## 2 Materials and Methods  
Experimental design and subjects  
A cross-sectional study was conducted. A total of 121 participants, 57 boys and 64 girls, aged between 10 and 18 years (mean, 13.8 \(\pm\) 1.9 years), from four Portuguese public schools and who were involved in different types of sports participation, joined the present study. All the participants filled out the sports injury questionnaires and were instructed to wear an ActiGraph GT3X activity monitor for 5 days. The other variables, related to maturity evaluation (according to Mirwald and TW3-bone age), were obtained at the same time \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Intrinsic Influence Factors**} & \multicolumn{2}{c}{**Extrinsic Influence Factors**} \\ \hline
**Non-Modifiable** & **Modifiable** & **Non-Modifiable** & **Modifiable** \\ \hline \multirow{4}{*}{Previous injuries; age; sex; anthropometric characteristics; maturation & Neuromuscular control; strength; flexibility; stability; general physical fitness; biomechanical factors; psychosocial factors & Type of sport (team/individual, contact/non contact); competition level; technical gestures; sports season period & Exposure (volume, intensity, frequency); practice environmental context; footwear and protective equipment; respect for rules and sports ethics \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sports injury influence factors in children and adolescents. as described below. Before inclusion in the study, all the participants' guardians gave their written informed consent. The research protocol was in accordance with the Helsinki Declaration and was approved by the Ethics Committee of the Faculty of Human Kinetics, University of Lisbon. Testing methods  
To assess the injury profile, the LESADO questionnaire was used. LESADO is a self-reported questionnaire that gathers information about the injury profile. Valid and reliable information about injury on children aged 10+ years [37] can be obtained through self-report surveys [38]. However, children under the age of 12 years may require assistance to complete it [38]. To prevent bias and interpretation difficulties, all the participants were guided by the investigator when completing the questionnaires. The time frame used was 6 months, as recommended in retrospective studies [39]. A clear definition of injury based on current epidemiological research was also provided [40; 41]. LESADO comes from an extensive literature review on the topic and was adapted and based on epidemiological questionnaires used in Portuguese sports samples [15; 16; 42; 43]. Daily physical activity was measured using an ActiGraph GT3X activity monitor (Actigraph LLC, Fort Walton Beach, FL, USA) worn around the waist, for five consecutive days (three weekdays and two weekend days). This device is a small (3.8 \(\times\) 3.7 \(\times\) 1.8 cm), lightweight (27 g) accelerometer that uses a piezoelectric acceleration sensor to collect motion data in three axes: vertical (Y), horizontal right-left (X) and horizontal front-back (Z). These data are filtered into signals of frequency in hertz, for an interval of time or epoch [44; 45]. The epochs were established as 1 s of time wear and then converted into 5 s counts of activity, which were linearly related to the intensity of PA during those periods of time [46]. A valid day was defined as a day with more than 600 min of device wear, and non-wear periods were determined as those with more than 60 continuous zero-activity counts [47]. Participants were only included in the study if they had at least three valid wear days. All the participants were instructed to wear the accelerometer while awake and to take it off for any water-based activity (e.g., showering or swimming), any activity that could compromise the physical performance or integrity of the device (e.g., gymnastics or sports fights) and activity that involved cycling or rolling. The participants were instructed to record the abovementioned instances when they took off the accelerometer in a diary [47].