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).

Reports on the design of a biorobotic actuator. Biological requirements are developed from published reports in the muscle physiology literature whose parameters are extracted and applied in the form of the Hill muscle model. Data from several vertebrate species (rat, frog, cat, and human) are used to evaluate the performance of a McKibben pneumatic actuator. The experimental results show the force-length properties of the actuator are muscle-like, but the force-velocity properties are not. The design of a hydraulic damper with fixed orifices, placed in parallel with the McKibben actuator, is proposed to improve the force-velocity performance. Simulation results of this practical design indicate a significant improvement.