An ergonomics study of thumb movements on smartphone touch screen

The impact of smartphone use duration and posture on the prevalence of hand pain among college students

BACKGROUND

Excessive smartphone usage among students can lead to discomfort in their hands and fingers. This study investigates the impact of smartphone holding posture, duration of usage, and the prevalence of wrist and finger pain among university students.

METHODS

This cross-sectional study involved 213 university students who were selected based on inclusion criteria. Data was collected through a demographic information questionnaire. Participants self-reported five different postures for holding and interacting with a smartphone. The prevalence, frequency, severity, and interference of wrist and finger discomfort were assessed using the Cornell Hand Discomfort Questionnaires (CHDQ).

RESULTS

The study revealed that the average age of participants was 21.3 ± 2.2 years. On average, they had been using smartphones for 7.9 ± 3.1 years and spent an average of 4.9 ± 2.5 h daily holding them in their hands. In terms of discomfort, more than 25% of students reported pain in areas C (thumb finger), E (Palm Pollicis), and F (wrist) of the right hand, which was significantly related to the duration of holding the smartphone in that hand. Additionally, smartphone holding duration significantly affected areas D (palm) and F of the left hand, with over 11% of students experiencing discomfort. The most prevalent posture among students (41% of participants) involved holding the smartphone with the right hand only, with the thumb touching the screen. Notably, areas B (χ2 = 21.7), C (χ2 = 10.27), D (χ2 = 65.54), and E (χ2 = 59.49) of the right hand, as well as areas C (χ2 = 6.58) and E (χ2 = 44.28) of the left hand, exhibited significant associations with the postures of holding the smartphone.

CONCLUSIONS

The duration of smartphone use and the postures in which it is held contribute to the prevalence of discomfort in the thumb area and related muscles among right-handed students.

Prevalence of Thumb and Wrist Pain Among Smartphone Users in the Saudi Arabian General Population: A Cross-Sectional Study

Background This study aims to investigate the prevalence of thumb and wrist pain among smartphone users in the general population of Saudi Arabia, examining the potential links between the duration and frequency of smartphone usage, specific smartphone activities, and the occurrence of discomfort in the thumb and wrist. Methodology This descriptive cross-sectional study was conducted at Jazan University, Saudi Arabia, between July 2022 and June 2023. The questionnaire developed following an extensive literature review, covered demographic information, smartphone usage patterns, assessment of thumb or wrist pain, and evaluation of the impact of this discomfort. Descriptive statistical methods were employed, and relationships between thumb or wrist pain and demographic variables were analyzed using chi-square and Wilcoxon rank-sum tests. Results In total, 811 participants were included in this study. Approximately 322 (39.7%) study participants reported wrist or thumb pain. Notably, female sex (P = 0.001) and prolonged daily smartphone usage exceeding five hours (P = 0.045) were linked to thumb or wrist pain. Additionally, emailing on smartphones was linked to thumb or wrist pain (P = 0.04). Concerning smartphone ergonomics, the majority of respondents reported holding their phones with one hand (215, 66.77%), in a downward position (290, 90.06%), and with their wrists bent downward (136, 42.24%). Conclusions Our study highlights a relatively high prevalence of wrist and thumb pain among smartphone users in the general Saudi Arabian population. Furthermore, we identified a connection between prolonged smartphone use and wrist and thumb pain, with a more pronounced prevalence observed among females.

Prevalence of Upper Limb Musculoskeletal Disorders and Their Association with Smartphone Addiction and Smartphone Usage among University Students in the Kingdom of Saudi Arabia during the COVID-19 Pandemic-A Cross-Sectional Study

This study aimed to investigate the prevalence of upper limb musculoskeletal disorders (MSDs) and their association with smartphone addiction and smartphone usage among university students in the Kingdom of Saudi Arabia during the COVID-19 pandemic. A total of 313 university students aged 18 years and older who owned a smartphone and used it during the preceding 12 months participated in this cross-sectional study. The prevalence of upper limb MSDs, smartphone addiction/overuse, and levels of physical activity were recorded using the standardized Nordic musculoskeletal questionnaire, the smartphone addiction scale (short version), and the international physical activity questionnaire (short form), respectively. Data collection was performed on campus between March and May 2021. Binary logistic regression was used to determine the association between the prevalence of upper limb MSDs and smartphone addiction/overuse and levels of physical activity. The 12-month prevalence of MSDs of the shoulder, elbow, and wrist/hand regions due to smartphone use among participants was found to be 20.13%, 5.11%, and 13.42%, respectively. Shoulder (odds ratio (OR) = 11.39, 95% confidence interval (CI) = 4.64−27.94, p < 0.001), elbow (OR = 15.38, 95% CI = 1.92−123.26, p = 0.01), and wrist/hand MSDs (OR = 7.65, 95% CI = 2.75−21.22, p < 0.001) were more prevalent among participants who were categorized as having smartphone addiction/overuse measures. Promoting awareness about the healthy use of smartphones, including postural education and decreasing screen time, is necessary to reduce smartphone-related MSDs.

Effect of icon size, icon position and sex on clicking motion when operating smartphones with single hand

Nowadays, increasingly more situations exist where smartphones are operated with one hand, requiring an in-depth understanding of human-computer interaction in single-hand scenarios. 104 volunteers (57 men, 47 women) participated in this study. We aimed to explore thumb movements with the right and left hand on smartphone touchscreens at different icon sizes (50, 80, 110 and 140 rpx) in different operation areas (a 4*7 icon matrix). The results partially conformed to Fitts' Law. The movement time (MT) significantly increased as the icon size decreased, but this effect was not found over 110 rpx. The MT increased with distance in the vertical direction, but icons with the same horizontal distance had different MTs, indicating that one-handed operation restricted the click on the same side. Additionally, subjects rated 140 rpx better than other sizes, and men clicked faster than women. Suggestions regarding one-handed interface design for different hands of different sexes are provided. Practitioner summary: This study investigated how icon size, position and sex influenced one-thumb click usability on touch-screen mobile phones with different hands of different sexes. The results indicate single-hand operation partially conformed to Fitts' Law. We suggested the most economical and comfortable size and the fast operation area in one-handed interface design.Abbreviations: MT: movement time; ID: index of difficulty; RPX: responsive pixel; NASA-TLX: task load index of National Aeronautics and Space Administration; ANOVA: analysis of variance.

Repetitive patterns in the locations of touch errors for two-thumb text entry on a smartphone

This study investigated repetitive patterns in the locations of touch errors as a function of the shapes and positions of soft buttons on a smartphone for two-thumb text entry. Forty-three right-handed college students with smartphone-use experience were recruited for testing. An experimental application was developed, and the locations and frequencies of touch errors were measured for the button combinations of seven shapes and eight positions. More than 70.0 % of touch errors occurred within 2 mm from the boundaries of the buttons. In terms of direction, touch errors were primarily observed below the buttons, across all the button shapes and positions. Simultaneously, touch errors often appeared on the lateral sides of the buttons: (1) close to the proximal phalange of the thumbs when the buttons were placed near the initial positions of the thumbs and (2) close to the initial positions of the thumbs when the buttons were placed near the top and bottom ends of the keyboard.

Understanding the Relationship between User’s Subjective Feeling and the Degree of Side Curvature in Smartphone

To develop a flexible display, smartphones with edge screens with curved displays on both sides of the main screen have been used widely. Considering that small differences in the form of smartphones, such as length, width, and thickness, could affect user experience, the effects of the curvature of the edge screen should be identified. This study aimed to investigate the effects of the curvature of edge screens on subjective feelings of smartphone users and to find out the optimal curvature. In the experiment, four nonfunctional samples with different radii of curvature (4R/6R/8R/10R) were used as samples, and participants evaluated the five subjective feelings: grip/control comfort, front/side visibility, and stability of the samples with four usage patterns. Our results revealed that 8R is the optimal curvature for the edge screen based on subjective feelings in smartphone usage. Moreover, the effect of the curvature of the edge screen on grip comfort and control comfort varied according to the usage patterns. The results of this study can be applied to design of the curvature of edge screens in smartphones and it is expected that it will contribute to improvement of users’ satisfaction.

Musculoskeletal disorder and pain associated with smartphone use: A systematic review of biomechanical evidence

The number of smartphone users is growing dramatically. Using the smartphone frequently forces the users to adopt an awkward posture leading to an increased risk of musculoskeletal disorders and pain. The objective of this study is to conduct a systematic review of studies that assess the effect of smartphone use on musculoskeletal disorders and pain. A systematic literature search of AMED, CINAHL, PubMed, Proquest, ScienceDirect using specific keywords relating to smartphone, musculoskeletal disorders and pain was conducted. Reference lists of related papers were searched for additional studies. Methodological quality was assessed by two independent reviewers using the modified Downs and Black checklist. From 639 reports identified from electronic databases, 11 were eligible to include in the review. One paper was found from the list of references and added to the review. The quality scores were rated as moderate. The results show that muscle activity of upper trapezius, erector spinae and the neck extensor muscles are increased as well as head flexion angle, head tilt angle and forward head shifting which increased during the smartphone use. Also, smartphone use in a sitting position seems to cause more shift in head-neck angle than in a standing position. Smartphone usage may contribute to musculoskeletal disorders. The findings of the included papers should be interpreted carefully in light of the issues highlighted by the moderate-quality assessment scores.

Armrests and back support reduced biomechanical loading in the neck and upper extremities during mobile phone use

Mobile phone use is known to be associated with musculoskeletal pain in the neck and upper extremities because of related physical risk factors, including awkward postures. A chair that provides adequate support (armrests and back support) may reduce biomechanical loading in the neck and shoulder regions. Therefore, we conducted a repeated-measures laboratory study with 20 participants (23 ± 1.9 years; 10 males) to determine whether armrests and back support during mobile phone use reduced head/neck flexion, gravitational moment, and muscle activity in the neck and shoulder regions. The results showed that the chair support (armrests and back support) reduced head/neck flexion (p < 0.001), gravitational moment (p < 0.001), and muscle activity (p < 0.01) in the neck and shoulder regions significantly compared to no chair support. These results indicate that a chair with adequate support can be an effective intervention to reduce the biomechanical exposures and associated muscular pain in the neck and shoulders during mobile phone use.

Texting with touchscreen and keypad phones - A comparison of thumb kinematics, upper limb muscle activity, exertion, discomfort, and performance

This study aimed to compare thumb kinematics and upper limb muscle activity, and the influence of hand size, when texting on a keypad smartphone and a touchscreen smartphone. Furthermore, the study compared exertion, discomfort, and performance when texting on the two phones. The thumb kinematics were tracked using a 3D motion analysis system and muscle activity was registered in six upper limb muscles using surface electromyography in 19 participants. When texting on the touchscreen phone compared to the keypad phone thumb flexion (p = 0.008) and flexion/extension range of motion were smaller (p = 0.02), the thumb was on average less internally rotated (p = 0.02), and activity (50th and 90th percentile) of the thumb and forearm muscles was lower (p ≤ 0.05). The differences in thumb flexion were found only in the group with shorter hands and the differences in muscle activity was found only in the group with longer hands. These findings suggest there are differences in risks for developing musculoskeletal disorders during smartphone use with different key activation mechanisms and different hand sizes.

Smartphone form factors: Effects of width and bottom bezel on touch performance, workload, and physical demand

This study aimed at investigating the effect of two smartphone form factors (width and bottom bezel) on touch behaviors with one-handed interaction. User experiments on tapping tasks were conducted for four widths (67, 70, 72, and 74 mm) and five bottom bezel levels (2.5, 5, 7.5, 10, and 12.5 mm). Task performance, electromyography, and subjective workload data were collected to examine the touch behavior. The success rate and task completion time were collected as task performance measures. The NASA-TLX method was used to observe the subjective workload. The electromyogram signals of two thumb muscles, namely the first dorsal interosseous and abductor pollicis brevis, were observed. The task performances deteriorated with increasing width level. The subjective workload and electromyography data showed similar patterns with the task performances. The task performances of the bottom bezel devices were analyzed by using three different evaluation criteria. The results from these criteria indicated that tasks became increasingly difficult as the bottom bezel level decreased. The results of this study provide insights into the optimal range of smartphone form factors for one-handed interaction, which could contribute to the design of new smartphones.

The associations of mobile touch screen device use with musculoskeletal symptoms and exposures: A systematic review

BACKGROUND

The use of mobile touch screen devices (MTSDs) has increased rapidly over the last decade, and there are concerns that their use may have negative musculoskeletal consequences; yet evidence on the association of MTSD use with musculoskeletal symptoms and exposures is currently dispersed. The aim of this study was to systematically review available literature on musculoskeletal symptoms and exposures associated with MTSD use. The synthesised information may facilitate wise use of MTSDs and may identify areas in need of further research.

METHODS

EMBASE, Medline, Scopus, PsycINFO and Proquest electronic databases were searched for articles published up to June 2016, using keywords describing MTSD, musculoskeletal symptoms (e.g. pain, discomfort) and musculoskeletal exposures (e.g. posture, muscle activity). Two reviewers independently screened the articles, extracted relevant data and assessed methodological quality of included studies. Due to heterogeneity in the studies, a meta-analysis was not possible and a structured narrative synthesis of the findings was undertaken.

RESULTS

A total of 9,908 articles were screened for eligibility with 45 articles finally included for review. Included articles were of cross-sectional, case-control or experimental laboratory study designs. No longitudinal studies were identified. Findings were presented and discussed in terms of the amount, features, tasks and positions of MTSD use and its association with musculoskeletal symptoms and musculoskeletal exposures.

CONCLUSIONS

There is limited evidence that MTSD use, and various aspects of its use (i.e. amount of usage, features, tasks and positions) are associated with musculoskeletal symptoms and exposures. This is due to mainly low quality experimental and case-control laboratory studies, with few cross-sectional and no longitudinal studies. Further research is warranted in order to develop guidelines for wise use of MTSDs.

The effect of smartphone addiction on hand joints in psoriatic patients: an ultrasound-based study

BACKGROUND

Distal interphalangeal (DIP) arthritis is a frequent form of psoriatic arthritis being often linked to nail psoriasis. Modern society is characterized by overuse of smartphones. Indeed, literature has recently focalized on research into smartphone addiction and health-related problems.

OBJECTIVES

As smartphone addiction is able to determine overuse and repeated movements of DIP joints and nails, the aim of this study was to evaluate the impact of smartphone use on hand joints of young psoriatic patients.

METHODS

An observational study involving four different groups such as non-smartphone-addicted (SA) psoriatic patients, SA psoriatic patients, non-SA controls and SA controls was performed. Each subject underwent an ultrasound examination of both hands by three independent and blinded to group assignment radiologists. A specific score was used to evaluate the inflammatory state of the analysed joints.

RESULTS

The total ultrasound score was statistically significantly higher in SA controls respect to non-SA controls (3.4 vs. 1.4; P < 0.05) as well as in SA psoriasis patients compared to non-SA psoriatic subjects (15.2 vs. 6.7; P < 0.01). Higher mean of ultrasound score was found for left hand in controls (both SA or not) and for right hand in psoriatic subjects (both SA or not), however without reaching statistical significance.

CONCLUSIONS

Smartphone overuse was found to be linked with higher signs of inflammation of musculoskeletal structures of hands joints in both psoriasis and controls through ultrasound examination. Therefore, smartphone overuse may be a factor which facilitate or speed up the possible development of psoriatic arthritis.

Effects of button position on a soft keyboard: Muscle activity, touch time, and discomfort in two-thumb text entry

Intensive use of the thumbs for text entry on smartphones may contribute to discomfort, pain, or musculoskeletal disorders. This study investigated the effect of twenty-five button positions (5 rows × 5 columns) on a soft keyboard for two-thumb entry. Two experiments measured muscle activity, touch time, and discomfort as a function of the button positions. In Phase I, the muscle activities of two intrinsic (abductor pollicis brevis and first dorsal interossei) and two extrinsic (abductor pollicis longus and extensor digitorum communis) muscles associated with thumb motions were observed for ten college students (age: 24.2). In Phase II, touch time and discomfort were measured for 40 college students (age: 23.6). The results demonstrated that the %MVCs of the intrinsic muscles significantly increased when the thumbs flexed and abducted. Also, the button positions near the rest positions of the thumbs resulted in significantly shorter touch times (0.66 s) and lower discomfort ratings (0.70 pt) than their peripheral buttons (0.76 s; 2.29 pt).

Thumb performance of elderly users on smartphone touchscreen

This study investigated the relationship between thumb muscle activity and thumb operating tasks on a smartphone touchscreen in elderly users (right hand posture). Three thumb muscles were targeted in the experiment, namely, abductor pollicis brevis, abductor pollicis longus (APL) and first dorsal interosseous (FDI). The results showed that the elderly participants developed fatigue rapidly and tapped more slowly when operating on smaller buttons (diameter 3.0 mm compared with 9.0 mm) and moving in the flexion–extension (compared with adduction–abduction) orientation. Meanwhile, electromyography and perceived exertion evaluation revealed significant increases in FDI in the small button task, and results for APL were significantly greater in the flexion–extension task. This study suggests that the use of small touch-buttons and flexion–extension movement should be minimised in the handheld touchscreen interface design for elderly users.

Effects of screen size on smartphone functionality and usability for stroke patients with hemiparalysis

[Purpose] The effect of screen size on smartphone functionality and usability for patients with stroke, considering both the non-dominant and dominant hand smartphone usage, was investigated in this study. [Subjects and Methods] Thirteen patients with stroke participated in this study—five pre-non-dominant hand users and eight pre-dominant hand users. The smartphone screen sizes used were 4.2, 4.5, and 5.6 inches. Usability was assessed in terms of discomfort experienced during dragging operations, which was self-reported using a four-point Likert scale. Functionality was assessed in terms of completion time and the frequency of errors in the task requiring users to quickly touch numbers 0 through 9 in order on the keypad. [Results] For all three screen sizes, a significant difference between the dominant and non-dominant hands was found in usability, completion time, and frequency of errors. For dominant hand users, differences in usability and completion time were found among the three screen sizes. Among the three screen sizes, no difference in the frequency of errors was found in either of the groups. [Conclusion] This study will be useful as basic research on usability and functionality with stroke patients using only pre-non-dominant or pre-dominant hand.