How do different standing positions affect trunk muscle activation in LBP-developers during prolonged standing?

Area of Science:

• Ergonomics
• Biomechanics
• Occupational Health

Background:

• Individuals at high risk for low back pain (LBP) experience exacerbation during prolonged standing.
• Prolonged standing is linked to increased trunk muscle co-contraction and elevated activity in trunk extensor muscles.
• Understanding risk factors is crucial for developing effective LBP prevention strategies.

Purpose of the Study:

• To investigate the impact of a normalized footrest height on muscle activity in individuals at high risk for LBP.
• To examine the effects of altered arm positions (shoulder flexion, hands crossed on clavicles) on muscle activity during prolonged standing.
• To assess the combined effects of footrest use and arm position adjustments on trunk muscle activation.

Main Methods:

• Twenty-four female participants identified as high-risk for LBP were recruited.
• Participants were randomly assigned to use a footrest intermittently (Group A) or a footrest with adjusted arm positions (Group B).
• Electromyography (EMG) was used to monitor muscle activity throughout a one-hour standing protocol.

Main Results:

• Both interventions significantly reduced lumbar erector spinae (LES) activity and trunk muscle co-contraction (p < 0.05).
• Group B, utilizing adjusted arm positions, showed a greater reduction in muscle activity (p = 0.05).
• Transversus abdominis (TrA) activity increased slightly in both groups, more so in Group B. Thoracic spine extensor (TES) activity increased in Group B, potentially compensating for reduced lumbar activity.

Conclusions:

• Cyclical footrest use and adjusted arm positions effectively mitigate low back pain during prolonged standing.
• These ergonomic interventions promote muscle relaxation, reduce fatigue, and enhance overall posture.
• Findings provide practical strategies for improving workplace ergonomics, especially for jobs requiring prolonged standing.