Shijun Yan

and 7 more

The goal of this study was to determine whether increasing motor variability by applying varied perturbation forces to the pelvis during sitting astride would facilitate motor learning of improved trunk postural control in children with cerebral palsy (CP). Fourteen children with spastic CP were tested in two conditions: CONSTANT and VARIED force perturbations in two training sessions with each session lasted for 15 minutes. A custom robotic system was used to deliver repetitive perturbation forces to the pelvis while participants sat astride. Postural reactions to the unpredicted perturbations in the anterior and posterior directions were tested before and after each training session. Kinematics of head, trunk, and pelvis movement, and muscle electromyography signals were recorded. One session of pelvis perturbation training with either the CONSTANT (P = 0.028) or VARIED force magnitudes (P = 0.009) induced an earlier onset of trunk extensor under unpredicted perturbations. In addition, one session of pelvis perturbation training with VARIED force magnitudes induced a significant decrease in peak angle of head extension (P = 0.016), and an improvement in recruitment order of the neck and trunk muscles under unpredicted perturbations (P = 0.020). These results suggest that repeated pelvis perturbations during sitting astride may induce improvement in muscle activation onset under unpredicted perturbations in children with CP. Moreover, repeated pelvis perturbations with varied force magnitudes, which may increase motor variability, may lead to improvements in head stability and muscle activation sequence of trunk and neck muscles in response to unpredicted perturbations in children with CP.

Hyosok Lim

and 1 more

Background: Cross-education, a phenomenon where unilateral strength (or skill) training enhances strength (or skill) in the contralateral untrained limb, has been well studied in able-bodied individuals. However, whether non-paretic leg movements can modulate corticomotor excitability (CME) and improve motor control of the paretic leg in stroke remains unclear. Objective: To determine the effects of non-paretic leg movements on corticomotor responses and motor control of the paretic leg in persons with severe stroke. Methods: Seventeen post stroke individuals with severe leg motor impairment performed three 20-min motor trainings using their non-paretic ankle: skill (targeted dynamic movements), strength (isometric resistance), and sham (sub-threshold electrical nerve stimulation). Transcranial magnetic stimulation measured CME of the contralateral pathways from the non-lesioned motor cortex (M1) to the non-paretic tibialis anterior (TA) muscle, ipsilateral pathways to the paretic TA, and transcallosal inhibition (TCI) from the non-lesioned to lesioned M1. Paretic ankle motor control was measured using a reaction time paradigm. Results: CME of the non-paretic TA increased after skill (23%) and strength (19%) training (p<0.01). Ipsilateral CME of the paretic TA (23%) and TCI (36%) increased after skill (p<0.05) but not strength training. Reaction time of the paretic ankle improved after skill and strength training (~12%; p<0.05) and was sustained at 60 minutes. No changes were observed during the sham condition. Conclusion: Our findings may inform future studies for using non-paretic leg movements as a priming modality, especially for those who are contraindicated to other priming paradigms (e.g., brain stimulation) or unable to perform paretic leg movements.