# Evaluation of Picker Discomfort and Its Impact on Maintaining Strawberry Picking Quality
## 3 Results
### Field Test Results--Surface Pressures  
Figure 10a,b shows the effect of a fixed fruit picking position on the values of the recorded parameters of the Tekscan(r) system. The highest loads exerted by the picker's index finger were observed during picking in the third--upright--position at 7.87 N, while the lowest were 5.72 N in the first--squatting--position. This was reflected in the maximum surface pressures generated, which increased with the change of working position from 0.168 MPa in position 1, through 0.172 MPa in position 2, to 0.19 MPa for position 3 (upright) (Figure 10b). Variations in the above parameters clearly indicate difficulties in the way strawberry fruit is picked. In the case of the upright position, they are caused by the least comfortable position of the wrist (wrist rotation angle) and reduction in maintaining the stability of the hand position, as well as the depth of inclination of the body posture in comparison with other working positions. The working position was shown to have a significant effect (\(p<0.05\)) on the increase in forces and surface pressures exerted by the picker's index finger. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Body Position**} & \multicolumn{3}{c}{**Load Measure \% MVC, Muscle Tested**} \\ \cline{2-5}  & \multicolumn{1}{c}{**Abductor Polllicis**} & **Lumbar Right, Left** & **Metacarpal Muscle** \\ \hline \multirow{2}{*}{Squatting} & Mean & 13.79 & 13.48 & 3.04 \\  & SD & 1.49 & 1.53 & 0.71 \\ \hline \multirow{2}{*}{Kneeling} & Mean & 23.30 & 22.99 & 4.19 \\  & SD & 2.57 & 3.78 & 0.72 \\ \hline \multirow{2}{*}{Straight legs} & Mean & 29.73 & 32.96 & 4.16 \\  & SD & 4.79 & 5.81 & 0.47 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mean values and standard deviations of the load on the tested muscles of the strawberry picker. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Muscle Tested/Variable** & \(F\) (N) & \(A_{\text{c}}\) (mm\({}^{2}\)) & \(p_{\text{max}}\) (MPa) \\ \hline Abductor pollicis & 0.54 & 0.54 & 0.51 \\ Lumbar right, left & 0.82 & 0.75 & 0.42 \\ Metacarpal muscle & 0.77 & 0.73 & 0.49 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Correlation coefficient. Visualized form of the surface pressures is shown in the contour images in Figure 11. The analysis of the images for the three working positions showed that the highest point pressure concentrations occurred at the contact between the sensor and the achenes evenly distributed on the fruit surface. The recorded images clearly show the change in pressure dispersion on the sensor working surface depending on the position of the finger in a given working position. In the first--squatting--position and second--kneeling--position, due to the easier access of the hand to the fruit and lower inclination of the picker's posture, unevenly distributed areas of surface pressure contours were obtained. In the third--upright--position, on the other hand, the increased discomfort of the work showed an increased but more even accumulation of pressure (increased picking force). Changes in contact between the index finger and the fruit being picked are presented in Figure 12a-c. In the squatting position, both the contact area and the duration of the picking pulse were the smallest (124.1 mm\({}^{2}\) and 0.81 s, Figure 12a,b). It is reasonable to believe that the squatting position, requiring less body lean and resulting in a wrist hand position at a lower angle, resulted in increased comfort, positional stability, and speed of picking. A slightly larger surface area and longer contact time between the index finger and the fruit to be picked was required in the kneeling position (151.2 mm\({}^{2}\) and 0.87 s), which was undoubtedly related to the different position of the center of gravity and the angular position of the different musculoskeletal members, affecting the speed and repetition of the activity. The variation of the contact area pulse distributions over time for the three harvest positions is shown in Figure 12c.