A report by Canadian researchers demonstrates that children who spent more time in sports activities and had higher aerobic fitness reported fewer "sick" days, and those with body fat higher than 25% reported significantly more such events. Their study also found evidence connecting reduced physical activity and excess body fat with higher incidences of upper respiratory tract infections (URTI).
A New Study
The investigation examines the relationships between mucosal immunity, physical fitness levels, stress levels, and relative body fat in 10- to 11-yr-old children attending public schools in Southern Ontario, Canada. Thomas J. Cieslak, Gail Frost, and Panagiota Klentrou from the Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario, CN, are the authors of the study, entitled "Effects of Physical Activity, Body Fat, and Salivary Cortisol on Mucosal Immunity in Children." Their findings appear in the December 2003 edition of the Journal Applied of Physiology. The Journal is one of 14 scientific journals published each month by the American Physiological Society (APS).
Methodology
The researchers followed the protocol outlined below:
Subjects: Sixty-one fifth grade students (29 boys, 32 girls) from three randomly selected schools in Southwestern Ontario participated in the study, which was conducted in May and June. Any medication taken for treatment of illness was recorded.
Physical activity and fitness assessments: Predicted peak aerobic power was estimated and recorded. An estimate of each individual's peak O2 was also determined. A Habitual Activity Estimation Scale (HAES) was used to estimate the time spent in all forms of habitual activity, i.e., the number of hours of habitual physical activity per day. Total duration of daily activity was used to calculate the total weekly habitual activity (h/wk). A Participation Questionnaire was used to estimate both the amount of physical activity and the nature of the participation. Total distance traveled per day was measured using a pedometer.
Body fat measurements: Estimates were made of the participant's percent body fat by using the input variables of physical activity level, body frame size, height, mass, and gender.
Saliva testing. Subjects provided two saliva samples. After collection of the first sample, temperature of the subject was taken to ensure that cortisol contained in the second saliva sample was not affected by acute stress. SIgA in saliva was measured by radial immunodiffusion and results were expressed as a SIgA-to-Alb ratio (SIgA/Alb).
Frequency of URTI: A 1-mo health log was used to record the incidence and duration (number of days) of URTIs. Subjects recorded cold and flu symptoms each day of the month by using a set of codes provided with the log. The severity of the symptoms was rated by each subject as mild, moderate, or severe. Parental supervision was required to ensure accurate recording of the symptoms. All logs were completed during the April to June period, which is a moderate- to high-infection season for Canada. The total number of days with URTI symptoms was calculated for each subject, with days being counted only if 2 or more consecutive days of cold or flu symptoms were reported. A randomly selected subgroup (n = 15) was assessed a second time, 6 wk after initial testing.
Statistical analysis: One-way ANOVA was used to compare boys and girls on physical activity, percent body fat, aerobic power, SIgA, and salivary cortisol. Analysis was conducted to detect relationships among all the variables, and intraclass correlation analysis was used to test the reproducibility of resting salivary cortisol and IgA measures (before and 6 wk after). A minimum value of P 0.05 indicated a statistically significant result.
Results
The researchers found that:
Conclusions
This study demonstrates the importance of physical activity for children's resistance to infection. Children who spent more time in sport activities and had higher aerobic fitness reported fewer sick days, whereas children with relative body fat exceeding 25% reported significantly more sick days than the rest of the cohort. With this in mind, the new parental warnings should, perhaps, be modified to: "Don't go outside with your hair wet -- but do go out!."
Source: December 2003 edition of the Journal Applied of Physiology. The Journal is one of 14 scientific journals published each month by the American Physiological Society (APS).
The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.
Journal
Journal of Applied Physiology