## 5 Discussion
The findings from this study revealed that harvesters 40-49 years of age experienced a higher risk of MSDs at the support shoulder region compared with those 20-29 years of age when placing the harvesting tool at the targeted FFB. Harvesters in the age groups of 40-49 and 30-39 years of age also tended to experience a higher risk of MSDs at the support shoulder region during their maximum posture of harvesting movement. This can be attributed to the fact that harvesters 40-49 and 30-39 years of age can be considered as more experienced harvesters, who were not practicing the proper manual handling of oil palm harvesting. This trend was also found by [3], 81% of the surveyed harvesters in an oil palm plantation were aware of the correct procedure and method of manual handling and lifting. However, only 17.1% of the harvesters practised the right method. According to [3], the reason that the harvesters were resisting to the proper manual handling was because the changes would slow down their work pace and they also felt uncomfortable in applying it. This may be the same case for this study. In this study there was a notable decline in the active harvesting movement with age. Harvesters 40-49 years of age were found to have a smaller active range of harvesting movements during the preparation phase at the support shoulder and wrist regions, with angles of 2.4\({}^{\circ}\) and 0.5\({}^{\circ}\), respectively. This result was consistent with a previous study [22] in which age was also associated with a declining performance of motor tasks. However, in this study the trend is not due to performance or ability to perform tasks as previously reported. The decrease in the active range of movement is influenced by the initial shoulder posture exhibited by the age groups of 40-49 and 30-39 years of age. The result showed that the initial and maximum posture at the support shoulder of these age groups were greater than to those 20-29 years of age which indicate that the age groups of 40-49 and 30-39 years of age were more capable in placing the harvesting tool at the higher target of FFB. Furthermore, the age categorization in this study was different from the age categorization in [22]. It was previously reported that the characteristics of oil palm trees affected the placement of the harvesting tool on the targeted FFBs. During the harvesting, harvesters must align their initial posture to obtain a suitable position to start the harvesting process. This may predispose the workers to unfavourable and awkward postures at the beginning of the process and subsequently result in MSDs. With the aim of collecting the data required in the design of ergonomic harvesting tools, this study evaluated the effect of the initial posture position on the maximum posture range of harvesting movements and range of harvesting movements during the three phases of the push-pull-cutting movement of upper arm among the oil palm harvesters. The results from previously published studies showed that those who worked with an initial support shoulder range of harvesting movements of \(\theta>90^{\circ}\) commonly experienced shoulder discomfort [31; 32; 33]. These groups of workers also had a greater maximum range of harvesting movements on the support and dominant shoulders in this study. Thus, they tended to continue elevating their arms and creating a greater risk of developing MSDs compared with those who worked at an initial support shoulder range of harvesting movements of 90\({}^{\circ}\geq\theta\geq 45^{\circ}\). Furthermore, working with an initial support shoulder range of harvesting movements of \(\theta>90^{\circ}\) generated a reduction in the support shoulder flexion and the ulnar deviation active range of harvesting movements of the dominant wrist at the preparation phase, by 9.0\({}^{\circ}\) and 5.0\({}^{\circ}\), respectively. Nevertheless, this study found that the initial dominant shoulder posture did not exert any effect on the active range of harvesting movements of the support arm.