This study investigates the joint mechanical power (JMP) distribution in the half squat (HS) exercise through the Power-Based Training (PBT) framework, aiming to validate its methodological usability and its suitability to characterize joint contributions across movement phases and load levels. Five professional weightlifters performed HS under five progressive loads (20–80% 1RM), while kinematics and kinetics were recorded with a Vicon motion capture system and force platforms. JMP at the hip, knee, and ankle was analyzed in four distinct movement phases. Results revealed that joint contributions varied significantly with both load and phase: under light loads, the knee contributed most to power production, whereas higher loads elicited a proximal shift, with the hip showing greater power absorption and production, and the ankle gaining relative contribution in the final lifting phase. The main eccentric (lowering deceleration) and concentric (lifting acceleration) phases concentrated the highest JMP values, though differences between phases diminished at higher loads, indicating a more homogeneous effort distribution. These findings highlight the adaptive inter-joint dynamics and support the PBT framework as a rigorous, replicable tool for biomechanical analysis. The results have direct implications for designing training, rehabilitation, and injury-prevention programs based on joint-specific mechanical demands.