@article{takahashi_lewek_sawicki_2015, title={A neuromechanics-based powered ankle exoskeleton to assist walking post-stroke: a feasibility study}, volume={12}, ISSN={["1743-0003"]}, DOI={10.1186/s12984-015-0015-7}, abstractNote={In persons post-stroke, diminished ankle joint function can contribute to inadequate gait propulsion. To target paretic ankle impairments, we developed a neuromechanics-based powered ankle exoskeleton. Specifically, this exoskeleton supplies plantarflexion assistance that is proportional to the user's paretic soleus electromyography (EMG) amplitude only during a phase of gait when the stance limb is subjected to an anteriorly directed ground reaction force (GRF). The purpose of this feasibility study was to examine the short-term effects of the powered ankle exoskeleton on the mechanics and energetics of gait.Five subjects with stroke walked with a powered ankle exoskeleton on the paretic limb for three 5 minute sessions. We analyzed the peak paretic ankle plantarflexion moment, paretic ankle positive work, symmetry of GRF propulsion impulse, and net metabolic power.The exoskeleton increased the paretic plantarflexion moment by 16% during the powered walking trials relative to unassisted walking condition (p < .05). Despite this enhanced paretic ankle moment, there was no significant increase in paretic ankle positive work, or changes in any other mechanical variables with the powered assistance. The exoskeleton assistance appeared to reduce the net metabolic power gradually with each 5 minute repetition, though no statistical significance was found. In three of the subjects, the paretic soleus activation during the propulsion phase of stance was reduced during the powered assistance compared to unassisted walking (35% reduction in the integrated EMG amplitude during the third powered session).This feasibility study demonstrated that the exoskeleton can enhance paretic ankle moment. Future studies with greater sample size and prolonged sessions are warranted to evaluate the effects of the powered ankle exoskeleton on overall gait outcomes in persons post-stroke.}, journal={JOURNAL OF NEUROENGINEERING AND REHABILITATION}, author={Takahashi, Kota Z. and Lewek, Michael D. and Sawicki, Gregory S.}, year={2015}, month={Feb} }
 @article{takahashi_horne_stanhope_2015, title={Comparison of mechanical energy profiles of passive and active below-knee prostheses: A case study}, volume={39}, number={2}, journal={Prosthetics and Orthotics International}, author={Takahashi, K. Z. and Horne, J. R. and Stanhope, S. J.}, year={2015}, pages={150–156} }
 @article{zelik_takahashi_sawicki_2015, title={Six degree-of-freedom analysis of hip, knee, ankle and foot provides updated understanding of biomechanical work during human walking}, volume={218}, ISSN={["1477-9145"]}, DOI={10.1242/jeb.115451}, abstractNote={ABSTRACT Measuring biomechanical work performed by humans and other animals is critical for understanding muscle–tendon function, joint-specific contributions and energy-saving mechanisms during locomotion. Inverse dynamics is often employed to estimate joint-level contributions, and deformable body estimates can be used to study work performed by the foot. We recently discovered that these commonly used experimental estimates fail to explain whole-body energy changes observed during human walking. By re-analyzing previously published data, we found that about 25% (8 J) of total positive energy changes of/about the body's center-of-mass and >30% of the energy changes during the Push-off phase of walking were not explained by conventional joint- and segment-level work estimates, exposing a gap in our fundamental understanding of work production during gait. Here, we present a novel Energy-Accounting analysis that integrates various empirical measures of work and energy to elucidate the source of unexplained biomechanical work. We discovered that by extending conventional 3 degree-of-freedom (DOF) inverse dynamics (estimating rotational work about joints) to 6DOF (rotational and translational) analysis of the hip, knee, ankle and foot, we could fully explain the missing positive work. This revealed that Push-off work performed about the hip may be >50% greater than conventionally estimated (9.3 versus 6.0 J, P=0.0002, at 1.4 m s−1). Our findings demonstrate that 6DOF analysis (of hip–knee–ankle–foot) better captures energy changes of the body than more conventional 3DOF estimates. These findings refine our fundamental understanding of how work is distributed within the body, which has implications for assistive technology, biomechanical simulations and potentially clinical treatment. Highlighted article: Six degree-of-freedom (6DOF) analysis of hip–knee–ankle–foot better captures energy changes of the body during gait than conventional 3DOF joint work estimates, revealing increased work contributions from the hip.}, number={6}, journal={JOURNAL OF EXPERIMENTAL BIOLOGY}, author={Zelik, Karl E. and Takahashi, Kota Z. and Sawicki, Gregory S.}, year={2015}, month={Mar}, pages={876–886} }
 @article{takahashi_stanhope_2013, title={Mechanical energy profiles of the combined ankle-foot system in normal gait: Insights for prosthetic designs}, volume={38}, number={4}, journal={Gait & Posture}, author={Takahashi, K. Z. and Stanhope, S. J.}, year={2013}, pages={818–823} }