## 3 Results  
Back curvature values were only altered over the familiarization protocol at the thoracic level (Figure 4). Indeed, the statistical analysis showed a significant main effect of familiarization on thoracic flexion for both STOOP (\(p=0.012\), \(\eta^{2}=0.02\)) and SQUAT (\(p=0.015\), \(\eta^{2}=0.02\)). For STOOP, post-hoc comparisons revealed that thoracic flexion in PRE-1 was significantly lower than POST-3, POST-4, and POST-6 (\(p<0.05\)). Moreover, the Student's \(t\)-tests revealed that PRE-CON (\(31.2\pm 10.1^{\circ}\)) was not different from PRE-1 (\(28.7\pm 10.8^{\circ}\); \(p=0.1\)) but significantly lower than POST-3 (\(33.2\pm 9.4^{\circ}\); \(p<0.01\)). For SQUAT, post-hoc comparisons revealed that only thoracic flexion in PRE-1 was significantly lower than in POST-3 and POST-6 (\(p<0.05\)). Student's \(t\)-tests showed that PRE-CON (\(27.6\pm 10.2^{\circ}\)) was not different from PRE-1 (\(27.6\pm 10.4^{\circ}\); \(p=0.9\)) but was significantly lower than POST-3 (\(31.7\pm 10.3^{\circ}\); \(p<0.01\)). There was no statistical main effect of familiarization on lumbar flexion, hip flexion, knee flexion, or smoothness (Table 1). Postural oscillations were also partially altered over the familiarization protocol (Table 2). There was a statistical main effect of familiarization on the confidence ellipse area for STOOP (\(p=0.002\), W = 0.17). Pairwise comparisons did not reveal a clear stabilization phase, as POST-6 yielded a smaller confidence ellipse value than POST-1 and POST-2 (\(p\leq 0.001\)) but not than PRE-1. There was also a statistical main effect on the confidence ellipse for SQUAT (\(p=0.02\), W = 0.12), but post-hoc tests could not tease out significant differences between sessions. The anteroposterior amplitude of CoP displacement was not significantly influenced by the familiarization protocol. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & **PRE-CON** & **PRE-1** & **POST-1** & **POST-2** & **POST-3** & **POST-4** & **POST-5** & **POST-6** \\ \hline \multirow{3}{*}{Lumber} & STOOP & 33 & 33.4 & 33.2 & 32.5 & 30.8 & 31.8 & 32.9 & 31.8 \\  & (9.9) & (8.9) & (9.6) & (10.6) & (8.7) & (9.7) & (9.2) & (9.8) \\ \cline{1-1}  & \multirow{3}{*}{SQUAT} & 16.1 & 16.6 & 16.4 & 16.1 & 14.0 & 14.2 & 14.8 & 14 \\  & & (10) & (9.5) & (9.6) & (11.9) & (9.7) & (12) & (9.6) & (11.6) \\ \hline \multirow{3}{*}{Hip} & STOOP & 77.7 & 81.5 & 82.4 & 82.0 & 83.1 & 82.5 & 82.3 & 82.7 \\  & & (11.7) & (10.8) & (12.4) & (9.2) & (10.2) & (10.3) & (10.5) & (11.6) \\ \cline{1-1}  & \multirow{3}{*}{SQUAT} & 94.8 & 96.5 & 94.3 & 94.8 & 96.2 & 95.3 & 94.0 & 95.8 \\ \cline{1-1}  & & (6.8) & (5.6) & (6.7) & (5.3) & (5.8) & (8.0) & (6.0) & (7.2) \\ \hline \multirow{3}{*}{Knee} & STOOP & 17.3 & 21.0 & 21.4 & 20.9 & 20.6 & 20.2 & 20.7 & 21.3 \\  & & (15.2) & (18.6) & (15.3) & (15.0) & (14.5) & (15.5) & (15.7) & (16.4) \\ \cline{1-1}  & \multirow{3}{*}{SQUAT} & 120.5 & 114.9 & 116.5 & 117.4 & 117.6 & 117.8 & 119.3 & 119.1 \\ \cline{1-1}  & & (19.4) & (19.0) & (17.0) & (17.8) & (18.7) & (16.5) & (15.1) & (14.4) \\ \hline \multirow{3}{*}{Smoothness} & STOOP & \(-1.6\) & \(-1.6\) & \(-1.6\) & \(-1.5\) & \(-1.6\) & \(-1.6\) & \(-1.6\) & \(-1.6\) \\  & (0.1) & (0.1) & (0.1) & (0.1) & (0.1) & (0.1) & (0.1) & (0.1) \\ \cline{1-1}  & \multirow{3}{*}{SQUAT} & \(-1.6\) & \(-1.5\) & \(-1.5\) & \(-1.5\) & \(-1.6\) & \(-1.6\) & \(-1.6\) & \(-1.6\) \\ \cline{1-1}  & & (0.1) & (0.1) & (0.1) & (0.1) & (0.1) & (0.1) & (0.1) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mean (standard deviation) of lumbar, hip, and knee kinematics and smoothness in STOOP and SQUAT in PRE-CON and over the familiarization protocol from PRE-1 to POST-6. Figure 4: Evolution of mean (SD) thoracic flexion (\({}^{\circ}\)) in PRE-CON and over the familiarization protocol from PRE-1 to POST-6 for STOOP and SQUAT. \({}^{\star}\) Statistically different from POST-3, POST-4, and POST-6 (\(p<0.05\)). # Statistically different from POST-3 and POST-6 (\(p<0.05\)). Neuromuscular parameters were only slightly influenced (Table 3).