Fingertip forces and completion time for index finger and thumb touchscreen gestures

Area of Science:

• Human-Computer Interaction
• Biomechanics
• Ergonomics

Background:

• Touchscreen devices are ubiquitous, with users interacting via finger forces.
• The magnitude, direction, and impulse of these forces during common gestures are not well understood.
• Understanding these forces is crucial for assessing musculoskeletal load and injury risk.

Purpose of the Study:

• To quantify the forces, their directions, and the impulse applied during single-finger (tap, slide) and two-finger (pinch, stretch) touchscreen gestures.
• To compare these biomechanical parameters across different gestures.
• To provide data for developing ergonomic guidelines for touchscreen use.

Main Methods:

• Thirteen subjects performed repeated trials of tapping, sliding (four directions), pinching, and stretching gestures on a touchscreen.
• Force transducers measured the resultant force, direction, and impulse.
• Gesture completion times were recorded.

Main Results:

• Mean resultant forces varied significantly by gesture: tap (0.50 N), slide (0.79–1.18 N), pinch (1.47 N), and stretch (2.05 N).
• Tap force was significantly lower than most other gestures (p<0.04).
• Two-finger gestures exhibited more vertical force application compared to single-finger gestures. Gesture completion times ranged from 133 ms (tap) to 920 ms (stretch).

Conclusions:

• Significant differences exist in force magnitude, direction, and timing across various touchscreen gestures.
• These biomechanical variations can inform the estimation of musculoskeletal exposure.
• The findings support the development of guidelines to mitigate the risk of musculoskeletal injury associated with touchscreen interaction.