A large majority of the world's 3.4 billion smartphone users are putting their necks at risk every time they send a text, scientist say. 'Text neck,' as it is colloquially called, places stress on the spine and alters the neck's natural curve, increasing the likelihood of associated soft tissue discomfort. The study, published in the journal PLOS One, highlights the high ergonomic risks to smartphone users, particularly young people, who are experiencing neck pain earlier than previous generations. Researchers from Khon Kaen University in Thailand and the University of South Australia video recorded 30 smartphone users in Thailand aged between 18-25 years, who spend up to eight hours a day on their phones. Using a Rapid Upper Limb Assessment tool (RULA) to measure ergonomic risk levels, they found that the average score for the participants was 6, compared to an acceptable score of between 1-2. "The results identified issues with unsuitable neck, trunk and leg postures which lead to musculoskeletal disorders," said lead researcher Suwalee Namwongsa, from Khon Kaen University. RULA has been used to assess the ergonomic impacts of desktop computers and laptops in the past but this is believed to be the first time the tool has been used to assess ergonomic risk levels of excessive smartphone use. Rose Boucaut, a physiotherapist at University of South Australia, said the awkward postures adopted by smartphone users can adversely affect the soft tissues. "Smartphone users typically bend their neck slightly forward when reading and writing text messages. They also sometimes bend or twist their neck sideways and put their upper body and legs in awkward positions," said Boucaut. "These postures put uneven pressure on the soft tissues around the spine, that can lead to discomfort," she said. In a seperate study published in the journal Work, the team surveyed 779 Thai university students who use smartphones, with 32 per cent reporting neck pain, 26 per cent shoulder pain, 20 per cent upper back pain and 19 per cent wrist and hand pain. Musculoskeletal disorders were more common among students with higher smartphone use (more than five hours a day) and those who smoked and did little exercise. Female smartphone users also experienced far more musculoskeletal disorders than men - 71 per cent compared to 28 per cent. "Health practitioners need to educate their patients about safe postures and curtailing time spent using smartphones to help prevent these issues," Boucaut said.