If you want to reduce the frequency and severity of symptoms of colds you should do exercise at least five times a week and remain physically fit, US researchers report in the British Journal of Sports Medicine. They stress that not only do fit people have much fewer colds, but also when they do their symptoms are significantly milder compared to those who do not work out regularly.

Researchers from North Carolina, USA, monitored upper respiratory tract infection frequency and symptom severity over a 12-week period during autumn/winter in 2008 on 1,000 individuals aged 18 to 85. 60% of them were female and 40% were aged 19 to 39. 25% of them were over sixty years of age while 40% were middle aged.

Information was gathered on how often they did aerobic exercises. The participants were also asked to rate their levels of fitness with a 10 point validated scoring system. Other data was collected, including participants’ diet, lifestyle, and recent stressful occurrences – factors which can have an impact on an individual’s immune system response, the authors explained.

Cold symptoms were present for an average of 13 days during the winter and 8 days during the autumn (fall). The researchers reveal married older men seem to catch colds less often.

However, after factoring out the most significant factors linked to upper respiratory tract infections (colds) the scientists found that an individual’s level of fitness as well as exercise frequency had the biggest impact in reducing occurrences and severity of colds.

Those who were physically fit and did exercise at least five times each week had a 43% to 46% lower frequency of colds compared to people who only did exercise once a week at the most.

The fittest participants had a 41% lower symptoms severity, while regular exercisers’ severity of symptoms was reduced by 31%, the authors wrote.

The average American adult has two to four colds each year. US children have an average of between 6 and 10 colds annually. The economic toll of colds on the American economy is estimated to be approximately $40 billion annually.

The researchers say that exercise sessions trigger a temporary increase in immune system cells that circulate within the body. Although immune system cell levels soon return to normal after exercise, they probably improve the body’s surveillance of pathogens – harmful bacteria, viruses and other organisms. Improved pathogen surveillance leads to fewer and less severe infections.

The authors concluded:

Perceived physical fitness and frequency of aerobic exercise are important correlates of reduced days with URTI (upper respiratory tract infection) and severity of symptoms during the winter and fall common cold seasons.
What is Aerobic Exercise
Aerobic exercise improves our body’s oxygen consumption – aerobic means with oxygen. Aerobic refers to the body’s use of oxygen in its energy-generating process (metabolic process). Aerobic exercises are generally done with a moderate level of intensity for long periods, when compared to other forms of exercise. Typically, a bout of aerobic exercise involves warming up, exertion for at least 20 minutes, and then a cool down. This type of exercise involves mainly the large muscle groups.

The term aerobic exercise was first used in the 1960s by Col. Pauline Potts, an exercise physiologist and Dr. Kenneth Cooper. They were both in the US Air Force. Dr. Cooper wondered why some physically strong individuals were poor at long-distance endurance sports. He used a bicycle ergometer to measure participants’ ability to use oxygen. In 1968 he published a book titled “Aerobics”, which included scientific programs using aerobic exercises. It became a bestseller. All current aerobic programs include Dr. Cooper’s data as a baseline.

“Upper respiratory tract infection is reduced in physically fit and active adults”
David C Nieman, Dru A Henson, Melanie D Austin, Wei Sha
Br J Sports Med doi:10.1136/bjsm.2010.077875