PHYSICAL ACTIVITY PATTERNS OF TURKISH ADOLESCENTS: INFLUENCE OF SOME SOCIAL FACTORS

Based on pilot studies, 21 activity types were selected. The frequency of participation (FREQi) was assessed by asking how often the activity type i was performed when it was in season. The response categories were daily, several times per week, once per week, several times per month, once a month, less than once a month, or never. These responses were coded as 24, 12, 4, 2.5, 1, 0.5, and 0 times per month, respectively. Each of these numbers was divided by 4.3 to get an estimated weekly frequency. Because the number of months during which a given activity is in season varies, the frequency reports were multiplied by a seasonal adjustment factor to estimate an average frequency of participation year around. For example soccer is usually played during 9 months of the year and, thus, has a seasonal adjustment factor of 0.75 (9/12). Adjustment factors for various activities are reported in Appendix 1.

To assess the average duration per episode (DURi), students were asked about how long they usually performed each activity type i on each occasion. The responses were coded as < 15 min, 15-30 min, 30-60 min, 1-2 hr, or if > 2 hr, the exact number of hours. These responses were converted to an estimate in hours of 0.125, 0.375, 0.75, 1.3, 3, and 4 respectively. Responses above 4 hr were coded as the number of hours.

Standard estimates of intensity were used to classify activities according to the energy expenditure typically associated with them (12,13). The types of activity measured were divided into two classes (Appendix 1): vigorous activities

- Those requiring an energy expenditure of = 7 metabolic equivalents (METs; 1MET is the energy expended by a person while sitting at rest) and moderate activities with MET values in the range of 3-6. This classification was based on tables of energy expenditure published by Durnin and Passmore (14) and McArdle et al. (15).

On the basis of this information, several indices were constructed: time spent per week for vigorous activities, time spent per week for moderate activities, and time spent per week for total activities.

Time spent per week for vigorous activities (TIMEvi) was calculated by multiplying the frequency (FREQvi) and the duration (DURvi) per episode for vigorous activities:

TIMEvi = FREQvi * DURvi

Time spent per week for moderate activities (TIMEm) was calculated by multiplying the frequency (FREQmi) and the duration (DURmi) per episode for moderate activities:

TIMEm = FREQmi * DURmi.