scholarly journals Contribution of blood oxygen and carbon dioxide sensing to the energetic optimization of human walking

2017 ◽  
Vol 118 (2) ◽  
pp. 1425-1433 ◽  
Author(s):  
Jeremy D. Wong ◽  
Shawn M. O’Connor ◽  
Jessica C. Selinger ◽  
J. Maxwell Donelan
Keyword(s):  
Perceived Exertion ◽  
Human Walking ◽  
Human Gait ◽  
Energetic Cost ◽  
Blood Oxygen ◽  
Blood Gas ◽  
Step Frequency ◽  
Gait Adaptation ◽  
Gait Optimization ◽  
Sensing Cost

Human gait adaptation implies that the nervous system senses energetic cost, yet this signal is unknown. We tested the hypothesis that the blood gas receptors sense cost for gait optimization by controlling blood O2 and CO2 with step frequency as people walked. At the simulated energetic minimum, ventilation and perceived exertion were lowest, yet subjects preferred walking at their original frequency. This suggests that blood gas receptors are not critical for sensing cost during gait.

scholarly journals Increasing the gradient of energetic cost does not initiate adaptation in human walking

2021 ◽  
Author(s):  
Surabhi N Simha ◽  
Jeremy D. Wong ◽  
Jessica C Selinger ◽  
Sabrina J Abram ◽  
J. Maxwell Donelan
Keyword(s):  
Nervous System ◽  
Lower Cost ◽  
Cost Savings ◽  
Control Policy ◽  
Human Walking ◽  
Energetic Cost ◽  
Mechatronic System ◽  
Step Frequency ◽  
Normalized Units ◽  
New Situation

When in a new situation, the nervous system may benefit from adapting its control policy. In determining whether or not to initiate this adaptation, the nervous system may rely on some features of the new situation. Here we tested whether one such feature is salient cost savings. We changed cost saliency by manipulating the gradient of participants' energetic cost landscape during walking. We hypothesized that steeper gradients would cause participants to spontaneously adapt their step frequency to lower costs. To manipulate the gradient, a mechatronic system applied controlled fore-aft forces to the waist of participants as a function of their step frequency as they walked on a treadmill. These forces increased the energetic cost of walking at high step frequencies and reduced it at low step frequencies. We successfully created three cost landscapes of increasing gradients, where the natural variability in participants' step frequency provided cost changes of 3.6% (shallow), 7.2% (intermediate) and 10.2% (steep). Participants did not spontaneously initiate adaptation in response to any of the gradients. Using metronome-guided walking-a previously established protocol for eliciting initiation of adaptation-participants next experienced a step frequency with a lower cost. Participants then adapted by -1.41±0.81 (p=0.007) normalized units away from their originally preferred step frequency obtaining cost savings of 4.80±3.12% That participants would adapt under some conditions, but not in response to steeper cost gradients, suggests that the nervous system does not solely rely on the gradient of energetic cost to initiate adaptation in novel situations.

scholarly journals A mechatronic system for studying energy optimization during walking.

2018 ◽  
Author(s):  
Surabhi N Simha ◽  
J. Maxwell Donelan
Keyword(s):  
Nervous System ◽  
System Design ◽  
Human Movement ◽  
Human Walking ◽  
Energetic Cost ◽  
Mechatronic System ◽  
Step Frequency ◽  
Coordination Strategies ◽  
Design Build ◽  
Optimal Coordination

A general principle of human movement is that our nervous system is able to learn optimal coordination strategies. However, how our nervous system performs this optimization is not well understood. Here we design, build, and test a mechatronic system to probe the algorithms underlying optimization of energetic cost in walking. The system applies controlled fore-aft forces to a hip-belt worn by a user, decreasing their energetic cost by pulling forward or increasing it by pulling backward. The system controls the forces, and thus energetic cost, as a function of how the user is moving. In testing, we found that the system can quickly, accurately, and precisely apply target forces within a walking step. We next controlled the forces as a function of the user's step frequency and found that we could predictably reshape their energetic cost landscape. Finally, we tested whether users adapted their walking in response to the new cost landscapes created by our system, and found that users shifted their step frequency towards the new energetic minima. Our system design appears to be effective for reshaping energetic cost landscapes in human walking to study how the nervous system optimizes movement.

scholarly journals Reducing gravity takes the bounce out of running

2017 ◽  
Author(s):  
Delyle T. Polet ◽  
Ryan T. Schroeder ◽  
John E. A. Bertram
Keyword(s):  
Stance Phase ◽  
Normal Gravity ◽  
Center Of Mass ◽  
Energetic Cost ◽  
Gravitational Acceleration ◽  
Reduced Gravity ◽  
Step Frequency ◽  
Energetic Costs ◽  
Gait Adaptation ◽  
Vertical Takeoff

AbstractIn gravity below Earth normal, a person should be able to take higher leaps in running. We asked ten subjects to run on a treadmill in five levels of simulated reduced gravity and optically tracked center of mass kinematics. Subjects consistentlyreducedballistic height compared to running in normal gravity. We explain this trend by considering the vertical takeoff velocity (defined as maximum vertical velocity). Energetically optimal gaits should balance energetic costs of ground-contact collisions (favouring lower takeoff velocity), and step frequency penalties such as leg swing work (favouring higher takeoff velocity, but less so in reduced gravity). Measured vertical takeoff velocity scaled with the square root of gravitational acceleration, following energetic optimality predictions and explaining why ballistic height decreases in lower gravity. The success of work-based costs in predicting this behaviour challenges the notion that gait adaptation in reduced gravity results from an unloading of the stance phase. Only the relationship between takeoff velocity and swing cost changes in reduced gravity; the energetic cost of the down-to-up transition for a given vertical takeoff velocity does not change with gravity. Because lower gravity allows an elongated swing phase for a given takeoff velocity, the motor control system can relax the vertical momentum change in the stance phase, so reducing ballistic height, without great energetic penalty to leg swing work. While it may seem counterintuitive, using less “bouncy” gaits in reduced gravity is a strategy to reduce energetic costs, to which humans seem extremely sensitive.Summary StatementDuring running, humans take higher leaps in normal gravity than in reduced gravity, in order to optimally balance the competing costs of stance and leg-swing work.

scholarly journals Increasing the gradient of energetic cost does not initiate adaptation in human walking

2020 ◽  
Author(s):  
Surabhi N. Simha ◽  
Jeremy D. Wong ◽  
Jessica C. Selinger ◽  
Sabrina J. Abram ◽  
J. Maxwell Donelan
Keyword(s):  
Nervous System ◽  
Lower Cost ◽  
Cost Savings ◽  
Control Policy ◽  
Human Walking ◽  
Energetic Cost ◽  
Mechatronic System ◽  
Step Frequency ◽  
Normalized Units ◽  
New Situation

AbstractWhen in a new situation, the nervous system may benefit from adapting its control policy. In determining whether or not to initiate this adaptation, the nervous system may rely on some features of the new situation. Here we tested whether one such feature is salient cost savings. We changed cost saliency by manipulating the gradient of participants’ energetic cost landscape during walking. We hypothesized that steeper gradients would cause participants to spontaneously adapt their step frequency to lower costs. To manipulate the gradient, a mechatronic system applied controlled fore-aft forces to the waist of participants as a function of their step frequency as they walked on a treadmill. These forces increased the energetic cost of walking at high step frequencies and reduced it at low step frequencies. We successfully created three cost landscapes of increasing gradients, where the natural variability in participants’ step frequency provided cost changes of 3.6% (shallow), 7.2% (intermediate) and 10.2% (steep). Participants did not spontaneously initiate adaptation in response to any of the gradients. Using metronome-guided walking— a previously established protocol for eliciting initiation of adaptation—participants next experienced a step frequency with a lower cost. Participants then adapted by −1.41±0.81 (p=0.007) normalized units away from their originally preferred step frequency obtaining cost savings of 4.80±3.12%. That participants would adapt under some conditions, but not in response to steeper cost gradients, suggests that the nervous system does not solely rely on the gradient of energetic cost to initiate adaptation in novel situations.

Preferred step frequency minimizes veering during natural human walking

2011 ◽  
Vol 505 (3) ◽  
pp. 291-293 ◽  
Author(s):  
Azusa Uematsu ◽  
Koh Inoue ◽  
Hiroaki Hobara ◽  
Hirofumi Kobayashi ◽  
Yuki Iwamoto ◽  
...  
Keyword(s):  
Human Walking ◽  
Step Frequency

scholarly journals Design of Biomechanical Legs with a Passive Toe Joint for Enhanced Human-like Walking

2017 ◽  
Vol 14 (2) ◽  
pp. 166 ◽  
Author(s):  
Riadh Zaier ◽  
A. Al-Yahmedi
Keyword(s):  
Design Procedure ◽  
Human Walking ◽  
Human Gait ◽  
Design Parameters ◽  
Sultan Qaboos University ◽  
Motion Trajectories ◽  
Normal Human ◽  
Working Principle ◽  
Mass Spring ◽  
Torsion Springs

This paper presents the design procedure of a biomechanical leg, with a passive toe joint, which is capable of mimicking the human walking. This leg has to provide the major features of human gait in the motion trajectories of the hip, knee, ankle, and toe joints. Focus was given to the approach of designing the passive toe joint of the biomechanical leg in its role and effectiveness in performing human like motion. This study was inspired by experimental and theoretical studies in the fields of biomechanics and robotics. Very light materials were mainly used in the design process. Aluminum and carbon fiber parts were selected to design the proposed structure of this biomechanical leg, which is to be manufactured in the Mechanical Lab of the Sultan Qaboos University (SQU). The capabilities of the designed leg to perform the normal human walking are presented. This study provides a noteworthy and unique design for the passive toe joint, represented by a mass-spring damper system, using torsion springs in the foot segment. The working principle and characteristics of the passive toe joint are discussed.  Four-designed cases, with different design parameters, for the passives toe joint system are presented to address the significant role that the passive toe joint plays in human-like motion. The dynamic motion that is used to conduct this comparison was the first stage of the stance motion. The advantages of the presence of the passive toe joint in gait, and its effect on reducing the energy consumption by the other actuated joints are presented and a comparison between the four-designed cases is discussed.

DEVELOPMENT OF MOTION CAPTURE SYSTEM USING DUAL VIDEO CAMERAS FOR THE GAIT DESIGN OF A BIPED ROBOT

2011 ◽  
Vol 08 (02) ◽  
pp. 275-299 ◽  
Author(s):  
JUNG-YUP KIM ◽  
YOUNG-SEOG KIM
Keyword(s):  
Motion Capture ◽  
Human Walking ◽  
Human Gait ◽  
Motion Capture System ◽  
System Calibration ◽  
Walking Gait ◽  
Video Cameras ◽  
Optical Motion ◽  
Optical Motion Capture ◽  
Motion Capture Systems

This paper, describes the development of a motion capture system with novel features for biped robots. In general, motion capture is effectively utilized in the field of computer animation. In the field of humanoid robotics, the number of studies attempting to design human-like gaits by using expensive optical motion capture systems is increasing. The optical motion capture systems used in these studies have involved a large number of cameras because such systems use small-sized ball markers; hence the position accuracy of the markers and the system calibration are very significant. However, since the human walking gait is a simple periodic motion rather than a complex motion, we have developed a specialized motion capture system for this study using dual video cameras and large band-type markers without high-level system calibration in order to capture the human walking gait. In addition to its lower complexity, the proposed capture method requires only a low-cost system and has high space efficiency. An image processing algorithm is also proposed for deriving the human gait data. Finally, we verify the reliability and accuracy of our system by comparing a zero moment point (ZMP) trajectory calculated by the motion captured data with a ZMP trajectory measured by foot force sensors.

scholarly journals Interlimb communication following unexpected changes in treadmill velocity during human walking

2015 ◽  
Vol 113 (9) ◽  
pp. 3151-3158 ◽  
Author(s):  
Andrew J. T. Stevenson ◽  
Svend S. Geertsen ◽  
Thomas Sinkjær ◽  
Jens B. Nielsen ◽  
Natalie Mrachacz-Kersting
Keyword(s):  
Dynamic Stability ◽  
Stance Phase ◽  
Biceps Femoris ◽  
The Body ◽  
Context Dependency ◽  
Human Walking ◽  
Human Gait ◽  
Velocity Change ◽  
Leg Muscles ◽  
Interlimb Reflex

Interlimb reflexes play an important role in human walking, particularly when dynamic stability is threatened by external perturbations or changes in the walking surface. Interlimb reflexes have recently been demonstrated in the contralateral biceps femoris (cBF) following knee joint rotations applied to the ipsilateral leg (iKnee) during the late stance phase of human gait (Stevenson AJ, Geertsen SS, Andersen JB, Sinkjær T, Nielsen JB, Mrachacz-Kersting N. J Physiol 591: 4921–4935, 2013). This interlimb reflex likely acts to slow the forward progression of the body to maintain dynamic stability following the perturbations. We examined this hypothesis by unexpectedly increasing or decreasing the velocity of the treadmill before (−100 and −50 ms), at the same time, or following (+50 ms) the onset of iKnee perturbations in 12 healthy volunteers. We quantified the cBF reflex amplitude when the iKnee perturbation was delivered alone, the treadmill velocity change was delivered alone, or when the two perturbations were combined. When the treadmill velocity was suddenly increased (or decreased) 100 or 50 ms before the iKnee perturbations, the combined cBF reflex was significantly larger (or smaller) than the algebraic sum of the two perturbations delivered separately. Furthermore, unexpected changes in treadmill velocity increased the incidence of reflexes in other contralateral leg muscles when the iKnee perturbations were elicited alone. These results suggest a context dependency for interlimb reflexes. They also show that the cBF reflex changed in a predictable manner to slow the forward progression of the body and maintaining dynamic stability during walking, thus signifying a functional role for interlimb reflexes.

scholarly journals A comparative collision-based analysis of human gait

2013 ◽  
Vol 280 (1771) ◽  
pp. 20131779 ◽  
Author(s):  
David V. Lee ◽  
Tudor N. Comanescu ◽  
Michael T. Butcher ◽  
John E. A. Bertram
Keyword(s):  
Velocity Vector ◽  
Human Walking ◽  
Human Gait ◽  
Centre Of Mass ◽  
Force Vector ◽  
Cost Of Transport ◽  
Functional Grouping ◽  
Collision Angle

This study compares human walking and running, and places them within the context of other mammalian gaits. We use a collision-based approach to analyse the fundamental dynamics of the centre of mass (CoM) according to three angles derived from the instantaneous force and velocity vectors. These dimensionless angles permit comparisons across gait, species and size. The collision angle Φ , which is equivalent to the dimensionless mechanical cost of transport CoT mech , is found to be three times greater during running than walking of humans. This threefold difference is consistent with previous studies of walking versus trotting of quadrupeds, albeit tends to be greater in the gaits of humans and hopping bipeds than in quadrupeds. Plotting the collision angle Φ together with the angles of the CoM force vector Θ and velocity vector Λ results in the functional grouping of bipedal and quadrupedal gaits according to their CoM dynamics—walking, galloping and ambling are distinguished as separate gaits that employ collision reduction, whereas trotting, running and hopping employ little collision reduction and represent more of a continuum that is influenced by dimensionless speed. Comparable with quadrupedal mammals, collision fraction (the ratio of actual to potential collision) is 0.51 during walking and 0.89 during running, indicating substantial collision reduction during walking, but not running, of humans.

Energetic Cost and Stability during Human Walking at the Preferred Stride Frequency

1995 ◽  
Vol 27 (2) ◽  
pp. 164-178 ◽  
Author(s):  
Kenneth G. Holt ◽  
Suh Fang Jeng ◽  
Robert Ratcliffe ◽  
Joseph Hamill
Keyword(s):  
Human Walking ◽  
Stride Frequency ◽  
Energetic Cost
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