Abstract
Individuals suffering from cerebral palsy (CP) often have involuntary, reflex-evoked muscle activity resulting in spastic hyperreflexia. Whole-body vibration (WBV) has been demonstrated to reduce reflex activity in healthy subjects, but evidence in CP patients is still limited. Therefore, this study aimed to establish the acute neuromuscular and kinematic effects of WBV in subjects with spastic CP. 44 children with spastic CP were tested on neuromuscular activation and kinematics before and immediately after a 1-min bout of WBV (16-25 Hz, 1.5-3 mm). Assessment included (1) recordings of stretch reflex (SR) activity of the triceps surae, (2) electromyography (EMG) measurements of maximal voluntary muscle activation of lower limb muscles, and (3) neuromuscular activation during active range of motion (aROM). We recorded EMG of m. soleus (SOL), m. gastrocnemius medialis (GM), m. tibialis anterior, m. vastus medialis, m. rectus femoris, and m. biceps femoris. Angular excursion was recorded by goniometry of the ankle and knee joint. After WBV, (1) SOL SRs were decreased (p < 0.01) while (2) maximal voluntary activation (p < 0.05) and (3) angular excursion in the knee joint (p < 0.01) were significantly increased. No changes could be observed for GM SR amplitudes or ankle joint excursion. Neuromuscular coordination expressed by greater agonist-antagonist ratios during aROM was significantly enhanced (p < 0.05). The findings point toward acute neuromuscular and kinematic effects following one bout of WBV. Protocols demonstrate that pathological reflex responses are reduced (spinal level), while the execution of voluntary movement (supraspinal level) is improved in regards to kinematic and neuromuscular control. This facilitation of muscle and joint control is probably due to a reduction of spasticity-associated spinal excitability in favor of giving access for greater supraspinal input during voluntary motor control.
Highlights
Whole-body vibration (WBV) has widely been applied in different areas of rehabilitative medicine, geriatrics, and as a training method for elite athletes [1]
Over 9 months (June 2014–February 2015) subjects with spastic cerebral palsy (CP) were medically examined by the attending physicians in terms of the inclusion criteria of the study, such as diagnosis of unilateral or bilateral spastic CP [gross motor function classification system (GMFCS) score 2–4], the ability to stand upright with support, and healthy cognitive performance, so that procedures were understood by the subjects
Protocol 1: Mechanically evoked SOL stretch reflex (SR) were significantly reduced after acute exposure to whole-body vibration (WBV) (−12 ± 16%, p < 0.01), changes observed for gastrocnemius medialis (GM) SR remained not significant (−5 ± 30%, p = 0.20, Figure 3)
Summary
Whole-body vibration (WBV) has widely been applied in different areas of rehabilitative medicine, geriatrics, and as a training method for elite athletes [1]. The respective research has increasingly been focused on the application and potential benefits of WBV as a therapy in neuro-rehabilitation, such as in adolescent patient groups with spastic cerebral palsy (CP) [2]. With the advantage of great neuroplasticity in children, training regimes commonly achieve higher efficiency compared to adolescent patient groups [3, 4]. Scientific evidence about possible beneficial effects of WBV on spasticity in CP has only reported the outcome, such as functional parameters of movement control. This is, for example, assessed by the clinical diagnostic tool “(Modified) Ashworth Scale” [5, 6]. Apart from the fact that this scale has been characterized with significant limitations of reliability [7,8,9] and validity for children with CP [10], objective neurophysiological diagnostics, which provide a deeper understanding of WBV and its underlying mechanisms, are lacking
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