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Neck muscle activation and head kinematics when using a smartphone while walking

Using a smartphone while walking has been common in countries with high smartphone penetration rates. While pedestrian safety issues have been studied frequently, research regarding ergonomics issues such as neck discomfort of smartphone use while walking has been limited. An experimental study was conducted to evaluate the neck muscular load of smartphone use while walking. Twenty-one asymptomatic young smartphone owners conducted one-handed browsing and two-handed texting while walking on a treadmill. Their neck muscle activation level, head and upper back posture were quantified. Compared to when walking upright without using a smartphone, the two smartphone-use tasks demanded 33.3% to 101.8% more activation of the neck extensor muscles. Mean head tilt angles (relative to upright standing) were 28.9° and 36.9° for the one-handed browsing and two-handed texting, respectively. Between the two smartphone tasks, the head tilt angle and the muscle activation level were significantly greater for texting than for browsing. Results indicated that conducting two-handed texting while walking would pose larger muscular load to the neck extensor muscles compared to when conducting one-handed browsing while walking due to the larger head tilt angle.