The mechanics of the in vivo infant and toddler trunk during respiratory physiotherapy

BackgroundThe purpose of this study is to quantify the in vivo mechanical response of the child trunk under loading during physiotherapy treatments.MethodsTwenty-six children aged 45 days to 7 years (14 girls and 12 boys) took part in this study. The forces applied by the physiotherapist were recorded using a force-plate embedded in the manipulation table supporting the child. Two synchronized cameras filmed the scene in a calibrated environment. The displacement of reflective targets glued on the physiotherapist's hands was calculated using an automatic tracking procedure and the 3D reconstruction “Direct Linear Transformation” algorithm. The progression of physical parameters was evaluated according to the age of the child. They included force, displacement, normalized displacement, loading speed, displacement and normalized displacement at the maximum force, force at the maximum displacement, viscous criterion and effective stiffness.FindingsFor all patients, the mean maximum displacement and load were 22 mm (SD 9 mm) and 240 N (SD 46 N) respectively. The force–displacement curves had shown the complexity of the in vivo behavior: four phases have been distinguished with cycles in respect with the respiratory phases. The increase in force always occurred before the increase in displacement.InterpretationThis study helps to understand the in vivo behavior of the child trunk subjected to repetitive non-injurious mechanical loading. Further analysis in other populations and with different therapeutic maneuvers would refine the results.