Reducing the Energy Cost of Human Running Using an Unpowered Exoskeleton

Nasiri, Rezvan; Ahmadi, Arjang; Ahmadabadi, Majid Nili

doi:10.1109/tnsre.2018.2872889

Cited by 113 publications

(109 citation statements)

References 26 publications

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“…Participants then completed four 10 min runs, with 5 min rests between each, on a treadmill (Woodway, Waukesha, WI, USA) at 2.67 m s −1 (10 min mile −1 ). Though slow for competitive runners, this pace allowed a larger pool of potential participants than a faster pace and is similar to that used in other studies of assistive devices for running (Lee et al, 2017;Nasiri et al, 2018). This pace is also similar to the pace chosen by healthy recreational runners in previous treadmill studies (Kong et al, 2012;Minetti et al, 2015) and to the 2.74 m s −1 (2.9 m s −1 for men and 2.5 m s −1 for women) average running pace measured across 36 million users who ran 1.5 billion kilometers (Strava, San Francisco, CA, USA; https://blog.strava.com/ press/2018-year-in-sport/, accessed 11 July 2019).…”

Section: Experiments 1running Economymentioning

confidence: 94%

“…Second, more distal placements ensure the line-of-action of the spring is predominantly along the flexion-extension axis of the hip, minimizing adduction moments on the leg. We note Nasiri et al (2018) have created an effective hip-mounted device, although the current, largely metal, design must contend with the challenges of added mass and comfortably transferring force from the device to the user.…”

Section: Materials and Methods Device Designmentioning

confidence: 99%

“…1D) (Alexander and Bennet-Clark, 1977;Alexander et al, 1985;Bennett, 1989;Craib et al, 1996;Dickinson and Lighton, 1995;Pabst, 2007;Wells, 1993). Interestingly, recent work both in simulation (Welker et al, 2017) and in experiments with a hipmounted metal torsional spring device (Nasiri et al, 2018) suggests that the savings resulting from assisting swing in humans are comparable to those seen when assisting stance. This is despite the fact that the energy expenditure associated with stance is an order of magnitude larger (Arellano and Kram, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Connecting the legs with a spring improves human running economy

Simpson

Welker

Uhlrich

et al. 2019

Journal of Experimental Biology

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Human running is inefficient. For every 10 calories burned, less than 1 is needed to maintain a constant forward velocitythe remaining energy is, in a sense, wasted. The majority of this wasted energy is expended to support the bodyweight and redirect the center of mass during the stance phase of gait. An order of magnitude less energy is expended to brake and accelerate the swinging leg. Accordingly, most devices designed to increase running efficiency have targeted the costlier stance phase of gait. An alternative approach is seen in nature: spring-like tissues in some animals and humans are believed to assist leg swing. While it has been assumed that such a spring simply offloads the muscles that swing the legs, thus saving energy, this mechanism has not been experimentally investigated. Here, we show that a spring, or 'exotendon', connecting the legs of a human reduces the energy required for running by 6.4±2.8%, and does so through a complex mechanism that produces savings beyond those associated with leg swing. The exotendon applies assistive forces to the swinging legs, increasing the energy optimal stride frequency. Runners then adopt this frequency, taking faster and shorter strides, and reduce the joint mechanical work to redirect their center of mass. Our study shows how a simple spring improves running economy through a complex interaction between the changing dynamics of the body and the adaptive strategies of the runner, highlighting the importance of considering each when designing systems that couple human and machine.

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Section: Experiments 1running Economymentioning

confidence: 94%

Section: Materials and Methods Device Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Connecting the legs with a spring improves human running economy

Simpson

Welker

Uhlrich

et al. 2019

Journal of Experimental Biology

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“…1D) [18]- [24]. Interestingly, recent work suggests that the savings resulting from assisting swing in humans are comparable to those seen when assisting stance [25], [26], despite the fact that the energy expenditure associated with stance is an order of magnitude larger [6]. Moreover, the savings associated with assisting swing may actually exceed the expected expenditure associated with swing [6], suggesting that the mechanism of savings when assisting swing is not understood.…”

Section: Introductionmentioning

confidence: 99%

Connecting the legs with a spring improves human running economy

Simpson

Welker

Uhlrich

et al. 2018

Preprint

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Spring-like tissues attached to the swinging legs of animals are thought to improve running economy by simply reducing the effort of leg swing. Here we show that a spring, or 'exotendon,' connecting the legs of a human runner improves economy instead through a more complex mechanism that produces savings during both swing and stance. The spring increases the energy optimal stride frequency; when runners adopt this new gait pattern, savings occur in both phases of gait. Remarkably, the simple device improves running economy by 6.4 ± 2.8%, comparable to savings achieved by motorized assistive robotics that directly target the costlier stance phase of gait. Our results highlight the importance of considering both the dynamics of the body and the adaptive strategies of the user when designing systems that couple human and machine.

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“…More interestingly, the developed device could generate efficiency above 674 100%. This phenomenon is also observed when passive exosuits can yield metabolic cost 675 reductions without consuming energy [79][80][81]. The total energy of the human body and 676 the assistive device can be decreased to less than the metabolic cost in the unassisted 677 gait because of: 1) storing and returning energy with compliant elements [79][80][81] and 2) 678 transferring energy from one joint to another with biarticular mechanisms [80,81].…”

mentioning

confidence: 95%

From a biological template model to gait assistance with an exosuit

Firouzi

Davoodi

Bahrami

et al. 2020

Preprint

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By invention of soft wearable assistive devices, known as exosuits, a new aspect in assisting unimpaired subjects is introduced. In this study, we designed and developed an exosuit with compliant biarticular thigh actuators, called BAExo. Unlike common method of using rigid actuators in exosuits, the BAExo is made of serial elastic actuators (SEA) resembling artificial muscles (AM). This bioinsipred design is complemented by the novel control concept of using the ground reaction force to adjust these AMs' stiffness in the stance phase. By locking the motors in the swing phase the SEAs will be simplified to passive biarticular springs, which is sufficient for leg swinging. The key concept in our design and control approach is synthesizing human locomotion to develop assistive device, instead of copying the outputs of human motor control. Analysing human walking assistance using an experiment-based OpenSim model demonstrates the advantages of the proposed design and control of BAExo, regarding metabolic cost reduction and efficiency of the system. In addition, pilot experiments with the recently developed BAExo hardware support the applicability of the introduced method. Author summaryAging and mobility of elderly people are of crucial concern in developed countries. The U.S. Census Bureau reports that by the middle of the 21st century, about 80 million Americans will be 65 or older. According to the group's research, medical costs resulting from falls by the elderly are expected to approach $32.4 billion by 2020. Therefore, assistance of elderly people and making the assistive devices more intelligent is a need in near future. However, this is not the only application of assistive devices. Exosuits, as soft wearable robots, introduced a new aspect in assisting a large range of population, even healthy young people. We introduce a novel design and control method for a new exosuit. As the research in the field of wearable assistive devices is growing in recent years and its application in daily life becomes more evident for the society, such studies with a unique view in design and control could have a significant impact. Our proposed biologically inspired approach could be potentially applied to other exosuits. Introduction 1 Lower limb exoskeletons for assisting people with decreased locomotion abilities has 2 attracted the attention of researchers [1] and the healthcare industry [2, 3]. Assistive 3 March 21, 2020 1/24 6 about aging. For example, by aging, muscle force and power decrease and to reduce the 7 cost of elderly and patients locomotion, assistive devices are demanded [6, 7]. 8 One of the common goals of assistive device designers is to reduce the metabolic cost 9 of locomotion [8]. This feature is important in all above-mentioned cases and situations. 10 In the last couple of years researchers have succeeded in significantly improving the 11 metabolic cost reduction in human gaits using powered exoskeletons [1,[9][10][11]. 12Powered exoskeletons can be categorized as (1) traditional ones with rigid stru...

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Reducing the Energy Cost of Human Running Using an Unpowered Exoskeleton

Cited by 113 publications

References 26 publications

Connecting the legs with a spring improves human running economy

Connecting the legs with a spring improves human running economy

Connecting the legs with a spring improves human running economy

From a biological template model to gait assistance with an exosuit

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