Relationships of kinematics indexes with amplitude and velocity of upper arm reaching movement

Arm reaching movements (ARM) are mainly used in rehabilitative settings, as robot mediated therapies, virtual reality and motion capture systems in exergaming. ARM typical consist of gaussian-like bell shaped velocity profile. No previous paper addressed in details their relationships with amplitude and speed of the movement and aim of the paper is to study existing correlations between quantitative kinematics indexes (KI) and to describe their relationships with the amplitude and the velocity of the movement in normal subjects. We studied about one thousands of horizontal and vertical ARM of 10 normal subjects at four amplitude's values (15-20-25-30°) and at three different target velocity (20-30-40°/s), quantitatively evaluated by symmetry, skewness, kurtosis and smoothness indexes. KI showed extremely low correlations to each other, clearly describing different ARM features, higher correlations with the velocity than with the amplitude of the movement, and in vertical antigravitary rather than horizontal ARM. Among all KI, smoothness showed the higher correlations' values, following an exponential growth relationship both with velocity and amplitude in horizontal and vertical ARM.