Muscle contractions during normal movements and regular exercises are believed to build strong bones or good bone health. Children with cerebral palsy (CP), especially those with moderate severity, are unable to perform the required amount of exercise to improve their bone health as their typically developing counterparts. As a result, non-traumatic fractures and bone pain are common in children with moderate to severe CP. This problem extends to their adulthood, causing osteopenia or osteoporosis.

Whole body vibration therapy (WBVT) has been recently proven to improve bone health and muscle function in healthy adults, post-menopausal women and individuals with mild to moderate severity of CP. It has been postulated that the vibration can stimulate the muscle spindles and elicit consistent muscle contractions. This would be a great advantage to the individuals with moderate severity of CP, who have limited control in their body movements and prevent them to perform regular exercises as the normal individuals. Among the research of the WBVT for children with CP, promising results have been shown on gross motor function, balance and muscle strength for children with mild disability. Most of the studies, which yielded positive results, required the study participants to perform simple exercises on the vibration platform as the intervention. Very limited studies have been conducted on children and young adults with moderate severity of CP and almost no study solely on individuals with dystonia CP. Other than this lack of knowledge on this sub-group of CP, there are other knowledge gaps of this potential intervention to improve bone health for individuals with CP. Firstly, we do not know if the effect of WBVT on this population group would be similar or more effective than those with mild CP in terms of their tone abnormalities, gross motor function and balance, because the moderate group is greatly compromised in their mobility and extent of regular exercises when compared with those with mild CP. Secondly, preliminary results of the WBVT are promising in children and young adults with moderate severity of spastic CP. However, we do not know if these promising effects will be similar to those with dystonia or spastic dystonia CP because the vast differences in their tone and movement patterns. This pilot study aims to fill in these knowledge gaps and examine the effect of WBVT on children and young adults with moderate severity of dystonia CP in terms of muscle tone, balance and functional motor abilities.

Methods A convenience sample of 5 children and adolescents aged between 6 to 17 years and 5 young adults aged between 18 to 45 years with dystonia or spastic dystonia CP will be recruited. As this is a pilot study, we recruit mild to moderate severity of CP, i.e. Gross Motor Function Classification System (GMFCS) levels I to IV. In general, individuals of levels I and II ambulate unaided and are able to perform more advanced motor skills such as running and jumping with limitations. Individuals of level III mobilise with hand-held mobility devices such as crutches or walking frames. Individuals of levels IV have very limited functional mobility and are mostly limited to an indoor environment. Individuals with level V are non-ambulatory or totally rely on wheeled mobility aids in all environment settings.

The presence of dystonia in the recruited participants will be firstly confirmed using the Hypertonia Assessment Tool (HAT). It is a reliable and valid clinical tool to confirm the presence of dystonia in individuals with CP. Only those confirmed with dystonia or spastic dystonia CP will be included in this study. Assessments will be performed at baseline and at completion of the intervention to examine the functional abilities of the study participants.

The study participants will receive the WBVT when standing still on a vibration platform independently or with own hand support on the platform rail. The vibration protocol is modified from the study by Gusso et al (2016) and has also been tested in a pilot study by PI on a group of children, adolescents and young adults with spastic CP. The WBVT training is of 20 Hertz, a peak-to-peak amplitude of 2 mm and peak acceleration of 15.79m/s or 1.61g. The sessions will be 18 minutes in length, 4 days per week for 4 weeks. The vibration frequency, duration and amplitude will be progressively increased over 2 weeks to the desired parameters.

The study results will be presented as means and standard deviations. Due to the small sample size, non-parametric Wilcoxon Signed Ranks test will be used to compare the results before and after the WBVT. The statistical significance level is set at p\< 0.05.