In-situ comparison of spinal postures during smartphone use versus non-use among university students

Nowadays it is common for young people to use the smartphone as the primary instrument for communication instead of desktop or laptop computer. Adopting the “head-down” posture for prolonged periods may lead to increased risk of neck-shoulder pain. Research in recent years have mainly examined the use of smartphones and tablet computers in the laboratory setting, involving short duration and standardized tasks. This field study compared the real-time spinal movements and postural variations during smartphone-use versus non-use in university students in their natural environment - the university campus. Ten males and eight females (mean age of 21.5+2.6 years) participated, with similar daily phone use time between the two sexes. Three-dimensional kinematics was recorded for 3 hours on a typical weekday while the participants went about their usual academic activities such as attending classes, meeting with other students or studying on their own. Five inertial motion sensors were attached to the cervical, thoracic and lumbar spinal regions, and the signals were captured on the data-logger worn on the waist. The active phone use time was captured on the smartphone of the participants during the data collection period. Kinematics data were recorded with a sampling frequency of 100 Hz and filtered using a low-pass Butterworth filter of 3rd order (Fcutoff: 3Hz). The data were examined in terms of: 1. Median 50th%APDF of the postural angles in the cervical, upper thoracic, lower thoracic and lumbar regions; 2. Zero crossing (ZC) per min, with a threshold set to the mean angle +10o before change of movement direction (Szeto et al., 2012) to assess changes in the amplitude and variations of the adopted spinal postures. Results showed that significantly greater degrees of cervical and upper thoracic flexion angles were adopted during phone use versus non-use time (p<0.01). The mean cervical flexion angle was recorded as 8.0o (+7.5) during phone use compared to -4.2o (+8.2) during non-use (p<0.01). There was also significantly greater frequency of postural variations (zero crossing per min) in all spinal regions in the sagittal plane (all p<0.05), and in some of the movements in the transverse and frontal planes. For example, the ZC per min in the cervical flexion plane was 10.5 (+6.3) per min during non-use compared to 5.5 (+3.1) during phone use. These results showed that the participants maintained a more static posture with less postural variations during phone use. The postural variables also showed some significant correlations with the self-reported pain score in the neck and upper back regions. The mean neck pain score among the participants was 2.1 (+1.6) for female participants and 2.4(+2.2) for male participants at baseline. The present results revealed that the university students maintained their neck and upper thoracic spine in more static postures and with increased flexion angles during phone use compared to non-use. This factor may contribute to increased risk of developing neck-shoulder pain in students population.