# Estimation of the Abduction/Adduction Movement of the Metacarpophalangeal Joint of the Thumb
## 2 Materials and Methods
### Experiment A. Prediction Model  
#### 2.1.1 Experimental Procedure  
Seventeen healthy-handed subjects participated in the experiments: 10 women and 7 men (Mean \(\pm\) SD; age: 36.8 \(\pm\) 9.5 years; hand length: 187.3 \(\pm\) 12.0 mm; hand width: 78.4 \(\pm\) 5.7 mm). The subjects were asked to grasp and transport diverse everyday objects (Figure 1) using the grasp types most commonly employed in ADL [14] (Table 1): Lumbrical grasp (Figure 1c), Oblique-palmar grasp (Figure 1d), Five-finger pinch grasp (Figure 1e), and Cylindrical grasp (Figure 1f). Each grasp type was tested with commonly manipulated objects with a range of shapes, sizes, textures, stiffnesses and weights (Table 1). Participants were asked to use different grasps and objects, so as to have 9-10 trials per combination (Table 1). Subjects were seated by a table and, after familiarization with the objects, moved each object from point B to point C (Figure 1b), starting with the hand resting at point A (Figure 1a) and the object at point B. This process was repeated three times for each type of grasp and object. The order of grasps for each subject was randomized. Finally, the total numbers of postures recorded for each grasp were 162 (Lumbrical grasp), 108 (Oblique-palmar grasp), 210 (Five-finger grasp), and 180 (Cylindrical grasp). Figure 1: Top: (**a**) starting posture; (**b**) final and initial posture of the hand (A) on the table, and initial (B) and final (C) positions of the object. Bottom: Lumbrical grasp (**c**), Oblique-palmar grasp (**d**), Five-finger grasp (**e**), and Cylindrical grasp (**f**). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Object** & **Weight (g)** & **Size (mm)** & **Subjects** & **Grasps** \\ \hline \multirow{3}{*}{Heavy/thin cylinder} & \multirow{3}{*}{470} & \multirow{3}{*}{35\(\O\)} & 9 & Lumbrical \\  & & & 10 & Cylindrical \\  & & & 10 & Five-finger \\  & & & 9 & Oblique-palmar \\ \hline \multirow{3}{*}{Heavy/medium cylinder} & \multirow{3}{*}{470} & \multirow{3}{*}{50\(\O\)} & 9 & Lumbrical \\  & & & 10 & Cylindrical \\  & & & 10 & Five-finger \\ \hline \multirow{3}{*}{Heavy/thick cylinder} & \multirow{3}{*}{470} & \multirow{3}{*}{65\(\O\)} & 9 & Lumbrical \\  & & & 10 & Cylindrical \\  & & & 10 & Five-finger \\ \hline \multirow{3}{*}{Light/medium cylinder} & \multirow{3}{*}{193} & \multirow{3}{*}{50\(\O\)} & 10 & Cylindrical \\  & & & 10 & Five-finger \\ \hline Sphere & 251 & 76 & 9 & Lumbrical \\ \hline Wallet & 40.5 & 120 & 9 & Lumbrical \\ \hline Remote controller & 74 & 450 \(\times\) 180 & 9 & Oblique-palmar \\ \hline Lighter & 100 & 510 \(\times\) 330 & 9 & Oblique-palmar \\ \hline Spoon & 33 & 40 \(\times\) 230 & 9 & Oblique-palmar \\ \hline Glass & 130 & 80\(\O\)\(\times\) 95 & 10 & Cylindrical \\  & & & 10 & Five-finger \\ \hline \multirow{3}{*}{Tennis ball} & \multirow{3}{*}{100} & \multirow{3}{*}{70} & 10 & Cylindrical \\  & & & 10 & Five-finger \\ \hline Marker pen & 30 & 10 \(\times\) 145 & 10 & Five-finger \\ \hline Book & 158 & 35 \(\times\) 105 \(\times\) 150 & 9 & Lumbrical \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Objects, properties (weight in grams (g) and size in millimeters (mm)), subjects and types of grasps performed during the postures recorded in the experiment. Hand posture (23 joint angles) was recorded by tracking the location of 29 markers on the subjects' hands using a Vicon motion capture system [15]. For this study, only the kinematic data of the thumb joints were considered: flexion of the interphalangeal joint (IPF), flexion and abduction of the MCP joint (MCPF and MCPA, respectively) and flexion and abduction of the CMC joint (CMCF and CMCA, respectively). One neutral posture was used as a reference (for comparison of measures) that indicated zero for all the thumb angles: the thumb resting, with the fingers flexed and in a relaxed posture, on the lateral side of the middle finger (Figure 2).