Effect of day time on smartphone use posture and related musculoskeletal disorders risk: a survey among university students

Background Musculoskeletal disorders (MSDs) are one of the most important problems among young smartphone users worldwide. Portability leads to a wide variety of postures during the different activities of the day. The objective evaluation of these postures coupled with ergonomic tools allows evaluating the level of MSD risk to which users are exposed. Methods The purpose was to investigate the effect of the time of day on the posture adopted during smartphone use among university students. The study was conducted through a cross-sectional survey of 263 university sports students. Four time of day, i.e. morning, afternoon, evening and night, and a taxonomy of 41 postures called SmarTaxo were considered. SmarTaxo included 18 sitting, 11 standing, 10 lying and 2 walking postures and their ergonomic score. After checking the normality of the data, a non-parametric Kruskal-Wallis test was used to study the effect of the time of day on the use duration of the different postures. Results The total mean duration use per typical weekday was 5.39 [+ or -] 2.19 h for males and 5.15 [+ or -] 1.60 h for females with maximal duration during evening. The average smartphone use durations were statistically longer in afternoon and evening for all sitting (9.44 and 9.22 min respectively, p < 0.05) and calling (3.38 and 3.33 min respectively, p < 0.05) postures. The longest duration for standing postures was recorded for afternoon (8.91 min, p < 0.05). The lying postures were significantly more present in evening (19.36 min). Some postures were more used during a time of day. The side-lying posture was used more in evening and has an ergonomic score of 6, i.e. a high MSD risk. Conclusions The survey showed that users are exposed to MSDs regardless of posture and time of day. Sitting postures are used more in the morning and afternoon while lying postures are used more in the evening. As long as the rate of use is so high (> 5 h per day), young people will remain highly exposed to MSDs. Keywords: Musculoskeletal disorders, Posture, Smartphone, Ergonomic assessment, Standing, Sitting, Lying, Walking, Cross-sectional