Questionnaires – children questionnaire was used to gather information about children’s smoking habits, alcohol intake, diet preferences, and various types of physical activity. Questions addressing psychosocial and environmental factors that influences children’s physical activity were also asked. The parents completed a separate questionnaire. The collected data included demographic data, self-reported health status, family income, level of education, ethnicity, level of cardiovascular disease risk, family history of cardiovascular disease, the child’s birth weight, and breast-feeding practices. Socio-economic position was assessed using parental education, occupation, and family income data.
Mental capacity – Raven’s Matrices was used. All of the questions on the Raven’s progressive matrices consist of visual geometric design with a missing piece. The test taker is given six to eight choices to pick from and fill in the missing piece to complete the logical task.
Computer tests – from the third data collection wave, the subjects perform different computerized experimental psychological tests to measure their impulsivity, reaction time and memory.
Physical measures – we measure height, body mass, waist and hip circumference, thickness of five skinfolds and percent of body fat.
Pubertal stage – assessed according to Tanner stages. Pubertal stage was identified using a 5-point scale of pictures – for girls according to breast development and pubic hair growth and for boys according to genital development and pubic hair growth.
Resting systolic and diastolic blood pressure – blood pressure and heart rate were measured automatically by the monitor. Five measurement were taken with 2-min intervals and the measurement was always taken before cardiorespiratory fitness test.
Blood sampling – Fasting (overnight) intravenous blood samples were taken at the start of the day from the antecubital vein.
Food intake – diet and nutrition card for youth and eating frequency questionnaire was filled before the study day. During the study day, face-to-face interview was performed. In baseline study participant followed his/her eating during the last 24-hours. In the second and third measurement time participant followed his/her eating for two days and from the fourth measurement time participant followed his/her eating during three days, including one weekend day.
Cardiorespiratory fitness – was defined as maximal power output per kilogram of body mass and was measured a graded maximal exercise test on an electronically braked cycle ergometer.
Determination of lung function – at the first measurement, forced vital capacity of the lungs was measured and quantity of forced exhaled air during the first second.
Physical activity – was assessed by accelerometer. At the beginning of the study participant wore accelerometer for four consecutive days and from year 2008 participant wore accelerometer for 7 consecutive days. In addition, participant filled a diary for that time he/she did not wear accelerometer.
Clinical interview – at the beginning of the fifth data collection wave, a structured interview by clinical psychologists is conduct to discover episodes of anxiety, mood disorders and addictive disorders during the study period and during lifetime