# Kinematic Analysis of Daily Activity of Touching Lateral Shoulder for Normal Subjects
## 4 Discussion  
This study discussed the relevant two-dimensional kinematic analysis of touching the contralateral shoulder for normal subjects. Kinematic data were expressed for movement times, velocity and angle of joints as well as the interjoint coordinate between the shoulder and elbow joints for healthy subjects in different age groups. Analysis of phases was also divided into three phases that included lifting a hand, resting and returning it to the original position. Several studies have been conducted on the kinematic properties of patients who have upper-limb problems [5; 7; 8; 25], but no details or analysis about activities such as touching the contralateral shoulder have been reported except in studies by [PERSON] et al. [6] and [PERSON] et al. [9]. The task of touching the contralateral shoulder is a relatively complex one in terms of kinematics. The task consists of several movements including lifting the hand, resting the hand on the contralateral shoulder and returning the hand to the original position. Most studies focused on forward reaching [1; 17; 26]. Only [PERSON] et al. [5], [PERSON] et al. [8] and [PERSON] et al. [9] studied the task of touching the contralateral shoulder as performed by normal subjects, and [PERSON] et al. [10] studied spinal cord injury patients performing contralateral-shoulder-touching movements. However, these studies only looked at the angle joints at the shoulder and elbow. There are no studies, to our knowledge, that discussed in detail the act of lifting the hand. Therefore, this temporal analysis of the task of touching the contralateral shoulder can be considered as unique. Furthermore, the activity of touching the contralateral shoulder is not fully vision-assisted. There is no ultimate agreement among researchers on which main kinematic parameters should be used to analyse upper-body motor performance. Kinematic analysis has been widely used in clinical fields as discriminative or evaluation measures, which shows the importance of legitimate specific kinematic parameter quantities for upper-limb movement. Analysis of the upper limb should include variables from the following factors: movement times, smoothness or velocity, as well as variables describing compensatory movement patterns or interjoint coordination [1]. The aim of this study was to analyse two-dimensional kinematic differences of healthy subjects among different age groups during the touching-the-contralateral-shoulder activity. Previous researchers treated all subjects in one group, for example, [PERSON] et al. [9] with a mean (SD) age of 28 \(\pm\) 5.7 years, [PERSON] et al. [8] with a mean (SD) age of 34.3 \(\pm\) 11 years and [PERSON] et al. [5] with a mean (SD) age of 36.8 \(\pm\) 11.8 years. The mean (SD) age group in this study was 39.1 \(\pm\) 10.3 years. [PERSON] et al. [6], [PERSON] et al. [8] and [PERSON] et al. [9] studied the touching of the contralateral shoulder by healthy subjects without separating the age groups. Studies on the elderly in performing daily living activities found out that the elderly found it difficult to perform activities compared to the younger group [27; 28; 29]. The current study differentiated each age group and found that there were differences in kinematic variables during the contralateral shoulder touching such as movement times and joint angles. The main finding of this study was that there were significant differences in kinematic variables between the 50s age group and the other age groups during the performance of touching the contralateral shoulder. The significant differences observed were the movement times and joint angles. Peak velocity with different age group variables showed no significant difference among age groups. [PERSON] et al. [1; 17] obtained total movement times of 4.9 s and 6.84 s, respectively, in five phases while subjects were drinking from a glass; meanwhile, this work obtained a total movement time of 2.1 s for three phases of the touching-the-contralateral-shoulder activity.