# Lifting Activities Assessment Using Lumbosacral Compression and Shear Forces
## 3 Results  
Figure 2 shows the mean and standard deviation for each lifting condition of the \(CF_{L5-S1}\) and \(SF_{L5-S1}\) evaluated with both lower (continuous lines) and upper models (dotted lines). Also, in Figure 2, the trunk flexion-extension angle curves were reported.  
Figures 3 and 4 show the means and standard deviations for each parameter for compression and shear forces, respectively.  
The repeated measures ANOVA revealed a significant effect of the LI on the Max, Mean, and Range for all forces evaluated with the lower model and upper model (\(CF_{L5-S1}\) [N], \(SF_{L5-S1}\) [N], \(CF_{L5-S1,\text{Norm}}\) [N/kg], \(SF_{L5-S1,\text{Norm}}\) [N/kg], \(|CF_{L5-S1}-CF_{L5-S1}\)Standing [N] and \(|SF_{L5-S1}-SF_{L5-S1,\text{Standing}}\) [N]) except for \(|CF_{L5-S1}-CF_{L5-S1,\text{Standing}}|\) [N] evaluated with lower model (\(p=0.058\)), see Table 2.  
The power analysis for the investigated sample was 0.83.  
Table 3 shows the \(p\) values of the paired t-test with [PERSON]'s corrections for Maximum, Mean, and Range for all considered forces, which highlight the differences between pairs of LI. Furthermore, the Cohen's d values were reported.  
Figure 2: Compression (\(CF_{L5-S1}\), (**a**)) and shear (\(SF_{L5-S1}\), (**b**)) forces evaluated with both lower (continuous lines) and upper models (dotted lines) and trunk flexion-extension (**c**) during the execution of the lifting tasks in the three different conditions (LI = 1 in green, LI = 2 in yellow, and LI = 3 in red). Curves represent the mean values with shaded SDs. Data are normalized to the lifting duration and reduced to 101 samples over the cycle.  
Figure 4: Means and standard deviations of Maximum, Mean, and Range values for shear forces in N (**a**), forces normalized with respect to the body weight in N/kg (**b**) and normalized with respect to the forces during standing phase in N (**c**) in each risk level condition for both lower and upper models. LI: lifting index. * Significant differences at post hoc analysis.  
\begin{table}
\begin{tabular}{l l l l l l l l l} \hline \hline  & & \multicolumn{2}{c}{**LI**} & \multicolumn{2}{c}{**Maximum**} & \multicolumn{2}{c}{**Mean**} & \multicolumn{2}{c}{**Range**} \\ \cline{3-10}  & & & \(p\) **Value** & **Cohen’s d** & \(p\) **Value** & **Cohen’s d** & \(p\) **Value** & **Cohen’s d** \\ \hline \multirow{4}{*}{Lower Model} & \multirow{4}{*}{\(CF_{L5-S1}\) [N]} & 1 vs. 2 & 1.000 & 0.007 & **0.005** & 0.41 & 0.053 & 0.55 \\  & & 1 vs. 3 & **0.001** & 1.16 & **<0.001** & 2.99 & **<0.001** & 2.63 \\  & & 2 vs. 3 & **0.001** & 1.05 & **<0.001** & 2.37 & **<0.001** & 2.10 \\  & & 1 vs. 2 & 1.000 & 0.02 & **0.008** & 0.52 & 0.066 & 0.53 \\  & & 1 vs. 3 & **<0.001** & 3.16 & **<0.001** & 4.74 & **0.002** & 1.52 \\  & & 2 vs. 3 & **<0.001** & 2.74 & **<0.001** & 3.95 & **0.010** & 0.95 \\  & & 1 vs. 2 & 0.487 & 0.32 & 0.051 & 0.54 & 0.178 & 0.55 \\  & & 1 vs. 3 & **<0.001** & 3.57 & 0.595 & 0.42 & **<0.001** & 3.78 \\  & & 2 vs. 3 & **<0.001** & 2.86 & 0.053 & 0.87 & **<0.001** & 3.72 \\ \hline \hline \end{tabular}
\end{table}
Table 3: \(p\) values of the paired t-test with Bonferroni’s corrections for Maximum, Mean, and Range for compression and shear forces in N (\(CF_{L5-S1}\) and \(SF_{L5-S1}\)), normalized with respect to the body weight (\(CF_{L5-S1,\text{Norm}}\) and \(SF_{L5-S1,\text{Norm}}\)) and normalized with respect to the \(F_{L5-S1}\) during the standing phase (\(|CF_{L5-S1}-CF_{L5-S1_{Smaling}}|\) and \(|SF_{L5-S1}-SF_{L5-S1_{Smaling}}|\)) evaluated with the lower model and upper model. [PERSON]’s d values indicate the effect size for the comparison between the LI pairs means (“small” if d = 0.2, “medium” if d = 0.5, “large” if d = 0.8, “Very large” if d = 1.20, “Huge” if d = 2.0). Bold type indicates significant differences.