# A Comparative Analysis of IMUs and Optical Systems in Layup Shot Biomechanics
## 2 Materials and Methods
### Testing Protocol  
Following a dynamic self-selected warm-up and familiarization with the lab setup, participants performed a total of 20 layup shots (Figure 2A). Each shot was taken from the right at a 45\({}^{\circ}\) angle after running approximately 5 to 6 m towards the hoop (Figure 2B). Of these trials, 10 were defended, and 10 were undefended. Calibration procedures and relevant anthropometric measurements were undertaken for each system following the manufacturer's guidelines prior to testing. The calibration process included both static (N-pose) and dynamic (walking) for Xsens and static (N-pose) and dynamic (walking) for Vicon. The Xsens biomechanical model was scaled using the anthropometric data (height, arm span, elbow span, shoulder and hip width and height, and knee and ankle height) collected from each participant before testing.  
Figure 1: Marker and sensor (green circles) placement on the participant. Markers were placed on the following body landmarks: C7, T10, the sternum, clavide, anterior/posterior shoulder, elbow lateral/medial epicondyles, distal ulna/radius, 1 st and 5 th metacarpal heads, distal middle finger, posterior heel, 1 st and 5 th metacarsal heads, 1 st toe, lateral and medial malleloi, lateral and medial femoral epicondyles, anterior and posterior superior iliac spines, greater trochanters, and the head (19 mm in diameter). Sensors are circled in green (right and left figures) and were placed on the back of the head, sternum, shoulders (middle of the scapula spine), upper arms (lateral side above elbow), forearms (lateral side above wrist), hands (posterior side), pelvis (middle of both the posterior superior iliac spines), thighs (lateral side above the knees), shanks (upper surface of the tibials), and forefeet (dorsal side).  
Figure 2: (**A**) Protocol workflow for data collection, illustrating the sequential steps of the testing procedure, circles are indicative of sensor application. (**B**) A top-down view of the testing lab set-up, including the camera arrangement around the capture volume, the position of the basketball hoop and defender, and the participant’s starting position and path of travel toward the basket. The cameras depicted as icons with a white interior indicate the presence of two cameras at the same position, arranged on two different levels: high-mounted cameras positioned overhead and middle-mounted cameras placed horizontally parallel to the capture volume. This configuration ensured comprehensive coverage, providing both top-down and horizontal perspectives for motion capture and analysis.  
Defence was administered by a second experimenter using a padded wooden stick. The stick was introduced at chest height, approximately 50 cm in front of the participant's leading shoulder, ensuring it required an in-air adjustment without obstructing natural movement. The timing and intensity of the defence were consistent across all trials, with the stick introduced at a predetermined point in the participant's movement to maintain standardization. The hoop was positioned 2.9 m above of the defender, preserving a consistent spatial relationship between the defensive action and the layup attempt (Figure 2A). To ensure randomization, the order of whether the defence was introduced or not was randomly assigned across trials. The defence was not physically forceful but aimed to simulate typical game constraints without interfering with the participant's ability to complete the layup.