Sagittal plane lumbar loading when navigating an obstacle and carrying a load

Area of Science:

• Biomechanics
• Occupational Health
• Spinal Loading Analysis

Background:

• Understanding the biomechanical demands on the lumbar spine during complex tasks like carrying loads and obstacle negotiation is crucial for injury prevention.
• Previous research has not fully elucidated the specific lumbar spine forces, particularly shear forces, experienced during combined carrying and obstacle-crossing activities.

Purpose of the Study:

• To quantify lumbar spine loading, including joint moments and muscle activation, in healthy males performing obstacle negotiation while carrying varying anterior load masses.
• To compare lumbar loading parameters at key kinematic events (mid-stance and toe-crossing) to understand load changes during obstacle traversal.

Main Methods:

• Eight healthy male participants completed obstacle crossings carrying loads of 2 kg, 5 kg, and 10 kg.
• Kinematic data (trunk pitch) and kinetic data (L4/L5 joint moments: compression, shear) were measured, alongside erector spinae muscle activation.
• Measurements were taken at left foot mid-stance (LMS) and right toe-crossing (TC) events.

Main Results:

• Obstacle crossing led to significant increases in postural extension (50%, 41%, 44% for 2, 5, 10 kg loads, respectively).
• Lumbar shear forces increased notably from LMS to TC (8%, 9%, 22% for 2, 5, 10 kg loads), suggesting shear loading is a critical factor during crossing.
• Trunk pitch and erector spinae activation also varied with load magnitude and crossing phase.

Conclusions:

• Navigating obstacles while carrying loads alters lumbar spine biomechanics, with a pronounced increase in shear loading during the crossing phase.
• The findings highlight that shear forces, in addition to compressive forces, are important considerations for lumbar spine health in tasks involving carrying and obstacle negotiation.
• This study provides valuable insights for developing targeted interventions to mitigate the risk of lumbar spine injury in occupational and daily activities.