Status: 20.11.2023, 21:18 PM
By: Lennart Schwenck
A new study finds a possible downside to intense physical activity. Is the body particularly susceptible to diseases after exercise?
Washington – Bad news for fitness fanatics and sports junkies: Excessive and high-intensity exercise can temporarily weaken the immune system. At least that's what a new study by a U.S. research institution suggests, in which healthy firefighters were examined after intense physical exertion.
To study the regulatory processes in real-world conditions, researchers conducted a multi-omics analysis of three body fluids (blood plasma, urine, and saliva) collected from healthy firefighters before and after a training session. To do this, the eleven test subjects had to lug up to 45 kilograms of equipment over hilly terrain for 20 minutes.
Too much fitness apparently makes the immune system more susceptible to respiratory infections
The result: "People who are very fit could be more susceptible to viral respiratory infections (such as corona or bronchitis) immediately after a strenuous workout," explains study leader Ernesto Nakayasu from the Pacific Northwest National Laboratory (PNNL). "The lower inflammatory activity to fight an infection could be one reason for this," says the scientist.
While there is strong evidence that moderate physical activity in healthy people can boost the immune system in the long term, what happens to the immune system immediately after a vigorous workout is controversial.
"We wanted to take a detailed look at what's going on in the body and see if we were able to detect the danger of exhaustion at the earliest stages," explains Kristin Burnum-Johnson, a bioanalytical chemist at PNNL.
If you have a cough, it is better to avoid exercising. (Symbolic image) © Imago
Does exercise damage the immune system? Risk of infections may be increased after exercise
There is so far little reliable evidence to support the claim that intense exercise increases the risk of infections, although patients have reported respiratory illness after exercise in some previous studies.
This could be problematic for workers who constantly engage in physically demanding activities in their daily work routine and who require intensive fitness training, such as paramedics, police officers, movers and athletes.
The result was worrying because the number of the body's own molecules, which support the defense against inflammation and other infections, decreased. This was accompanied by an increase in opiorphin, an endorphin that acts like an endogenous opioid, i.e. pain-relieving.
Does the body reduce its immune defenses during exercise? Study continues
What these changes ultimately mean for the short-term function of the immune system is unclear, but the researchers have a few ideas: "Most secreted opiorphin could increase blood flow to muscles during exercise to improve the supply of oxygen and nutrients," the team writes in their paper.
It continues: "We suspect that the decrease in inflammatory molecules we observed in saliva after exercise may be an adaptive mechanism to improve gas exchange in response to the higher cellular oxygen demand." In order to clarify this, further investigations and studies need to be carried out.
There's no question that exercise does wonders for our health, from lifting our mood to boosting our immune system. But as in previous studies, the new study also found possible signs of immune suppression in the trained firefighters. (ls)