What scientists learned from trainee firefighters

Newswise — The 11 young firefighters went through rigorous training exercises, carrying up to 40 pounds of gear over hilly terrain during a 45-minute training exercise under the California sun. Gloves, helmets, flashlights, goggles and more weighed them down as they sprinted across the countryside wearing fire-resistant clothing to show they were ready to serve as wildland firefighters.

When the training was over, they immediately went to the medical tent – not to rest and recover, but to give their blood, saliva and urine samples for analysis by a team of scientists equipped with needles, tubes, cold compresses and the equipment of their trade.

Scientists at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) then analyzed more than 4,700 molecules — proteins, lipids and metabolites — from each of the firefighters, seeking to understand what happens when the body is subjected to intense physical exercise. Measuring and interpreting the data from thousands of such measurements is the specialty of PNNL scientists who investigate questions related to climate science and human health by analyzing millions of sensitive measurements using mass spectrometry each year.

For this study, the intent was to increase safety for first responders and others.

“Heat stress can be life-threatening,” said Christine Barnum-Johnson, corresponding author of the study. “We wanted to take a deep look at what’s going on in the body and see if we can detect the danger of exhaustion in its earliest stages.” Perhaps we can reduce the risk of strenuous exercise for first responders, athletes and members of the military.

As expected, the team found hundreds of molecular changes in the firefighters. Pre- and post-exercise differences highlight the body’s efforts to repair and repair tissue, maintain fluid balance, cope with increased energy and oxygen demand, and the body’s attempts to repair and regenerate its proteins and other important substances.

But in the saliva, the team found some unexpected results. There was a change in the microbial mix in the mouth – the oral microbiome – indicating that the body is increasingly on alert for bacterial invaders. The scientists also noticed a decrease in signaling molecules important for inflammation and for fighting viral infections.

Reducing inflammation makes sense for people who exercise vigorously; less inflammation allows people to inhale air more quickly, meeting the body’s desperate need for more oxygen. Having fewer inflammatory signals in the respiratory system helps the body improve breathing and blood flow.

Less inflammation, better breathing

But less inflammation makes the body more vulnerable to viral respiratory infections — which is exactly what other scientists have observed in elite athletes and others who exercise vigorously. Some studies show that a person is up to twice as likely to get a respiratory viral infection in the days after a particularly vigorous workout.

“People who are very fit may be more susceptible to a viral respiratory infection immediately after vigorous exercise. Having less inflammatory activity to fight infection could be one reason,” said Ernesto Nakayasu, corresponding author of the paper. He notes that the work provides a molecular basis for what clinicians have observed in their patients doing strenuous exercise.

The team hopes the findings will help explain why people are more vulnerable to respiratory infections after exercise.

The study was published Oct. 18 in Military Medical Research.

In addition to Nakayasu and Burnum-Johnson, PNNL authors include Marina A. Gritsenko, Young-Mo Kim, Jennifer E. Kyle, Kelly G. Stratton, Carrie D. Nicora, Natalie Munoz, Yuqian Gao, Carl K. Weitz, Vanessa L. Paurus, Kent J. Bloodsworth, Kelsey A. Allen, Lisa M. Brammer, Fernando Montes, Kathleen A. Clark, Grant Tietje, and Justin Tiguarden.

The work was funded by PNNL. Some of the mass spectrometry measurements were performed at the Environmental Molecular Sciences Laboratory, a Department of Energy Office of Science user facility at PNNL.

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