DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY
LETTER TO THE EDITOR
Measurement of habitual physical activity and sedentary behaviour of youth with cerebral palsy: work in progress Jan Willem Gorter1, Brian W Timmons2 1 CanChild Centre for Childhood Disability Research, Department of Pediatrics, McMaster University, Hamilton, ON; 2 Child Health & Exercise Medicine Program, CanChild Centre for Childhood Disability Research, Department of pediatrics, McMaster University, Hamilton, ON, Canada. Correspondence to: [email protected] doi: 10.1111/dmcn.12503
SIR–We read with great interest the recent publication by Shkedy Rabani et al.1 which described the duration and patterns of habitual physical activity in adolescents and young adults with cerebral palsy (CP). The authors should be commended because this study could be the largest study of its kind in terms of sample size, while reporting the objective measurement of habitual physical activity (HPA) and sedentary time. But while this is an important article, there are some measurement and study design issues that we believe require clarification. Contemporary challenges in the measurement of HPA of individuals with CP are how to record activity in a reliable and valid fashion, and how to ensure that the data are representative of usual activities of daily living, including sleep and rest. Shkedy Rabani et al. used the ActivPAL3 activity monitor. To our knowledge, there are no published reports of the validity or reliability of this monitor. What the authors referred to were studies that investigated the reliability and validity of the older generation uniaxial ActivPAL monitor. The authors reported HPA measures of participants’ activity according to a mean of 4 days (SD 5h) according to three Gross Motor Function Classification System (GMFCS) levels (II, III, and IV). To interpret the data, it is important to know what the average wear time for each group was. Although the results appear to be reported per 24-hour period, we also need to know whether this 24-hour period is, in fact, representative of the individual’s habitual living experience. Pitfalls of any observational study are to draw conclusions on causation between the condition, personal or environmental factors, and the outcome of interest. For example, the authors made an interesting comparison between individuals with CP attending educational
institutions (students) and those who remained at home. The authors reported, ‘there were no significant differences in HPA between student and homebound participants only among participants at GMFCS level III; no significant differences between these two categories were found at GMFCS levels II and IV’. For some reason, the authors then combined the entire group and found that students were more active than homebound individuals. Surprisingly, the authors then concluded that, ‘this study provides evidence that the physical structure of educational facilities is beneficial for this population’. We do not agree with the manipulation of statistical analysis and the associated misleading conclusion regarding students compared with homebound individuals. Clearly, any differences were found only for those individuals at GMFCS level III. Finally, Shkedy Rabani et al. indicated that, ‘this is the first study to present detailed analysis of HPA levels and patterns in adolescents and young adults with CP . . . and including GMFCS levels III and IV as separate groups’. However, it appeared that for each variable reported there were previously published reports that could substantiate or refute the findings of Shkedy Rabani et al. including the patterns of sedentary time and transitions. In 2012, Gorter et al. published a study of the feasibility of physical activity monitoring in ambulatory and non-ambulatory adolescents (GMFCS levels I–IV) using the ActiGraph GT1M activity monitor.2 Therefore, this may not be the first study to present objectively measured HPA in individuals with CP with GMFCS levels III and IV, or such analysis. It is important to continue the study of physical activity and sedentary behaviour of individuals with CP. We agree with Taylor who wrote in his recent commentary accompanying the article by Shkedy Rabani et al.: ‘if strategies to reduce sedentary behaviour are going to be trialled, sedentary behaviour first needs to be measured.’3 Therefore, we need to do this with the most reliable and valid methods available, making sure that data collection periods are representative of the participant’s normal routine, and that we advance the state of knowledge by answering important questions. We commend the work of Shkedy Rabani et al. towards these goals.
REFERENCES 1. Shkedy Rabani A, Harries N, Namoora I, Al-Jarrah
2. Gorter JW, Noorduyn SG, Obeid J, Timmons BW. Ac-
3. Taylor NF. Sedentary behaviour in adolescents and
MD, Karniel A, Bar-Haim S. Duration and patterns of
celerometry: a feasible method to quantify physical activ-
young adults with cerebral palsy. Dev Med Child Neurol
habitual physical activity in adolescents and young adults
ity in ambulatory and nonambulatory adolescents with
2014; 56: 609–10.
with cerebral palsy. Dev Med Child Neurol 2014; 56:
cerebral palsy. Int J Pediatr 2012; 2012: 329284. Doi: 10.
673–80.
1155/2012/329284.
© 2014 Mac Keith Press
911
LETTER TO THE EDITOR
Measurement of habitual physical activity and sedentary behaviour of youth with cerebral palsy: work in progress Jan Willem Gorter1, Brian W Timmons2 1 CanChild Centre for Childhood Disability Research, Department of Pediatrics, McMaster University, Hamilton, ON; 2 Child Health & Exercise Medicine Program, CanChild Centre for Childhood Disability Research, Department of pediatrics, McMaster University, Hamilton, ON, Canada. Correspondence to: [email protected] doi: 10.1111/dmcn.12503
SIR–We read with great interest the recent publication by Shkedy Rabani et al.1 which described the duration and patterns of habitual physical activity in adolescents and young adults with cerebral palsy (CP). The authors should be commended because this study could be the largest study of its kind in terms of sample size, while reporting the objective measurement of habitual physical activity (HPA) and sedentary time. But while this is an important article, there are some measurement and study design issues that we believe require clarification. Contemporary challenges in the measurement of HPA of individuals with CP are how to record activity in a reliable and valid fashion, and how to ensure that the data are representative of usual activities of daily living, including sleep and rest. Shkedy Rabani et al. used the ActivPAL3 activity monitor. To our knowledge, there are no published reports of the validity or reliability of this monitor. What the authors referred to were studies that investigated the reliability and validity of the older generation uniaxial ActivPAL monitor. The authors reported HPA measures of participants’ activity according to a mean of 4 days (SD 5h) according to three Gross Motor Function Classification System (GMFCS) levels (II, III, and IV). To interpret the data, it is important to know what the average wear time for each group was. Although the results appear to be reported per 24-hour period, we also need to know whether this 24-hour period is, in fact, representative of the individual’s habitual living experience. Pitfalls of any observational study are to draw conclusions on causation between the condition, personal or environmental factors, and the outcome of interest. For example, the authors made an interesting comparison between individuals with CP attending educational
institutions (students) and those who remained at home. The authors reported, ‘there were no significant differences in HPA between student and homebound participants only among participants at GMFCS level III; no significant differences between these two categories were found at GMFCS levels II and IV’. For some reason, the authors then combined the entire group and found that students were more active than homebound individuals. Surprisingly, the authors then concluded that, ‘this study provides evidence that the physical structure of educational facilities is beneficial for this population’. We do not agree with the manipulation of statistical analysis and the associated misleading conclusion regarding students compared with homebound individuals. Clearly, any differences were found only for those individuals at GMFCS level III. Finally, Shkedy Rabani et al. indicated that, ‘this is the first study to present detailed analysis of HPA levels and patterns in adolescents and young adults with CP . . . and including GMFCS levels III and IV as separate groups’. However, it appeared that for each variable reported there were previously published reports that could substantiate or refute the findings of Shkedy Rabani et al. including the patterns of sedentary time and transitions. In 2012, Gorter et al. published a study of the feasibility of physical activity monitoring in ambulatory and non-ambulatory adolescents (GMFCS levels I–IV) using the ActiGraph GT1M activity monitor.2 Therefore, this may not be the first study to present objectively measured HPA in individuals with CP with GMFCS levels III and IV, or such analysis. It is important to continue the study of physical activity and sedentary behaviour of individuals with CP. We agree with Taylor who wrote in his recent commentary accompanying the article by Shkedy Rabani et al.: ‘if strategies to reduce sedentary behaviour are going to be trialled, sedentary behaviour first needs to be measured.’3 Therefore, we need to do this with the most reliable and valid methods available, making sure that data collection periods are representative of the participant’s normal routine, and that we advance the state of knowledge by answering important questions. We commend the work of Shkedy Rabani et al. towards these goals.
REFERENCES 1. Shkedy Rabani A, Harries N, Namoora I, Al-Jarrah
2. Gorter JW, Noorduyn SG, Obeid J, Timmons BW. Ac-
3. Taylor NF. Sedentary behaviour in adolescents and
MD, Karniel A, Bar-Haim S. Duration and patterns of
celerometry: a feasible method to quantify physical activ-
young adults with cerebral palsy. Dev Med Child Neurol
habitual physical activity in adolescents and young adults
ity in ambulatory and nonambulatory adolescents with
2014; 56: 609–10.
with cerebral palsy. Dev Med Child Neurol 2014; 56:
cerebral palsy. Int J Pediatr 2012; 2012: 329284. Doi: 10.
673–80.
1155/2012/329284.
© 2014 Mac Keith Press
911
