scholarly journals Connecting the legs with a spring improves human running economy

2018 ◽  
Author(s):  
Cole S. Simpson ◽  
Cara G. Welker ◽  
Scott D. Uhlrich ◽  
Sean M. Sketch ◽  
Rachel W. Jackson ◽  
...  
Keyword(s):  
Stance Phase ◽  
Adaptive Strategies ◽  
Gait Pattern ◽  
The Body ◽  
Assistive Robotics ◽  
Running Economy ◽  
Simple Device ◽  
Stride Frequency ◽  
Complex Mechanism ◽  
Human Running

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.

Stride Frequency and Submaximal Treadmill Running Economy in Adults and Children

1990 ◽  
Vol 2 (2) ◽  
pp. 149-155 ◽  
Author(s):  
Viswanath B. Unnithan ◽  
Roger G. Eston
Keyword(s):  
Stride Length ◽  
Oxygen Demand ◽  
The Body ◽  
Running Economy ◽  
Treadmill Running ◽  
Stride Frequency ◽  
Oxygen Cost ◽  
Demand Characteristics ◽  
Adults And Children ◽  
All Speeds

Previous studies have consistently shown that the body mass/relative oxygen cost of submaximal treadmill running is greater in children than in young adults. It has been suggested that the obligatory increased stride frequency in children might be at least partly responsible. This hypothesis was investigated by examining the association between stride frequency and oxygen demand characteristics in 10 aerobically fit prepubescent boys (ages 9-10 yrs) and 10 fit young men (ages 18-25 yrs) while running at fixed submaximal speeds on an electronically driven treadmill. The oxygen demand was higher at all running speeds in the boys’ group. To compensate for a shorter stride length, the boys demonstrated higher stride frequency at all speeds. To determine if the inferior running economy in the boys was partly due to the greater stride frequency, the relative oxygen demand per stride was compared between groups at all speeds. This value was similar in both groups. It is concluded that the apparently greater oxygen demand of running in boys may be due in part to the greater stride frequency required to maintain similar running speeds.

Actuated Slip Model of Human Running With an Elastically-Suspended Load

2013 ◽  
Author(s):  
Karna Potwar ◽  
Jeffrey Ackerman ◽  
Justin Seipel
Keyword(s):  
Human Body ◽  
Suspended Load ◽  
The Body ◽  
Stride Frequency ◽  
Energetic Cost ◽  
Slip Model ◽  
Inverted Pendulum Model ◽  
Suspension Stiffness ◽  
Human Running ◽  
Suspended Loads

An elastically-suspended load can reduce the peak forces acting on the body and the energetic cost of human walking compared to a rigidly-attached load. However, limited knowledge exists on how elastically-suspended loads affect the biomechanics of human running. We develop a variant of an Actuated SLIP (Spring Loaded Inverted Pendulum) model to analyze human running with an elastically-suspended load. This model consists of a suspended load attached to the body mass of an Actuated SLIP model with approximate human parameters. The model enables the investigation of the coupled dynamics of the load and the human body and shows that the stride frequency of running is affected by the load suspension stiffness. The model also shows that the peak forces of the load acting on the body are reduced compared to a rigidly-attached load when the load suspension stiffness is minimized. However, the energetic cost of running with an elastically-suspended load is shown to increase compared to a rigidly-attached load. Further, the peak forces and the energetic cost of running are maximized when the natural frequency of the load suspension is tuned near the stride frequency. This model could lead to a better understanding of human running with elastically-suspended loads and may enable the design of load suspension systems that are optimized to reduce stress on the human body while running with a load.

Physiological function and neuromuscular recruitment in elite South African distance runners

2004 ◽  
Vol 1 (4) ◽  
pp. 261-271 ◽  
Author(s):  
Timothy D Noakes ◽  
Yolande XR Harley ◽  
Andrew N Bosch ◽  
Frank E Marino ◽  
Alan St Clair Gibson ◽  
...  
Keyword(s):  
South African ◽  
Exercise Physiology ◽  
The Body ◽  
Running Economy ◽  
Superior Performance ◽  
Black Athletes ◽  
Training Environment ◽  
Complex Biological System ◽  
Black African ◽  
Black South African

AbstractPhysiological studies of elite and sub-elite black South African runners show that these athletes are typically about 10–12 kg lighter than white athletes and that they are able to sustain higher exercise intensities for longer than white runners. Such superior performance is not a result of higher V O2max values and hence cannot be due to superior oxygen delivery to the active muscles during maximal exercise, as is predicted by the traditional cardiovascular/anaerobic/catastrophic models of exercise physiology. A marginally superior running economy is also unlikely to be a crucial determinant in explaining this apparent superiority. However, black athletes are able to sustain lower rectal and thigh, but higher mean skin, temperatures during exercise. Furthermore, when exercising in the heat, lighter black athletes are able to maintain higher running speeds than are larger white runners matched for running performance in cool environmental conditions. According to the contrasting theory that the body acts as a complex system during exercise, the superiority of black African athletes should be sought in an enhanced capacity to maintain homeostasis in all their inter-dependent biological systems despite running at higher relative exercise intensities and metabolic rates. In this case, any explanation for the success of East African runners will be found in the way in which their innate physiology, training, environment, expectations and genes influence the function of those parts of their subconscious (and conscious) brains that appear to regulate the protection of homeostasis during exercise as part of an integrative, complex biological system.

scholarly journals Functional Electrical Stimulation Changes Dynamic Resources in Children With Spastic Cerebral Palsy

2006 ◽  
Vol 86 (7) ◽  
pp. 987-1000 ◽  
Author(s):  
Chia-Ling Ho ◽  
Kenneth G Holt ◽  
Elliot Saltzman ◽  
Robert C Wagenaar
Keyword(s):  
Cerebral Palsy ◽  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Stride Length ◽  
The Body ◽  
Stride Frequency ◽  
Spastic Cerebral Palsy ◽  
Significant Difference ◽  
Muscle Complex ◽  
Spring System

Abstract Background and Purpose. Children with cerebral palsy (CP) often are faced with difficulty in walking. The purpose of this experiment was to determine the effects of functional electrical stimulation (FES) applied to the gastrocnemius-soleus muscle complex on the ability to produce appropriately timed force and reduce stiffness (elastic property of the body) and on stride length and stride frequency during walking. Subjects and Methods. Thirteen children with spastic CP (including 4 children who were dropped from the study due to their inability to cooperate) and 6 children who were developing typically participated in the study. A crossover study design was implemented. The children with spastic CP were randomly assigned to either a group that received FES for 15 trials followed by no FES for 15 trials or a group that received no FES for 15 trials followed by FES for 15 trials. The children who were having typical development walked without FES. Kinematic data were collected for the children with CP in each walking condition and for the children who were developing typically. Impulse (force-producing ability) and stiffness were estimated from an escapement-driven pendulum and spring system model of human walking. Stride length and stride frequency also were measured. To compare between walking conditions and between the children with CP and the children who were developing typically, dimensional analysis and speed normalization procedures were used. Results. Nonparametric statistics showed that there was no significant difference between the children with CP in the no-FES condition and the children who were developing typically on speed-normalized dimensionless impulse. In contrast, the children with CP in the FES condition had a significantly higher median value than the children who were developing typically. The FES significantly increased speed-normalized dimensionless impulse from 10.02 to 16.32 when comparing walking conditions for the children with CP. No significant differences were found between walking conditions for stiffness, stride length, and stride frequency. Discussion and Conclusion. The results suggest that FES is effective in increasing impulse during walking but not in decreasing stiffness. The effect on increasing impulse does not result in more typical spatiotemporal gait parameters. [Ho CL, Holt KG, Saltzman E, Wagenaar RC. Functional electrical stimulation changes dynamic resources in children with spastic cerebral palsy. Phys Ther. 2006;86:987–1000.]

Stretch of Quadriceps Inhibits the Soleus H Reflex During Locomotion in Decerebrate Cats

1997 ◽  
Vol 78 (6) ◽  
pp. 2975-2984 ◽  
Author(s):  
John E. Misiaszek ◽  
Keir G. Pearson
Keyword(s):  
Stretch Reflex ◽  
Stance Phase ◽  
Background Level ◽  
Afferent Input ◽  
H Reflex ◽  
The Body ◽  
Afferent Feedback ◽  
Electromyographic Activity ◽  
Locomotor Rhythm ◽  
Decerebrate Cats

Misiaszek, John E. and Keir G. Pearson. Stretch of quadriceps inhibits the soleus H reflex during locomotion in decerebrate cats. J. Neurophysiol. 78: 2975–2984, 1997. Previously, it has been demonstrated that afferent signals from the quadriceps muscles can suppress H reflexes in humans during passive movements of the leg. To establish whether afferent input from quadriceps contributes to the modulation of the soleus H reflex during locomotion, the soleus H reflex was conditioned with stretches of the quadriceps muscle during bouts of spontaneous treadmill locomotion in decerebrate cats. We hypothesized that 1) in the absence of locomotion such conditioning would lead to suppression of the soleus H reflex and 2) this would be retained during periods of locomotor activity. In the absence of locomotion, slow sinusoidal stretches (0.2 Hz, 8 mm) of quadriceps cyclically modulated the amplitude of the soleus H reflex. The H reflex amplitude was least during the lengthening of the quadriceps and greatest as quadriceps shortened. Further, low-amplitude vibrations (48–78 μm) applied to the patellar tendon suppressed the reflex, indicating that the muscle spindle primaries were the receptor eliciting the effect. During bouts of locomotion, ramp stretches of quadriceps were applied during the extensor phase of the locomotor rhythm. Soleus H reflexes sampled at two points during the stance phase were reduced compared with phase-matched controls. The background level of the soleus electromyographic activity was not influenced by the applied stretches to quadriceps, either during locomotion or in the absence of locomotion. This indicates that the excitability of the soleus motoneuron pool was not influenced by the stretching of quadriceps, and that the inhibition of the soleus H reflex is due to presynaptic inhibition. We conclude that group Ia afferent feedback from quadriceps contributes to the regulation of the soleus H reflex during the stance phase of locomotion in decerebrate cats. This afferent mediated source of regulation of the H reflex, or monosynaptic stretch reflex, would allow for rapid alterations in reflex gain according to the dynamic needs of the animal. During early stance, this source of regulation might suppress the soleus stretch reflex to allow adequate yielding at the ankle and facilitate the movement of the body over the foot.

scholarly journals Elastic energy savings and active energy cost in a simple model of running

2021 ◽  
Vol 17 (11) ◽  
pp. e1009608
Author(s):  
Ryan T. Schroeder ◽  
Arthur D. Kuo
Keyword(s):  
Elastic Energy ◽  
Energy Cost ◽  
Energy Savings ◽  
Mechanical Energy ◽  
Metabolic Cost ◽  
The Body ◽  
Metabolic Energy ◽  
Energetic Cost ◽  
Mass Model ◽  
Human Running

The energetic economy of running benefits from tendon and other tissues that store and return elastic energy, thus saving muscles from costly mechanical work. The classic “Spring-mass” computational model successfully explains the forces, displacements and mechanical power of running, as the outcome of dynamical interactions between the body center of mass and a purely elastic spring for the leg. However, the Spring-mass model does not include active muscles and cannot explain the metabolic energy cost of running, whether on level ground or on a slope. Here we add explicit actuation and dissipation to the Spring-mass model, and show how they explain substantial active (and thus costly) work during human running, and much of the associated energetic cost. Dissipation is modeled as modest energy losses (5% of total mechanical energy for running at 3 m s-1) from hysteresis and foot-ground collisions, that must be restored by active work each step. Even with substantial elastic energy return (59% of positive work, comparable to empirical observations), the active work could account for most of the metabolic cost of human running (about 68%, assuming human-like muscle efficiency). We also introduce a previously unappreciated energetic cost for rapid production of force, that helps explain the relatively smooth ground reaction forces of running, and why muscles might also actively perform negative work. With both work and rapid force costs, the model reproduces the energetics of human running at a range of speeds on level ground and on slopes. Although elastic return is key to energy savings, there are still losses that require restorative muscle work, which can cost substantial energy during running.

scholarly journals Supervised Exercise Training Improves 6 min Walking Distance and Modifies Gait Pattern during Pain-Free Walking Condition in Patients with Symptomatic Lower Extremity Peripheral Artery Disease

Sensors ◽  
2021 ◽  
Vol 21 (23) ◽  
pp. 7989
Author(s):  
Stefano Lanzi ◽  
Joël Boichat ◽  
Luca Calanca ◽  
Lucia Mazzolai ◽  
Davide Malatesta
Keyword(s):  
Stride Length ◽  
Gait Pattern ◽  
Walking Distance ◽  
Stride Frequency ◽  
Walk Test ◽  
Relative Duration ◽  
Foot Kinematics ◽  
Supervised Exercise ◽  
Artery Disease ◽  
Kinematics Parameters

This study aimed to investigate the effects of supervised exercise training (SET) on spatiotemporal gait and foot kinematics parameters in patients with symptomatic lower extremity peripheral artery disease (PAD) during a 6 min walk test. Symptomatic patients with chronic PAD (Fontaine stage II) following a 3 month SET program were included. Prior to and following SET, a 6 min walk test was performed to assess the 6 min walking distance (6MWD) of each patient. During this test, spatiotemporal gait and foot kinematics parameters were assessed during pain-free and painful walking conditions. Twenty-nine patients with PAD (65.4 ± 9.9 years.) were included. The 6MWD was significantly increased following SET (+10%; p ≤ 0.001). The walking speed (+8%) and stride frequency (+5%) were significantly increased after SET (p ≤ 0.026). The stride length was only significantly increased during the pain-free walking condition (+4%, p = 0.001), whereas no significant differences were observed during the condition of painful walking. Similarly, following SET, the relative duration of the loading response increased (+12%), the relative duration of the foot-flat phase decreased (−3%), and the toe-off pitch angle significantly increased (+3%) during the pain-free walking condition alone (p ≤ 0.05). A significant positive correlation was found between changes in the stride length (r = 0.497, p = 0.007) and stride frequency (r = 0.786, p ≤ 0.001) during pain-free walking condition and changes in the 6MWD. A significant negative correlation was found between changes in the foot-flat phase during pain-free walking condition and changes in the 6MWD (r = −0.567, p = 0.002). SET was found to modify the gait pattern of patients with symptomatic PAD, and many of these changes were found to occur during pain-free walking. The improvement in individuals’ functional 6 min walk test was related to changes in their gait pattern.

scholarly journals Living With Assistive Robotics: Exploring the Everyday Use of Exoskeleton for Persons With Spinal Cord Injury

2021 ◽  
Vol 3 ◽  
Author(s):  
Roberto Lusardi ◽  
Stefano Tomelleri ◽  
Joseph Wherton
Keyword(s):  
Skill Acquisition ◽  
Deep Understanding ◽  
The Body ◽  
Assistive Robotics ◽  
Sensor Technology ◽  
Collaborative Effort ◽  
Self Identity ◽  
Cord Injury ◽  
The Everyday ◽  
Assistive Robotic

Background: Recent advancements in sensor technology and artificial intelligence mechanisms have led to a rapid increase in research and development of robotic orthoses or “exoskeletons” to support people with mobility problems. The purpose of this case study was to provide insight into the lived reality of using the assistive robotic exoskeleton ReWalk.Method: We used ethnographic techniques to explore the everyday experience and use of the assistive robotic device.Results: We found that the appropriation and integration of the technology within the patient's everyday lives required a social and collaborative effort, which continued into use. The decisions to utilise the technology (or not) was closely tied to physical, social, cultural, environmental, and psychological factors. Consequently, there was much variation in patients' perception of the technology and opportunities for support. Four themes emerged:(a) Meaning of mobility—physical mobility represents more than functional ability. Its present socio-cultural meaning is associated with an individual's self-identity and life priorities.(b) Accomplishing body-technique—integration with the body requires a long process of skill acquisition and re-embodiment.(c) Adaptation and adjustment in use—successful use of the technology was characterised by ongoing adjustment and adaptation of the technology and ways of using it.(d) Human element—introduction and sustained use of the exoskeleton demand a social and collaborative effort across the user's professional and lay resources.Conclusions: This study highlights that the development and implementation of the technology need to be grounded in a deep understanding of the day-to-day lives and experiences of the people that use them.

Long bone cross-sectional geometry

2020 ◽  
pp. 307-320
Author(s):  
Christopher B. Ruff ◽  
Ryan W. Higgins ◽  
Kristian J. Carlson
Keyword(s):  
Mechanical Properties ◽  
Cross Sections ◽  
Lateral Displacement ◽  
Center Of Mass ◽  
Gait Pattern ◽  
Locomotor Behavior ◽  
The Body ◽  
Long Bone ◽  
Cross Sectional ◽  
Body Center

Long bone diaphyseal cross-sectional geometries reflect the mechanical properties of the bones, and can be used to aid in inferences of locomotor behavior in extinct hominins. This chapter considers all available long bone diaphyseal and femoral neck cross-sections of specimens from Sterkfontein Member 4, and presents comparisons of these section properties and other cross-sectional dimensions with those of other early hominins as well as modern samples. The cross-sectional geometry of the Sterkfontein Member 4 long bone specimens suggests some similarities to, but also interesting differences in, mechanical loading of these elements relative to modern humans. The less asymmetric cortical bone distribution in the Sterkfontein femoral necks is consistent with other evidence above indicating an altered gait pattern involving lateral displacement of the body center of mass over the stance limb. The relatively very strong upper limb of StW 431 implies that arboreal behavior formed a significant component of its locomotor repertoire. Bipedal gait may have been less efficient and arboreal climbing more prevalent in the Sterkfontein hominins.

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