Author ’ s response to reviews Title : Thoracic dysfunction in whiplash associated disorders : a systematic review and meta-analysis protocol Authors :

R 2.1 The abstract is appropriated. RESPONSE: Thank you for your positive comment. Introduction R 2.2 Although the introduction is reasonably well written it should be more informative regarding the last findings in this field. RESPONSE: Thank you for your suggestion. We enriched the Introduction part as follows: “BACKGROUND Children use of electronic media, including Internet and video gaming, has increased also among children with health condition like ADHD. The Internet environment and virtual reality offers very atrractive features for them. It provides very broad content for potential stimulations or various activities in simultaneously open windows, which might lead to fixation to the online world. Furthermore, video games offer immediate rewards with a strong incentive to increase the reward by trying the next level (Weiss et al. 2011, Ko et al. 2012). “ Methods The methods should be in detail and should be written in order to allow the replication of the study. There is much information that misses in methods section: R 2.3 Authors stated in lines 82-83 that the "Following the recommendations of the American Academy of Pediatrics [20], responses were dichotomized into two categories of children. ". This not correctly said. American Academy of Pediatrics did not recommend to dichotomized responses into two categories. Authors should complete their description to inform readers properly. RESPONSE: Thanks for raising this issue. We revised relevant text as follows: “METHODS . Responses were dichotomized into two categories of children: those who spent less than 2 hours per day and those who spent 2 or more hours per day on screen-based activities, as AAP recommended that children should not spend time with media no more than 1 to 2 hours per day. ” R 2.4 In lines 84-122 authors explain the "excessive Internet use" variable. They stated: "Responses were measured on a 4-point scale: very often, often, rarely, never [21]. We computed a sum score and dichotomized it into two categories represented by (1) adolescents with no symptom and (2) adolescents with at least one symptom. " My questions are: how was this converted in a score? How many points were attributed to which question regarding the 4-point scale used? Do we need a score when it is only needed one symptom in a dichotomized variable? RESPONSE: Thank you for noting. We clarify the way of using the variable and revised the text. “METHODS . Those who reported to experience the particular situation very of often or often during past year were considered to „have a symptom“. Then we divided adolescents on those who do not have any symptom excessive use of internet and those who have at least one symptom of excessive use of internet. ” R 2.5 I have several major concerns and doubts regarding the variables Long-term illness and chronic diseases. Authors need to describe carefully the terminology and concepts used and supported them with appropriated references, justifying the inclusion of which one illness, disability or medical condition in the respective variable. For example, why do you characterize hearing impairment as a chronic disease and diabetes as a Long-term illness? RESPONSE: We agree with the reviewer that we did not use right these terms and it can be confusing. We corrected part of the Methods as follows: “METHODS . Long-term illness prevalence was assessed using the item: “Do you have a long-term illness, disability or medical condition (like diabetes, arthritis, allergy or cerebral palsy) that has been diagnosed by a doctor? ” with “yes” and “no” as the response categories. The response used in statistical analyses referred to the occurrence of long-term illness. ” Besides this question we asked adolescents if they have asthma and learning disabilities (dyslexia, dysgraphia, orthography, dyscalculia) confirmed by a doctor. Results R 2.6 I have also several major concerns in the results section. The results section should be improved to characterize the participants in order to a better understanding of the results and to answer properly to the aims of the study. Authors wanted to study a human behavior and they do not provide to the reader any other variables that help them to know who the participants are, in order to understand their behavior. Their condition is not the whole explanation why they choose to engage in a Screen-based behavior. Therefore, their gender, sex, socioeconomic condition, etc are basic important information that should be in this table. Furthermore, literature in this field has already found other important variables associated to sedentary behavior that authors also needed to acknowledge and controlled in their analyses. Without these potential confounders' are acknowledged we cannot interpret properly the results and authors are not contributing to move this field forward. RESPONSE: We would like to thank for your comment. We agree that more possible variables associated with screen-based behaviour among adolescents exist. Moreover, a lot of evidence is present focused on the social context of screen-based behaviour, like parental rules or availability of electronic devices in bedrooms (e.g. Brindova et al. 2014, Livingstone et al. 2012). However, our aim was not to study all possible variables associated with the social context, because this would require another type of analysis which could be part of another manuscript. Despite of this, we took into consideration your suggestions and in our analysis we added other possible confounders, such as gender and family affluence represented by e.g. having a computer, car or bathroom, into our model. The results showed that the effect of gender and family affluence were significant only in case of PC games and PC work. Boys with long-term illness, asthma and learning disabilities had a significantly higher chance of excessive playing computer games. Children with long-term illness, asthma, learning disabilities and low socio-economic position had significantly lower chance of excessive computer work. However, no interactions were confirmed. Results are presented in the following table. We do not add these findings into Result part as significance of main findings did not change. References: Brindova D, Pavelka J, Ševčikova A, Žežula I, van Dijk J.P, Reijneveld SA, Madarasova Geckova A. How parents can affect excessive spending of time on screen-based activities. BMC Public Health. 2014;14:1261. Livingstone S, Helsper E. Balancing opportunities and risks in teenager’ use of the internet: the role of online skills and internet self-efficacy. New Media Soc. 2010;12(2):309–329. Table 2 Screen-based behaviour of children with and without long-term illness, asthma and learning disabilities: Logistic regression models, adjusted for gender and family affluence watching TV (≥2 hours) playing PC games (≥2 hours) computer work (≥2 hours) excessive use of internet (≥1 symptom) N (%) OR (95% CI) N (%) OR (95% CI) N (%) OR (95% CI) N (%) OR (95% CI) long-term illness yes 369 (72.4) 1.06 (0.851.32) 256 (50.5) 1.12 (0.911.38) 306 (60.4) 0.96 (0.781.17) 190 (38.9) 1.21 (0.981.50) no 1,346 (70.8) 1 (ref) 936 (49.0) 1 (ref) 1,168 (61.3) 1 (ref) 615 (34.1) 1 (ref) Asthma yes 104 (74.8) 1.17 (0.781.73) 81 (57.4) 1.57 (1.092.27) * 92 (65.7 )1.20 (0.831.72) 48 (35.8) 1.02 (0.701.47) no 1,600 (70.9) 1 (ref) 1,101 (48.7) 1 (ref) 1,370 (60.7) 1 (ref) 86 (64.2) 1 (ref) learning disability yes 90 (67.2) 0.81 (0.551.18) 71 (52.6) 1.00 (0.691.45) 85 (63.4) 1.18 (0.811.71) 60 (46.9) 1.76 (1.222.54) ** no 1,607 (71.2) 1 (ref) 1,110 (49.1) 1 (ref) 1,373 (60.9) 1 (ref) 740 (34.6) 1 (ref) * p<0.05, ** p<0.01, *** p<lt;0.001 N=number of children with and without long-term illness, asthma and learning disabilities in each screen-based behaviour and excessive use of internet Discussion R 2.7 Discussion should be revised in order to incorporate the changes proposed to the results. RESPONSE: As we did not enriched results part, we did not revised discussion, respectively.