## 2 Materials and Methods
### Shooting  
Participants completed a 15-min warm-up that included jogging, diribbling, shooting, and dynamic stretching. After the warm-up, nine anatomical landmarks (1.5 cm in diameter) with reflective markers were placed over the skin and clothes in the following positions: on the tragus to define the ear; on the greater trochanter of the humerus to define the shoulder; on the lateral epicondyle of the humerus to define the elbow; on the ulnar styloid process to define the wrist; on the head of the fifth metacarpal to define the hand; on the greater trochanter of the femur to define the hip; on the lateral epicondyle of the fibula to define the knee; on the lateral malleolus of the fibula to determine the ankle; and on the head of the fifth metatarsal to define the foot [17]. A single investigator placed all landmarks on each participant's dominant side. Each participant performed 10 BS trials from a frontal position at 5.75 m from the basket with both ball sizes: a smaller and lighter ball (Wilson MVP Size 5, 480 g); and the standard ball size for their age (Wilson Evolution Size 6, 566 g). One investigator caught the rebound of each shot, and the ball was given back to the shooter through a direct pass. A second investigator was responsible for filming each BS attempt with a digital camera (Sony Cyber-Shot RX100, 120 Hz) positioned in the sagittal plane at 7 m from the participant's dominant side and 1.20 m from the floor (Figure 1). A third investigator recorded the BS outcome using an efficacy rating system composed of five levels [6]: (4 points) successful attempts that did not hit the rim; (3 points) successful attempts that hit exclusively any part of the rim; (2 points) successful attempts that hit the backboard or any part of the rim; (1 point) unsuccessful attempts that hit either the rim or the backboard; and (0) unsuccessful attempts that did not hit anything (\"air ball\"). After data collection, a total of 540 video recordings (20 from each participant) were exported and analyzed using Tracker software (Open-Source Physics--Video Analysis and Modelling Tool, 5.1.5) to assess the kinematic variables. Video calibration was performed using a reference object with known dimensions placed in the plane of the movement. The calibration factor was evaluated using a 2D-DLT (direct linear transformation) [26; 27], considering the vertical and horizontal dimensions of the reference object. A single investigator performed all analyses. A previous pilot study to assess our methods was conducted on ten female basketball players aged 14.7 \(\pm\) 0.6 years. From the 300 video recordings collected, 30 files were randomly selected to calculate the intra-observer reliability coefficient (R). For the ball release variables, the following results were obtained: angle (R = 0.91), velocity (R = 0.87), and height (R = 0.90); these values show a good consistency of the analysis. Figure 1: Schematic representation of data collection. For the BS analysis, the following kinematic parameters were assessed: ball release variables (angle, velocity, and height); the 2D position of the center of mass (CoM) (total horizontal displacement and the maximum height attained); the position of the hip (maximum height and height at ball release); the shoulder, elbow, and knee joint angles at ball release and the minimum angle formed by the knee (transition between the first and second phases of the movement) for the sagittal plane of movement (flexion-extension); the angular velocities of the shoulder, elbow, and knee joints (the peak of angular velocity and the angular velocity at ball release), also for the sagittal plane. Ball release was defined by the last perceptible frame where the player's hand was in contact with the ball. The ball trajectory was studied at the ball release point and five frames before and after the ball release point [28]. The ball release velocity was defined by the velocity value immediately after ball release.