## 4 Discussion
### Predictors of Injury Profile  
The injury type presented two predictors: the time spent on moderate PA and bone age. The odds of having a strain or a fracture compared to having a strain increased by 1.04 times per unit increment (minute) in the time spent on moderate PA. The nature of organized youth sports participation with longer periods of extensive training and participation in large numbers of competitive events may contribute to the increase in sports injuries [1; 14; 16]. Moreover, specialized athletes, in order to achieve their goals, may push themselves harder and play despite pain [10; 21; 24], often not respecting the adequate resting periods for a developing child [16; 24]. Likewise, repetitive movements expose the neuromuscular system and musculoskeletal tissues to repeated loads [30]. If sport specialization has already occurred, only one set of motor patterns will be trained, increasing the chance of injury [30]. Recent studies have emphasized that recreational free play is important precisely because regular and diversified PA allows the development of motor skills that are effective in preventing injuries [10; 13; 14; 21; 24; 66]. However, a transition in PA behavior in adolescence has been observed [57]. A shift from unstructured free PA towards sedentary activities during leisure time makes sports club participation the more important contributor to the daily time spent on MVPA [57], which can, as explained above, create favorable conditions for the occurrence of specific injuries. Also, as already seen in a larger sample [8], strains and fractures are more likely to occur near the PHV. Descriptive data showed that the majority of the study participants were near or in the PHV stage. The combination of more time spent on PA of moderate intensity and PHV may create conditions allowing strains and fractures to occur. Fractures are common during pubertal maturation due to deficits in bone mass [8; 20; 67], and at this stage, there are more accidental and traumatic injuries during sports practice [8; 26; 67; 60]. On the other hand, strains are more likely to occur in participants who have recently passed PHV. This condition makes them more vulnerable to excessive loads [8; 23; 68]. Although, after PHV, tissue and structural dynamic equilibrium begins to be reached, some degree of fragility still persists, especially in soft tissues [8; 20; 25]. Participants who have not developed certain skills such as strength, endurance and motor control may be at increased risk of injury as they begin to spend more time on moderate PA [14; 19]. Similar results were obtained for bone age. The odds of having a strain or fracture compared to having a strain decreased by 1.7 times per unit increment (years) in the bone age. It is observed that the participants of a lower biological age are normally more engaged in sports practice, which clearly increases the exposure to risk. Also, the growth process and biological development start at these ages, and an unbalanced phase of motor control and tissue adaptations occurs [16; 24; 69]. As mentioned above, strains and fractures are common in this stage [8; 13; 30; 70]. Increased vulnerability to traumatic and overuse injuries has been reported [2; 5; 30]. In addition to these factors, in PA, maturing children and adolescents are not grouped according to their biological age [14; 66]. Participants are normally grouped by chronological age. Children of the same chronological age may vary considerably in their biological maturity status, leading to apparent individual differences [22; 33; 36]. Athletes with higher biological ages perform better, being structurally and functionally stronger than those with lower biological ages [22; 30]. The direct confrontation between these two groups may represent a risk for injury [71]. Furthermore, younger children may not be cognitively prepared to participate in highly structured PA. Children who are easily distracted and have a lower capacity for understanding may present a higher injury risk [35].