# A Review on Ergonomics in Agriculture. Part II: Mechanized Operations
## 4 Results
### Preliminary Data Visualization Analysis
#### 4.1.3 Keyword Information Clustering  
The keyword information clustering is presented in this subsection in an effort to roughly capture the issues that are going to affect the present investigation. In addition, we got a first idea of the negative consequences of agricultural mechanized operations on operator's health and their root causes. To achieve these goals, at about 155 keywords were collected from the 32 selected articles, which are mentioned in the corresponding section of each journal. Then, out of these keywords the 10 most frequently used ones were identified, which are listed in Figure 5. In this figure, the size of the font corresponding to each word is proportional to its frequency, while the same color indicates equivalent occurrence.  
Figure 4: Distribution of all contributing international journals.  
Clearly, \"agriculture\" is the most usual keyword due to the field of this study. The keyword \"whole-body vibration\", which follows divulged the main risk factor for the development of MSDs in agricultural machinery. The word \"tractor\", that comes next, seems to be the principal risky agricultural machine, probably owing to its versatile and frequent use. Apart from WBV, the \"hand-arm transmitted vibration\" appears to have contributed to a great extent, primarily because of the inclusion of machineries such as grass trimmers, handheld olive beaters and power tillers. These machines are notorious for the HATV. The \"low back pain\" that follows indicates the most affected body part during agricultural activities in general, which is in accordance with the relative published works [48; 49; 50; 51; 52; 53]. The keyword \"seat\" that appears afterwards shows the efforts for ergonomically designed seats in order to improve the comfort of the operator. \"Ergonomics\" is plausibly presented, since it is the subject of this review study, however, with relatively small incidence than we expected. This is conjectured to occur as a result of the relatively smaller number of the existing ergonomic interventions comparing to the urgency of MSDs in agricultural workers.  
Three keywords are presented with equal frequency which are depicted with the same color. The first one is associated with the \"comfort\", which an operator seeks for, \"shock\" with the frequent jolts, that an operator experiences, and \"all-terrain vehicle\" with the second most examined machinery of this review study. Finally, frequently presented keywords, however with less incidence, were \"safety\", \"health\" and \"musculoskeletal disorders\" which are obviously related with the injuries caused from mechanized operations. Moreover, \"electromyography\" was presented, which is a medical procedure for assessing the electrical activity of muscles, as well as \"suspension\" denoting the systems which are utilized for lessening the vibration levels.  
In brief, there seems to be a strong relationship between the above keywords. Apart from agriculture that plausibly appeared, the riskiest agricultural machines were presented, namely tractor and all-terrain vehicle. The main risk factors were also gleaned from this analysis, namely WBV and HATV, the health impact of which was elaborated in the Section 2. The principal reported MSD for operators, namely low back pain, appeared that made physicians to engage with this field. Furthermore, ergonomists and manufacturers have cooperated with physicians to develop ergonomic interventions such as comfortable seats and suspensions justifying the words \"comfort\" and \"seat\". The analysis that follows supported the frequency of these keywords, while also other aspects were found and investigated.