Trunk muscle balance and muscular force.

Area of Science:

• Biomechanics
• Human anatomy
• Muscle physiology

Background:

• Understanding the absolute strength of the erector spinae muscle is crucial for biomechanical analysis of the human trunk.
• Previous studies have often focused on relative muscle strength, leaving a gap in understanding absolute force production.
• The erector spinae and rectus abdominis muscles play key roles in trunk stability and movement.

Purpose of the Study:

• To investigate the absolute strength of the in vivo human erector spinae muscle.
• To compare the trunk extensor and flexor moments.
• To explore the anatomical factors contributing to trunk muscle strength.

Main Methods:

• Magnetic resonance tomography was employed to assess muscle cross-sectional area.
• Dynamic muscular testing was used to measure muscle force production.
• Calculations included absolute muscle strength (N/cm2), muscle area (cm2), and internal moment arm (cm).

Main Results:

• The absolute strength of the erector spinae muscle was determined to be 48 N/cm2.
• The rectus abdominis had an area of 15.1 cm2, while the erector spinae had an area of 54.5 cm2.
• Trunk extensor moment was found to be only 30% greater than the flexor moment.

Conclusions:

• The absolute strength of the erector spinae muscle is a significant factor in trunk biomechanics.
• The relatively small difference between extensor and flexor moments suggests a complex interplay of anatomical and physiological factors.
• Further research into anatomical contributions is warranted to fully understand trunk muscle function.