Included volunteer participants were aged between 18-30 years, competing in the highest-level Portuguese volleyball league with a minimum of 10 years of volleyball practice. Participants were excluded in presence of injuries or discomfort that impeded maxi- mal jumping tests, history of surgery within the last 12 months or illness during data collection.

Ultrasound Tissue Characterization (UTC) captures tendon structure and quantifies the number of altered fibers. This technology classifies tendon structure into four echo types, reflecting tendon integrity and fibrillar organization. Data collection for the patellar tendon will be conducted with participants seated, hips and knees at 90° flexion, and feet supported on a stable surface. For the Achilles tendon, the participants will be lying down with ankle in neutral position. This positioning ensures the probe is aligned transversely to the tendons, enabling the acquisition of optimal ultrasound images without anisotropy. Ultrasound parameters will be standardized for all scans: a 40-second B-mode ultrasound using a 7-10 Hz linear transducer, with the probe attached to a tracking device that moves automatically along the tendon's perpendicular axis, capturing consecutive images at 0.2 mm intervals. A single scan of the tendons will be performed for each knee.

The data collection protocol includes the following tasks: countermovement jump and tuck jump test. Kinematic variables will be analyzed by recording the spatial positions of reflective markers placed on specific anatomical regions. Data will be captured using the Qualisys Motion Capture System (version 2021.2). Ground reaction forces will be measured using a force platform connected to a signal amplifier. The platform records the three components of ground reaction forces-anteroposterior, mediolateral, and vertical-via four sensors. The image capture hardware is connected to the Qualisys USB Analog Acquisition interface, synchronizing temporal, kinetic, and kinematic data with the Qualisys Track Manager (QTM) software.