A 15-Minute Workout May Boost the Immune System

A short moderate-intensity workout may increase the levels of natural cancer-killing cells.

Previous research has suggested that exercise increases levels of natural killer (NK) cells, a type of white blood cell that is the first-line defender in the immune system.

NK cells are called “natural killers” because they can identify and eliminate dangerous cells, including cancer cells, without being previously exposed to abnormal pathogens.

A new study presented at the American Physiology Summit, the annual meeting of the American Physiological Society (APS), suggests that just 15 minutes of moderate-intensity exercise may be sufficient to boost immunity by increasing levels of NK cells.

“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,” said Rebekah Hunt, a Ph.D. candidate at the University of Houston and first author of the study.

The study involved 10 volunteers aged 18 and 40 who exercised on a stationary bicycle for 30 minutes at moderate intensity.

The researchers drew the volunteers’ blood before the cycling session and again at the 15- and 30-minute marks.

They found that the levels of NK cells in the blood increased after 15 minutes of exercise but did not reach higher levels after 30 minutes of cycling.

The findings could be encouraging for people who have trouble finding time to exercise or prefer shorter workouts.

Our results don’t point to a clear advantage in terms of increasing NK cells in the bloodstream by exercising for longer than 15 minutes at a moderate intensity.


The authors say the potential immune system boost may benefit people with cancer, as NK cells are known to kill tumor cells.

Observational studies have linked physical activity to lower risk of various cancers, including breast, bladder, colon, and endometrial cancers. However, these studies cannot fully rule out the possibility that active people are less likely to develop cancer because they engage in other healthy lifestyle behaviors.

Exercising for better health

Exercising can reduce the risk of heart disease and stroke, type 2 diabetes, metabolic syndrome, and infections. It also improves brain health, strengthens bones and muscles, and helps manage weight.

Adults need 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic activity and at least two days of muscle-strengthening activity each week, according to the current Physical Activity Guidelines for Americans.

Moderate-intensity aerobic physical activity includes fast walking, water aerobics, riding a bike on level ground, and doubles tennis.

When you engage in vigorous-intensity aerobic activity, you’re breathing hard and fast, and your heart rate goes up. This can include jogging or running, swimming laps, cycling fast or on hills, and playing basketball.

Although exercising can raise the levels of cancer-killing cells, cancer prevention should not solely rely on physical activity. Adopt other healthy lifestyle behaviors and discuss any symptoms that are concerning with your healthcare provider.

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