Fatigue task-dependent effect on spatial distribution of lumbar muscles activity

Area of Science:

• Biomechanics
• Kinesiology
• Exercise Physiology

Background:

• Muscle fatigue alters neuromuscular control strategies.
• Understanding spatial muscle activation patterns is crucial for injury prevention and rehabilitation.
• Trunk extension endurance tasks are commonly used to study lumbar muscle fatigue.

Purpose of the Study:

• To investigate how different trunk extension fatigue tasks modulate the spatial distribution of lumbar muscle activity.
• To compare the effects of the modified Sorensen test and the inverted modified Sorensen test on lumbar muscle activation patterns.
• To determine if muscle recruitment strategies change over time and differ between tasks.

Main Methods:

• Twenty healthy adults performed two isometric trunk extension endurance tasks until exhaustion.
• High-density electromyography recorded bilateral superficial lumbar muscle activity.
• Spatial distribution was analyzed using centroid coordinates (medio-lateral and cranio-caudal) and repeated measures ANOVA.

Main Results:

• A significant lateral shift in muscle activation centroid occurred on both sides during fatigue tasks, with no task-specific difference.
• Cranio-caudal centroid location showed significant task × time interactions, with a more caudal shift in the modified Sorensen test initially.
• These findings indicate task-dependent spatial modulation in the pre-fatigue phase.

Conclusions:

• Lumbar muscle spatial activation patterns are influenced by the specific fatigue task, particularly before significant fatigue onset.
• As fatigue progresses, similar recruitment strategies are employed across different tasks to maintain performance.
• This suggests adaptable neuromuscular responses to sustained effort in the lumbar musculature.