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BACKGROUND: Rocker shoes can be used to reduce foot pressure and adjust lower limb kinetics for various patient population, such as people with diabetic peripheral neuropathy. Selecting adequate properties of the rocker sole is of great importance for its efficacy. This study investigated the capability of human-in-the-loop optimization (HILO) to individually optimize apex position and angle of rocker shoe to reduce peak pressure and collision work simultaneously. METHODS: Peak pressure, kinetic, and kinematic data were recorded from 10 healthy participants while walking at preferred speed wearing rocker shoes with adjustable apex position and angle. An evolutionary algorithm was used to find optimal apex parameters to reduce both peak pressure in medial forefoot and collision work. The optimized shoe (HILO shoe) was compared with generic optimal rocker settings (Chapman settings) and normal shoe. FINDINGS: Compared to normal shoe, the HILO shoe had lower plantar pressure (pHILO = 0.007; pChapman = 0.044) and Chapman shoe showed higher collision work (pHILO = 0.025; pChapman = 0.014). Both HILO and Chapman shoe had smaller push-off work than normal shoe (pHILO = 0.001; pChapman < 0.001) with the Chapman shoe exhibited earlier push-off onset (pHILO = 0.257; pChapman = 0.016). INTERPRETATION: The Human-in-the-loop optimization approach resulted in individualized apex settings which performed on average similar to Chapman settings but, were superior in selected cases. In these cases, medial forefoot could be further offloaded with apex angles larger than generic settings. The larger apex angle might increase the external ankle moment arm and push-off work. However, there is limited room for improvement on collision work compared to generic settings.

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Carbon-fiber running-specific prostheses have enabled individuals with lower extremity amputation to run by providing a spring-like leg function in their affected limb. When individuals without amputation run at a constant speed on level ground, the net external mechanical work is zero at each step to maintain a symmetrical bouncing gait. Although the spring-like "bouncing step" using running-specific prostheses is considered a prerequisite for running, little is known about the underlying mechanisms for unilateral transfemoral amputees. The aim of this study was to investigate external mechanical work at different running speeds for unilateral transfemoral amputees wearing running-specific prostheses. Eight unilateral transfemoral amputees ran on a force-instrumented treadmill at a range of speeds (30, 40, 50, 60, 70, and 80% of the average speed of their 100-m personal records). We calculated the mechanical energy of the body center of mass (COM) by conducting a time-integration of the ground reaction forces in the sagittal plane. Then, the net external mechanical work was calculated as the difference between the mechanical energy at the initial and end of the stance phase. We found that the net external work in the affected limb tended to be greater than that in the unaffected limb across the six running speeds. Moreover, the net external work of the affected limb was found to be positive, while that of the unaffected limb was negative across the range of speeds. These results suggest that the COM of unilateral transfemoral amputees would be accelerated in the affected limb's step and decelerated in the unaffected limb's step at each bouncing step across different constant speeds. Therefore, unilateral transfemoral amputees with passive prostheses maintain their bouncing steps using a limb-specific strategy during running.

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BACKGROUND AND AIM: To accurately quantify the cost of physical activity and to evaluate the different components of energy expenditure in humans, it is necessary to evaluate external mechanical work (WEXT). Large platform systems surpass other currently used techniques. Here, we describe a calculation method for force-platforms to calculate long-term WEXT. METHODS: Each force-platform (2.46×1.60m and 3.80×2.48m) rests on 4 piezoelectric sensors. During long periods of recording, a drift in the speed of displacement of the center of mass (necessary to calculate WEXT) is generated. To suppress this drift, wavelet decomposition is used to low-pass filter the source signal. By using wavelet decomposition coefficients, the source signal can be recovered. To check the validity of WEXT calculations after signal processing, an oscillating pendulum system was first used; then, 10 healthy subjects performed a standardized exercise (squatting exercise). A medical application is also reported in eight Parkinsonian patients during the timed "get-up and go" test and compared with the same test in ten healthy subjects. RESULTS: Values of WEXT with the oscillating pendulum showed that the system was accurate and reliable. During the squatting exercise, the average measured WEXT was 0.4% lower than theoretical work. WEXT and mechanical work efficiency during the "get-up and go" test in Parkinson's disease patients in comparison with that of healthy subjects were very coherent. CONCLUSIONS: This method has numerous applications for studying physical activity and mechanical work efficiency in physiological and pathological conditions.

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