The common cold is one of the most frequently occurring illnesses in humans worldwide. There are over 200 different viruses that can cause colds, and no cure has been found that will actually stop the common cold. Medication can relieve the symptoms for the short term, but the body must build up its own resistance, a process that normally takes three or four days to get going.

Old age, cigarette smoking, mental stress, poor nutrition and a lack of adequate sleep have all been associated with a decrease in immune system functioning. When the immune system is weakened, a virus has more chance of taking hold.

In many studies, people that exercise at moderate intensities have been shown to report fewer colds than people who do not exercise. On top of this, people that exercised experienced around half the days with symptoms compared with the control group that did not do any exercise. Moderate exercise, such as brisk walking or cycling, has been shown to produce positive changes in the immune system.

Not all exercise is good however. High intensity exercise, or heavy exertion, will actually decrease immune functioning. A steep drop in immune functioning will occur after exercise, possibly for as long as six to nine hours. This is due to the release of stress hormones that are secreted in high doses during and after the exercise. These stress hormones suppress immune functioning and allow viruses to spread and gain a hold. This is why many athletes are highly susceptible to common colds and why the average athlete always tends to become sick at the height of their fitness levels.

Should I Exercise When Sick?
This will depend on what type of virus you actually have. If it is just the common cold (runny nose, sore throat, without fever), mild to moderate exercise such as walking can be undertaken without any negative effects. Intensive training could be undertaken within a few days of recovery.
If the virus produces muscle aches, fevers, and extreme tiredness, around two to four weeks should be allowed before resuming intensive training.
There is little evidence to support the fact that moderate exercise will produce any benefits to the body while it is fighting of a virus. Intensive exercise while sick will actually be detrimental to the body.

Exercise is definitely beneficial to the bodies' immune system when performed in moderation. Brisk walking and cycling have been shown to be among the most favourable. High intensity exercise takes its toll on the body and immune functioning is among its targets. If you are training at high intensities make sure you schedule in plenty of rest days and attempt to follow up the high intensity workouts with lower intensity sessions. We all want to work hard in our sessions but what is the point if we are going to spend the pinnacle of our fitness in a sick bed?

Shaun Brodison
Secrets to Effective Weight Loss

About Author / Additional Info:
Author Shaun Brodison is a qualified exercise physiologist through the Australian Association of Exercise and Sports Science (AAESS). Born in South Africa, he has lived in Australia since he was young. He now resides in Bunbury, Western Australia. He has personally trained over 1,000 individuals and takes great joy in helping people work through the things holding them back to help them meet their goals.