A group of 11 young firefighters in California underwent tough training, carrying heavy gear over hilly terrain under the sun.
After the exercise, they went to a medical tent to give blood, saliva, and urine samples for analysis.
It turned out that tough workouts can be potentially dangerous to some people.
How it was tested
Scientists examined over 4,700 molecules from each firefighter to understand the body's response to intense physical activity.
The goal was to improve safety for first responders, athletes, and the military by detecting signs of danger from exhaustion early on.
The study revealed expected changes related to tissue repair, fluid balance, and energy demand.
Surprisingly, in the saliva, the scientists observed a shift in the oral microbiome, suggesting increased vigilance against bacterial invaders, and a decrease in signaling molecules for inflammation and fighting viral infections.
While less inflammation aids breathing during exercise, it also makes the body more susceptible to viral respiratory infections, a phenomenon noted in elite athletes.
The research provides a molecular basis for understanding the vulnerability to respiratory infections after vigorous workouts.
