## 1 Introduction  
Being able to properly perform daily activities is very important for the normal functioning of human beings. Indeed, correct functioning of the upper limbs has an impact on both physical and mental well-being. Evaluation of movements of the upper limbs is most frequently achieved by assessing motion kinematics. Previous research into upper limb movement has focused on analysing ranges of motion [1, 2, 3, 4, 5] and performance during everyday activities, such as drinking from a mug [6, 7, 8, 9, 10, 11] drinking from a glass, pouring from a kettle, turning a handle, lifting a bag to a shelf, turning a key [7], cup and box reach, as well as grasp and transfer [12], among others [13, 14, 15, 16]. Current evaluation methods of upper limb functioning focus on obtaining quantitative data, which allows for the objective assessment of the degree of deviation of certain movements from a reference. It is assumed that the application of such objective methods contributes to a better and more precise understanding of movement patterns among healthy individuals and those with motor deficits. The most common clinical method used to assess upper limb movement pathology is observation. Unfortunately, this method is subjective and depends on the experience of the person performing the test. The clinician's inexperience may also cause him or her to subconsciously look for preconceived deviations from the norm. Although there are scales for functional assessment of the upper limbs related to observation, these scales are subjective. Their outcome depends directly on the person responsible for performing the test. Simultaneous observation of all body segments can also be a difficulty. Three-dimensional motion analysis is frequently applied to the evaluation of upper limb movements, however, such analysis of complex kinematic courses is challenging and time-consuming for clinicians. Furthermore, it is often difficult to determine unequivocally from the above variables whether there has been an improvement or worsening of the upper limb movement stereotype. Some parameters may improve, while others may move away from the accepted movement norm. For this reason, indicators of movement evaluation are attracting greater interest. Such indicators enable assessment by means of just one non-dimensional value, which can be compared to data obtained from a reference group. Indicators of movement are also meaningful in assessing treatment progress. Treatment progress can be quantified and is not subjective/dependent on the clinician. Indicator methods are mainly based on the application of statistical methods to identify mutual dependences between data, such as kinematic and spatio-temporal parameters. The use of indicators in the assessment of upper limb functions is an effective method of supporting kinematic analysis [17; 18]. However, there have only been a small number of studies carried out on the use of indicators for the assessment of the upper limbs [15; 17; 18; 19; 20; 21; 22]. Recent studies have devised a number of indexes for the upper limbs, such as the Arm Profile Score (APS) [15; 19; 20; 21], the Pediatric Upper Limb Motion Index (PULMI) [17] and the Global Upper Limb Deviation Index (GULDI) [22; 23]. The introduction of these indexes has allowed researchers to circumvent the analysis of large amounts of kinematic data, accelerating the evaluation of motor dysfunctions. Furthermore, an important asset of the use of indicators is the simplicity by which the data can be interpreted. The APS is calculated on the basis of the difference in the root mean square (RMS) between kinematic parameters of a person with upper limb motor deficits and the mean values of healthy individuals [15]. This index considers 13 parameters that define the kinematics of the trunk, shoulder blade, shoulder joint, elbow joint and wrist. The APS may be broken down into 13 variables, these so-called Arm Variable Scores (AVS) represent the deviation of particular movement parameters of a given person from mean standard values [15].