Kinematic Indexes’ Reproducibility of Horizontal Reaching Movements

Upper limb reaching movements are the most used motor task both in diagnosis and rehabilitation treatments of several movement disorders of the arm and the shoulder of various central and peripheral etiology. One of the most appealing features of these new technologies consists in the possibility to record and measure motions and mechanical indexes, allowing quantitative kinematics evaluations, while traditional clinical scales permit only qualitative and potentially disagreeing evaluations, since carried out by different therapists. Few papers have actually addressed this issue and aim of the study is the assessment the reproducibility of kinematics indexes of upper arm horizontal reaching movements in normal subjects during RMT. We studied 10 normal subjects (35±8 year old, males). Each subject underwent to 2 sessions, repeating each reaching protocol at four different target amplitudes of 15°, 20°, 25° and 30° and at three different target velocity, respectively of 20°/s, 30°/s and 40°/s, with at least intervals of 15’ of resting time between each trial. Reaching movements have been performed by a shoulder rehabilitation, the Multi-Joint-System (MJS) of the Tecnobody, equipped by a four freedom ranges mechanical arm, was used. Although all parameters generally showed a poor reproducibility, it can be noted that both kurtosys and symmetry indexes showed the lower bias values, ranging between 8 to 9% , while both symmetry and smoothness indexes showed doubled bias values. The kurtosys is also the parameter with the lower standard deviation of the bias and so it can be considered as the more reproducible kinematic index between the studied parameters. Bland-Altman plots showed that the scatter of all kinematic indexes measures around the bias line is not constant but getting larger as the average gets higher, like for example for the kurtosys, or getting larger as the average gets lower, like for example for the skewness.