Reliability and validity of two frequently used self-administered physical activity questionnaires in adolescents

Background: To create and find accurate and reliable instruments for the measurement of physical activity has been a challenge in epidemiological studies. We investigated the reliability and validity of two different physical activity questionnaires in 71 adolescents aged 13¿18 years; the WHO, Health Behaviour in Schoolchildren (HBSC) questionnaire, and the International Physical Activity Questionnaire (IPAQ, short version). Methods: The questionnaires were administered twice (8¿12 days apart) to measure reliability. Validity was assessed by comparing answers from the questionnaires with a cardiorespiratory fitness test (VO2peak) and seven days activity monitoring with the ActiReg, an instrument measuring physical activity level (PAL) and total energy expenditure (TEE). Results: Intraclass correlation coefficients for reliability for the WHO HBSC questionnaire were 0.71 for frequency and 0.73 for duration. For the frequency question, there was a significant difference between genders; 0.87 for girls and 0.59 for boys (p