Isometric force complexity may not fully originate from the nervous system.

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Nervous system signals are translated into muscle force for movement.
• Understanding this translation across the lifespan is crucial for motor control research.

Purpose of the Study:

• Investigate motor control dynamics during isometric contractions across different age groups.
• Examine age-related changes in the translation of neural information into muscle force.

Main Methods:

• Recorded sensorimotor cortex EEG, muscle EMG, and force during isometric plantar- and dorsiflexion in children, adolescents, young adults, and older adults.
• Utilized surrogate analysis to assess signal determinism.
• Applied multiscale entropy and entropic half-life analyses to evaluate signal complexity and temporal dependencies.

Main Results:

• A deterministic origin was suggested for all recorded signals (EEG, EMG, force).
• Multiscale entropy analysis revealed an inverted U-shaped relationship between age and force signal complexity, but not for EEG or EMG.
• Entropic half-life analyses indicated that the musculoskeletal system increases the time scale of temporal dependency in force signals compared to neural signals.

Conclusions:

• The musculoskeletal system modulates temporal information from the nervous system during force production.
• The complexity and temporal dynamics of muscle force do not solely reflect the underlying neural signals.
• Age influences the modulation of neural information by the musculoskeletal system, impacting motor control outcomes.