## 6 Conclusions  
When it is necessary to carry out work at height and it is not possible (or not convenient) to use fixed systems such as scaffolding, the use of a ladder is necessary, carrying out a task, even a simple one, on a ladder compromises balance and freedom of movement, resulting in strong perceived discomfort and reduced safety for the user. The aim of this study was to compare simple tasks, performed on the ground and a ladder, in subjective and objective terms. For the subjective data, questionnaires were used; for the objective data, the RULA and CAMan analysis were carried out. The research questions are: how much does perceived discomfort affect performing a simple task on a ladder instead of on the ground? Is the difference in perceived discomfort linked to biomechanical overload? Summarizing, the RULA analysis does not highlight significant differences, neither between the right and left side of the body nor between the activities carried out from the ground and on a ladder (with the exception of the frontal screwing in which there is a significant difference, for the right arm, between the ground and the ladder). The RULA values for all activities, ground, and ladder, are always high, therefore the activities selected are significant for the analysis. The activities are compromising in terms of discomfort and biomechanical overload. CAMan confirms the results of the questionnaire. The cross-analysis shows strong negative correlations between the CAMan results and the questionnaire. The areas of the body that obtain the highest results in terms of perceived discomfort (questionnaires) are the same ones that are most compromised from a postural comfort point of view (CAMan). From the questionnaires, however, it emerges that, for all operations, there is a significant difference between the activity carried out on the ladder and the same activity carried out from the ground. Furthermore, the perceived discomfort is always less when the operation is carried out from the ground. As for localized discomfort, the knee is the most critical body part. The difference in knee discomfort between ladder and ground is always significant; statistical analyses show correlations between knee discomfort and perceived discomfort and effort: as perceived knee discomfort increased, the perception of global discomfort and perceived effort increased. Carrying out the operation on the ladder creates weight imbalance and therefore balance problems. From the videos, it appears that the subjects, to maintain balance, rest their knee on one of the steps of the ladder and this causes localized pain. The results also show a correlation between knee discomfort and participants' height: to increase the participants' height the discomfort knee perceived decreases. Direct observation showed that as the height of the participants increased, contact between knees and ladder steps was reduced until it was lost completely. Thus, the absence of pressure in the knee on the step caused less discomfort to the subjects. In the frontal object picking, Spearman indices show two important correlations. Neck discomfort is strongly related to general discomfort and perceived exertion. This shows how the neck is the most critical part of the body for this operation. For all tasks, the perceived effort is greater for the operation carried out on a ladder. This result can be found using the CAMan indices. The neck takes on low postural comfort values. The findings would have a significant impact on ladder design. The ladder has not undergone major evolutions over time and remains a simple tool for reaching points that are difficult to reach but do not require specific platforms and scaffolding. However, the risks deriving from its use should not be underestimated, especially when performing tasks involving both arms. Not being able to use arms, because engaged in an activity, the knees contact on the ladder plays a fundamental role in maintaining balance and stability.