Acceleration effects on manual performance with isometric and displacement joysticks

Area of Science:

• Human motor control
• Aerospace physiology
• Centrifuge research

Background:

• Novice subjects exhibit exaggerated isometric forces under high Gz (+3 Gz).
• Prior training in high Gz compensates for this force deficit.
• This study investigates if normal G training mitigates high Gz deficits and examines hand displacement.
• High Gz environments pose challenges to motor control and pilot performance.

Purpose of the Study:

• To determine if training in normal gravity (normal G) can compensate for exaggerated force production in high Gz (+3 Gz).
• To investigate whether subjects exhibit exaggerated hand displacements in addition to exaggerated forces under +3 Gz.
• To compare the effectiveness of normal G training versus +3 Gz training on motor performance.

Main Methods:

• Experiments conducted in a centrifuge simulating normal G and +3 Gz.
• Subjects used isometric or regular joysticks to produce forces or hand displacements.
• Visual feedback provided during practice trials, withheld during test trials.
• Focus on dominant hand performance under prescribed response directions and magnitudes.

Main Results:

• Exaggerated force production in +3 Gz persisted regardless of prior practice in normal G.
• Exaggerated hand displacements were not observed in +3 Gz.
• Normal G training did not overcome the force exaggeration deficit in +3 Gz.

Conclusions:

• Task practice in normal G is ineffective in overcoming exaggerated force production in +3 Gz, unlike practice in +3 Gz.
• Pilot training should include extensive force production practice during high Gz phases to prevent motor deficits.
• Distinct neural mechanisms underlie isometric and regular joystick control, with varying +Gz dependence.
• Regular joysticks may offer advantages over isometric joysticks in high-performance aircraft due to their +Gz performance characteristics.