# Biomechanical Effects on Lower Extremities in Human-Robot Collaborative Agricultural Tasks
## 3 Results  
The measured GRFs, kinematic and kinetic variables during the symmetric lifting task for the three deposit heights are presented in Table 2. Overall, significant interactions were observed for KNEE MOMENT 3, KNEE ANGLE MAX, and HIP MOMENT 2. In particular, post hoc analysis showed that KNEE MOMENT 3 was significantly higher while performing the lifting task with 70 cm deposit height compared to 80 cm (\(p<0.05\)). This knee moment corresponds to phase 3, during which the participant leaves the crate on the custom-made shelf. As regards the maximum knee flexion angle, it was observed that it was significantly lower when performing the task with a height of 70 cm in comparison to the other two heights (\(p<0.05\)). Moreover, HIP MOMENT 2 was significantly lower for the height of 90 cm as compared to the height of 70 cm (\(p<0.05\)). No significant interactions or main effects were found for the remaining biomechanical variables examined (\(p>0.05\)).  
The results regarding the EMG measurements are presented in Table 3. In brief, interactions were noted for three variables, namely Mean EMG VM during phase 1, Peak EMG VM during phase 1, and Peak EMG ES during phase 1 (\(p<0.05\)). Post hoc analysis demonstrated that for the Mean EMG VM and Peak EMG ES during phase 1, the EMG activity was higher while lifting the agricultural crate with a destination height of 90 compared to 70 cm (\(p<0.05\)). On the other hand, Peak EMG VM during phase 1 was higher for both 80 and 90 cm heights compared to 70 cm (\(p<0.05\)). No significant differences were observed for the EMG variables during the other two phases (\(p>0.05\)).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Variables**} & \multicolumn{3}{c}{**Height**} & \multirow{2}{*}{\(p\)} \\ \cline{2-2} \cline{4-5}  & **70 cm** & & **80 cm** & & **90 cm** \\ \hline GRF1 & 34.81 \(\pm\) 5.00 & 35.35 \(\pm\) 5.55 & 36.87 \(\pm\) 4.18 & NS \\ GRF2 & 76.64 \(\pm\) 7.33 & 77.69 \(\pm\) 6.88 & 74.63 \(\pm\) 5.73 & NS \\ GRF3 & 43.08 \(\pm\) 7.77 & 45.39 \(\pm\) 5.76 & 44.98 \(\pm\) 4.60 & NS \\ GRF4 & 63.22 \(\pm\) 6.58 & 62.39 \(\pm\) 4.06 & 62.50 \(\pm\) 5.70 & NS \\ KNEE MOMENT 1 & 0.65 \(\pm\) 0.34 & 0.69 \(\pm\) 0.27 & 0.74 \(\pm\) 0.27 & NS \\ KNEE MOMENT 2 & \(-\)0.27 \(\pm\) 0.16 & \(-\)0.25 \(\pm\) 0.13 & \(-\)0.22 \(\pm\) 0.10 & NS \\ KNEE MOMENT 3 & \(-\)0.91 \(\pm\) 0.32 & \(-\)0.82 \(\pm\) 0.26 & \(-\)0.81 \(\pm\) 0.24 & <0.05 \\ KNEE ANGLE MAX & 88.55 \(\pm\) 17.59 & 91.93 \(\pm\) 17.94 & 93.44 \(\pm\) 17.42 & <0.05 \\ HIP ANGLE MAX & 101.45 \(\pm\) 4.40 & 101.50 \(\pm\) 4.95 & 101 \(\pm\) 6.20 & NS \\ HIP MOMENT 1 & 1.73 \(\pm\) 0.20 & 1.78 \(\pm\) 0.25 & 1.75 \(\pm\) 0.24 & NS \\ HIP MOMENT 2 & 1.34 \(\pm\) 0.26 & 1.22 \(\pm\) 0.28 & 1.11 \(\pm\) 0.22 & <0.05 \\ ANKLE ANGLE MAX & 28.26 \(\pm\) 10.82 & 29.33 \(\pm\) 11.11 & 29.01 \(\pm\) 9.99 & NS \\ ANKLE MOMENT 1 & 0.97 \(\pm\) 0.16 & 0.97 \(\pm\) 0.15 & 0.92 \(\pm\) 0.15 & NS \\ ANKLE MOMENT 2 & 0.92 \(\pm\) 0.15 & 0.90 \(\pm\) 0.14 & 0.89 \(\pm\) 0.15 & NS \\ KNEE POWER 1 & \(-\)1.12 \(\pm\) 0.51 & \(-\)1.03 \(\pm\) 0.40 & \(-\)1.07 \(\pm\) 0.63 & NS \\ KNEE POWER 2 & 0.94 \(\pm\) 0.81 & 1.03\(\pm\) 0.77 & 1.05 \(\pm\) 1.10 & NS \\ HIP POWER 1 & \(-\)1.84 \(\pm\) 0.44 & \(-\)1.88 \(\pm\) 0.58 & \(-\)1.76\(\pm\) 0.49 & NS \\ HIP POWER 2 & 3.14 \(\pm\) 0.84 & 3.30 \(\pm\) 0.91 & 3.11 \(\pm\) 0.72 & NS \\ ANKLE POWER 1 & \(-\)0.21 \(\pm\) 0.09 & \(-\)0.21 \(\pm\) 0.09 & \(-\)0.18 \(\pm\) 0.07 & NS \\ ANKLE POWER 2 & 0.69 \(\pm\) 0.39 & 0.63 \(\pm\) 0.21 & 0.64 \(\pm\) 0.29 & NS \\ ANKLE POWER 3 & 0.20 \(\pm\) 0.07 & 0.21 \(\pm\) 0.09 & 0.20 \(\pm\) 0.57 & NS \\ \hline \hline \end{tabular} GRF: Ground Reaction Forces; NS: Non-Significant.  
\end{table}
Table 2: Biomechanical variables during the symmetric lifting task for heights 70, 80, and 90 cm; data are reported as mean \(\pm\) standard deviation. Please, refer to Figure 3 for the graphical representation of the selected variables and Table 1 for full variable description.