Application of stages of change model to adolescents' physical activity in relation to psychological variables.

AIM: This study investigated the stages of change in physical activity in relation to psychological variables: self-efficacy, physical self-concept and barriers to physical activity, as well as gender. Furthermore, cluster profiles were created based on psychological variables to be compared with stages of change groups. METHODS: Data were obtained from a representative sample of adolescents (N.=1618, 14.46±1.28 years) from Aragon region (Spain). The different strata were selected according to the geographical region, environment, type of school, age and gender RESULTS: Males (75.5%) and very active adolescents (96.9% participant boys and 93.5% participants girls) were more prevalent in the action and maintenance groups. We found significant differences in psychosocial variables by stages of change and gender, showing higher scores in active groups for physical self-concept (effects of gender and stages of change: F(1, 1618)=313.82 P<0.001, η²=0.230) and self-efficacy (F(1, 1618)=324.34 P<0.001, η²=0.236), and lower scores in passive groups for intrapersonal (F(1, 1618)=179.73 P<0.001, η²=0.146) and extrapersonal barriers (F(1, 1618)=189.42 P<0.001, η²=0.153). Psychological cluster profiles created with these variables showed significant relationships with stages of change groups (χ²(1)=162,76, P<0.001; Pearson R=0.359 P<0.001). CONCLUSION: The findings of the research suggest the importance of the study, showing strong determinants of PA, physical self-concept, self-efficacy and perceived barriers, in relation to the intention to change behaviour, not only stage of change model variables. Furthermore, the study can be relevant to designing more effective health promotion programmes in the adolescent population.

Do epoch lengths affect adolescents' compliance with physical activity guidelines?

AIM: This study examined the effect of different epoch lengths (from 3 to 60 s) on (a) moderate to vigorous physical activity (MVPA), (b) 10 minutes bouts of MVPA and (c) compliance with World Health Organization (WHO) guidelines, as measured with an ActiGraph accelerometer. METHODS: A sample of 401 adolescents (14.48±0.69 years) wore a GT3X accelerometer to measure physical activity (PA) for 7 consecutive days. Data, originally collected in 1-s epoch(s), were then reintegrated into epochs of 3-, 5-, 10-, 15-, 30-, 45- and 60-s. RESULTS: The results showed a significant epoch effect (P=0.000) for time spent in MVPA, 10-min bouts of MVPA and the extent of compliance with guidelines percentage of compliance of guidelines. Bland-Altman analysis showed good agreement between 5- and 10-, 5- and 15-, and 10- and 15-s data, both for MVPA and 10-min bouts of MVPA. CONCLUSION: Epidemiological studies should take into account the sampling interval to offer accurate conclusions with regard to levels of MVPA and the extent to which adolescents comply with guidelines. Shorter epochs, such as 5-, 10- or 15-s are proposed for comparative studies carried out with adolescents in this area.

Barriers to adolescent girls' participation in physical activity defined by physical activity levels.

AIM: Perceived barriers were the single most powerful predictors of a change in health behaviours and the most consistent negative correlate of children's actual physical activity (PA). The purpose of this study was to compare the perceived barriers of physical activity in 714 adolescent girls defined by physical activity levels. METHODS: The final sample consisted of 714 adolescent, student girls. The age of these students ranged from 12 to 15 years, with a mean age of 13.5 ± 0.7 years. Perceived physical activity and perceived barriers to physical activity were measured using the Physical Self-Description Questionnaire and a Scale of Barriers that includes 17 units of barriers divided into two categories: intrapersonal barriers and environmental/contextual barriers. RESULTS: In our study, girls with a low activity level perceived a greater number of barriers than those with a high activity level, more specifically three intrapersonal barriers and two environmental/contextual barriers. Girls with a low activity level reported greater barriers to physical activity than high-active girls for these barriers: don't like physical activity (F=23.405, p=0.001), not good at physical activity and sports (F=24.160, p=0.001), I'm too lazy to do physical activity (F=8.415, P=0.001), it is not safe to do physical activity outdoors (F=11.39, P<0.001) and there is no-one to do physical activity with (F=15.22 P<0.001). CONCLUSION: This study shows the need to learn and effectively use time management strategies that emphasize prioritising and better scheduling of physical activities.

Physical activity patterns in normal-weight adolescents on week-days and week-ends.

AIM: This study aimed to assess the day-to-day variability of children's physical activity by accelerometer on week-days and week-end days, and to determine the proportion of children that comply with the established physical activity (PA) guidelines. METHODS: Physical activity was recorded every minute by uniaxial accelerometer in 104 normal-weight adolescent students (64 boys and 40 girls) for up to two different weeks (in winter and spring) and over seven consecutive days each week. We examined the difference in minutes for each gender and for the intensity of physical activity over the days of the week. The study took place in the north-east of Spain in 2009. RESULTS: Gender was found to produce the most significant results. Boys engaged in more moderate, vigorous and moderate to vigorous physical activity (MVPA) than girls. Children accumulated more physical activity on week-days than on week-end days. Adolescents' PA is mainly derived from their engagement in light activities. The majority of the adolescents did not reach the recommended ≥60 minutes of MVPA. CONCLUSION: This study suggests that Spanish adolescents engage in limited amounts of MVPA on week-days and week-ends, with activity levels differing according to sex and day of the week. Given that less activity is accumulated at the week-end, especially amongst girls, the out-of-school environment should be the focus for more activity.