Individual finger forces acting on a grasped object during shaking actions

Area of Science:

• Biomechanics
• Human Motor Control
• Neuroscience

Background:

• Understanding how humans maintain a stable grip on objects during dynamic tasks is crucial for preventing drops and ensuring safety.
• Previous research has explored grip force modulation but often under static or simpler dynamic conditions.

Purpose of the Study:

• To investigate individual finger grip force adjustments during various shaking tasks and locomotion.
• To determine the role of each finger in maintaining grip stability under dynamic conditions.
• To explore the anticipatory nature of grip force control.

Main Methods:

• Subjects performed precision grip tasks while shaking a force transducer-equipped object in vertical, horizontal, and mediolateral directions at different speeds.
• Grip forces were also measured during walking and running in place while holding the object.
• Analysis focused on temporal and spatial changes in grip forces relative to object acceleration.

Main Results:

• Grip forces dynamically coupled with object acceleration, indicating active and anticipatory control.
• The index finger exerted the largest absolute grip force, playing a primary role in control.
• Finger force contributions varied with shaking direction, with increased involvement of the ring and little fingers in horizontal/mediolateral movements.

Conclusions:

• Grip force control is an active, anticipatory process that adapts to external forces and movement dynamics.
• The index finger is central to grip stabilization, but other fingers contribute dynamically based on task demands.
• Specific finger coordination strategies are employed depending on the direction of external perturbations, highlighting the dexterity of the human hand.