Hausselle, Jérôme

Auditory feedback is a simple, low-cost training solution that can be used in rehabilitation, motor learning, and performance development. The use has been limited to the instruction of a single kinematic or kinetic target. The goal of this study was to determine if auditory feedback could be used to simultaneously train 2 lower-extremity parameters to perform a bodyweight back squat. A total of 42 healthy, young, recreationally active males participated in a 4-week training program to improve squat biomechanics. The Trained group (n = 22) received 4 weeks of auditory feedback. Feedback focused on knee flexion angle and center of pressure under the foot at maximum squat depth. The Control group (n = 20) performed squats without feedback. Subjects were tested pre, post, and 1 week after training. The Trained group achieved average target knee flexion angle within 1.73 (1.31) deg (P < .001) after training and 5.36 (3.29) deg (P < .01) at retention. While achieving target knee flexion angle, the Trained group maintained target center of pressure (P < .001). The Control group improved knee range of motion, but were not able to achieve both parameter targets at maximum squat depth (P < .90). Results from this study demonstrate that auditory feedback is an effective way to train 2 independent biomechanical targets simultaneously.

Advancements in computational musculoskeletal biomechanics are constrained by a lack of experimental measurement under real-time physiological loading conditions. This paper presents the design, configuration, capabilities, accuracy, and repeatability of The University of Texas at El Paso Joint Load Simulator (UTJLS) by testing four cadaver knee specimens with 47 real-time tests including heel and toe squat maneuvers with and without musculotendon forces. The UTJLS is a musculoskeletal simulator consisting of two robotic manipulators and eight musculotendon actuators. Sensors include eight tension load cells, two force/torque systems, nine absolute encoders, and eight incremental encoders. A custom control system determines command output for position, force, and hybrid control and collects data at 2000 Hz. Controller configuration performed forward-dynamic control for all knee degrees-of-freedom (DOFs) except knee flexion. Actuator placement and specimen potting techniques uniquely replicate muscle paths. Accuracy and repeatability standard deviations across specimen during squat simulations were equal or less than 8 N and 5 N for musculotendon actuators, 30 N and 13 N for ground reaction forces (GRFs), and 4.4 N·m and 1.9 N·m for ground reaction moments. The UTJLS is the first of its design type. Controller flexibility and physical design support axis constraints to match traditional testing rigs, absolute motion, and synchronous real-time simulation of multiplanar kinematics, GRFs, and musculotendon forces. System DOFs, range of motion, and speed support future testing of faster maneuvers, various joints, and kinetic chains of two connected joints.