Learning ballet technique modulates the stretch reflex in students with cerebral palsy: Case series

Abstract Background: Cerebral palsy (CP) is considered the most prevalent developmental motor disorder in children. There is a need for training programs that enhance motor abilities and normalize function from an early age. Previous studies report improved motor outcomes in dance interventions for CP. Investigating the neurophysiological mechanisms underlying such improvements is necessary for efficient and safe intervention design. This study reports changes in stretch reflex responses as the primary neurophysiological motor outcome of a targeted ballet class intervention. Results: A case series of participants with mixed spastic and dyskinetic CP (n = 4, mean age = 12.5 years, SD = 6.9S years, three female, one male) who learned ballet technique in a course of one-hour classes twice per week for six weeks is presented. Changes in stretch reflex responses and in clinical motor tests as secondary outcomes were observed after the course and at one-month follow-up. Quantitative measures of elbow or ankle stretch reflex were obtained using electromyography and electrogoniometry. The joint angle of the stretch reflex onset varied across velocities of stretch, and its variability decreased after the intervention. Within-subject tests of the central tendency of stretch reflex angle coefficients of variation and frequency distribution demonstrated significant changes (p-values< 0.05). Secondary outcomes included the Quality of Upper Extremity Skills Test (QUEST), Pediatric Balance Scale (PBS), Modified Tardieu Scale (MTS), Dyskinesia Impairment Scale (DIS), and Selective Control Assessment of the Lower Extremity (SCALE). All the participants demonstrated improvements larger than the minimal clinical important difference (MCID) or the smallest detectable difference (SDD), as applicable. Conclusions: Evidence of changes in the stretch reflex responses in these four cases of mixed CP was observed. The observed variability in the stretch reflex responses may be due to the dyskinetic component of the mixed CP presentations. More studies with a larger sample size and longer duration of learning and practice of ballet technique are necessary to establish the extent of possible modulation and adaptation of the stretch reflex response as a neurophysiological basis for observed improvements in clinical measures. This study was registered in the Clinical Trials Protocol Registration and Results System (NCT04237506, January 17, 2020).