Daniela Kahlert, Ralf Brand

• According to the results of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) published in 2009, only 5% to 8% of the 15-17-year-old adolescents reach the current recommendations on health-enhancing physical activity This result (besides others in the survey) rests on data measured with the 25-item physical activity questionnaire for children and adolescents (MoMo-AFB). The present study compares two different methods of assessing physical activity with the purpose of testing the validity of the MoMo-AFB self-report. First, we measured the physical activity status of 73 15 to 18-year-old pupils (32 boys and 41 girls) over seven days via objective accelerometry (ActiGraph GT1M), then the pupils completed the MoMo-AFB for the same (previous) period. Results show that using the MoMo-AFB leads to higher levels of self-reported physical activity than measuring it with accelerometers. Furthermore, only the MoMo-AFB subscale MVPA (moderate-to-vigorous physical activity), that uses two single items toAccording to the results of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) published in 2009, only 5% to 8% of the 15-17-year-old adolescents reach the current recommendations on health-enhancing physical activity This result (besides others in the survey) rests on data measured with the 25-item physical activity questionnaire for children and adolescents (MoMo-AFB). The present study compares two different methods of assessing physical activity with the purpose of testing the validity of the MoMo-AFB self-report. First, we measured the physical activity status of 73 15 to 18-year-old pupils (32 boys and 41 girls) over seven days via objective accelerometry (ActiGraph GT1M), then the pupils completed the MoMo-AFB for the same (previous) period. Results show that using the MoMo-AFB leads to higher levels of self-reported physical activity than measuring it with accelerometers. Furthermore, only the MoMo-AFB subscale MVPA (moderate-to-vigorous physical activity), that uses two single items to decide whether the health-enhancing physical activity recommendation is reached or failed, corresponds statistically significantly with the accelerometry data. For all other subscales (e.g. school- or leisure time activity), we found no agreement. Further research, first of all on the measurement quality of the MoMo-AFB but also on the physical (in)activity status of children and adolescents, is needed.…