## 2 Materials and Methods
### Instrumentation  
Acceleration data were collected via a tri-axial accelerometer measuring the magnitude of acceleration in the three axes (\(x\) = anterior-posterior, \(y\) = medial-lateral, \(z\) = vertical) and sampling at 100 Hz (ZephyrTM BioHarness v3, Zephyr Technology Corp., Annapolis, MD, USA). Using the chest strap provided by the manufacturer, the accelerometer was securely placed at the level of the xiphoid process, along the midsternal line. The sensor calibration and error model of the sensor is propriety to the manufacturer and has not been described by ZephyrTM. Four accelerometry derived metrics were used in this study; the formula for each accelerometry based metric is described in Table 3. To expedite data analysis, the beginning and end of each trial were marked by the participant tapping on the accelerometer four times.  
A triple GNSS sensor sampling at 10 Hz and acquiring signals from GPS, GLONASS, and Galileo networks (Titan Sensors 2, Houston, TX, USA) was used to measure the distance covered by each participant (GNSSD). All trials were performed on an outside field, clear of large buildings, and with a clear sky to enhance satellite acquisitions. The number of satellites connected to the receiver during the trials ranged between 19-26. A previous study that used GNSS reported the horizontal dilution of precision (HDOP) 0.4 \(\pm\) 0, while the satellites connected held between 18-20 [25]. The GNSS unit was activated 10-15 min prior to data collection and securely fixed to clothing on the back of participants at the base of the cervical spine between scapulae. Video was recorded (iPhone 6; 1080 p at 30 fps, Cupertino, CA, USA) and synced with GNSS data to verify the beginning and end of each trial.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Participants** & **Large Circle** & **Known Distance/m** & **Small Circle** & **Known Distance/m** \\ \hline
19 & 9.5 & 238.76 & 24 & 150.80 \\
20 & 10 & 251.33 & 22 & 138.23 \\
21 & 10.5 & 263.89 & 20 & 125.66 \\
22 & 11 & 276.46 & 18 & 113.10 \\
23 & 11.5 & 289.03 & 16 & 100.53 \\
24 & 12 & 301.59 & 14 & 87.96 \\
25 & 12.5 & 314.16 & 12 & 75.40 \\
26 & 13 & 326.73 & 10 & 62.83 \\
27 & 13.5 & 339.29 & 8 & 50.27 \\
28 & 14 & 351.86 & 6 & 37.70 \\
29 & 14.5 & 364.42 & 4 & 25.13 \\
30 & 15 & 376.99 & 2 & 12.57 \\ \hline \hline \end{tabular}
\end{table}
Table 2: _Cont._  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Metric** & **Definition and Formula * \\ \hline SUM & \(SUM=\sum\limits_{s=1}^{n}\sqrt{x_{s}^{2}}+\sqrt{y_{s}^{2}}+\sqrt{z_{s}^{2}}\) \\ MAG & \(MAG=\sum\limits_{s=1}^{n}\sqrt{x_{s}^{2}+y_{s}^{2}}+z_{s}^{2}\) \\ Impulse Load ** & \(IL=\sum\limits_{s=1}^{n}\frac{\sqrt{x_{s}^{2}+y_{s}^{2}+z_{s}^{2}}}{9.8067}\) \\ Player Load & \(PL=\sum\limits_{s=1}^{n}\frac{\sqrt{(x_{s=i+1}-x_{s=i})^{2}}+(y_{s=i+1}-y_{s=i})^ {2}+(z_{s=i+1}-z_{s=i})^{2}}{100}\) \\ \hline \hline \end{tabular}  
* In the formulas above, \(x\) = forward and backward acceleration, \(y\) = lateral acceleration and \(z\) = vertical acceleration. ** IL is propriety to the manufacturer and is only associated with locomotor events that are detected by Zephyr (e.g., walking, running, bounding, jumping).  
\end{table}
Table 3: Formula for each accelerometry based metric.