Local dynamic stability of the trunk after prolonged seating with axial load

Area of Science:

• Biomechanics
• Neuromuscular Physiology
• Occupational Health

Background:

• Prolonged seated postures, common in many occupations, can lead to fatigue.
• This fatigue may compromise trunk neuromuscular control and spine stability.
• Such impairments could elevate the risk of low back pain (LBP) during subsequent dynamic tasks.

Purpose of the Study:

• To assess the impact of prolonged seating on local dynamic trunk stability.
• To evaluate changes in trunk muscle coactivation patterns following extended seated periods.
• To understand the potential link between seating-induced fatigue and impaired neuromuscular control.

Main Methods:

• Twenty participants underwent a cyclic trunk flexion task before and after three hours of simulated helicopter seating with a weighted vest.
• Local dynamic trunk stability was quantified using the maximum Lyapunov exponent (λMAX).
• Trunk muscle coactivation and abdominal activation were measured, alongside trunk range of motion.

Main Results:

• A statistically significant decrease in λMAX indicated reduced trunk stability post-seating (p=0.002).
• Trunk cumulative coactivation index and abdominal activation also decreased significantly (p=0.0095 and p=0.0146, respectively).
• Trunk extension range of motion was reduced post-seating (p=0.0004).

Conclusions:

• Three hours of simulated helicopter seating significantly reduced trunk stability and altered neuromuscular control.
• These findings suggest that prolonged seating can induce fatigue, potentially impacting spine stability and increasing LBP risk.
• The results have implications for occupations involving prolonged seated postures followed by dynamic tasks, highlighting the need for further research into interventions.