We all recognize the immune benefits of exercise, yet fitting it into busy schedules may often turn challenging. The results of a recent study offer hope to those seeking immunity benefits from exercise but do not have long hours to spend.

As per the current WHO guidelines, adults are advised to partake in at least 150 minutes of moderate physical activity per week or 75 minutes of vigorous physical activity for overall health.

However, the researchers of the latest study found that just 15 minutes of moderate exercise can enhance immunity by raising natural killer (NK) cell levels, a type of white blood cell that serves as the immune system's initial line of defense. The study was presented at the American Physiological Society's flagship annual meeting in Long Beach, California.

Natural killer cells are named so because they can target and kill harmful cells even without prior exposure to the pathogens. They "search and destroy" infected cells, including cancerous cells, in the body.

Earlier studies show that exercise increases levels of NK cells in the bloodstream, providing a period of heightened immunity.

"Mobilizing more of these cells can lead to protecting the body against infections, reduces the likelihood of developing certain diseases, and helps to improve disease outcomes by controlling infections more effectively," Rebekah Hunt, the study's first author and a PhD candidate at the University of Houston, said in a news release.

For the study, researchers evaluated 10 volunteers aged 18 to 40, who were engaged in 30 minutes of moderate-intensity cycling on stationary bikes. Before the start of each session and at 15 and 30-minute intervals during the session, blood samples were taken from the volunteers. The results of their blood work revealed that NK cell levels rose after 15 minutes of exercise but did not further increase after 30 minutes of cycling.

"This potential boost to the immune system may be particularly notable for people with cancer, as NK cells are known to kill tumor cells. Exercising for mere minutes before seeing an increase in NK cells can be encouraging for people who have trouble finding time to exercise or prefer shorter workouts," the researchers wrote in the news release.

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