Force and Directional Force Modulation Effects on Accuracy and Variability in Low-Level Pinch Force Tracking.

Area of Science:

• Motor control
• Human physiology
• Biomechanics

Background:

• Accurate force production is crucial for daily tasks.
• Understanding factors influencing force control variability is important for rehabilitation and ergonomics.

Purpose of the Study:

• To investigate the impact of force level and direction of force change on accuracy and variability in a cyclic isometric pinch force tracking task.
• To compare the performance of the thumb and index finger under different force conditions.

Main Methods:

• Eighteen healthy adults performed a pinch force tracking task.
• The task involved 3 different force ranges and varying directions of force change.
• Accuracy was measured using root mean square error (RMSE), and variability using coefficient of variation (CV).

Main Results:

• Higher RMSE and CV were observed at lower force levels and during minimum reversals compared to maximum reversals.
• The thumb exhibited greater RMSE and CV than the index finger during maximum reversals, but not during minimum reversals.
• Impaired performance during minimum reversals may be linked to history-dependent force production mechanisms and digit coupling.

Conclusions:

• Force control accuracy and consistency are reduced at lower force levels and during specific directional changes.
• The thumb and index finger display distinct performance characteristics depending on the task demands.
• Findings suggest that motor control strategies and inter-digit coordination play significant roles in pinch force variability.