Repetitive or prolonged head flexion posture while using a smartphone is known as one of risk factors for pain symptoms in the neck. To quantitatively assess the amount and range of head flexion of smartphone users, head forward flexion angle was measured from 18 participants when they were conducing three common smartphone tasks (text messaging, web browsing, video watching) while sitting and standing in a laboratory setting. It was found that participants maintained head flexion of 33-45° (50th percentile angle) from vertical when using the smartphone. The head flexion angle was significantly larger (p < 0.05) for text messaging than for the other tasks, and significantly larger while sitting than while standing. Study results suggest that text messaging, which is one of the most frequently used app categories of smartphone, could be a main contributing factor to the occurrence of neck pain of heavy smartphone users. Practitioner Summary: In this laboratory study, the severity of head flexion of smartphone users was quantitatively evaluated when conducting text messaging, web browsing and video watching while sitting and standing. Study results indicate that text messaging while sitting caused the largest head flexion than that of other task conditions.
BackgroundNon-specific low back pain (LBP) has been one of the most frequently occurring musculoskeletal problems. Impairment in the mechanical stability of the lumbar spine has been known to lower the safety margin of the spine musculature and can result in the occurrence of pain symptoms of the low back area. Previously, changes in spinal stability have been identified by investigating recruitment patterns of low back and abdominal muscles in laboratory experiments with controlled postures and physical activities that were hard to conduct in daily life. The main objective of this study was to explore the possibility of developing a reliable spine stability assessment method using surface electromyography (EMG) of the low back and abdominal muscles in common physical activities.MethodsTwenty asymptomatic young participants conducted normal walking, plank, and isometric back extension activities prior to and immediately after maintaining a 10-min static upper body deep flexion on a flat bed. EMG data of the erector spinae, external oblique, and rectus abdominals were collected bilaterally, and their mean normalized amplitude values were compared between before and after the static deep flexion. Changes in the amplitude and co-contraction ratio values were evaluated to understand how muscle recruitment patterns have changed after the static deep flexion.ResultsMean normalized amplitude of antagonist muscles (erector spinae muscles while conducting plank; external oblique and rectus abdominal muscles while conducting isometric back extension) decreased significantly (P < 0.05) after the 10-min static deep flexion. Normalized amplitude of agonist muscles did not vary significantly after deep flexion.ConclusionsResults of this study suggest the possibility of using surface EMG in the evaluation of spinal stability and low back health status in simple exercise postures that can be done in non-laboratory settings. Specifically, amplitude of antagonist muscles was found to be more sensitive than agonist muscles in identifying changes in the spinal stability associated with the 10-min static deep flexion. Further research with various loading conditions and physical activities need to be performed to improve the reliability and utility of the findings of the current study.
Body discomfort development of desktop touchscreen users may be influenced by their hand usage pattern. Findings of this laboratory study suggest that user discomfort may be moderated by placing menu items in the lower area within the display or training users to alternate hands when conducting touch gestures.
Finger touch interface has been less popular for desktop touchscreens than for mobile IT devices, and it could be attributable to difficulties in reaching and conducting touch gestures comfortably and accurately. In the current study, performance variation of tap gesture by target location and display position was quantitatively evaluated to generate empirical data that can be used to determine proper target location and display position for improving usability of desktop touchscreen interface. Twenty one participants in three handedness groups participated in a laboratory experiment. Touch error, time to complete a single tap gesture, and a hand of choice for tap gesture were measured while conducting repetitive tap gestures on fifteen distributed targets in two positions (upright, near flat) of a 23" touchscreen display. Results found significant differences (p<0.05) in the performance measures and hand preference between target locations. Greater touch error and shorter completion time were observed from targets on the lower area of the display. To improve the usability of desktop touchscreen, it is recommended to place targets in lower areas with larger sensing area or target size. It is also recommended to determine proper target location and size depending on user's individual handedness.
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