This paper presents the Modular Assistive Vertebra (MAV), a key component of the FleXo exoskeleton. FleXo is a passive, soft back-support exoskeleton designed to enhance ergonomic support by providing lifting support without compressing the user's vertebrae. This study systematically investigates the MAV's force transmission properties through theoretical and experimental methods. The results demonstrate the MAV's capability to convert linear forces exerted by a pulling cable into torque while minimizing the transmission of linear forces. Experimental setups with varying geometrical configurations validate the theoretical models, providing insights into the design and optimization of ergonomic support devices.