Written by David C. Nieman, DrPH, FACSM
The common cold is the most frequent illness you will have during your lifetime. More than 200 different viruses cause colds, with adults suffering two or three colds each year and young children about six or seven. Rhinoviruses and coronaviruses are to blame 25 to 60 percent of the time. Rhinoviruses often attack during the fall and spring seasons, while the coronavirus is common during the winter.
Cold viruses are passed from person to person by being inhaled into the nose and air passageways (i.e., spread through the air). Severe colds transmit viruses more readily than mild ones because a greater amount of virus is passed into the air by coughing and sneezing. Thus, to hinder the spread of cold viruses, coughs, sneezes and nose-blows should be smothered with clean handkerchiefs, facial tissues or your bent arm.
Cold viruses are also spread by simple hand-to- hand contact with an infected person or with contaminated objects such as door knobs, phones or computer keyboards. Cold viruses can live for hours on hands and hard surfaces. When the hand is then brought to the nose or eyes, self-inoculation with the cold virus occurs. Thoroughly washing your hands and cleaning surfaces with Lysol or other disinfectants will protect against transmission. Also, keeping your hands away from your face is a good preventive measure.
Damp, cold or drafty weather does not increase the risk of getting a cold. According to most cold researchers, cold or bad weather simply brings people together indoors and leads to more person-to-person contact. Vitamin C, another common remedy, does not prevent colds, but it may slightly reduce the severity and duration of symptoms. Resting, drinking plenty of hot fluids and seeking what comfort one can derive from over-the-counter cold remedies is still about all that can be done to treat most colds.
Whether one gets sick with a cold after a sufficient amount of virus has entered the body depends on many factors that affect the immune system. Mental stress, low food intake, rapid weight loss, lack of sleep and poor hygienic practices have all been associated with impaired immune function and increased risk of infection.
Can you prevent a cold through regular exercise? When surveyed, people who exercise on a regular basis report fewer colds than their inactive peers. Several exercise training studies with adults support this belief. In these studies, subjects in the exercise groups walked briskly 35-45 minutes, five days a week, for 12-15 weeks during the winter/spring or fall, while the control groups remained physically inactive. The results were in line with the fitness enthusiasts’ claims—walkers experienced about half the days with cold symptoms of the sedentary controls. Several large population studies have also shown that frequent aerobic activity compared to a sedentary lifestyle predicts fewer sick days during the cold season.
During moderate-to-vigorous exercise (e.g., brisk walking, cycling, swimming, sports play), several positive changes occur in your immune system, including an enhanced movement of important immune cells throughout the body. Stress hormones, which can suppress immunity, are not elevated during moderate exercise. Although the immune system returns to pre-exercise levels very quickly after the exercise session is over, each session represents a boost that reduces the risk of infection over the long term.
Heavy doses of exercise, however, can have the opposite effect. For example, after running a marathon race, the body is inflamed for about one-half day with high stress hormones, cytokines and suboptimal immune function. During the ensuing one to two weeks, the odds of becoming sick increase two- to sixfold, depending on the time of year. During periods of heavy training, the immune system reflects the physiologic stress experienced by the athlete, and illness rates climb. Even a good thing like exercise can be carried too far, and each individual needs to find the right balance between training workloads and rest. For more information, check out ACSM’s free Exercise and the Common Cold Current Comment Fact Sheet. We live in a world where viruses and bacteria are omnipresent, waiting to pounce on any of us with weakened immune systems. In summary, your best strategy is to keep immune defenses operating normally by following a variety of lifestyle habits:
- Exercise moderately on most days of the week. This will improve the ability of the immune system to detect and destroy viruses.
- Avoid overtraining and chronic fatigue. Heavy exertion causes immune dysfunction in multiple body compartments leading to an increased risk of illness. Another word of caution: do not exercise when ill with a fever. This can lead to more severe symptoms, relapse and sustained feelings of fatigue.
- Eat a well-balanced diet to keep vitamin and mineral pools in the body at optimal levels. Nutrient supplements are typically not needed by healthy adults and will not boost immune function above normal levels.
- Keep life stresses to a minimum and practice stress management techniques. Mental stress increases the risk of the common cold, so learn to control the burden and pace of life.
- Obtain adequate sleep on a regular schedule. Sleep disruption has been linked to suppressed immunity.
- Limit exposure to viruses and bacteria by practicing good hygiene. Wash your hands frequently, and avoid touching your eyes and nose (the primary route of introducing viruses into the body). Also, give your immune system an edge by receiving the flu shot and other recommended vaccinations each and every year.
View the full winter 2011 issue of the ACSM Fit Society® Page supported by Liberty Mutual online.