It is already known that too much training and less rest causes problems such as insomnia, weakening of immunity and pain.
A group of Brazilian researchers has pioneered going beyond – in fact, into the body: they seek the effects of excessive physical exercise on vital organs like the heart and liver.
Scientists from the state universities of São Paulo (USP) in Ribeirão Preto and Campinas (Unicamp) in Limeira have already studied a decade ago the impact of this excess on the organism – and gathered their main findings in a recently published article in the international journal Cytokine. The research was supported by the Foundation for Research Support of the State of São Paulo (FAPESP).
Heart, liver, muscle and nervous system showed, in experiments with mice conducted by the researchers, alterations – some harmful ones – after very intense training. The tests included racing on the plane, ascent and descent for eight weeks.
The practice is harmful to the body, warn the authors, if there is an adequate period of rest and recovery.
Liver comes on the scene to help muscle
As a negative effect of over-exertion, the scientists also found a greater accumulation of fat in the liver and signs of inflammation. – Photo: Pexels
In the muscles, the cells have shown more difficulty in capturing blood glucose – a substance that is a source of energy for cells, like the fuel in our body. In the descent mode, the animals also showed signs of atrophy and poor protein formation within the cells.
But if in the muscle cells, there was more difficulty in capturing glucose, how did the body supply this lack? New tests have shown that the liver had a role in this, since the organ is one of the most important in controlling the sugar in the body.
The body can "store" glucose – for situations as perceived by researchers, where intense training has led to a difficulty for muscles to absorb glucose. Guinea pigs, in the experiment, showed an increase in this stock.
But as a negative effect of over-exertion, the scientists also found increased fat accumulation in the liver and signs of inflammation. This may be related to the compensatory action of the liver in the administration of the glucose stock, but has not yet been confirmed by the investigators.
"The increase in fat in the liver is very bad because it has to do with a number of diseases, such as obesity and diabetes, but it is important to point out that in the experiments we did not find these diseases, only the accumulation of fat," says Adelino Sanchez Ramos da Silva, research coordinator and professor at USP.
Even the heart increased its participation in the uptake of glucose, with greater accumulation of the substance in its tissues.
But as a negative effect on the heart, after eight weeks of excessive training, signs of fibrosis (tissue hardening) in the left ventricle were also observed – alterations present in pathological conditions such as heart failure.
In this organ, as well as in the liver, blood and muscles, substances that indicate inflammation have been detected.
The importance of rest
It is essential to combine the exercises with an adequate rest period. – Photo: Pexels
The research coordinator further points out that the problem is not in the intense exercise itself – "it is necessary, even" – but when it is not combined with an adequate recovery period.
A two-week rest, for example, was sufficient in the experiments for mice to regain their weight and appetite, two classic changes in the study of intensity exercises.
In the exercise routine of athletes or amateurs, says Silva, the recommended rest time varies. For the former, it is usually indicated a reduction in training time and load and a possible increase in the recovery period; for amateurs, the recommended interval depends on the person and the exercises performed, but tends to go from 24 to 48 hours.
"The practice of physical exercise in a regular, moderate and supervised way by a physical education professional is extremely beneficial, since it can serve as a non-pharmacological strategy to prevent and treat a number of diseases," he says.
"However, in the event of an imbalance between over-exercise and recovery periods, the effect of exercise may become detrimental to health."
Another innovation proposed by researchers concerns the role of cytokines, proteins produced by defense cells and which play an important role in inflammation.
One well-accepted explanation in the scientific literature so far is that cytokines would be released with excessive exercise, leading to various changes in the body and a drop in performance.
But the team led by Silva has shown that even when cytokines are already in normal levels after a high, performance may continue to be impaired.
Thus, Brazilian scientists argue that cytokines are not the only explanation for the decline in performance – now, the search for other justifications continues.