Reliability of distal upper extremity posture matching using slow-motion and frame-by-frame video methods

Area of Science:

• Ergonomics and Human Factors
• Occupational Health
• Biomechanics

Background:

• Video analysis is common in ergonomic assessments.
• The impact of video playback speed on posture observation reliability needs further investigation.

Purpose of the Study:

• To determine how video playback speed affects the reliability of posture matching for the distal upper extremity.
• To evaluate the utility of different video playback speeds and frame-by-frame analysis for ergonomic assessments.

Main Methods:

• Seven experienced graduate students assessed distal upper extremity postures (forearm, wrist, hand) from workplace videos.
• Videos were reviewed at real-time, half-speed, and quarter-speed using categorical posture scales.
• Wrist flexion/extension was also analyzed using a frame-by-frame method.

Main Results:

• Posture counts for wrist and hand increased with slower playback speeds.
• Percentage durations of postures remained consistent across different playback speeds.
• Interrater reliability for posture matching improved with slower speeds but remained low; frame-by-frame analysis yielded the highest reliability (84.9% agreement, kappa=0.54).

Conclusions:

• Slower video playback speeds offer marginal improvements in distal upper extremity posture matching reliability.
• Ergonomic assessment tools relying on percentage duration are not significantly enhanced by slowing video speed.
• The benefits of slower playback speeds must be weighed against the increased time commitment for accurate ergonomic assessments.