Rotational ranges of human precision manipulation when grasping objects with two to five digits

Area of Science:

• Biomechanics
• Human Factors Engineering
• Robotics

Background:

• Hand manipulation is vital for daily tasks and human-computer interaction.
• Understanding rotational capabilities informs the design of ergonomic tools and haptic interfaces.

Purpose of the Study:

• To quantify the rotational range of the human hand for objects of varying sizes.
• To investigate the influence of finger count and rotation axis on object manipulation.
• To provide data for optimizing the design of handheld devices.

Main Methods:

• 17 unimpaired subjects rotated objects (50 and 80 mm diameter) using 2-5 digits.
• Rotations were performed around three orthogonal axes (distal-proximal, palmar-dorsal, ulnar-radial) for 30 seconds.
• Finger-object contact locations were maintained throughout the trials.

Main Results:

• Average rotational range was 47 degrees, with a maximum of 82 degrees (3 digits, distal-proximal axis).
• Smaller objects yielded larger rotation workspaces around palmar-dorsal and ulnar-radial axes (p < 0.001).
• Rotation around the distal-proximal axis showed greater sensitivity to finger count than object size.

Conclusions:

• The orientation of the rotation axis significantly influences hand rotation capabilities.
• Designers of handheld tools and haptic devices must consider the required rotation axes for optimal user interaction.
• Findings contribute to the biomechanics of hand function and human-robot interaction.