ah that all-too-familiar ache at the back of the neck with roughly 80% of jobs being sedentary and often requiring several hours of sitting stooped in front of a computer screen neck pain is a growing occupational hazard smartphones and other devices have also caused people to bend their necks for prolonged periods but is bad posture solely to blame in a recent study researchers at texas a&m university have found that while poor neck and head postures are indeed the primary determinants of neck pain body mass index age and the time of the day also influence the necks ability to perform sustained or repeated movements neck pain is one of the leading and fastest-growing causes of disability in the world said dr xudong zhang professor in the wm michael barnes '64 department of industrial and systems engineering our study has pointed to a combination of work and personal factors that strongly influence the strength and endurance of the neck over time more importantly since these factors have been identified they can then be modified so that the neck is in better health and pain is avoided or deterred the results of the study are published online in the journal human factors a flagship journal in the field of human factors and ergonomics according to the global burden of disease study by the institute for health metrics and evaluation neck pain is ranked as the fourth leading cause of global disability one of the main reasons for neck pain has been attributed to lifestyle particularly when people spend long durations of time with their necks bent forward however zhang said a systematic quantitative study has been lacking on how personal factors such as sex weight age and work-related habits can affect neck strength and endurance for their experiments zhang and his team recruited 20 adult men and 20 adult women with no previous neck-related issues to perform controlled head-neck exertions in a laboratory setting further instead of asking the participants to hold a specific neck posture for a long time similar to what might happen at a workplace they performed sustained-till exhaustion head-neck exertions in the laboratory conducting experiments where subjects do long tasks with their neck can take several hours of data collection which is not very practical for the experimenters and of course the participants in our study said zhang to solve this problem our experiments were strategically designed to mimic workplace neck strains but in a shorter period of time in these exercises subjects were seated and asked to put on an augmented helmet that allowed them to exert measurable force by the neck then the researchers asked them to either keep their necks straight or maintain their neck tilted in a forward or backward position in this position a force was applied to their head and neck on an adjustable frame this exertion was either to their maximum capacity or half of it before testing the researchers noted their subjects age body mass index and the time of day when zhang and his team analyzed their data they found that as expected work-related factors like head/neck posture play a very important role in determining both neck strength and endurance but they also observed that while there was no significant difference between male and female subjects in neck endurance body mass index was a significant predictor of neck endurance also to their surprise the time of day affected the necks ability to sustain an exertion without fatigue it is intuitive to think that over the course of the day our necks get more tired since we use it more said zhang but roughly half of our participants were tested in the morning and the remaining in the afternoon also some of the participants had day jobs and some worked the night shift despite this we consistently found the time-of-day effect on neck endurance the researchers said their database of neck strength and endurance is also necessary for building advanced musculoskeletal biomechanical models of the neck which can then be used to for example tease apart specific neck muscles that are more vulnerable to injury looking ahead we might have the data to begin evaluating if patients recovering from neck injuries are ready to return to work based on whether their neck strength and endurance are within the norm said zhang also engineers and designers could utilize our data to make wearable devices like helmets that are more ergonomic and less stressful on the neck other contributors to this work include dr suman chowdhury from texas tech university and yu zhou bocheng wan and curran reddy from the industrial and systems engineering department this research is funded by the national institute for occupational safety and health part of the centers for disease control and prevention