of propagation of nervous stimuli and increases the metabolism, facilitating the production of energy, it is easy to explain the improvement of the sporting performance that it involves.
  • In the morning there is instead an improvement in intellectual capacity.

Also the plasma concentrations of some hormones can positively or negatively influence sports performance in the various phases of the day.

Notes on circadian hormonal secretions

Cortisol is subject to an almost constant basal secretion in 24 hours, with maximum peak (acrophase) recorded around the first hours of the morning (3-4) and minimum peak that coincides with the first hours of night rest (22-24).

The plasma concentration of GH or somatotropin reaches its acrophase at around 24 and shows its minimum values ​​from 8 to 20.

Testosterone has its peak around 2-3 in the morning, while the minimum peak is recorded around 18.

TSH, the main hormone that regulates thyroid functions, has a trend very similar to that of testosterone.

Walking and training

Influence of hormones on physical performance: what time is best to train?

The cortisol peak causes a greater predisposition of our body to use fatty acids as an energy substrate. Therefore for weight loss it is useful to train in the morning in conditions of hypoglycemia .

At the same time, however, it is necessary to consider the risks associated with this practice (dizziness, illness, hunger crisis and possible fainting). It may be useful to carry some sugar bags with you as soon as the symptoms listed above occur.

Any intake of food prior to the morning training session reduces cortisol levels, eliminating its positive effects on lipolysis.

Those who want to lose weight by preserving or even increasing their muscular masses must also bear in mind that morning hypercortisolism favors the catabolism of amino acids, a fundamental process to produce glucose and keep blood sugar constant.

Chronic hypercortisolism favors the accumulation of fat, especially in the abdominal region, at the same time reducing the muscular masses and triggering a catabolic process that mainly affects the muscles of the lower limbs. Therefore, for those who lead a stressful life, with incorrect eating habits, this slimming strategy is not recommended. To reduce cortisol levels it is instead important to consume an abundant breakfast, rich in carbohydrates both at low and medium and high glycemic index.

The hormonal profile that is unsaturated in the evening hours favors glycogen synthesis, predisposing the body to the accumulation of glycogen and fatty acids in the form of adipose tissue; this explains why it is inadvisable to take a meal rich in carbohydrates at dinner.

In the early hours of the night there is a predisposition to protein accumulation which favors muscular anabolism; this explains why bodybuilders are often advised to take a casein-based protein supplement (special milk proteins) before going to bed.

The circadian rhythms of these hormones can be used in their favor even during training.

Anabolic hormones are stimulated during the first minutes of physical activity, especially if this is performed at a particularly high rate, with overproduction and consequent accumulation of lactic acid. The catabolic hormones are sensibly activated after the 45th minute of exercise. Also the lymphocytes (the main constituents of the immune system) decrease after a too intense training, in relation to the increased secretion of cortisol and its immunosuppressive activity. One speaks in these cases of stress immunology reaction. An inadequate and / or excessive training program will not only increase the risk of injuries but, above all, will cause in the long run a decrease in the immune system, predisposing the body to a greater risk of infections. In this regard it is worth underlining the danger of training performed in the presence of fever, due to the serious risk of serious complications, such as pneumonia and myocarditis, which they involve.

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What time is it better to train?