Many recent studies suggest that the practice of resistance exercises in polluted environments can produce undesirable effects on human health. But a work recently published in the American Journal of Physiology by scientists of the Aerobic Performance Study Group of the Faculty of Physical Education and Sports of the University of São Paulo points out that, perhaps, this is not true for practitioners who are already accustomed to vehicle pollution.
The team evaluated ten male amateur cyclists, most of whom used to train on a cycle path and within the Campus of the University of São Paulo, where Cetesb (Environment Agency of the State of São Paulo) reports pollution levels of vehicles that exceed the annual limits imposed by the WHO (World Health Organization).
Contrary to what was expected, they found that markers of inflammation in the blood of these cyclists, such as interleukins 6 and 10 (IL-6 and IL-10), did not change. And, on the other hand, it increased the blood level of the protein BDNF (or “brain-derived neurotophic factor”), related to the benefits of exercise for brain neuroplasticity.
From these results, the researchers formulated another hypothesis: that there would be a certain type of acclimatization of these individuals to the polluted environment. After all, they are residents of São Paulo and are used to training in an open environment. “So, we can say that, in this case, the benefits of exercise outweigh the deleterious effects of the polluted environment,” summarizes André Casanova Silveira, first author of the article.
He explains that the group started from two studies published by Professor Rômulo Bertuzzi, coordinator of the Aerobic Performance Study Group, in which a model of constant load exercise was used with physically active people. In these studies, Bertuzzi noted that there was an increase in inflammatory markers in the practitioners after 60 minutes of exercise.
“However, constant load exercise models do not evaluate performance, they do not mimic sports performance well, they are very different from a test. Therefore, we idealized an experiment with a long duration exercise, exceeding 60 minutes and mimicking a competition”.
The study was supported by FAPESP through a PhD grant in Brazil awarded to Silveira.
‘real’ pollution
The experiment was conducted in a chamber located in the parking lot of the FM-USP (USP Faculty of Medicine), on Avenida Doutor Arnaldo, in São Paulo, 20 meters from the roadside and 150 m from an intersection with busy traffic . The room was designed by the group of Professor Paulo Saldiva (FM-USP), with whom Bertuzzi collaborates.
The cyclists simulated participation in a 50 km race (about an hour and a half of exercise), against the clock. “We put the individual’s bike on the roller and he did a virtual reality circuit. It’s a simulated competition, he sees a track on the computer. The track has a certain pressure, it’s like he’s cycling on the street. He can control the intensity and shift gears.”
The chamber has two ducts through which air from the street enters, which is thrown into the cabin with the help of a pump. There is also a particulate filter system, as well as chemical filters to rid the air of formaldehyde, hydrogen sulphide, sulfur dioxide, nitrogen oxide (NO), nitrogen dioxide (NO2) and other gases that may enter the chamber . “But the marker in our study is particulate matter, which is also the most used in the literature.”
The cyclists completed the circuit on two different days, with an interval of at least 48 hours. At random, they performed the test in a polluted environment (without a filter) or in an environment with filtered air. “The pollution mimics a more real situation. Previous studies use a diesel engine to mimic the pollution, but it generates a very high concentration of particulate matter and isn’t mixed with anything else. In our case, it’s real pollution, from where the road comes from.”
All tests were performed with room temperature control (20ºC to 24ºC) and two hours after the last meal. The data collection took place in 2019, before the Covid-19 pandemic, between 10:00 and 16:00. The inflammatory markers IL-6, C-reactive protein (CRP), IL-10 and intercellular adhesion molecule-1 (ICAM-1), and neuroplasticity (BDNF) were measured in blood samples collected before and after the 50km.
surprising results
The team concluded that there were no significant differences between experiments conducted under different conditions for the responses of IL-6, CRP and IL-10 markers. However, testing under the effect of vehicle pollution caused an exercise-induced increase in BDNF levels, as well as a decrease in ICAM-1 levels.
“Increased levels of BDNF promote growth and proliferation of cells in the hippocampus [fenômeno ligado à formação das memórias e associado ao aprendizado e às emoções]. BDNF is also involved in neuronal differentiation, plasticity, cell survival and learning. This increase in BDNF levels that we diagnosed in a polluted environment was the most curious result of our work, because the literature says that exercise in a polluted environment would suppress the expression of this protein. In the future, in addition to measuring BDNF, we also want to perform cognitive tests to see if there is a correlation between exposure to pollution and performance and cognition, which we ended up not doing this time,” reveals Silveira.
ICAM-1, on the other hand, is an adhesion molecule (which allows the connection between cells) linked to inflammatory processes. “At the beginning of the inflammatory process there is an increase in ICAM-1 because it is what binds macrophages (cells of the immune system) to the injured cells. It is an early marker of inflammation, it indicates the inflammatory state at the very beginning. In In our experiment, if we had observed an increase in inflammation due to pollution, ICAM-1 could have been well expressed in the test done in a polluted environment, and that is not what happened, but there is too little in the literature to be able to I know. I still discuss ICAM-1 and related results.”
Silveira says the team figured there would be a detriment to cliclist performance because they assumed that, in a polluted environment, there would be an increase in subjective perception of effort. “In the competition, the participant has control over the intensity of the exercise through the subjective perception of effort and makes adjustments during the competition based on this. I imagined that we would have an increase in this perception of effort in the polluted environment caused gives the subjective symptoms of pollution (burning eyes, runny nose) and this would affect performance, but this has not been confirmed. Another surprising point was that of inflammatory markers because, as we had previous studies of the group showing that after 60 minutes there was an increase in these markers, we imagine that in a long-term run, at a higher intensity than the constant load test, there would also be an increase. Not seeing any difference in these markers was surprising.”
According to him, the biggest conclusion of the work is that exercise is good even in polluted environments, for people adapted to this type of environment. “In my postdoctoral study, just presented, I intend to make a distinction and separate groups increasingly exposed to pollution. I want to make this comparison to find out if the previous level of exposure somehow interferes with inflammation, cardiovascular adaptations and the exercise”.
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