In our evaluation of the mediolateral COM displace-ment at several walking speeds, 10 normal subjects walked attheir self-selected speed and then at 0.7, 1.0, 1.2, and 1.6 m/s inrandom order. We calculated COM location from a 15-segment, full-body kinematic model using segmental analysis.

The C-Leg (Otto Bock, Duderstadt, Germany) is a microprocessor-controlled prosthetic knee that may enhance amputee gait. This intrasubject randomized study compared the gait biomechanics of transfemoral amputees wearing the C-Leg with those wearing a common noncomputerized prosthesis, the Mauch SNS (Ossur, Reykjavik, Iceland). After subjects had a 3-month acclimation period with each prosthetic knee, typical gait biomechanical data were collected in a gait laboratory. At a controlled walking speed (CWS), peak swing phase knee-flexion angle decreased for the C-Leg group compared with the Mauch SNS group (55.2 degrees +/- 6.5 degrees vs 64.41 degrees +/- 5.8 degrees , respectively; p = 0.005); the C-Leg group was similar to control subjects' peak swing knee-flexion angle (56.0 degrees +/- 3.4 degrees ). Stance knee-flexion moment increased for the C-Leg group compared with the Mauch SNS group (0.142 +/- 0.05 vs 0.067 +/- 0.07 N"m, respectively; p = 0.01), but remained significantly reduced compared with control subjects (0.477 +/- 0.1 N"m). Prosthetic limb step length at CWS was less for the C-Leg group compared with the Mauch SNS group (0.66 +/- 0.04 vs 0.70 +/- 0.06 m, respectively; p = 0.005), which resulted in increased symmetry between limbs for the C-Leg group. Subjects also walked faster with the C-Leg versus the Mauch SNS (1.30 +/- 0.1 vs 1.21 +/- 0.1 m/s, respectively; p = 0.004). The C-Leg prosthetic limb vertical ground reaction force decreased compared with the Mauch SNS (96.3 +/- 4.7 vs 100.3 +/- 7.5 % body weight, respectively; p = 0.0092).

Background: Plantar pressure measurements often are used as a tool to evaluate pathologic gait. Previous studies, often done at self-selected walking speeds, have used peak plantar pressure to try to predict ulcer formation, compare surgical outcomes, and evaluate orthotic device efficacy. However, the relationship between walking speed and plantar pressures at specific plantar regions has not been clearly defined. Methods: Twenty normal subjects walked on a treadmill at six speeds (0.75 to 2.00 m/s). In-shoe peak plantar pressure was measured at five plantar regions and compared across the range of speeds. Results: Walking speed affected peak plantar pressure differently at the five examined plantar regions. The hallux and heel regions had the highest pressures, which increased linearly with faster speeds. The central and medial forefoot pressures initially increased but plateaued at the faster speeds, while the lateral forefoot had the lowest overall peak pressures, which decreased at the faster walking speeds. Therefore, significant quadratic effects were found at the forefoot. Best-fit regression equations defined distinct pressurespeed relationships at each plantar region (p < 0.0001). Conclusion: The effect of walking speed on peak plantar pressure varied with plantar region. To achieve more robust peak plantar pressure measurements, walking speed should be controlled. Determining the normal plantar function across a range of speeds can aid in the development of shoes and foot orthoses. The pressurespeed relationships presented in this study can be used as a comparative tool for evaluating the efficacy of clinical interventions for pressure reduction, especially when walking speed changes may confound the outcomes.

Lower-limb amputees expend more energy to walk than non-amputees and have an elevated risk of secondary disabilities. Insufficient push-off by the prosthetic foot may be a contributing factor. We aimed to systematically study the effect of prosthetic foot mechanics on gait, to gain insight into fundamental prosthetic design principles. We varied a single parameter in isolation, the energy-storing spring in a prototype prosthetic foot, the controlled energy storage and return (CESR) foot, and observed the effect on gait. Subjects walked on the CESR foot with three different springs. We performed parallel studies on amputees and on non-amputees wearing prosthetic simulators. In both groups, spring characteristics similarly affected ankle and body center-of-mass (COM) mechanics and metabolic cost. Softer springs led to greater energy storage, energy return, and prosthetic limb COM push-off work. But metabolic energy expenditure was lowest with a spring of intermediate stiffness, suggesting biomechanical disadvantages to the softest spring despite its greater push-off. Disadvantages of the softest spring may include excessive heel displacements and COM collision losses. We also observed some differences in joint kinetics between amputees and non-amputees walking on the prototype foot. During prosthetic push-off, amputees exhibited reduced energy transfer from the prosthesis to the COM along with increased hip work, perhaps due to greater energy dissipation at the knee. Nevertheless, the results indicate that spring compliance can contribute to push-off, but with biomechanical trade-offs that limit the degree to which greater push-off might improve walking economy.