Why is physical exercise so good for your health? Scientists are finding answers in our cells

Over the last few decades, several studies have proven the effectiveness that sport has on the human body. Whether it’s running, walking or training at the gym, it’s no secret that physical activity helps improve physical and mental health. However, the changes that occur at the molecular level when physical activity occurs remain little studied by science.

A new scientific study, published in the journal Nature, concluded that the human body’s response to physical exercise is more complex than previously believed. A team of researchers, belonging to the Molecular Transducers of Physical Activity Consortium – also known as MoTrPAC – used a sample of mice to discover the effects that physical activity has on the body.

During the research, scientists used a series of laboratory techniques to analyze the molecular changes that occurred in mice when subjected to eight weeks of intense physical exercise. During the investigation, 19 different organs in the sample were monitored – such as the heart, brain, liver and lungs – and the effects that physical activity had on them were observed. In total, thousands of shared and specific molecular changes were identified at the tissue level, and differences were also found between the sexes of mice. Scientists believe their findings provide data relevant to many human health conditions.

The researchers were able to conclude that each of the organs analyzed changed with physical exercise, helping the body to regulate the immune system, respond to stress and control pathways linked to liver disease, heart disease and even to tissue damage.

The consortium also concluded that there are differences between the sexes in several organs, especially when related to the immune response over time. Most of the immune signaling molecules unique to females underwent changes between one and two weeks of training, while those of male mice only showed differences after four to eight weeks.

Scientists also discovered that physical activity has an impact on the adrenal gland – the organ responsible for producing hormones and regulating processes such as immunity, metabolism and blood pressure.

Furthermore, scientists have also found a possible explanation for the changes that occur in the liver during exercise, as this could have an impact on the development of new treatments for non-alcoholic liver disease. “Although the liver is not directly involved in exercise, it undergoes changes that can improve health. Nobody speculated that we would see these changes in acetylation and phosphorylation in the liver after physical training”, explained Pierre Jean-Beltran, one of the authors involved in the study.

Until now, the scientific production that existed on molecular changes resulting from physical practice focused mainly on changes in a single organ, sex or moment, including only one or two types of data. “Many large-scale studies focus on just one or two types of data. But here we have a range of many different experiments in the same tissues, which gives us a global view of how all these different molecular layers contribute to the response to exercise”, said Natalie Clark, a computational scientist involved in the research.

The researchers hope that their findings can be used to develop treatments that mimic the effects of physical activity for people unable to exercise. “This is the first whole-body map that analyzes the effects of training on several different organs. The resource produced will be extremely valuable and has already produced a lot of potentially new biological knowledge for future exploration”, explained Steve Carr, one of the study’s authors.

The MoTrPAC project, which began in 2016, brings together scientists from several institutes and universities – such as the Broad Institute of MIT and Harvard, Stanford University and the National Institutes of Health – and other institutions and is intended to investigate the processes biological factors underlying the health benefits of physical exercise.

All of the consortium’s findings were made available in a public online repository, so that other scientists can access the findings.