The effect of walking while typing on neck/shoulder patterns

Effects of anti-fatigue lenses on performance, muscle activity and subjective discomfort responses during a seated computer task

Anti-fatigue lenses (AFL) intend to provide health benefits in association with computer work. Their effects on visual and muscle discomfort mechanisms and task performance remain unclear. Twenty-three computer users (n = 12 males) underwent two 90-min computer sessions with AFL or placebo lenses. Eye strain, body discomfort, typing performance, upper trapezius (UT) activation amplitude and variability, and neck posture were analyzed for time, condition, and sex effects. No significant effects of condition were observed on the dependent measures evaluated. Discomfort increased over time (neck/shoulder: p < .001), more so in females (eye strain: p < .001). Females' UT activation amplitude was negatively correlated to eye strain in the placebo condition (p = .05).

The Effect of Cycling While Typing on Patterns of Upper Body Muscle Activation

OBJECTIVE

To investigate the effect of one's sex and pedaling intensity on upper body muscle activation patterns during typing while cycling.

BACKGROUND

Females are at a higher risk for computer work-related musculoskeletal disorders, and mobile workstations have been suggested to induce healthier muscular patterns compared with sitting. However, the neuromuscular characteristics of performing computer work in a cycling workstation have not been investigated.

METHOD

Twenty-two participants (10 females) completed a 60-min computer typing task while pedaling on a cycle ergometer at two different intensities (25%, 4% heart rate reserve). Surface electromyography (EMG) was recorded from seven muscles of the upper body. Effects of time, sex, and intensity were assessed for muscle activation (RMS), activation variability (CV), and normalized mutual information (NMI) via generalized estimating equations.

RESULTS

With time, neck/shoulder CV increased in males during higher pedaling intensity, whereas in females it decreased during lower intensity. In females, RMS of neck/shoulder and NMI of neck/shoulder muscle pairs were lower, whereas forearm RMS was 34.2% higher with higher intensity cycling compared with lower intensity. Lower back RMS decreased 28.3% in the initial half of the task in females, but in males it increased 14.4% in the later half.

CONCLUSION AND APPLICATION

Cycling workstation showed a sex- and intensity-specific EMG response. These differing responses should be considered when implementing the use of cycling workstation and may be important for preventing/managing sex-specific muscle fatigue and musculoskeletal disorders.

The effects of dual screen layout on neck-shoulder muscle activity and head-neck posture variability during computer tasks

BACKGROUND

Larger dual screens have been widely used during office work and their biomechanical exposure should be explored.

OBJECTIVE

To investigate the biomechanical effect of two dual screen layouts on neck-shoulder muscle activity and the variability of head-neck posture in computer users.

METHODS

A preliminary study of the user-preferred dual screen angles was carried out in V-shaped and L-shaped layouts. Twenty healthy participants aged 19 to 26 years were recruited and assigned to perform reading, typing, and searching tasks for 30 minutes in both workstation layouts. Electromyography was measured at bilateral cervical erector spinae (CES), sternocleidomastoid (SCM), and upper trapezius (UT). The head-neck lateral bending, rotation, and flexion angles were recorded. The visual analog scale (VAS) was used to evaluate visual strain.

RESULTS

The muscle activity at the left UT and right CES sites when using the V-shaped layout was significantly higher than the L-shaped. There were significant differences in head-neck rotation and flexion angles between the two layouts in reading and typing tasks. In the searching task, there was no significant difference in the head-neck rotation and flexion angles between the two layouts. The visual strain score was significantly higher in the V-shaped layout.

CONCLUSION

The CES and UT muscles displayed higher levels of activation while using the V-shaped layout in comparison to the L-shaped layout. The head-neck rotation and flexion angles differed due to varied types of work when using V-shaped and L-shaped layouts.

A Study on sEMG-Based Motor Variability and Functional Connectivity of the Upper Limb Depending on Weight Distributions in a Handle of a Cordless Stick-Type Vacuum Cleaner

This study investigated the muscle activities, motor variability, and functional connectivity of the upper limb as a function of weight distributions in a handle of a cordless stick-type vacuum cleaner. Eighteen female college students with experience of vacuum cleaner-use participated in testing. Five handles with different centers of mass (CM) were prepared (centroid, top-rear, top-front, bottom-front, and bottom-rear), and electromyography for the muscles of the upper limb were measured during vacuuming. The results showed that the %MVC values of the Extensor Carpi Ulnaris (p = 0.0038) and Deltoid Middle (p = 0.0094) increased but that of the Biceps Brachii (p = 0.0001) decreased, as the CM moved from the top to bottom area of the handle. The motor variability of the Extensor Carpi Ulnaris (p = 0.0335) and Brachioradialis (p = 0.0394) significantly varied depending on the CM locations but failed to show significance in the post-hoc analyses. Lastly, the functional connectivity values of the muscle pairs such as the Extensor Carpi Ulnaris–Deltoid Middle (p = 0.0016), Extensor Carpi Ulnaris–Upper Trapezius (p = 0.0174), Brachioradialis–Biceps Brachii (p = 0.0356), and Biceps Brachii–Upper Trapezius (p = 0.0102) were significantly altered as a function of the CM locations. The lowest functional connectivity was found with the handle of which CM was at centroid.

Effect of standing desk use on cognitive performance and physical workload while engaged with high cognitive demand tasks

It is clear that the cognitive resources invested in standing are greater than in sitting, but six of eight previous studies suggested that there is no difference in cognitive performance. This study investigated the effects of sitting and standing workstations on the physical workload and cognitive performance under variable cognitive demand conditions. Fifteen participants visited two times for testing sitting and standing workstations, and were asked to play two difficulty levels of Tetris game for 40 min while kinematic variables, CoP regularity, CoP SD, and cognitive performances were captured every 5 min. Results revealed a more neural posture in standing than in sitting, but using the standing workstation degraded attention and executive function. The CoP SD was 7 times greater in standing, but the CoP regularity was 1/4 in sitting, denoting greater attentional investment while engaged at the standing workstation.

Effects of cycling while typing on upper limb and performance characteristics

Active computer workstations may help reduce workplace sedentarism. However, their impact on the upper limb musculoskeletal system is unknown. Subjects participated in two 60-min computer laptop-based Bike-and-Type sessions at different cycling intensities (LOW, HIGH). Upper trapezius and wrist extensor muscle blood flow, sensitivity and pain thresholds, and typing performance were measured intermittently. Neck/shoulder discomfort increased over time (p < 0.001), and was higher in the HIGH intensity (p = 0.036). Blood flow to the trapezius (p = 0.041) and wrist (p = 0.021) muscles were higher during HIGH, and wrist blood flow increased over time (p = 0.01). Trapezius sensitivity threshold significantly decreased over time (p = 0.003). There were no effects on pressure pain thresholds (interaction p = 0.091). Average typing speed was greater during HIGH (p = 0.046) and increased over time (p < 0.001). Time spent biking while typing effectively improved performance, which may facilitate muscle regeneration, although effects depend on biking intensity.

Health and productivity at work: which active workstation for which benefits: a systematic review

In order to reduce sedentary behaviour at work, research has examined the effectiveness of active workstations. However, despite their relevance in replacing conventional desks, the comparison between types of active workstations and their respective benefits remains unclear. The purpose of this review article is thus to compare the benefits between standing, treadmill and cycling workstations. Search criteria explored Embase, PubMed and Web of Science databases. The review included studies concerning adults using at least two types of active workstations, evaluating biomechanical, physiological work performance and/or psychobiological outcomes. Twelve original articles were included. Treadmill workstations induced greater movement/activity and greater muscular activity in the upper limbs compared with standing workstations. Treadmill and cycling workstations resulted in elevated heart rate, decreased ambulatory blood pressure and increased energy expenditure during the workday compared with standing workstations. Treadmill workstations reduced fine motor skill function (ie, typing, mouse pointing and combined keyboard/mouse tasks) compared with cycling and standing workstations. Cycling workstations resulted in improved simple processing task speeds compared with standing and treadmill workstations. Treadmill and cycling workstations increased arousal and decreased boredom compared with standing workstations. The benefits associated with each type of active workstation (eg, standing, treadmill, cycling) may not be equivalent. Overall, cycling and treadmill workstations appear to provide greater short-term physiological changes than standing workstations that could potentially lead to better health. Cycling, treadmill and standing workstations appear to show short-term productivity benefits; however, treadmill workstations can reduce the performance of computer tasks.

Effects of standing on typing task performance and upper limb discomfort, vascular and muscular indicators

Standing is a popular alternative to traditionally seated computer work. However, no studies have described how standing impacts both upper body muscular and vascular outcomes during a computer typing task. Twenty healthy adults completed two 90-min simulated work sessions, seated or standing. Upper limb discomfort, electromyography (EMG) from eight upper body muscles, typing performance and neck/shoulder and forearm blood flow were collected. Results showed significantly less upper body discomfort and higher typing speed during standing. Lower Trapezius EMG amplitude was higher during standing, but this postural difference decreased with time (interaction effect), and its variability was 68% higher during standing compared to sitting. There were no effects on blood flow. Results suggest that standing computer work may engage shoulder girdle stabilizers while reducing discomfort and improving performance. Studies are needed to identify how standing affects more complex computer tasks over longer work bouts in symptomatic workers.

Effects of Dual Monitor Computer Work Versus Laptop Work on Cervical Muscular and Proprioceptive Characteristics of Males and Females

OBJECTIVE

The effects of performing a 90-minute computer task with a laptop versus a dual monitor desktop workstation were investigated in healthy young male and female adults.

BACKGROUND

Work-related musculoskeletal disorders are common among computer (especially female) users. Laptops have surpassed desktop computer sales, and working with multiple monitors has also become popular. However, few studies have provided objective evidence on how they affect the musculoskeletal system in both genders.

METHODS

Twenty-seven healthy participants (mean age = 24.6 years; 13 males) completed a 90-minute computer task while using a laptop or dual monitor (DualMon) desktop. Electromyography (EMG) from eight upper body muscles and visual strain were measured throughout the task. Neck proprioception was tested before and after the computer task using a head-repositioning test. EMG amplitude (root mean square [RMS]), variability (coefficients of variation [CV]), and normalized mutual information (NMI) were computed.

RESULTS

Visual strain ( p < .01) and right upper trapezius RMS ( p = .03) increased significantly over time regardless of workstation. Right cervical erector spinae RMS and cervical NMI were smaller, while degrees of overshoot (mean = 4.15°) and end position error (mean = 1.26°) were larger in DualMon regardless of time. Effects on muscle activity were more pronounced in males, whereas effects on proprioception were more pronounced in females.

CONCLUSION

Results suggest that compared to laptop, DualMon work is effective in reducing cervical muscle activity, dissociating cervical connectivity, and maintaining more typical neck repositioning patterns, suggesting some health-protective effects.

APPLICATION

This evidence could be considered when deciding on computer workstation designs.