The effect of keyboard key spacing on typing speed, error, usability, and biomechanics: Part 1

Going Short: The Effects of Short-Travel Key Switches on Typing Performance, Typing Force, Forearm Muscle Activity, and User Experience

This study examined the effects of 4 micro-travel keyboards on forearm muscle activity, typing force, typing performance, and self-reported discomfort and difficulty. A total of 20 participants completed typing tasks on 4 commercially available devices with different key switch characteristics (dome, scissors, and butterfly) and key travels (0.55, 1.3, and 1.6 mm). The device with short-travel (0.55 mm) and a dome-type key switch mechanism was associated with higher muscle activities (6%-8%, P < .01), higher typing force (12%, P < .01), slower typing speeds (8%, P < .01), and twice as much discomfort (P < .05), compared with the other 3 devices: short-travel (0.55 mm) and butterfly switch design and long travel (1.3 and 1.6 mm) with scissor key switches. Participants rated the devices with larger travels (1.3 and 1.6 mm) with least discomfort (P = .02) and difficulty (P < .01). When stratified by sex/gender, these observed associations were larger and more significant in the female participants compared with male participants. The devices with similar travel but different key switch designs had difference in outcomes and devices with different travel were sometimes not different. The results suggest that key travel alone does not predict typing force or muscle activity.

Differences in typing forces, muscle activity, wrist posture, typing performance, and self-reported comfort among conventional and ultra-low travel keyboards

This study investigated the relative impact of ultra-low travel keyboards on typing force, muscle activity, wrist posture, typing performance, and self-reported comfort/preference as compared to a conventional keyboard. In a repeated-measures laboratory-based study, 20 subjects were invited to type for 10 min on each of five keyboards with different travel distances of 0.5, 0.7, 1.2, 1.6 (ultra-low travel keyboards), and 2.0 mm (a conventional keyboard). During the typing sessions, we measured typing force; muscle activity in extrinsic finger muscles (flexor digitorum superficialis and extensor digitorum communis), shoulder (trapezius) and neck (splenius capitis); wrist posture; typing performance; and self-reported comfort/preference. While using the ultra-low travel keyboards, subjects typed with less force and wrist extension, and had more ulnar deviation (p's < 0.0001) compared with conventional keyboard. However, these differences in typing forces were less than 0.5 N and less than 4° for both wrist extension and ulnar deviation. The general trend of data did not show any consistent or substantial differences in muscle activity (less than 2 %MVC) and typing performance (<5 WPM in speed; < 3% in accuracy), despite the observed statistical difference in the finger flexors and extensors muscle activity (p's < 0.19) and typing performance (p < 0.0001). However, the subjects preferred using conventional keyboards in most of the investigated self-reported comfort and preference criteria (p's < 0.4). In conclusion, these small differences indicate that using ultra-low travel keyboards may not have substantial differences in biomechanical exposures and typing performance compared to conventional keyboard; however, the subjective responses indicated that the ultra-low keyboards with the shortest key travel tended to be the least preferred.

Mind the Gap: The Effect of Keyboard Key Gap and Pitch on Typing Speed, Accuracy, and Usability, Part 3

OBJECTIVE

The aim of this study was to evaluate the effects of key gap (distance between edges of keys) on computer keyboards on typing speed, percentage error, preference, and usability.

BACKGROUND

In Parts 1 and 2 of this series, a small key pitch (center-to-center distance between keys) was found to reduce productivity and usability, but the findings were confounded by gap. In this study, key gap was varied while holding key pitch constant.

METHOD

Participants (N = 25) typed on six keyboards, which differed in gap between keys (1, 3, or 5 mm) and pitch (16 or 17 mm; distance between centers of keys), while typing speed, accuracy, usability, and preference were measured.

RESULTS

There was no statistical interaction between gap and pitch. Accuracy was better for keyboards with a gap of 5 mm compared to a 1-mm gap (p = .04). Net typing speed (p = .02), accuracy (p = .002), and most usability measures were better for keyboards with a pitch of 17 mm compared to a 16-mm pitch.

CONCLUSIONS

The study findings support keyboard designs with a gap between keys of 5 mm over 1 mm and a key pitch of 17 mm over 16 mm.

APPLICATIONS

These findings may influence keyboard standards and design, especially the design of small keyboards used with portable devices, such as tablets and laptops.

The Effect of Pressure Glove Tightness on Forearm Muscle Activity and Psychophysical Responses

OBJECTIVE

The impact of pressure glove tightness on maximum grip force, muscle activity, and psychophysical responses is investigated to facilitate the prescription of a suitable reduction factor (RF) for pressure treatment.

BACKGROUND

The wearing of pressure therapy gloves is often considered to hinder hand performance and cause discomfort, resulting in unsatisfactory treatment adherence during burn rehabilitation.

METHOD

A wear trial was carried out with 10 participants for three custom-made pressure gloves that consist of different RFs-10%, 15% and 20%-as well as for the bare hand. The surface electromyography of three forearm muscles was measured during tasks that involve moving marbles, buttoning a shirt, and typing. The psychophysical responses were also recorded.

RESULTS

The use of pressure gloves results in a reduction in the maximum gripping force. Gloves with tighter pressure contribute to lower perceived comfort and ease of hand motion. Increased glove tightness (with RFs of 15% and 20%) decreases muscle activity as compared to the bare-hand condition when buttoning a shirt. In terms of typing, the forearm muscle activity increases with high glove pressure (RF of 20%).

CONCLUSION

The forearm muscles are significantly affected by glove tightness in performing different daily tasks that required gripping, pinching, and typing. The increase of RF of pressure gloves causes negative impact on psychophysical response and handgrip strength. Glove tightness in relation to hand performance and comfort is important in prescribing an optimal pressure therapy glove for hypertrophic scar treatment.

APPLICATION

The findings give insight into the impacts of pressure glove tightness on muscle activity, thus providing a reference for glove development.

The effect of key size of touch screen virtual keyboards on productivity, usability, and typing biomechanics

OBJECTIVE

We investigated whether different virtual keyboard key sizes affected typing force exposures, muscle activity, wrist posture, comfort, and typing productivity.

BACKGROUND

Virtual keyboard use is increasing and the physical exposures associated with virtual keyboard key sizes are not well documented.

METHOD

Typing forces, forearm/shoulder muscle activity, wrist posture, subjective comfort, and typing productivity were measured from 21 subjects while they were typing on four different virtual keyboards with square key sizes, which were 13, 16, 19, and 22 mm on each side with 2-mm between-key spacing.

RESULTS

The results showed that virtual keyboard key size had little effect on typing force, forearm muscle activity, and ulnar/radial deviation. However, the virtual keyboard with the 13-mm keys had a 15% slower typing speed (p < .0001), slightly higher static (10th percentile) shoulder muscle activity (2% maximum voluntary contractions, p = .0 I), slightly greater wrist extension in both hands (2 degrees to 3 degrees, p <.01), and the lowest subjective comfort and preference ratings (p < .1).

CONCLUSIONS

The study findings indicate that virtual keyboards with a key size less than 16 mm may be too small for touch typing given the slower typing speed, higher static shoulder muscle activity, greater wrist extension, and lowest subjective preferences.

APPLICATIONS

We evaluated the effects of virtual keyboard key sizes on typing force exposures, muscle activity, comfort, and typing productivity.

Differences in typing forces, muscle activity, comfort, and typing performance among virtual, notebook, and desktop keyboards

The present study investigated whether there were physical exposure and typing productivity differences between a virtual keyboard with no tactile feedback and two conventional keyboards where key travel and tactile feedback are provided by mechanical switches under the keys. The key size and layout were same across all the keyboards. Typing forces; finger and shoulder muscle activity; self-reported comfort; and typing productivity were measured from 19 subjects while typing on a virtual (0 mm key travel), notebook (1.8 mm key travel), and desktop keyboard (4 mm key travel). When typing on the virtual keyboard, subjects typed with less force (p's < 0.0001) and had lower finger flexor/extensor muscle activity (p's < 0.05). However, the lower typing forces and finger muscle activity came at the expense of a 60% reduction in typing productivity (p < 0.0001), decreased self-reported comfort (p's < 0.0001), and a trend indicating an increase in shoulder muscle activity (p's < 0.10). Therefore, for long typing sessions or when typing productivity is at a premium, conventional keyboards with tactile feedback may be more suitable interface.

The effect of keyboard key spacing on typing speed, error, usability, and biomechanics, Part 2: Vertical spacing

OBJECTIVE

The objective was to evaluate the effects of vertical key spacing on a conventional computer keyboard on typing speed, percentage error, usability, forearm muscle activity, and wrist posture for both females with small fingers and males with large fingers.

BACKGROUND

Part I evaluated primarily horizontal key spacing and found that for male typists with large fingers, productivity and usability were similar for spacings of 17, 18, and 19 mm but were reduced for spacings of 16 mm. Few other key spacing studies are available, and the international standards that specify the spacing between keys on a keyboard have been mainly guided by design convention.

METHOD

Experienced female typists (n = 26) with small fingers (middle finger length < or = 7.71 cm or finger breadth of < or = 1.93 cm) and male typists (n = 26) with large fingers (middle finger length > or = 8.37 cm or finger breadth of > or = 2.24 cm) typed on five keyboards that differed primarily in vertical key spacing (17 x 18, 17 x 17, 17 x 16, 17 x 15.5, and 18 x 16 mm) while typing speed, error, fatigue, preference, forearm muscle activity, and wrist posture were recorded.

RESULTS

Productivity and usability ratings were significantly worse for the keyboard with 15.5 mm vertical spacing compared to the other keyboards for both groups.There were few significant differences on usability ratings between the other keyboards. Reducing vertical key spacing,from 18 to 17 to 16 mm, had no significant effect on productivity or usability.

CONCLUSIONS

The findings support the design of keyboards with vertical key spacings of 16, 17, or 18 mm.

APPLICATIONS

These findings may influence keyboard design and standards.

Design and evaluation of small, linear QWERTY keyboards

Miniature keyboard design is motivated by the need for smaller mobile devices with maximum user display area. Thus, this study developed four miniature keyboard designs which varied from conventional keyboard design in terms of their configuration and layout. The purpose of this study was to evaluate the input speed, accuracy, comfort, likability and learnability of four miniature keyboards. Sixteen fast typists and 16 slow typists were recruited to use these four miniature keyboards. The results showed that the rectangular-shaped keycaps of 3 letters with separated keycaps of numerals obtained the best proficiency speed, highest comfort and greatest user acceptance among the four keyboards. Moreover, the keyboards with square-shaped keycaps had better input accuracy compared to rectangular-shaped keycaps. Finally, the proposed keyboards were smaller than current keyboards, and the performance for all of the small keyboards was worse than that of the conventional keyboard.