Background & Study Rationale

Although a physically active lifestyle has established health benefits, a large proportion of children and adolescents fail to meet the health related guidelines for physical activity recommendations (Corbin & Pangrazi, 2004; Riddoch, Mattocks, Deere et al, 2007). This public health guideline advises children and adolescents to achieve one hour of moderate intensity physical activity per day, continuous or intermittent throughout the day (Riddoch, Mattocks, Deere et al, 2007). Longitudinal studies of physical activity levels and health amongst children have shown that although physical activity levels steadily increase during childhood (5-11 yrs), there is a steep decline during adolescence, 12 yrs and onwards (Janz et al, 2000; Kimm et al 2000; Sallis, 2000), shown to track into adulthood (Deflandre et al, 2001). Childhood obesity is now recognized as a global epidemic (Tremblay & Willms, 2000), and the development of interventions to promote physical activity amongst children and adolescents has as a result, become critical (Rowe et al, 2007; van der Horst et al, 2006).

There are important environmental and situational factors that relate to children's physical activity (Harwood, 2002). There is however less evidence detailing the strength of association between these factors. Gaining a better understanding of what combined impact the type of physical activity, time of day it is performed (before, during and after school), and context (school or non school day) have upon physical activity levels of children, is critical.

Aim and research questions

The main aim of this study is to assess how active and inactive children (identified using accelerometer data) differ in the types of physical activities they participate in, and the time of day they do this, on both school days and non school days (as reported in the PDPAR questionnaire).

RQ1a. Do the physical activity patterns of children who are active differ to those who are inactive, on school and non school days?

RQ1b.How is this related to the type of activity, and time of day it is performed?

RQ2. Are there differences in the times of day that active and inactive children are physically active, and how do the patterns of physical activity compare?

RQ3. Are the gender, SES and weight of active and inactive children associated with the differing level of physical activity, and does this relate to the types of activities they do, and when they do them?

To address these questions, a secondary analysis will be conducted using data from the ALSPAC study, of children aged 13 years.

Methods

The data for physical activity levels will be taken from the ActiGraph accelerometer, worn over a 7-day period. Data for the time of physical activity participation and type if activity will be taken from the Previous Day Physical Activity Recall Questionnaire (PDPAR).

Questionnaire Data

Data will represent both school and non school days. Six separate times of day will be considered for a school day and four separate times for a non-school day (see below). There will be seven different categories of physical activity behaviour for both a school and non-school day (see below).

The specific times of the day that the type of physical activity was recorded, include;

School Day-

1. Getting up - Start of School

2. Starting School - Lunch

3. Lunch Break

4. Lunch - End of School

5. End of School - Teatime/Dinner

6. Teatime/Dinner - Going to Bed

Non-School Day-

1. Getting up - Breakfast

2. Breakfast - Lunch

3. Lunch - Tea/Dinner

4. Tea/Dinner - Going to Bed

The types of activity measured are;

1. Watching TV/playing computer game/reading/homework.

2. Work around the house

3. Play a game outside

4. Do any sport/games/PE

5. Do a job/activity

6. Travel to and from school

7. Walk/cycle anywhere

Two main physical activity variables will be used to define active/inactive children;

1. Total physical activity - total average accelerometer counts/mins over the full period of valid recording. The recommended total time spent in MVPA is greater than 60 mins per day.

2. Time spent in MVPA - the average minutes of moderate and vigorous physical activity per valid day. The lower threshold of moderate intensity activity considered as 3600 counts/min.