In a biomechanical study in 2014 Dr Hansrajj demonstrated that the more the neck flexes to look at a mobile phone, the more weight loads through the cervical spine, specifically; 27 pounds, at 30 degrees it’s 40 pounds, at 45 degrees it’s 49 pounds, and at 60 degrees it's 60 pounds! 
Published online, ahead of print, a Swedish group have been following a group of young adults (20-24years old) over the last 5 years.  They assessed a whole host of factors, including their mobile phone usage (e.g. number of text messages sent per day) and presence of muscular pain, such as neck pain. Reassessing this group of almost 8000 young adults periodically over 5 years, they found that overall the presence of neck pain was related to the number of text messages sent. Digging a little deeper into the data, in those young adults who went on to develop neck pain during the study, symptoms were only present after one year and did not persist at 5 years.
These studies are headline grabbing, and we need to be clear - the dots can not yet be connected directly between mobile phone use, wear and tear and subsequent issues like CSM. However the thought process appears to have some logic to it. As we cannot live without mobile phones and technology, whilst we wait for more definitive data to emerge, I suppose its simply 'chin up and text on'.
 Hansrajj KK Surg Technol Int Assessment of stresses in the cervical spine caused by posture and position of the head Jan 2017
 Gustafason E et al Appel Ergon Texting on mobile phones and musculoskeletal disorders in young adults: a five year cohort study. Jan 2017
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