Variability, frequency composition, and temporal regularity of submaximal isometric elbow flexion force in subacute...

Area of Science:

• Neurology
• Rehabilitation Science
• Motor Control

Background:

• Stroke frequently leads to motor impairments, affecting upper limb function.
• Understanding motor control deficits in the early stages post-stroke is crucial for effective rehabilitation.

Purpose of the Study:

• To compare force control characteristics (variability, frequency composition, temporal regularity) of elbow flexion in subacute stroke survivors versus controls.
• To investigate the relationship between these force control parameters and motor impairment in the paretic arm.

Main Methods:

• Isometric elbow flexion submaximal force production at various intensities (10-50% peak torque).
• Quantification of force variability (coefficient of variation), frequency composition (median frequency, power bands), and regularity (sample entropy).
• Comparison between paretic, non-paretic, and control arms; correlation with motor impairment scores.

Main Results:

• Paretic elbow flexors showed significantly increased force variability (CV) and reduced muscle regularity (SampEn) compared to non-paretic and control limbs.
• Altered frequency composition in paretic muscles, with increased low-frequency power (0-3 Hz) and decreased higher-frequency power (4-12 Hz).
• Force control parameters showed complex, non-linear relationships with contraction intensity and were not correlated with motor impairment severity.

Conclusions:

• Subacute stroke significantly impacts elbow flexor force control, characterized by increased variability and decreased regularity.
• Motor control deficits in the paretic arm are present early post-stroke and manifest differently across muscle groups.
• Current motor impairment assessments may not fully capture the underlying force control abnormalities.