Mobility related physical and functional losses due to aging and disease - a motivation for lower limb exoskeletons

Abstract

BackgroundPhysical and functional losses due to aging and diseases decrease human mobility, independence, and quality of life. This study is aimed at summarizing and quantifying these losses in order to motivate solutions to overcome them with a special focus on the possibilities by using lower limb exoskeletons.MethodsA narrative literature review was performed to determine a broad range of mobility-related physical and functional measures that are affected by aging and selected cardiovascular, respiratory, musculoskeletal, and neurological diseases.ResultsThe study identified that decreases in limb maximum muscle force and power (33% and 49%, respectively, 25–75 yrs) and in maximum oxygen consumption (40%, 20–80 yrs) occur for older adults compared to young adults. Reaction times more than double (18–90 yrs) and losses in the visual, vestibular, and somatosensory systems were reported. Additionally, we found decreases in steps per day (75%, 60–85 yrs), maximum walking speed (24% 25–75 yrs), and maximum six-minute and self-selected walking speed (38% and 21%, respectively, 20–85 yrs), while we found increases in the number of falls relative to the number of steps per day (800%), injuries due to falls (472%, 30–90 yrs) and deaths caused by fall (4000%, 65–90 yrs). Measures were identified to be worse for individuals with impaired mobility. Additional detrimental effects identified for them were the loss of upright standing and locomotion, freezing in movement, joint stress, pain, and changes in gait patterns.DiscussionThis review shows that aging and chronic conditions result in wide-ranging losses in physical and sensory capabilities. While the impact of these losses are relatively modest for level walking, they become limiting during more demanding tasks such as walking on inclined ground, climbing stairs, or walking over longer periods, and especially when coupled with a debilitating disease. As the physical and functional parameters are closely related, we believe that lost functional capabilities can be indirectly improved by training of the physical capabilities. However, assistive devices can supplement the lost functional capabilities directly by compensating for losses with propulsion, weight support, and balance support.ConclusionsExoskeletons are a new generation of assistive devices that have the potential to provide both, training capabilities and functional compensation, to enhance human mobility.

Biarticular muscles in light of template models, experiments and robotics: a review

“…Some of the recent developments indicate potential benefits of incorporating biarticular designs in prosthetic and exoskeleton designs. However, for real-world applications and the range of subject populations, technological difficulties remain to be solved, such as human-machine interfaces, durability of hardware designs and flexible control concepts [169]. Biarticular actuation might be one useful approach to tackle some of these challenges by synchronous joint coordination and improved controllability.…”

Simulation of Stand-to-Sit Biomechanics for Design of Lower-Limb Exoskeletons and Prostheses with Energy Regeneration

“…regenerative powertrains have focused exclusively on level-ground walking [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][33][34][35]. However, geriatric and rehabilitation patients often exhibit slower walking speeds (e.g., 24 % speed reduction from 25 to 75 years age) and take fewer steps/day (e.g., 75 % reduction from 60 to 85 years age) [3], therein limiting the potential for energy regeneration during level-ground walking. In contrast, sitting and standing movements are seemingly more representative activities of clinical populations and therefore should be considered when designing such biomechatronic devices.…”

“…There are approximately 2 million Americans with limb amputations [2]. These numbers are expected to significantly increase with the emergent aging population and growing incidences of cancer and diabetes [1][2][3]. Robotic lower-limb prostheses and exoskeletons can enable geriatric and rehabilitation patients to perform common movements (e.g., sit-to-stand) that necessitate net positive mechanical power by mimicking their amputated or unimpaired biological muscle actuators [4][5][6][7][8][9].…”

From a biological template model to gait assistance with an exosuit

“…Eqs. 231 (5) to (7) clearly show that the ABC control approach is independent of time, and the 232 GRF and AM forces are used to detect the switching time and required forces. searched for the optimal actuation to minimize the approximated metabolic cost.…”

“…The GRF is considered as an informative sensory signal for control which 663 removes the need to realize gait phasing. In equations (5) to (7) we removed the 664 dependency to time, by using the GRF and the artificial muscle properties (e.g., length 665 and force). In addition, external perturbations will be reflected in the GRF patterns 666 and in the case of designing an appropriate controller, this sensory information could 667 potentially robustify the system against perturbations.…”