Motor unit recruitment for dynamic tasks: current understanding and future directions.

Area of Science:

• Neuroscience
• Skeletal Muscle Physiology
• Motor Control

Background:

• Skeletal muscles comprise motor units, functionally grouped muscle fibers essential for movement.
• The 'size principle' traditionally dictates motor unit recruitment order based on size.
• Motor units possess diverse contractile, energetic, and fatigue properties influencing task performance.

Purpose of the Study:

• To review current understanding of motor unit recruitment patterns.
• To assess the appropriateness of different recruitment strategies for various movement tasks.
• To explore factors influencing motor unit recruitment and propose integrative research approaches.

Main Methods:

• Review of existing literature on motor unit recruitment.
• Discussion of various methods for assessing motor unit recruitment patterns.
• Highlighting wavelet-analysis for assessing recruitment during natural movements.

Main Results:

• Motor unit recruitment patterns during natural movements are variable and do not always adhere to the size principle.
• Recruitment patterns are likely influenced by the mechanical function of muscles.
• Factors including mechanics, sensory feedback, and central control modulate recruitment.

Conclusions:

• An integrative approach is necessary to understand motor unit recruitment control.
• In vivo studies linking recruitment to mechanics and behavior are crucial.
• Future research should investigate motor recruitment across different tasks and muscle compartments.