Conceptual development of a lower-limb performance measurement device

Abstract

This study develops a prototype-oriented lower-limb performance measurement device that combines adjustable resistance with synchronized force, angle and pressure measurement during knee extension and flexion exercises. The work bridges the gap between conventional resistance machines, which are mechanically simple but provide limited measurement feedback, and advanced rehabilitation systems, which often involve higher cost and system complexity. A requirements-driven mechanical design approach is used to define functional needs, compare resistance and angle-measurement alternatives, and develop the selected concept into a buildable device layout. The final design is based on a seated combined leg-extension and leg-curl arrangement with a rotating exercise arm, leg roller and double-acting pneumatic cylinder for adjustable resistance. Measurement integration is achieved using a uniaxial strain-gauge load cell for transmitted user-contact force, an incremental rotary encoder for exercise-arm angle, a gauge-pressure transducer for pneumatic resistance monitoring and a microcontroller-based data acquisition system (DAQ) for synchronized signal recording. The resulting design provides a compact and manufacturable basis for a measurement-capable prototype by defining the mechanical layout, pneumatic circuit, measurement integration, structural implementation and safety provisions required for prototype construction. Further work should include prototype fabrication, sensor calibration, pneumatic testing, safety verification and experimental validation.