New Study Measures Effect of Strenuous Exercise on Soldiers’ Immune Systems

It may be possible to predict a soldier’s infection risks during and after strenuous physical exercise by pre-exercise immune system status or from a blood sample taken at rest, according to a recent study.1

According to the Swedish researchers, strain is put on the troops’ immune system in a military setting in many ways. This includes strenuous physical activity, sleep deprivation, caloric deficit and, environmental and mental stress.

“All these factors lead to immunological changes, resulting in a high rate of dropouts because of infections during military training,” they wrote in “Immunological Alterations Used to Predict Infections in Response to Strenuous Physical Training.”

For the study the researchers conducted a small scale pilot investigation that was designed to study immunological changes in the blood in 10 troops from the Swedish Coastal Ranger team before and after six days of military training and then to search for useful predictors of infections.

The troops worked, walked and kayaked as a group for 20 to 24 hours per day. During the training, four of the members had to leave because they were not able to perform the exercise due to illness. They were assigned to the Failed group. The other six completed the training and were assigned to the Completed group.

Blood samples were drawn from the troops in the morning of the first day of the study and immediately after the soldiers reached the military camp on day six. According to the researchers, only three of the measured variables differed between the Failed and Completed groups.

“The MESF (molecules of equivalent soluble fluorochrome) of CD3 on CD8+lymphocytes (T-cell receptor density on cytotoxic T cells) and the percent CD8+CD3+ lymphocytes (cytotoxic T cells) before the six days of training was lower and the CD4/CD8 ratio was higher in subjects who later failed to complete the course,” the authors wrote.

The researchers said that the findings indicate that the six days of military exercise “did not cause a major immune system depression.”

“Nevertheless, 4 out of 10 soldiers became ill and failed to complete the training period. It would have been possible to accurately predict these four subjects before their engagement in the training course based on their higher CD4/CD8 ratio and lower CD3 expression on CD8+ lymphocytes and percent CD8+CD3+ lymphocytes.”

The researchers suggested that a larger scale study with a focused analysis on T-cell surface receptors should be conducted to verify the results.

1. Ekblom O,Ekblom B, Malm C. Immunological Alterations Used to Predict Infections in Response to Strenuous Physical Training. Mil Med. 2011 July;176(7):785-790.

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