## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & & \multicolumn{3}{c}{**h\({}_{\text{peak}}\)**} & \multicolumn{3}{c}{**L**} \\ \cline{2-9}  & **CV\%** & **TE (cm)** & **r** & **p** & **CV\%** & **TE (cm)** & **r** & **p** \\ \hline Validity & 2.24 & 6.16 & 0.97 & 0.06 & 4.64 & 10.59 & 0.98 & 0.43 \\ Intrarater reliability & 0.44 & 1.21 & 0.99 & 0.81 & 0.87 & 1.98 & 0.99 & 0.14 \\ Interrater reliability & 0.51 & 1.40 & 0.99 & 0.55 & 0.72 & 1.63 & 0.99 & 0.44 \\ \hline \end{tabular}
\end{table} 
Table 2: Random error (CV%), typical error (TE), correlation coefficient, and systematic error (p) of peak height (h\({}_{\text{peak}}\)) and length of flight (L) of vaults, when comparing first 2D video analysis (2D\({}_{1}\)) evaluations to 3D motion capture (validity) and to second 2D analysis (intrarater reliability), as well as second 2D video analysis (2D\({}_{2}\)) and expert 2D video analysis (2D\({}_{\text{e}}\)) (interrater reliability). caused the reference length to be slightly too long, although this effect was too small to be apparent in our results (nonsignificant p-value). In this study, we observed a tendency toward a systematic underestimation of hpeak with 2D analysis. Since the measurements of the experienced assessor were not statistically different from the values of the first-time assessor, it can be assumed that both assessors encountered the same basic problem that may have led to this tendency. In particular, it was difficult to determine the zero-point on the landing mat vertically underneath the highest point of the center of gravity during the second flight phase. We assume that this was the reason for the (almost significant) underestimation of hpeak. Nonetheless, considering the small measurement error when determining hpeak, 2D analysis may be considered a valid method. This knowledge is especially worthwhile since the height of flight dictates the potential to perform somersaults and twists during the second flight phase, and it is therefore an important performance-determining factor for vaults. When comparing 2D analysis at two consecutive points in time, the variation coefficients of the hpeak and L of vaults were very low. For instance, the differences of 2D analysis were only 1.21 cm (hpeak) and 1.98 cm (L), at a mean height of 2.75 m and a mean length of 2.28 m. These minor random errors are likely due to slightly different definitions of the zero-points (on the landing mat or at the end of the vaulting table), or of the gymnast's center of gravity (hpeak) or ankle (L), rather than a different determination of the frame at which hpeak or L were determined. Therefore, the almost perfect correlation of the first and second 2D analysis and the low variation coefficient values demonstrate a very high intrarater reliability. Thus, 2D analysis using Dartfish (Dartfish SA, Fribourg, CH) is a reliable and reproducible measure for the hpeak and L of vaults. This result is in line with the findings of [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] (2015), who, among other things, examined intrarater reliability of 2D analyses of joint angles during running. They measured kinematic variables during running on a treadmill with the same video analytical software we used (Dartfish SA, Fribourg, CH), and they reported excellent intrarater reliability [7]. Other studies have also shown 2D analyses to be reliable for measuring joint angles [6] and flight height [9]. Lastly, we compared the values of hpeak and L evaluated by an experienced assessor with those evaluated by a first-time assessor. Our results show that the hpeak and L of vaults are similar, as the coefficients of variance are low and the correlations are high. In this context, it should be mentioned that a brief introduction to the measurement software and determination of center of gravity is sufficient but indispensable. Therefore, 2D analysis is a straightforward measurement tool, where values of an inexperienced assessor, for example, those evaluated by a coach, are comparable to those of an expert.