Quantification of oxidative stress and physiological parameters due to schoolbag carriage in normal, overweight/obese male schoolchildren of West Bengal
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Abstract
Background: The physical activity of schoolbag carriage is a form of mandatory load carriage with a myriad of physiological consequences, the most common being pain occurrence and changes in physiological responses. The cardio-pulmonary response to a physical activity is dependent on its intensity which translates to weight of schoolbag being carried. The response to each physical activity is also dependent on the fat or lean body mass (body composition) of the individual performing it. Response to physical activity in subjects with an abundance of body fat is also concurrent with development of oxidative stress in the body. So, it is hypothesised that schoolbag carriage engenders different physiological response in terms of cardio-pulmonary, pain, postural and oxidative stress response in children belonging to different categories of body mass index (BMI).
Methodology: Parental survey about awareness regarding behaviour and practices of their children with respect to schoolbag carriage was assessed by survey sheets. Anthropometric measurements for schoolchildren (males aged 10-15 years, n=60) were recorded and they were categorised into normal and overweight/obese BMI groups. They walked for 20-minutes with backpacks of varying weight (0%, 4%, 8%, 12% and 16% of bodyweight) during which their cardio-pulmonary parameters were assessed via COSMED k4b2. During the walks, pain reports for the entire body were mapped. The walks were video-graphed for analysis of postural undulations. Cognitive ability was assessed by ruler drop test (RDT). Before and after each walk, saliva collection was accomplished via passive drooling and the collected bio-fluid was assayed for biomarkers pertinent to oxidative stress. The parameters studied were evaluated for continuity, distribution and comparison was then further conducted by parametric or non-parametric tests whichever applicable. A mathematical model predicting the percentage change in antioxidant capacity using standardized pain, load of schoolbag carried and BMI as the predictors was developed employing linear regression.
Results: Parental reports suggested that children carried heavy schoolbags in general and complained of pain causing high discomfort in neck, shoulder and back region. Majority of the parents never received any recommendations about safe load limits. All recorded anthropometric measurements for the age matched BMI categories were significantly higher (p<0.05) in overweight/obese BMI category compared to the normal category. During schoolbag carriage, heart regulation was better in case of normal BMI individuals. The lung volumes and energy expenditure were higher in overweight/obese participants (p<0.05). Cognition improved in children with normal BMI after carrying lower weight backpacks. The pain perceived was highest in the neck, shoulder and back region with shoulder. Pain perceived was higher in overweight/obese children. Posture worsened over time, and the postural undulations were more deleterious in overweight/obese children. Antioxidant status improved after carrying lower weight schoolbags. Nitric oxide mediated vasodilation was comparable in both BMI groups. The pain perception, load of schoolbag carried and BMI successfully predicted the percentage change in non-enzymatic antioxidant capacity via significant (p<0.05) mathematical regression model.
Conclusion: For the same physiological load of schoolbag carried, the overweight/obese children are relatively inefficient in regulating their cardio-pulmonary responses, they suffered from higher cognitive and postural decline besides developing greater oxidative stress compared to their age-matched normal BMI counterparts. The load limit of schoolbag pertaining to 8% and 4% load of bodyweight is recommended for normal BMI and overweight/obese children based on the cumulative results on all parameters studied. The prediction equation developed realises the customized determination of safe load limit in every child. This study can be used by policy makers to formulate schoolbag load limit recommendations keeping in mind the BMI of children thus ameliorating the derogatory effects of carrying heavy schoolbags in children and safeguarding child health.
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Schoolbag carriage, Body Mass Index (BMI), Physical activity, Cognition, Posture, Oxidative stress, Reactive Nitrogen Species (RNS), Dietary antioxidant intake