Learning effect on the dynamical strategies in sitting position on seesaw motion for idiopathic scoliosis patients

Our study meant to determine, for idiopathic scoliosis patients, the biomechanical processes involved in postural regulation when self-imposed disturbances occur in seated position in both directions during successive trials. 12 female adolescents with right thoracic scoliosis (SG) and 15 control adolescents (CG) were included in this study. Ground reaction forces were studied using a force platform while the subjects were maintaining their balance in sitting position on a seesaw. Every test is recorded with eyes opened, arms on shoulders and legs free. The force platform data (AP and ML forces data) obtained were processed to determine the following normalized force parameters: delta value (difference between maxima and minima), maximal and minimal force values (peak and occurrence), and the variability of AP and ML forces. We used a variance analysis (ANOVA test) to analyze and compare 3 trials and groups.Our results show that, whatever the directions of destabilization (AP versus ML), SG was always in a learning situation. Indeed, the first test is always less stable than the second and third trials. However, for CG, adaptability between the tests is only highlighted during ML imbalance. Significant differences of strategies between the groups are only visible for the AP force component.For all conditions imposed, scoliotic patients perform specific trunk balance strategies. Clinical tests and rehabilitation methods should include the learning effect within the spatio-temporal adaptation to ground reaction forces.

► Assessing the learning effect on the dynamical strategies in unstable sitting. ► Adolescents with idiopathic scoliosis (AIS) and control group (CG) were tested. ► AIS: the learning effect is visible for mediolateral end anteroposterior unstable sitting. ► CG: the learning effect is only visible for the mediolateral destabilization. ► Clinical tests should include the learning effect in the dynamical strategies.