[Electromyogram measuring method for low back load evaluation of handling weight and forward bending posture]

Area of Science:

• Biomechanics
• Occupational Health
• Ergonomics

Context:

• Assessing low back load is crucial for preventing injuries in manual handling tasks.
• Electromyography (EMG) is a potential tool for quantifying muscle activity during such tasks.
• Understanding the relationship between EMG, handling weight, and posture is essential for developing effective safety measures.

Purpose:

• To establish a reliable method for measuring electromyogram (EMG) to evaluate low back load during manual handling.
• To investigate the influence of handling weight and forward bending angles on EMG activity in different spinal regions.
• To determine the optimal spinal location for EMG measurement to assess specific load types.

Summary:

• EMG activity was measured at various spinal levels (Th5-6 to L3-4) in ten male subjects under different handling weights (0-30 kg) and forward bending angles (0-90 degrees).
• EMG increased with handling weight across all angles, with higher rates observed at Th5-6, suggesting its suitability for assessing handling load.
• EMG at L1-2 and L3-4 correlated with bending angles for lighter weights (≤10 kg) and moderate angles (≤60 degrees), but this relationship became inconsistent with heavier weights or greater angles.

Impact:

• Identifies Th5-6 EMG as a suitable indicator for handling weight-related low back load.
• Suggests L1-2 and L3-4 EMG can assess posture load under specific conditions (light weight, moderate bending).
• Highlights limitations in using EMG for evaluating posture load with heavy weights or extreme bending angles, informing ergonomic risk assessment.