Analysis of The Two Studies on The Association of Specific Functions and Musculoskeletal Discomfort

Two studies deemed to be of acceptable quality examined the association of specific functions and MSK discomfort. Some evidence was found for the association of use of ancillary functions and messaging and MSK discomfort (in both tablets and mobile phones), while the association between phone call frequency with MSK discomfort was inconclusive. Both Kwok et al. (2017) and Yang et al. (2016) found those who used ancillary functions, such as browsing information and messaging on their devices to be associated with MSK discomfort.

In the study by Kwok et al. (2017), adolescents who perceived MSK discomfort spent significantly more time per day browsing information (z=-5. 96), watching TV/movies (z=-5. 92) and messaging (z= -4. 36), while the number of body parts with discomfort increased with hours spent using ancillary functions (F=6. 009, p

However, both studies had many potential sources of bias and so these results should be analysed with caution. Future studies should seek to measure the level of discomfort brought on by these tasks and examine how each may affect muscle activity and postures in adolescents. Yang et al. (2016) found that the participants who spent >3hours/day talking on their smartphone had a significant correlation (p=0. 04) with upper back discomfort. Similar results have been found in the adult population and is likely due to the prolonged static postures adopted while holding a phone during phone calls. The upper back may become a stabiliser for the head and neck while talking on the phone, with this position potentially resulting in the development of upper back pain if sustained.

Interestingly, Yang et al. (2016) also found that the group that spent the most time talking experienced less discomfort in the wrist and hands than the group that spent less than 1 hour talking on the phone (OR=0. 27, p=0. 03). This may have been due to the isometric grip maintained when holding the phone, or spending less time doing other repetitive tasks such as messaging. However, as only this study examined phone calls as risk factor, these results must be interpreted with caution and future studies should examine this association further in the adolescent population.

One study deemed to be of high quality study and one deemed to be of low quality study found associations between adopting different awkward postures during device use and the risk of MSK discomfort. However, different postures were examined in these studies and therefore results should be interpreted with caution due to the limited evidence.

Further research is therefore warranted to determine if these associations are strong. No studies reported specifically on neck flexion postures, although this has been shown to be a risk factor in other reviews in the general population. Nevertheless, it is likely that the high prevalence of neck and neck/shoulder pain seen in all studies in this review was related to sustained neck flexion postures and so future studies should examine this in the adolescent population.