By Jo Finzi
As the seasons change, the chillier weather means an increased risk of common colds. The good news is that exercise may help you ward off the nasty bugs. A new trial has revealed that just 30 minutes exercise a day reduces the risk of catching colds by half.
A brisk walk is all you need, and it was found that longer you continue to exercise daily the greater the benefit.
The trial involved 115 older women from Seattle, Washington state. All were sedentary and either overweight or obese. They were randomly divided into two groups. For a year the first group exercised daily while the second group did a 45-minute stretching class once a week.
Every quarter both groups filled in questionnaires asking them whether they had suffered colds or other upper respiratory infections in the previous three months.
The results, published in The American Journal of Medicine, showed that the daily exercise group had only half as many colds as the weekly stretch-class group. During the final three months of the study the gap was even wider, with the weekly exercise group suffering three times as many colds as ones doing daily exercise.
“This adds another good reason to put exercise on your to-do list,” said Cornelia Ulrich, the paper’s senior author, and an associate member of the public health sciences division of Seattle’s Fred Hutchinson Cancer Research Centre.
She said that the likeliest cause of any benefit was the enhancement of the immune system. “It has been shown that just a 30 minute walk can increase levels of leukocytes, which are part of the family of immune cells that fight infection,” she said.
The exercise group was asked to do 45 minutes of exercise a day, five days a week, but managed only 30 minutes, mainly brisk walking. But even a half hour walk seems to have been enough to achieve a benefit that increased over time.
“The enhanced immunity was strongest in the final quarter of the year,” Dr Ulrich said. “This suggests that, when it comes to preventing colds, it’s important to stick with the exercise.
But the findings are by no means definitive. If all upper respiratory infections, rather than just colds, were counted there was not such a massive difference between the two groups. Other researchers have also called for longer studies to see if the results remain the same.
However, the women in the study group are happy to feel healthier. As well as reducing their incidence of colds, they reduced their weight, total-body fat and intra-abdominal fat, which should also reduce their risk of cancer.
But don’t overdo it. Moderation is the key, as other studies have shown that excessive exercise can actually increase the risk of colds and other illnesses.
Too strenuous a workout that repeatedly leaves athletes exhausted is thought to reduce the immune system’s efficiency.
Over-training produces a mild immunodeficiency, which means an increased susceptibility to recurrent minor infections such as the coughs and colds of winter.
It also makes you vulnerable to the viruses and bacteria responsible for minor gastrointestinal infections throughout the year, while increasing the risk of complications in otherwise minor diseases, especially respiratory infections, and the occurrence among over-trained athletes of uncommon infections.
Athletes also need to avoid violent exercise when suffering from a severe cold or undiagnosed viral infection. One of the recognised causes of myocarditis, or inflammation of the heart muscle, is violent heavy exercise while suffering from a viral infection.
Myocarditis can be very serious. It’s an occasional cause of death in young footballers who may even drop dead on the pitch, or who may die a few days after playing when having been thought to be suffering from nothing more than a heavy cold or other winter respiratory virus.
So if you want to ward off the wintertime bugs, take regular exercise but don’t overdo it, and avoid over-training completely if you’ve already got the sniffles.