## 1 Introduction  
In recent years, three-dimensional (3D) motion analysis has proven to be a powerful tool to quantitatively assess movement in all degrees of freedom [1] and the fast progress in resolution and accuracy has resulted in improved measurement of fine motor movements, such as those involving the hand and fingers [2]. However, the area of hand analysis is yet in its infancy and the current lack of standardization in human hand motion capture [3; 4; 5] has been shown to impede the comparison of upper extremity kinematics between different studies. Kinematic model description, model calibration including the joint coordinate systems (JCS), marker placement and kinematic estimation appear to be the four main problems in this research area [3; 6]. The choice of marker placement, in particular, has been revealed to be greatly variable [7; 8]. Markers on the many hand and finger segments become highly concentrated in a small volume and therefore impede simultaneous motion tracking of all fingers [9]. The four most common, but also controversially discussed, marker placements for the fingers are currently as follows [5; 8; 10]:  
1. One marker per segment--linear placement on the joint head (FM1);
2. Two markers per segment--linear placement proximally and distally on the segment (FM2);
3. Three markers per segment--noncollinear triangular-shaped placement (FM3a);
4. Rigid marker cluster consisting of three noncollinear markers fixed on a base (FM3b).  
When markers are placed on the finger joint heads, skin movement artefacts are high due to skin wrinkles [8; 10], but FM1 has still been presented to offer a repeatable and valid method that is simple and fast [11; 12; 13]. FM2-FM3b have been recommended for precise evaluations in a biomechanical setting because they are less affected by skin movement and marker misplacement artefacts [8]. Methods FM3a and FM3b reveal a high robustness against skin movement artefacts [10] and allow the recording of three-dimensional kinematics [9; 14]. Due to the high number of markers, however, these techniques are much more time consuming and marker occlusion may occur [13]. To our knowledge, none of the studies using FM3a or FM3b have measured complex activities of daily living [5; 9; 15].  
The scarce literature comparing different marker sets demands further validity and repeatability investigations between different hand and finger marker placements, especially for future functional and more complex hand movement assessments, which are of special relevance in a clinical setting [2; 16]. With this in mind, an easily applicable marker set is needed that allows for the assessment of all wrists and finger joints simultaneously when performing functional tasks. Special attention should be given to the appropriate representation of the complex 3D movements of the thumb. In a clinical setting, the range of motion (ROM) of a joint, defined as the maximum angular movement of the joint in the anatomical planes, is the most important kinematic parameter. Based on the quantification of the measurement error, an estimate of the smallest change in ROM that can be detected is of great importance for data interpretation. So far, a motion analysis protocol for the measurement of all joints of the fingers and hand and also including a definite statement on its ROM repeatability is missing.  
Following the recommendations for protocol standardizations by [PERSON] et al. [3], this study presents a motion analysis protocol with a biomechanical approach targeting a repeatable, objective joint kinematic evaluation. The focus lies on the following three specific objectives: (i) the comparison of the two marker concepts for the fingers most commonly used in clinical settings (FM1 and FM2), (ii) the development and presentation of a kinematic approach that allows an assessment of all hand and finger joints simultaneously in basic and complex movements, and (iii) the assessment of the ROM and quantification of the test-retest repeatability.