Persons with Parkinson's disease exhibit decreased neuromuscular complexity during gait

Objective: Individual muscle activation patterns may be controlled by motor modules constructed by the central nervous system to simplify motor control. This study compared modular control of gait between persons with Parkinson's disease (PD) and neurologically-healthy older adults (HOA) and investigated relationships between modular organization and gait parameters in persons with PD. Methods: Fifteen persons with idiopathic PD and fourteen HOA participated. Electromyographic recordings were made from eight leg muscles bilaterally while participants walked at their preferred walking speed for 10. min on an instrumented treadmill. Non-negative matrix factorization techniques decomposed the electromyographic signals, identifying the number and nature of modules accounting for 95% of variability in muscle activations during treadmill walking. Results: Generally, fewer modules were required to reconstruct muscle activation patterns during treadmill walking in PD compared to HOA (p< .05). Control of knee flexor and ankle plantar flexor musculature was simplified in PD. Activation timing was altered in PD while muscle weightings were unaffected. Simplified neuromuscular control was related to decreased walking speed in PD. Conclusion: Neuromuscular control of gait is simplified in PD and may contribute to gait deficits in this population. Significance: Future studies of locomotor rehabilitation in PD should consider neuromuscular complexity to maximize intervention effectiveness.