Mechanical work for step-to-step transitions is a major determinant of the metabolic cost of human walking

2002 ◽  
Vol 205 (23) ◽  
pp. 3717-3727 ◽  
Author(s):  
J. Maxwell Donelan ◽  
Rodger Kram ◽  
Arthur D. Kuo
Keyword(s):  
Metabolic Rate ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
Step Length ◽  
Mechanical Work ◽  
Major Determinant ◽  
Fourth Power ◽  
Mass Motion ◽  
Step Frequency ◽  
Positive Work

SUMMARY In the single stance phase of walking, center of mass motion resembles that of an inverted pendulum. Theoretically, mechanical work is not necessary for producing the pendular motion, but work is needed to redirect the center of mass velocity from one pendular arc to the next during the transition between steps. A collision model predicts a rate of negative work proportional to the fourth power of step length. Positive work is required to restore the energy lost, potentially exacting a proportional metabolic cost. We tested these predictions with humans (N=9) walking over a range of step lengths(0.4-1.1 m) while keeping step frequency fixed at 1.8 Hz. We measured individual limb external mechanical work using force plates, and metabolic rate using indirect calorimetry. As predicted, average negative and positive external mechanical work rates increased with the fourth power of step length(from 1 W to 38 W; r2=0.96). Metabolic rate also increased with the fourth power of step length (from 7 W to 379 W; r2=0.95), and linearly with mechanical work rate. Mechanical work for step-to-step transitions, rather than pendular motion itself, appears to be a major determinant of the metabolic cost of walking.

scholarly journals Taking advantage of external mechanical work to reduce metabolic cost: the mechanics and energetics of split-belt treadmill walking

2018 ◽  
Author(s):  
Natalia Sanchez ◽  
Surabhi Simha ◽  
J. Maxwell Donelan ◽  
James Micah Finley
Keyword(s):  
Control Strategies ◽  
Metabolic Cost ◽  
Step Length ◽  
Mechanical Work ◽  
Heel Strike ◽  
Recent Effort ◽  
External Assistance ◽  
External Sources ◽  
Walking Economy ◽  
Positive Work

In everyday tasks such as walking and running, we exploit the work performed by external sources such as gravity to reduce the work performed by muscles. There has been considerable recent effort to design devices capable of performing mechanical work to improve walking function or reduce effort. The success of these devices relies on the user adapting their natural control strategies to take advantage of assistance provided by the device. Although locomotor adaptation is central to this process, the study of adaptation is often done using approaches that on the surface, seem to have little in common with the use of external assistance. Here, we show that one of the most common approaches for studying this process, which is adaptation to walking on a split-belt treadmill, can be understood from a perspective in which people learn to take advantage of mechanical work performed by the treadmill. During adaptation, people systematically adjust their step lengths, defined as the distance between the feet at heel strike, from one step to the next. Initially, the step length on the slow belt is longer than the step length on the fast belt, measured as a negative step length asymmetry, but people naturally reduce this asymmetry with practice. Here, we demonstrate that these modifications of step length asymmetry allow people to extract positive work from the treadmill belts to reduce the positive work performed by the legs and simultaneously reduce metabolic cost. Moreover, we show that walking with a positive step length asymmetry minimizes metabolic cost, and people prefer to walk in this manner when allowed to select their walking pattern. Together, our results suggest that split-belt adaptation can be interpreted as a process by which people learn to take advantage of mechanical work performed by an external device to improve walking economy.

Effects of Fatigue on Running Mechanics: Spring-Mass Behavior in Recreational Runners After 60 Seconds of Countermovement Jumps

2015 ◽  
Vol 31 (6) ◽  
pp. 445-451 ◽  
Author(s):  
Gabriela Fischer ◽  
Jorge L.L. Storniolo ◽  
Leonardo A. Peyré-Tartaruga
Keyword(s):  
Center Of Mass ◽  
Force Plate ◽  
Vertical Displacement ◽  
Step Length ◽  
Vertical Force ◽  
Step Frequency ◽  
Mass Model ◽  
Vertical Stiffness ◽  
Recreational Runners ◽  
Running Mechanics

The purpose of this study was to investigate the effects of acute fatigue on spring-mass model (SMM) parameters among recreational runners at different speeds. Eleven participants (5 males and 6 females) performed running trials at slower, self-selected, and faster speeds on an indoor track before and after performing a fatigue protocol (60 s of countermovement jumps). Maximal vertical force (Fmax), impact peak force (Fpeak), loading rate (LR), contact time (Tc), aerial time (Ta), step frequency (SF), step length (SL), maximal vertical displacement of the center of mass (ΔZ), vertical stiffness (Kvert), and leg work (Wleg) were measured using a force plate integrated into the track. A significant reduction (–43.1 ± 8.6%; P < .05) in mechanical power during jumps indicated that the subjects became fatigued. The results showed that under fatigue conditions, the runners adjusted their running mechanics at slower (≈2.7 ms–1; ΔZ –12% and SF +3.9%; P < .05), self-selected (≈3.3 ms–1; SF +3%, SL –6.8%, Ta –16%, and Fmax –3.3%; P < .05), and faster (≈3.6 ms–1 SL –6.9%, Ta –14% and Fpeak –9.8%; P < .05) speeds without significantly altering Kvert (P > .05). During constant running, the previous 60 s of maximal vertical jumps induced mechanical adjustments in the spatiotemporal parameters without altering Kvert.

scholarly journals Persons post-stroke improve step length symmetry by walking asymmetrically

2020 ◽  
Author(s):  
Purnima Padmanabhan ◽  
Keerthana Sreekanth ◽  
Shivam Gulhar ◽  
Kendra M. Cherry-Allen ◽  
Kristan A. Leech ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Metabolic Cost ◽  
Step Length ◽  
Gait Pattern ◽  
Future Research ◽  
Cost Of Transport ◽  
Post Stroke ◽  
Paretic Limb ◽  
Gait Parameters ◽  
The Many

Abstract Background Restoration of step length symmetry is a common rehabilitation goal after stroke. Persons post-stroke often retain the ability to walk with symmetric step lengths ("symmetric steps") at an elevated metabolic cost relative to healthy adults. Two key questions with direct implications for rehabilitation have emerged: 1) how do persons post-stroke generate symmetric steps, and 2) why do symmetric steps remain so effortful? Here, we aimed to understand how persons post-stroke generate symmetric steps and explored how the resulting gait pattern may relate to the metabolic cost of transport. Methods We recorded kinematic, kinetic, and metabolic data as nine persons post-stroke walked on an instrumented treadmill under two conditions: preferred walking and symmetric stepping (using visual feedback). Results Gait kinematics and kinetics remained markedly asymmetric even when persons post-stroke improved step length symmetry. Impaired paretic propulsion and abnormal movement of the center of mass were evident during both preferred walking and symmetric stepping. These deficits contributed to diminished positive work performed by the paretic limb on the center of mass in both conditions. Within each condition, decreased positive paretic work correlated with increased metabolic cost of transport and decreased walking speed across participants. Conclusions It is critical to consider the mechanics used to restore symmetric steps when designing interventions to improve walking after stroke. Future research should consider the many dimensions of asymmetry in post-stroke gait, and additional within-participant manipulations of gait parameters are needed to improve our understanding of the elevated metabolic cost of walking after stroke.

scholarly journals Center of mass motion and the effects of ankle bracing on metabolic cost during submaximal walking trials

2006 ◽  
Vol 24 (12) ◽  
pp. 2170-2175 ◽  
Author(s):  
Stephanie K. Herndon ◽  
Bradford C. Bennett ◽  
Adam Wolovick ◽  
Andrew Filachek ◽  
Glenn A. Gaesser ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Metabolic Cost ◽  
Mass Motion ◽  
Ankle Bracing

scholarly journals Persons post-stroke improve step length symmetry by walking asymmetrically

2020 ◽  
Author(s):  
Purnima Padmanabhan ◽  
Keerthana Sreekanth ◽  
Shivam Gulhar ◽  
Kendra M. Cherry-Allen ◽  
Kristan A. Leech ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Metabolic Cost ◽  
Step Length ◽  
Gait Pattern ◽  
Future Research ◽  
Cost Of Transport ◽  
Post Stroke ◽  
Paretic Limb ◽  
Gait Parameters ◽  
The Many

Abstract Background Restoration of step length symmetry is a common rehabilitation goal after stroke. Persons post-stroke often retain the ability to walk with symmetric step lengths ("symmetric steps"); however, the resulting walking pattern remains effortful. Two key questions with direct implications for rehabilitation have emerged: 1) how do persons post-stroke generate symmetric steps, and 2) why do symmetric steps remain so effortful? Here, we aimed to understand how persons post-stroke generate symmetric steps and explored how the resulting gait pattern may relate to the metabolic cost of transport. Methods We recorded kinematic, kinetic, and metabolic data as nine persons post-stroke walked on an instrumented treadmill under two conditions: preferred walking and symmetric stepping (using visual feedback). Results Gait kinematics and kinetics remained markedly asymmetric even when persons post-stroke improved step length symmetry. Impaired paretic propulsion and aberrant movement of the center of mass were evident during both preferred walking and symmetric stepping. These deficits contributed to diminished positive work performed by the paretic limb on the center of mass in both conditions. Within each condition, decreased positive paretic work correlated with increased metabolic cost of transport and decreased walking speed across participants. Conclusions It is critical to consider the mechanics used to restore symmetric steps when designing interventions to improve walking after stroke. Future research should consider the many dimensions of asymmetry in post-stroke gait, and additional within-participant manipulations of gait parameters are needed to improve our understanding of the elevated metabolic cost of walking after stroke.

Multiple Sclerosis Alters the Mechanical Work Performed on the Body’s Center of Mass During Gait

2013 ◽  
Vol 29 (4) ◽  
pp. 435-442 ◽  
Author(s):  
Shane R. Wurdeman ◽  
Jessie M. Huisinga ◽  
Mary Filipi ◽  
Nicholas Stergiou
Keyword(s):  
Multiple Sclerosis ◽  
Elastic Energy ◽  
Stance Phase ◽  
Center Of Mass ◽  
Mechanical Work ◽  
Healthy Controls ◽  
Double Support ◽  
Negative Work ◽  
Positive Work

Patients with multiple sclerosis (MS) have less-coordinated movements of the center of mass resulting in greater mechanical work. The purpose of this study was to quantify the work performed on the body’s center of mass by patients with MS. It was hypothesized that patients with MS would perform greater negative work during initial double support and less positive work in terminal double support. Results revealed that patients with MS perform less negative work in single support and early terminal double support and less positive work in the terminal double support period. However, summed over the entire stance phase, patients with MS and healthy controls performed similar amounts of positive and negative work on the body’s center of mass. The altered work throughout different periods in the stance phase may be indicative of a failure to capitalize on passive elastic energy mechanisms and increased reliance upon more active work generation to sustain gait.

Do mechanical gait parameters explain the higher metabolic cost of walking in obese adolescents?

2009 ◽  
Vol 106 (6) ◽  
pp. 1763-1770 ◽  
Author(s):  
Nicolas Peyrot ◽  
David Thivel ◽  
Laurie Isacco ◽  
Jean-Benoît Morin ◽  
Pascale Duche ◽  
...  
Keyword(s):  
Body Fat ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Metabolic Cost ◽  
Normal Weight ◽  
Mechanical Work ◽  
Percent Body Fat ◽  
External Work ◽  
Obese Subjects

Net metabolic cost of walking normalized by body mass ( CW·BM−1; in J·kg−1·m−1) is greater in obese than in normal-weight individuals, and biomechanical differences could be responsible for this greater net metabolic cost. We hypothesized that, in obese individuals, greater mediolateral body center of mass (COM) displacement and lower recovery of mechanical energy could induce an increase in the external mechanical work required to lift and accelerate the COM and thus in net CW·BM−1. Body composition and standing metabolic rate were measured in 23 obese and 10 normal-weight adolescents. Metabolic and mechanical energy costs were assessed while walking along an outdoor track at four speeds (0.75–1.50 m/s). Three-dimensional COM accelerations were measured by means of a tri-axial accelerometer and gyroscope and integrated twice to obtain COM velocities, displacements, and fluctuations in potential and kinetic energies. Last, external mechanical work (J·kg−1·m−1), mediolateral COM displacement, and the mechanical energy recovery of the inverted pendulum were calculated. Net CW·BM−1 was 25% higher in obese than in normal-weight subjects on average across speeds, and net CW·BM−67 (J·kg−0.67·m−1) was significantly related to percent body fat ( r2 = 0.46). However, recovery of mechanical energy and the external work performed (J·kg−1·m−1) were similar in the two groups. The mediolateral displacement was greater in obese subjects and significantly related to percent body fat ( r2 = 0.64). The mediolateral COM displacement, likely due to greater step width, was significantly related to net CW·BM−67 ( r2 = 0.49). In conclusion, we speculate that the greater net CW·BM−67 in obese subjects may be partially explained by the greater step-to-step transition costs associated with wide gait during walking.

scholarly journals Bionic ankle–foot prosthesis normalizes walking gait for persons with leg amputation

2011 ◽  
Vol 279 (1728) ◽  
pp. 457-464 ◽  
Author(s):  
Hugh M. Herr ◽  
Alena M. Grabowski
Keyword(s):  
Metabolic Cost ◽  
Mechanical Work ◽  
Metabolic Energy ◽  
Energy Costs ◽  
Transtibial Amputation ◽  
Walking Gait ◽  
Walking Velocity ◽  
Leg Amputation ◽  
Positive Work ◽  
Over Time

Over time, leg prostheses have improved in design, but have been incapable of actively adapting to different walking velocities in a manner comparable to a biological limb. People with a leg amputation using such commercially available passive-elastic prostheses require significantly more metabolic energy to walk at the same velocities, prefer to walk slower and have abnormal biomechanics compared with non-amputees. A bionic prosthesis has been developed that emulates the function of a biological ankle during level-ground walking, specifically providing the net positive work required for a range of walking velocities. We compared metabolic energy costs, preferred velocities and biomechanical patterns of seven people with a unilateral transtibial amputation using the bionic prosthesis and using their own passive-elastic prosthesis to those of seven non-amputees during level-ground walking. Compared with using a passive-elastic prosthesis, using the bionic prosthesis decreased metabolic cost by 8 per cent, increased trailing prosthetic leg mechanical work by 57 per cent and decreased the leading biological leg mechanical work by 10 per cent, on average, across walking velocities of 0.75–1.75 m s −1 and increased preferred walking velocity by 23 per cent. Using the bionic prosthesis resulted in metabolic energy costs, preferred walking velocities and biomechanical patterns that were not significantly different from people without an amputation.

scholarly journals Persons post-stroke restore step length symmetry by walking asymmetrically

2019 ◽  
Author(s):  
Purnima Padmanabhan ◽  
Keerthana Sreekanth Rao ◽  
Shivam Gulhar ◽  
Kendra M. Cherry-Allen ◽  
Kristan A. Leech ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Metabolic Cost ◽  
Step Length ◽  
Gait Pattern ◽  
Vertical Movement ◽  
Cost Of Transport ◽  
Post Stroke ◽  
Paretic Limb ◽  
Rehabilitation Goal ◽  
Limb Kinematics

ABSTRACTBackgroundRestoration of step length symmetry is a common rehabilitation goal after stroke. Persons post-stroke often retain the capacity to walk with symmetric step lengths (“symmetric steps”); however, the resulting walking pattern remains effortful. Two key questions with direct implications for rehabilitation have emerged: 1) how do persons post-stroke generate symmetric steps, and 2) why do symmetric steps remain so effortful?ObjectiveTo understand how persons post-stroke generate symmetric steps and how the resulting gait pattern relates to the metabolic cost of transport.MethodsTen persons post-stroke walked on an instrumented treadmill under two conditions: preferred walking and symmetric stepping (using visual feedback). We recorded kinematic, kinetic, and metabolic data during both conditions.ResultsPersons post-stroke restored step length symmetry using energetically expensive, asymmetric patterns. Impaired paretic propulsion and abnormal vertical movement of the center of mass were evident during both preferred walking and symmetric stepping. These deficits contributed to diminished positive work performed by the paretic limb on the center of mass in both conditions. Decreased positive paretic work correlated with increased metabolic cost of transport, decreased self-selected walking speed, and increased asymmetry in limb kinematics.ConclusionsIt is important to consider the mechanics used to restore symmetric steps when designing interventions to improve walking after stroke. Facilitating symmetric steps via increased paretic propulsion or enabling paretic limb advancement without excessive vertical movement may enable persons post-stroke to walk with a less effortful, more symmetric gait pattern.

scholarly journals Using asymmetry to your advantage: learning to acquire and accept external assistance during prolonged split-belt walking

2020 ◽  
Author(s):  
Natalia Sanchez ◽  
Surabhi N Simha ◽  
J. Maxwell Donelan ◽  
James M Finley
Keyword(s):  
Energy Cost ◽  
Metabolic Cost ◽  
Mechanical Work ◽  
Energetic Cost ◽  
Sufficient Time ◽  
Adaptation Studies ◽  
Spatiotemporal Changes ◽  
External Assistance ◽  
The Difference ◽  
Positive Work

People can learn to exploit external assistance during walking to reduce energy cost. For example, walking on a split-belt treadmill affords the opportunity for people to redistribute the mechanical work performed by the legs to gain assistance from the difference in belts' speed and reduce energetic cost. Though we know what people should do to acquire this assistance, this strategy is not observed during typical adaptation studies. We hypothesized that extending the time allotted for adaptation would result in participants adopting asymmetric step lengths to increase the assistance they can acquire from the treadmill. Here, participants walked on a split-belt treadmill for 45 minutes while we measured spatiotemporal gait variables, metabolic cost, and mechanical work. We show that when people are given sufficient time to adapt, they naturally learn to step further forward on the fast belt, acquire positive mechanical work from the treadmill, and reduce the positive work performed by the legs. We also show that spatiotemporal adaptation and energy optimization operate over different timescales: people continue to reduce energy cost even after spatiotemporal changes have plateaued. Our findings support the idea that walking with symmetric step lengths, which is traditionally thought of as the endpoint of adaptation, is only a point in the process by which people learn to take advantage of the assistance provided by the treadmill. These results provide further evidence that reducing energetic cost is central in shaping adaptive locomotion, but this process occurs over more extended timescales than those used in typical studies.

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