Fang Ying, Harshe Karl, Franz Jason R, Lerner Zachary F
Department of Mechanical Engineering, Northern Arizona University, Flagstaff, AZ, United States.
Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, United States.
Wearable Technol. 2022;3. doi: 10.1017/wtc.2022.12. Epub 2022 Jul 1.
Age-related deficits in plantar flexor muscle function during the push-off phase of walking likely contribute to the decline in mobility that affects many older adults. Isolated strengthening of the plantar flexor muscles has failed to improve push-off power or walking economy in this population. New mobility aids and/or functional training interventions may help slow or prevent ambulatory decline in the elderly.
The overarching objective of this study was to explore the feasibility of using an untethered, dual-mode ankle exoskeleton for treating walking disability in the elderly; testing the device in assistance mode as a mobility aid to reduce energy consumption, and as a resistive gait training tool to facilitate functional recruitment of the plantar flexor muscles.
We recruited 6 older adults between the ages of 68 to 83 years to evaluate the feasibility of the dual-mode exoskeleton across two visits. On the first visit, we quantified acute metabolic and neuromuscular adaption to ankle exoskeleton assistance during walking in older adults, and subsequently determined if higher baseline energy cost was related to an individual's potential to benefit from untethered assistance. On the second visit, we validated the potential for push-off phase ankle resistance combined with plantar pressure biofeedback to facilitate functional utilization of the ankle plantar flexors during walking. We also conducted a twelve-session ankle resistance training protocol with one pilot participant to explore the effects of gait training with wearable ankle resistance on mobility and plantar flexor strength.
Participants reached the lowest net metabolic power, soleus variance ratio, and soleus iEMG at 6.6 ± 1.6, 19.8 ± 1.6, and 5.8 ± 4.9 minutes, respectively, during the 30-minute exoskeleton assistance adaptation trial. Four of five participants exhibited a reduction (up to 19%) in metabolic power during walking with assistance relative to baseline, but there was no group-level change. Participants who had greater baseline metabolic power exhibited a greater reduction during walking with assistance. Walking with resistance increased stance-phase soleus iEMG by 18 - 186% and stance-phase average positive ankle power by 9 - 88% compared to baseline. Following ankle resistance gait training, the participant exhibited a 5% increase in self-selected walking speed, a 15% increase in fast walking speed, a 36% increase in 6-min-walk-test distance, and a 31% increase in plantar flexor strength compared to pre-intervention measurements.
Our results suggest that dual-mode ankle exoskeletons appear highly applicable to treating plantar flexor dysfunction in the elderly, with assistance holding potential as a mobility aid and resistance holding potential as a functional gait training tool. We used an untethered design to maximize the relevance of this for informing the design of intervention studies that may take place at home and in the community to improve mobility and quality of life in older adults. Future studies with larger sample sizes are recommended to expand on the results of this feasibility investigation.
在步行蹬离阶段，与年龄相关的跖屈肌功能缺陷可能导致许多老年人行动能力下降。对跖屈肌进行单独强化训练未能改善该人群的蹬离力量或步行经济性。新型移动辅助设备和/或功能训练干预措施可能有助于减缓或预防老年人的步行能力下降。
本研究的总体目标是探索使用一种无束缚的双模式踝关节外骨骼治疗老年人步行障碍的可行性；在辅助模式下测试该设备作为移动辅助工具以降低能量消耗，并作为阻力步态训练工具以促进跖屈肌的功能性募集。
我们招募了6名年龄在68至83岁之间的老年人，分两次就诊评估双模式外骨骼的可行性。在第一次就诊时，我们量化了老年人在步行过程中对踝关节外骨骼辅助的急性代谢和神经肌肉适应性，随后确定较高的基线能量消耗是否与个体从无束缚辅助中获益的潜力相关。在第二次就诊时，我们验证了蹬离阶段踝关节阻力结合足底压力生物反馈在步行过程中促进踝关节跖屈肌功能性利用的潜力。我们还对一名试点参与者进行了为期12节的踝关节阻力训练方案，以探索可穿戴踝关节阻力步态训练对行动能力和跖屈肌力量的影响。
在30分钟的外骨骼辅助适应性试验中，参与者分别在6.6±1.6、19.8±1.6和5.8±4.9分钟时达到最低净代谢功率、比目鱼肌方差比和比目鱼肌肌电图。五名参与者中有四名在辅助步行时相对于基线的代谢功率降低（高达19%），但在组水平上没有变化。基线代谢功率较高的参与者在辅助步行时降低幅度更大。与基线相比，阻力步行使站立期比目鱼肌肌电图增加了18 - 186%，站立期平均正向踝关节功率增加了9 - 88%。经过踝关节阻力步态训练后，与干预前测量相比，该参与者的自选步行速度提高了5%，快走速度提高了15%，6分钟步行测试距离增加了36%，跖屈肌力量增加了31%。
我们的结果表明，双模式踝关节外骨骼似乎非常适用于治疗老年人的跖屈肌功能障碍，辅助模式具有作为移动辅助工具的潜力，阻力模式具有作为功能性步态训练工具的潜力。我们采用无束缚设计以最大限度地提高其相关性，为可能在家庭和社区中进行的干预研究设计提供参考，以改善老年人的行动能力和生活质量。建议未来进行更大样本量的研究以扩展这项可行性调查的结果。
