Postural strategy changes with fatigue of the lumbar extensor muscles

Area of Science:

• Biomechanics
• Neuromuscular Physiology
• Human Movement Science

Background:

• Postural control is crucial for maintaining balance during perturbations.
• Neuromuscular fatigue is known to affect motor control, but its specific impact on postural strategies requires further investigation.
• Understanding how fatigue influences balance strategies is vital for injury prevention and rehabilitation.

Purpose of the Study:

• To examine the influence of lumbar extensor fatigue on postural control strategies during balance perturbations.
• To quantify changes in joint kinematics and kinetics associated with fatigue-induced alterations in postural responses.
• To assess the impact of varying fatigue levels on postural adjustments.

Main Methods:

• Participants underwent a fatiguing protocol targeting lumbar extensor muscles to induce three distinct levels of fatigue.
• Anteriorly-directed force perturbations were applied using a pendulum to challenge the postural control system.
• Postural strategy was assessed by analyzing center of pressure, joint angles (ankle, knee, hip, low back), and joint torques before and after fatigue induction.

Main Results:

• Fatigue induced proactive changes, such as a slight anterior lean before perturbation, and reactive shifts towards a hip-dominant strategy.
• Individuals relying more on hip movement for balance prior to fatigue were more susceptible to its effects.
• Higher fatigue levels exacerbated some, but not all, observed changes in postural strategy.

Conclusions:

• Neuromuscular fatigue significantly influences postural strategy in response to balance perturbations.
• Fatigue promotes a shift towards hip-based postural adjustments and can alter proactive anticipatory behaviors.
• Individual differences in baseline postural strategies modulate the effects of lumbar extensor fatigue.