Grip force regulates hand impedance to optimize object stability in high impact loads.

Area of Science:

• Motor control
• Human sensorimotor system
• Robotics and biomechanics

Background:

• Anticipatory grip force adjustments demonstrate the predictive capacity of motor control.
• Precision grip stabilization relies on grip force modulation against inertial load forces during movement.
• Sudden impact loads necessitate predictive control due to limited sensory feedback time.

Purpose of the Study:

• Investigate grip force control during a targeted tapping task involving object manipulation.
• Examine grip force adjustments in response to smooth versus impact load forces.
• Determine if grip force peaks during impact are pre-programmed or reactive.

Main Methods:

• Participants performed a targeted tapping task with a hand-held object.
• Load force and grip force were measured during object transport and collision.
• Catch trials and a virtual environment were used to probe predictive control mechanisms.

Main Results:

• During the transport phase, grip force and load force were in phase.
• During collision, grip force peaked approximately 65 ms after the peak load.
• This grip force peak was demonstrated to be pre-programmed, independent of target stiffness and movement direction.

Conclusions:

• The central nervous system pre-programs grip force to optimize stability during object manipulation, particularly during impacts.
• Grip force regulation is crucial for coordinating mechanical parameters like stiffness and damping.
• This research offers new insights into neural coordination of grip force during object interaction with the environment.