Assessment of physical activity in adolescents: protocols, compliance and participants’ perceptions

Joseph J Scott

Background: The identification of appropriate and accurate tools for measuring physical activity is an international research priority. There is now a plethora of existing physical activity questionnaires that have been designed to assess activity patterns; few, however, are both valid and reliable. Existing questionnaires vary extensively in length and complexity with some requiring high level cognitive recall, rendering them unsuitable for some population groups. In particular, adolescents represent a problematic and complex sub-population in which to measure physical activity, due to incomplete or inaccurate reporting. There is thus a need for simplified and validated physical activity questionnaires designed specifically for use with adolescents. Objective: monitoring devices such as pedometers and accelerometers have acceptable feasibility, validity and reliability. In addition, as both motion sensors share similar technical and adherence issues. There is, however, a lack consensus regarding the optimal monitoring protocols. Poor adherence to objective monitoring protocols is a common reason why assessing activity patterns of adolescents remains complex. This may explain why adolescents are one of the least studied sub-population groups in physical activity research. As physical activity levels decline through adolescence, it is important that we improve our understanding of physical activity assessment in this target population. Pedometers are now commonly used to measure physical activity in different age groups (that is, children, adolescents, adults and older adults); however, little is known about the influence of different pedometer protocols on the accuracy of physical activity measurement. Previous studies in children and adults have investigated reactivity and tampering with pedometer monitoring, however the research in the adolescent domain remains relatively sparse. Furthermore, no studies have explored adolescents’ perceptions of the pedometer monitoring process to gain insight into how and why they do not comply with monitoring protocols. To date, accelerometers have predominantly been worn on the hip. However, in an attempt to increase participant compliance, researchers have more recently trialled the use of wrist-worn accelerometers in various populations. Currently, no studies have investigated the comparability and feasibility of hip- and wrist-worn accelerometers in adolescents. Given the importance of accurate physical activity measurement, there is a clear need for standardised physical activity monitoring protocols. Aims: This thesis-by-publication presents a series of studies that were conducted to address the gap in the evidence base surrounding physical activity assessment in adolescents. The overarching aim of this thesis was to investigate current physical activity measurement protocols to assess physical activity levels in this sub-population. This thesis presents a series of studies that investigated six key study objectives, which are described briefly below. As these studies provide important context for the overall aim, the thesis is presented in the following order: Study objective 1: assess the test–retest reliability of a single-item physical activity questionnaire for adolescents. Study objective 2: determine the concurrent validity of a single-item physical activity measure for adolescents compared to accelerometry. Considering the large number of existing physical activity measures available, the wide-ranging variability in their format; length and complexity and their limitations in accuracy, there is a need for more direct comparisons of questionnaires to improve our understanding of the most appropriate physical activity measures. The aim of this study was to investigate the test–retest reliability and validity of a single-item questionnaire in free-living adolescents (n = 123) by testing it against a more extensive existing physical activity questionnaire (The Oxford Physical Activity Questionnaire [OPAQ]) and accelerometer output. The single-item (intra-class correlation coefficient [ICC] = 0.75, 95% confidence interval [CI] = 0.64 - 0.83, p < 0.001) and the OPAQ (ICC = 0.79, 95% CI = 0.69 - 0.86, p < 0.001) were both found to have moderate-to-strong reliability. Correlations between self-reported and objectively-measured moderate-to-vigorous physical activity (MVPA) were similar for the single-item measure (r = 0.44, 95% CI = 0.24 - 0.63, p < 0.001) and the OPAQ (r = 0.50, 95% CI = 0.30 - 0.65, p < 0.001). The single-item questionnaire compared well to both the OPAQ and accelerometer derived activity counts. Study findings suggest the single-item measure can provide a reliable and valid assessment of adolescent physical activity. The single-item measure is easy to administer and may have utility for screening purposes and for use in population surveys. Study objective 3: explore the impact of different pedometer monitoring protocols on compliance, reactivity and tampering in a sample of adolescents. The aim of this study was to investigate adolescents’ potential reactivity and tampering while wearing pedometers. In this study, adolescents were randomised to one of three pedometer monitoring protocols: (i) daily sealed pedometer group, (ii) unsealed pedometer group or (iii) weekly sealed pedometer group. Participants wore pedometers (Yamax Digi-Walker CW700, Yamax Corporation, Kumamoto City, Japan) and accelerometers (ActiGraph GT3X+, Pensacola, USA) simultaneously for seven days and completed a pedometry behaviour questionnaire. Repeated measures analysis of variance was used to examine potential reactivity. Bivariate correlations between step counts and accelerometer output were calculated to explore potential tampering. The correlation between accelerometer output and pedometer steps/day was strongest among participants in the weekly sealed group (r = 0.82, p ≤ 0.001), compared with the unsealed (r = 0.63, p ≤ 0.001) and daily sealed (r = 0.16, p > 0.05) groups. The daily sealed (p ≤ 0.001) and unsealed (p ≤ 0.001) groups, but not the weekly sealed (p = 0.886) group, showed evidence of reactivity. Responses from the questionnaire indicated that almost half the participants reported shaking their pedometers to increase their step count, 40% reported that they did not like wearing pedometers, 81% found wearing a pedometer uncomfortable, and 69% reported that they found wearing a pedometer ‘embarrassing at times’. Contrary to previous research, the study findings suggest that the protocol selected for pedometer monitoring impacts behaviour and compliance. A seven-day monitoring protocol using sealed pedometers capable of storing at least seven days of step count data in their internal memory is recommended to limit reactivity and tampering in adolescents. Study objective 4: explore adolescents’ perceptions of wearing pedometers and investigate behaviours exhibited while wearing pedometers. The aim of this study was to explore adolescents’ perceptions of pedometer monitoring and investigate the physical activity behaviours exhibited whilst wearing the devices. Six focus groups (3 boys’ groups and 3 girls’ groups), each involving four participants, were completed. The focus group participants were selected from the larger group of students participating in the monitoring protocol study; that is, from the 123 participants who wore pedometers (Yamax CW700) and accelerometers (ActiGraph GT3X+) simultaneously for seven days. Students were then grouped based on their daily accelerometer-determined MVPA level: i) low active: < 30 minutes/day in MVPA, ii) medium active 30 - 60 minutes/day in MVPA and iii) high active ≥ 60 minutes/day in MVPA over their monitoring period). Participants were questioned on the behaviours exhibited while they were wearing activity monitors and their perceptions of the monitoring process. A large proportion of the participants (approximately 60%) reported purposely changing their levels of physical activity during the monitoring process, and 21 of the 24 focus group participants reported shaking their pedometers to increase their step counts. More participants in the medium and high active groups reported changing their activity patterns than in the low active groups. The study findings suggest that the reasons for non-adherence to pedometer protocol were not related to sex or physical activity level. The high amount of reported reactivity indicates that pedometers are still a useful tool to promote physical activity in adolescents, but are less useful, however, when attempting to obtain habitual activity patterns. Study objective 5: test the comparability and feasibility of the wrist- and hip-worn accelerometers in the free-living adolescent population. Study objective 6: compare wear-time, missing data and participant perceptions regarding wrist- and hip-worn accelerometers. The aim of this study was to determine the comparability and feasibility of wrist- and hip-worn accelerometers among free-living adolescents. In addition, the study focused on participants’ perceptions of wrist- and hip-worn accelerometers to assist in determining the superior site placement for accelerometers when assessing adolescents in free-living conditions. The sample included 89 adolescents (age = 13 - 14 years) from eight secondary schools in New South Wales (NSW), Australia. Participants wore wrist-worn GENEActiv and hip-worn ActiGraph (GT3X+) accelerometers simultaneously for seven days and completed an accelerometry behaviour questionnaire. Bivariate correlations between the wrist- and hip-worn output were used to determine concurrent validity. Paired samples t-test were used to compare minutes per day in MVPA. Group means and paired sample t-tests were used to analyse participants’ perceptions of the wrist- and hip-worn monitoring protocols to determine feasibility. Wrist-worn accelerometers compared favourably with hip-worn in average activity (r = 0.88, p < 0.001) and MVPA (r = 0.84 p < 0.001, mean difference = 3.54 mins/day, SD = 12.37). The wrist-worn accelerometer had 50% fewer non-valid days (75 days, 12%) than the hip-worn accelerometer (n = 152, 24.4%). Participants reported they preferred to wear the device on the wrist (p < 0.001), and that it was less uncomfortable (p = 0.023) and less embarrassing to wear on the wrist (p < 0.001). Furthermore, they reported they would be more willing to wear the device on the wrist than on the hip (p < 0.001). Study findings revealed a strong linear relationship between wrist- and hip-worn accelerometer output among adolescents in free-living conditions. Compliance was significantly higher for wrist placement, with participants reporting that it was more comfortable and less embarrassing to wear and, importantly, they would be more willing to wear it again on the wrist than on the hip. Summary: This thesis reviews the existing literature surrounding existing pedometer protocols among adolescents to investigate gaps in the research. The single item physical activity questionnaire designed specifically for adolescents compared well to an existing physical activity questionnaire. As such, this measure may utility for determining whether or not adolescents are meeting physical activity guidelines. In addition, this thesis presents findings that support that reactivity and tampering are inherent risks to validity when assessing adolescents’ physical activity with pedometers. Strategies to limit reactivity and tampering should be considered by researchers during studies when attempting to accurately assess adolescents’ physical activity patterns. In an attempt to increase compliance with monitoring protocols in the adolescent population, it is recommended that future research utilise wrist-worn accelerometers. The original contribution of this thesis is the collection of data using both quantitative and qualitative methods to improve our understanding of adolescents’ compliance to physical activity monitoring protocols. The evidence collected in this thesis may assist in the development of pedometer and accelerometer measurement protocols designed for adolescents.

Assessment of physical activity in adolescents: protocols, compliance and participants’ perceptions

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