Accelerometer-Measured Physical Activity Levels and Patterns Vary in an Age- and Sex-Dependent Fashion among Finnish Children and Adolescents.

BACKGROUND: The purpose of this study was to measure physical activity (PA), sedentary behavior (SB), and hour-by-hour PA patterns with an accelerometer in a population-based sample of Finnish children and adolescents. METHODS: A total of 3274 participants (3rd, 5th, 7th, 9th graders) from 176 schools wore a hip-worn triaxial accelerometer for seven days during waking hours. Mean amplitude deviation of the acceleration data was used to assess PA intensity that was converted to metabolic equivalents and categorized into light, moderate, and vigorous PA. Angle for posture estimation was used to measure SB and standing. RESULTS: The majority of participants' PA consisted of light PA, and they were sedentary for more than half of their waking hours. Children were more active than adolescents, and boys were more active than girls. Participants took, on average, 9890 steps daily, and one third met the PA recommendation. The participants were divided into tertiles based on daily steps to investigate the variation in PA patterns. Compared to the least active tertile, the most active tertile took twice as many steps on weekdays and nearly three times as many steps on the weekend. CONCLUSIONS: The majority of the participants were not active enough, and there was a great variation in PA levels and patterns, especially among the adolescents and on weekends.

Mean amplitude deviation calculated from raw acceleration data: a novel method for classifying the intensity of adolescents' physical activity irrespective of accelerometer brand.

BACKGROUND: Using raw acceleration data to assess the intensity of physical activity enables direct comparisons between studies using different accelerometer brands. Mean amplitude deviation (MAD in mg) calculated from resultant tri-axial raw acceleration signal was recently shown to perform best in classifying the intensity of physical activity in adults irrespective of the accelerometer brand. This study compared MAD values and cut-points between two different accelerometers in adolescents. METHODS: Twenty voluntary participants (10 girls and 10 boys) of average age of 14 wore two accelerometers (Actigraph GTX3, Pensacola FL, USA and Hookie AM13, Espoo, Finland) and heart rate monitors (M61, Polar Electro Oy, Kempele, Finland) while completing ten 2-min patterns of typical activities ranging from sedentary behaviour to light, moderate and vigorous-intensity locomotion. Bland-Altman method examined the agreement of MAD values between the accelerometers. Correlation coefficient between individual heart rates and MAD values indicated the validity of pattern-based intensity classification. Generalized ordinal logistic regression determined the intensity-specific MAD cut-points for both accelerometers. RESULTS: MAD values varied from 3 mg (lying supine) to 1609 mg (running). Hookie gave higher values than Actigraph in accelerations exceeding 700 mg. The correlation coefficient between MAD values and heart rates was 0.96 for Hookie and 0.97 for Actigraph. Respectively, the MAD cut-points were 29 and 27 (light), 338 and 330 (moderate), and 604 and 558 (vigorous). CONCLUSIONS: MAD values and cut-points of Hookie and Actigraph showed excellent agreement. Analysing raw accelerometer data with MAD values may enable the comparison of accelerometer results between different studies also in adolescents.

KIDS OUT! Protocol of a brief school-based intervention to promote physical activity and to reduce screen time in a sub-cohort of Finnish eighth graders.

BACKGROUND: Adolescents' physical activity (PA) is decreasing and sedentary behavior (SB) increasing alarmingly. Insufficient PA and excessive SB are both related to various health risks indicating that interventions to promote adolescents' PA and to reduce their SB are needed. Schools have a great potential to reach most adolescents, and in Finland health education (HE) as stand-alone subject provides an excellent platform for health promotion. This paper describes the protocol and evaluation (RE-AIM) of an intervention developed for three HE lessons to increase PA and reduce SB during leisure among 8(th) graders. METHODS/DESIGN: All city-owned secondary schools in Tampere (n = 14) were invited to the study and were randomized in pairs to intervention (n = 7) and comparison group (n = 7). A specific content on PA and SB based on Health Action Process Approach model was integrated into routinely scheduled three HE lessons with the help of educational material: SoftGIS-questionnaire followed by feedback views on adolescents' current PA and SB, FeetEnergy-homework leaflet for adolescents, FeetEnergy-video in YouTube, FeetEnergy-poster for classroom and FeetEnergy-leaflet for parents. In the comparison group standard HE lessons were held. The primary indicators of Effectiveness are changes in PA and SB and in their psychosocial factors as well as in parental interference with PA and SB. The measurement points are baseline, 4 weeks after the intervention and 7 months from baseline, the last indicating also the measurement point for individual level Maintenance. The measures are accelerometers, 7-day activity diaries and questionnaires. The evaluation of Reach, Adoption and Implementation is based on the data collected during the intervention. Maintenance at organizational level is assessed two years after the intervention with a questionnaire to the HE teachers. The intervention was implemented in 2012 and the last measurements to assess organizational Maintenance were conducted in the end of 2014. A detailed description of the protocol and evaluation is provided to enable replication and better understanding of the findings, which will be reported in 2015. DISCUSSION: The findings will add our current knowledge about the feasibility and effectiveness of integrating simple structured elements into the HE lessons to increase PA and reduce SB in adolescents. TRIAL REGISTRATION: NCT01633918 (June 27th, 2012).