Trunk muscle behaviors during the full-cycle stoop and squat lifting tasks

Area of Science:

• Biomechanics
• Occupational Health
• Musculoskeletal Research

Background:

• Lifting is a known risk factor for low back pain.
• Understanding trunk muscle function during lifting is crucial for risk assessment and strategy improvement.

Purpose of the Study:

• To compare trunk muscle activities between stoop and squat lifting tasks.
• To investigate muscle activation patterns during different phases of lifting.

Main Methods:

• Surface electromyography (EMG) measured trunk muscle activity during stoop and squat lifting of a 5-kg weight.
• Lifting tasks were divided into four stages: bending, lifting, lowering, and returning to upright.
• Eighteen healthy males (aged 20-35) participated in the study.

Main Results:

• Trunk muscle activation showed no significant difference between stoop and squat lifting across all stages.
• Absolute and normalized EMG activities were highest during the lifting (stage 2) and returning (stage 4) phases.
• Muscle activation was lowest during bending (stage 1) and lowering (stage 3) phases.

Conclusions:

• Trunk muscles exhibit similar activation patterns during both stoop and squat lifting.
• Lowering the weight involved less muscle activation compared to returning to an upright position.
• Findings can inform the development of personalized lifting strategies to prevent occupational low back pain.