## 3 Results  
The Pearson correlation between radar and GPS 1 was moderate for \(\tau\) (r \(=\) 0.49 [CI \(=\) 0.26-0.66]), and very strong for F\({}_{0}\) (r \(=\) 0.84 [CI \(=\) 0.75-0.91]), P\({}_{\text{max}}\) (r \(=\) 0.97 [CI \(=\) 0.95-0.98]), V\({}_{0}\) (r \(=\) 0.99 [CI \(=\) 0.98-0.99]) and V\({}_{\text{max}}\) (r \(=\) 0.99 [CI \(=\) 0.98-0.99]). The Pearson correlation for radar and GPS 2 data was poor for \(\tau\) (r \(=\) 0.38 [CI \(=\) 0.13-0.58]), strong for F\({}_{0}\) (r \(=\) 0.79 [CI \(=\) 0.67-0.87]), and very strong for P\({}_{\text{max}}\) (r \(=\) 0.95 [CI \(=\) 0.92-0.97]), V\({}_{0}\) (r \(=\) 0.99 [CI \(=\) 0.98-0.99]) and V\({}_{\text{max}}\) (r \(=\) 0.99 [CI \(=\) 0.99-1]). The concurrent validity analysis results are presented in Table 1 and overall show that mean biases are small to moderate, and typical errors are small to large for the various variables. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **P\({}_{\text{max}}\) (W\(\cdot\)kg\({}^{-1}\))** & **F\({}_{0}\) (N\(\cdot\)kg\({}^{-1}\))** & **V\({}_{0}\) (m\(\cdot\)s\({}^{-1}\))** & **V\({}_{\text{max}}\) (m\(\cdot\)s\({}^{-1}\))** & **\(\tau\) (s)** \\ \hline GPS 1 Validity & & & & & \\ \hline Radar & 14.3 \(\pm\) 3.1 & 6.7 \(\pm\) 0.69 & 8.5 \(\pm\) 1.2 & 8.2 \(\pm\) 1.1 & 1.2 \(\pm\) 0.1 \\ \hline GPS 1 & 14.3 \(\pm\) 3.6 & 6.6 \(\pm\) 0.97 & 8.5 \(\pm\) 1.2 & 8.2 \(\pm\) 1.1 & 1.2 \(\pm\) 0.1 \\ \hline Mean bias (\%) & 1.3 & 1.4 & 0.08 & 0.11 & \(-\)1.3 \\ \hline Standardized mean bias & 0.01 & 0.08 & 0.00 & 0.01 & \(-\)0.17 \\ \hline TEE as CV (\%) & 5.5 & 5.7 & 2.2 & 1.9 & 7.6 \\ \hline Standardized TEE & 0.26 & 0.64 & 0.16 & 0.15 & 1.8 \\ \hline GPS 2 Validity & & & & & \\ \hline Radar & 14.3 \(\pm\) 3.1 & 6.7 \(\pm\) 0.69 & 8.5 \(\pm\) 1.2 & 8.2 \(\pm\) 1.1 & 1.2 \(\pm\) 0.1 \\ \hline GPS 2 & 14.4 \(\pm\) 3.8 & 6.7 \(\pm\) 0.97 & 8.5 \(\pm\) 1.2 & 8.2 \(\pm\) 1.1 & 1.2 \(\pm\) 0.1 \\ \hline Mean bias (\%) & 0.77 & 1.3 & \(-\)0.54 & \(-\)0.49 & \(-\)1.8 \\ \hline \end{tabular}
\end{table} 
Table 1: Concurrent validity analysis. Means and standard deviations [SD] of raw data are presented for the reference device (radar) and the tested devices (GPS 1 and GPS 2). CV: coefficient of variation. TEE: typical error of estimate. P\({}_{\text{max}}\): maximal horizontal power. F\({}_{0}\): theoretical maximal horizontal force. V\({}_{0}\): theoretical maximal horizontal running velocity. V\({}_{\text{max}}\): actual maximal running velocity. \(\tau\): acceleration time constant. The results of inter-unit reliability are shown in Table 2 and overall show that correlations between the two GPS are excellent to moderate, and typical errors are small to large for the different variables. The results of the Bland and Altman analysis are illustrated in Figure 2. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & \(\mathbf{P_{max}}\) (W\(\cdot\)kg\({}^{-1}\)) & \(\mathbf{F_{0}}\) (N\(\cdot\)kg\({}^{-1}\)) & \(\mathbf{V_{0}}\) (m\(\cdot\)s\({}^{-1}\)) & \(\mathbf{V_{max}}\) (m\(\cdot\)s\({}^{-1}\)) & \(\boldsymbol{\tau}\) (s) \\ \hline \multicolumn{6}{c}{Reliability} \\ \hline GPS 1 (mean \(\pm\) SD) & 14.3 \(\pm\) 3.6 & 6.6 \(\pm\) 0.97 & 8.5 \(\pm\) 1.2 & 8.2 \(\pm\) 1.1 & **1.2**\(\pm\) 0.1 \\ \hline GPS 2 (mean \(\pm\) SD) & 14.4 \(\pm\) 3.8 & 6.7 \(\pm\) 0.97 & 8.5 \(\pm\) 1.2 & 8.2 \(\pm\) 1.1 & **1.2**\(\pm\) 0.1 \\ \hline TE as CV (\%) & 5.0 & 6.0 & 1.9 & 1.6 & 6.4 \\ \hline Standardized TE & 0.20 & 0.43 & 0.14 & 0.12 & 0.75 \\ \hline ICC (90\% CI) & 0.96 (0.94–0.98) & 0.85 (0.76–0.91) & 0.98 (0.97–0.99) & 0.99 (0.98–0.99) & 0.65 (0.47–0.78) \\ \hline ICC interpretation & Excellent & Good & Excellent & Excellent & Moderate \\ \hline SWC (\%) & 5.1 & 3.1 & 2.8 & 2.7 & 2.1 \\ \hline Sensitivity & Good & Poor & Good & Good & Poor \\ \hline \end{tabular}
\end{table} 
Table 2: Inter-unit reliability. Means and standard deviations (SD) for the raw data are presented for the two devices tested (GPS 1 and GPS 2). CV: coefficient of variation. TE: typical error. ICC: intra-class correlation. CI: confidence interval.