# A Comparative Analysis of IMUs and Optical Systems in Layup Shot Biomechanics
## 3 Results
### Continuous Measures  
Between-system offset (RMSD) were calculated for joint angles (Table 1). Flexion-extension shoulder joint angles exhibited consistently high RMSD levels (right: 9.3\({}^{\circ}\), left: 9.3\({}^{\circ}\)) despite trajectories showing overall consistency. Shoulder abduction-adduction and external-internal joint angles demonstrated RMSD values of 11.2\({}^{\circ}\) (1.22) and 12.8\({}^{\circ}\) (0.70) for the right shoulder abduction-adduction and external-internal joint angles and 6.9\({}^{\circ}\) (1.13) and 10.2\({}^{\circ}\) (2.81) for the left shoulder abduction-adduction and external-internal joint angles, respectively. Smaller joints, such as the wrist and ankle, exhibited lower RMSD values for flexion-extension angles (right wrist: 4.9\({}^{\circ}\), left wrist: 5.1\({}^{\circ}\); right ankle: 5.6\({}^{\circ}\), left ankle: 6.4\({}^{\circ}\)) and for ulnar-radial deviation at the wrist and external-internal rotation at the ankle (right wrist: 5.4\({}^{\circ}\), left wrist: 4.3\({}^{\circ}\); right ankle: 4.9\({}^{\circ}\), left ankle: 6.7\({}^{\circ}\)). Although flexion-extension angles of the knee and elbow showed relatively higher errors (Table 1), the overall trajectory patterns for these joints were consistent across systems (Figure 4).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**Between-System RMSD (\({}^{\circ}\))**} & \multicolumn{2}{c}{**Between-Condition RMSD (\({}^{\circ}\))**} \\ \hline \multicolumn{2}{c}{**Joint Angle**} & & **Right Limb** & **Left Limb** & **XSENS** & **VICON** & **Offset *** \\ \hline \multirow{3}{*}{Shoulder} & Flexion-extension & 9.3 (0.79) & 9.3 (3.88) & 21.4 & 23.5 & 2.1 \\ \cline{2-7}  & Abduction-adduction & 11.2 (1.22) & 6.9 (1.13) & 11.2 & 10.9 & 0.3 \\ \cline{2-7}  & External-internal & 12.8 (0.70) & 10.2 (2.81) & 17.8 & 22.7 & 4.9 \\ \hline \multirow{3}{*}{Elbow} & Flexion-extension & 7.1 (0.74) & 5.5 (4.71) & 17.6 & 17.3 & 0.3 \\ \cline{2-7}  & Supination-pronation & 9.9 (0.95) & 6.9 (1.60) & 17.2 & 20.7 & 3.5 \\ \hline \multirow{3}{*}{Wrist} & Flexion-extension & 4.9 (0.98) & 5.1 (3.56) & 17.5 & 17.2 & 0.3 \\ \cline{2-7}  & Ulnar-Radial Deviation & 5.4 (0.56) & 4.3 (1.23) & 8.3 & 7.6 & 0.7 \\ \hline \multirow{3}{*}{Hip} & Flexion-extension & 9.2 (0.81) & 9.4 (0.60) & 12.9 & 12.1 & 0.8 \\ \cline{2-7}  & Abduction-adduction & 7.6 (1.46) & 7.26 (0.54) & 6.8 & 5.9 & 0.8 \\ \cline{2-7}  & External-internal & 7.7 (0.70) & 7.6 (0.77) & 9.2 & 7.5 & 1.6 \\ \hline \multirow{3}{*}{Knee} & Flexion-extension & 6.7 (0.74) & 7.3 (2.95) & 12.9 & 12.9 & 0.0 \\ \cline{2-7}  & Flexion-extension & 5.6 (0.52) & 6.4 (1.37) & 9.4 & 8.9 & 0.5 \\ \cline{2-7}  & External-internal & 4.9 (0.48) & 6.7 (0.59) & 4.9 & 4.1 & 0.8 \\ \hline \end{tabular}  
* Difference between the change detected by Xsens and change detected by Vicon when comparing defended to undefended conditions.  
\end{table}
Table 1: Offset between joint angles of both systems in degrees (\({}^{\circ}\)) presented as group mean (standard deviation) and the between-condition changes detected by each system and the offset between the systems; results of the jumping leg (right side).  
Figure 3: Single participant example of the Bland–Altman plots of the jump height (meters) and take-off angle (\({}^{\circ}\)) data. For all participants, no more than two data points fell outside the acceptable difference range, with most participants displaying no data points falling outside the limits of agreement range, indicating high agreeability between the outputs from both systems.  
Xsens' COM tracking (displacement in meters) during the layup shot was closest to Vicon in the vertical direction (z), with a 0.029 m (0.002) offset. The resultant horizontal displacement of the COMx and COMy had a mean 8% difference between the systems over roughly 2 m of total travel.