scholarly journals The metabolic cost of changing walking speeds is significant, implies lower optimal speeds for shorter distances, and increases daily energy estimates

2015 ◽  
Vol 11 (9) ◽  
pp. 20150486 ◽  
Author(s):  
Nidhi Seethapathi ◽  
Manoj Srinivasan
Keyword(s):  
Metabolic Rate ◽  
Metabolic Cost ◽  
Laboratory Frame ◽  
Constant Speed ◽  
Metabolic Energy ◽  
Energy Estimates ◽  
Walking Speeds ◽  
The Cost ◽  
Speed Fluctuations ◽  
Energy Cost Of Walking

Humans do not generally walk at constant speed, except perhaps on a treadmill. Normal walking involves starting, stopping and changing speeds, in addition to roughly steady locomotion. Here, we measure the metabolic energy cost of walking when changing speed. Subjects (healthy adults) walked with oscillating speeds on a constant-speed treadmill, alternating between walking slower and faster than the treadmill belt, moving back and forth in the laboratory frame. The metabolic rate for oscillating-speed walking was significantly higher than that for constant-speed walking (6–20% cost increase for ±0.13–0.27 m s −1 speed fluctuations). The metabolic rate increase was correlated with two models: a model based on kinetic energy fluctuations and an inverted pendulum walking model, optimized for oscillating-speed constraints. The cost of changing speeds may have behavioural implications: we predicted that the energy-optimal walking speed is lower for shorter distances. We measured preferred human walking speeds for different walking distances and found people preferred lower walking speeds for shorter distances as predicted. Further, analysing published daily walking-bout distributions, we estimate that the cost of changing speeds is 4–8% of daily walking energy budget.

The cost of transport of human running is not affected, as in walking, by wide acceleration/deceleration cycles

2013 ◽  
Vol 114 (4) ◽  
pp. 498-503 ◽  
Author(s):  
Alberto E. Minetti ◽  
Paolo Gaudino ◽  
Elena Seminati ◽  
Dario Cazzola
Keyword(s):  
Field Experiments ◽  
Metabolic Cost ◽  
Constant Speed ◽  
Metabolic Energy ◽  
Recent Theory ◽  
Cost Of Transport ◽  
Unit Distance ◽  
The Cost ◽  
Speed Fluctuations ◽  
Human Running

Although most of the literature on locomotion energetics and biomechanics is about constant-speed experiments, humans and animals tend to move at variable speeds in their daily life. This study addresses the following questions: 1) how much extra metabolic energy is associated with traveling a unit distance by adopting acceleration/deceleration cycles in walking and running, with respect to constant speed, and 2) how can biomechanics explain those metabolic findings. Ten males and ten females walked and ran at fluctuating speeds (5 ± 0, ± 1, ± 1.5, ± 2, ± 2.5 km/h for treadmill walking, 11 ± 0, ± 1, ± 2, ± 3, ± 4 km/h for treadmill and field running) in cycles lasting 6 s. Field experiments, consisting of subjects following a laser spot projected from a computer-controlled astronomic telescope, were necessary to check the noninertial bias of the oscillating-speed treadmill. Metabolic cost of transport was found to be almost constant at all speed oscillations for running and up to ±2 km/h for walking, with no remarkable differences between laboratory and field results. The substantial constancy of the metabolic cost is not explained by the predicted cost of pure acceleration/deceleration. As for walking, results from speed-oscillation running suggest that the inherent within-stride, elastic energy-free accelerations/decelerations when moving at constant speed work as a mechanical buffer for among-stride speed fluctuations, with no extra metabolic cost. Also, a recent theory about the analogy between sprint (level) running and constant-speed running on gradients, together with the mechanical determinants of gradient locomotion, helps to interpret the present findings.

Joint-Space Dynamic Model of Metabolic Cost With Subject-Specific Energetic Parameters

2014 ◽  
Author(s):  
Dustyn Roberts ◽  
Howard Hillstrom ◽  
Joo H. Kim
Keyword(s):  
Dynamic Model ◽  
Metabolic Cost ◽  
Joint Space ◽  
Human Motion ◽  
Metabolic Energy ◽  
Model Parameters ◽  
Cost Of Transport ◽  
Walking Speeds ◽  
The Cost ◽  
Metabolic Energy Expenditure

Metabolic energy expenditure (MEE) is commonly used to characterize human motion. In this study, a general joint-space dynamic model of MEE is developed by integrating the principles of thermodynamics and multibody system dynamics in a joint-space model that enables the evaluation of MEE without the limitations inherent in experimental measurements or muscle-space models. Muscle-space energetic components are mapped to the joint space, in which the MEE model is formulated. A constrained optimization algorithm is used to estimate the model parameters from experimental walking data. The joint-space parameters estimated directly from active subjects provide reliable estimates of the trend of the cost of transport at different walking speeds. The quantities predicted by this model, such as cost of transport, can be used as strong complements to experimental methods to increase the reliability of results and yield unique insights for various applications.

scholarly journals Metabolic cost of generating muscular force in human walking: insights from load-carrying and speed experiments

2003 ◽  
Vol 95 (1) ◽  
pp. 172-183 ◽  
Author(s):  
Timothy M. Griffin ◽  
Thomas J. Roberts ◽  
Rodger Kram
Keyword(s):  
Metabolic Rate ◽  
Stance Phase ◽  
Metabolic Cost ◽  
Direct Proportion ◽  
Muscular Force ◽  
Active Muscle ◽  
Cost Coefficient ◽  
Load Carrying ◽  
Leg Muscle ◽  
The Cost

We sought to understand how leg muscle function determines the metabolic cost of walking. We first indirectly assessed the metabolic cost of swinging the legs and then examined the cost of generating muscular force during the stance phase. Four men and four women walked at 0.5, 1.0, 1.5, and 2.0 m/s carrying loads equal to 0, 10, 20, and 30% body mass positioned symmetrically about the waist. The net metabolic rate increased in nearly direct proportion to the external mechanical power during moderate-speed (0.5–1.5 m/s) load carrying, suggesting that the cost of swinging the legs is relatively small. The active muscle volume required to generate force on the ground and the rate of generating this force accounted for >85% of the increase in net metabolic rate across moderate speeds and most loading conditions. Although these factors explained less of the increase in metabolic rate between 1.5 and 2.0 m/s (∼50%), the cost of generating force per unit volume of active muscle [i.e., the cost coefficient ( k)] was similar across all conditions [ k = 0.11 ± 0.03 (SD) J/cm3]. These data indicate that, regardless of the work muscles do, the metabolic cost of walking can be largely explained by the cost of generating muscular force during the stance phase.

scholarly journals Optimized hip–knee–ankle exoskeleton assistance at a range of walking speeds

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Gwendolyn M. Bryan ◽  
Patrick W. Franks ◽  
Seungmoon Song ◽  
Alexandra S. Voloshina ◽  
Ricardo Reyes ◽  
...  
Keyword(s):  
Walking Speed ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Positive Power ◽  
Fast Walking ◽  
Slow Walking ◽  
Limited Success ◽  
Ankle Exoskeleton ◽  
Walking Speeds ◽  
The Relationship

Abstract Background Autonomous exoskeletons will need to be useful at a variety of walking speeds, but it is unclear how optimal hip–knee–ankle exoskeleton assistance should change with speed. Biological joint moments tend to increase with speed, and in some cases, optimized ankle exoskeleton torques follow a similar trend. Ideal hip–knee–ankle exoskeleton torque may also increase with speed. The purpose of this study was to characterize the relationship between walking speed, optimal hip–knee–ankle exoskeleton assistance, and the benefits to metabolic energy cost. Methods We optimized hip–knee–ankle exoskeleton assistance to reduce metabolic cost for three able-bodied participants walking at 1.0 m/s, 1.25 m/s and 1.5 m/s. We measured metabolic cost, muscle activity, exoskeleton assistance and kinematics. We performed Friedman’s tests to analyze trends across walking speeds and paired t-tests to determine if changes from the unassisted conditions to the assisted conditions were significant. Results Exoskeleton assistance reduced the metabolic cost of walking compared to wearing the exoskeleton with no torque applied by 26%, 47% and 50% at 1.0, 1.25 and 1.5 m/s, respectively. For all three participants, optimized exoskeleton ankle torque was the smallest for slow walking, while hip and knee torque changed slightly with speed in ways that varied across participants. Total applied positive power increased with speed for all three participants, largely due to increased joint velocities, which consistently increased with speed. Conclusions Exoskeleton assistance is effective at a range of speeds and is most effective at medium and fast walking speeds. Exoskeleton assistance was less effective for slow walking, which may explain the limited success in reducing metabolic cost for patient populations through exoskeleton assistance. Exoskeleton designers may have more success when targeting activities and groups with faster walking speeds. Speed-related changes in optimized exoskeleton assistance varied by participant, indicating either the benefit of participant-specific tuning or that a wide variety of torque profiles are similarly effective.

Metabolic Cost of Stair Climbing

1986 ◽  
Vol 30 (10) ◽  
pp. 985-988 ◽  
Author(s):  
T. L. Doolittle
Keyword(s):  
Vertical Velocity ◽  
Protective Clothing ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Stair Climbing ◽  
Energy Costs ◽  
The Cost

Metabolic energy costs were determined on sixteen male firefighters ascending a stairmill in an unladen and a laden condition at a vertical velocity of 12.2 m/min. In the unladen condition they wore shorts and tennis shoes, while lagen they wore full protective clothing, including a SCBA, and carried a hose pack. Mean mass of the load was 39.2 kg. Caloric costs were compared with selected equations from the literature. All of the equations overpredicted for the unladen condition. One continued to overpredict, one underestimated, and a third was very close for the cost for the laden condition. An equation derived from data for eight of the subjects, yielded better predictions for the remaining eight, under both conditions, than any of the equations from the literature. Limitations and the need for further research are discussed.

scholarly journals Energetics of terrestrial locomotion of the platypus Ornithorhynchus anatinus

2001 ◽  
Vol 204 (4) ◽  
pp. 797-803 ◽  
Author(s):  
F.E. Fish ◽  
P.B. Frappell ◽  
R.V. Baudinette ◽  
P.M. MacFarlane
Keyword(s):  
Metabolic Rate ◽  
Metabolic Cost ◽  
Standard Metabolic Rate ◽  
Cost Of Transport ◽  
Terrestrial Locomotion ◽  
Terrestrial Mammals ◽  
Video Recordings ◽  
Ornithorhynchus Anatinus ◽  
The Cost ◽  
Limb Structure

The platypus Ornithorhynchus anatinus Shaw displays specializations in its limb structure for swimming that could negatively affect its terrestrial locomotion. Platypuses walked on a treadmill at speeds of 0.19-1.08 m × s(−1). Video recordings were used for gait analysis, and the metabolic rate of terrestrial locomotion was studied by measuring oxygen consumption. Platypuses used walking gaits (duty factor >0.50) with a sprawled stance. To limit any potential interference from the extensive webbing on the forefeet, platypuses walk on their knuckles. Metabolic rate increased linearly over a 2.4-fold range with increasing walking speed in a manner similar to that of terrestrial mammals, but was low as a result of the relatively low standard metabolic rate of this monotreme. The dimensionless cost of transport decreased with increasing speed to a minimum of 0.79. Compared with the cost of transport for swimming, the metabolic cost for terrestrial locomotion was 2.1 times greater. This difference suggests that the platypus may pay a price in terrestrial locomotion by being more aquatically adapted than other semi-aquatic or terrestrial mammals.

Independent metabolic costs of supporting body weight and accelerating body mass during walking

2005 ◽  
Vol 98 (2) ◽  
pp. 579-583 ◽  
Author(s):  
Alena Grabowski ◽  
Claire T. Farley ◽  
Rodger Kram
Keyword(s):  
Body Weight ◽  
Metabolic Rate ◽  
Body Mass ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
Added Mass ◽  
Normal Walking ◽  
Reduced Gravity ◽  
The Cost ◽  
Support Body Weight

The metabolic cost of walking is determined by many mechanical tasks, but the individual contribution of each task remains unclear. We hypothesized that the force generated to support body weight and the work performed to redirect and accelerate body mass each individually incur a significant metabolic cost during normal walking. To test our hypothesis, we measured changes in metabolic rate in response to combinations of simulated reduced gravity and added loading. We found that reducing body weight by simulating reduced gravity modestly decreased net metabolic rate. By calculating the metabolic cost per Newton of reduced body weight, we deduced that generating force to support body weight comprises ∼28% of the metabolic cost of normal walking. Similar to previous loading studies, we found that adding both weight and mass increased net metabolic rate in more than direct proportion to load. However, when we added mass alone by using a combination of simulated reduced gravity and added load, net metabolic rate increased about one-half as much as when we added both weight and mass. By calculating the cost per kilogram of added mass, we deduced that the work performed on the center of mass comprises ∼45% of the metabolic cost of normal walking. Our findings support the hypothesis that force and work each incur a significant metabolic cost. Specifically, the cost of performing work to redirect and accelerate the center of mass is almost twice as great as the cost of generating force to support body weight.

scholarly journals The influence of traumatic transfemoral amputation on metabolic cost across walking speeds

2017 ◽  
Vol 42 (2) ◽  
pp. 214-222 ◽  
Author(s):  
Elizabeth Russell Esposito ◽  
Christopher A Rábago ◽  
Jason Wilken
Keyword(s):  
Heart Rate ◽  
Metabolic Rate ◽  
Perceived Exertion ◽  
Metabolic Cost ◽  
Rating Of Perceived Exertion ◽  
Transfemoral Amputation ◽  
Cross Sectional ◽  
Rehabilitative Care ◽  
The Individual ◽  
Walking Speeds

Background: Recent literature indicates equivalent costs of walking can be achieved after a transtibial amputation when the individual is young, active, and/or has extensive access to rehabilitative care. It is unknown if a similar cohort with transfemoral amputation can also achieve lower metabolic costs of walking than previously reported. Objective: Compare metabolic cost in individuals with a transfemoral amputation to controls and to the literature across a range of walking speeds. Study design: Cross-sectional. Methods: A total of 14 individuals with a unilateral transfemoral amputation (27 ± 5 years, N = 4 mechanical knee, N = 10 microprocessor knee) and 14 able-bodied controls (26 ± 6 years) walked at self-selected and four standardized speeds. Heart rate, metabolic rate (mL O2/kg/min), metabolic cost (mL O2/kg/m), and rating of perceived exertion were calculated. Results: Self-selected speed was 8.6% slower in the transfemoral amputation group ( p = 0.031). Across standardized speeds, both metabolic rate and metabolic cost ranged from 44%–47% greater in the transfemoral amputation group ( p < 0.001), heart rate was 24%–33% greater ( p < 0.001), and perceived exertion was 24%–35% greater ( p < 0.009). Conclusion: Although the transfemoral amputation group was relatively young, physically fit, and had extensive access to rehabilitative care, the metabolic cost of walking fell within the ranges of the literature on older or presumably less fit individuals with transfemoral amputation. Clinical relevance Developments in prosthetic technology and/or rehabilitative care may be warranted and may reduce the metabolic cost of walking in individuals with a transfemoral amputation.

scholarly journals Impact of elastic ankle exoskeleton stiffness on neuromechanics and energetics of human walking across multiple speeds

2020 ◽  
Author(s):  
Richard W. Nuckols ◽  
Gregory S. Sawicki
Keyword(s):  
Metabolic Rate ◽  
Muscle Activation ◽  
Walking Speed ◽  
Metabolic Cost ◽  
Weighted Sum ◽  
Joint Mechanics ◽  
Muscle Dynamics ◽  
Activation Rate ◽  
Ankle Exoskeleton ◽  
Walking Speeds

Abstract Background: Elastic ankle exoskeletons with springs of intermediate stiffness in parallel with the human plantarflexors can reduce the metabolic cost of walking by ~7% at 1.25 m s -1 . In a move toward ‘real-world’ application, we examined whether the unpowered approach has metabolic benefit across a range of walking speeds, and if so, whether the optimal exoskeleton stiffness was speed dependent. We hypothesized that, for any walking speed, there would be an optimal ankle exoskeleton stiffness - not too compliant and not too stiff - that minimizes the user’s metabolic rate. In addition, we expected the optimal exoskeleton stiffness to increase with walking speed. Methods: Eleven participants walked on a level treadmill at 1.25, 1.50, and 1.75 m s -1 while we used a state-of-the-art exoskeleton emulator system to apply bilateral ankle exoskeleton assistance at five controlled rotational stiffnesses (k exo = 0, 50, 100, 150, 250 Nm rad -1 ). We measured metabolic cost, lower limb joint mechanics, and EMG of muscles crossing the ankle, knee, and hip. Results: We measured significant reductions in metabolic cost at the lowest exoskeleton stiffness (50 Nm rad -1 ) for assisted walking at both 1.25 (4.2%; p = 0.032) and 1.75 m s -1 (4.7%; p = 0.009). At these speeds, the metabolically optimal ankle exoskeleton stiffness provided peak assistive torques of ~0.20 Nm kg -1 that resulted in reduced biological ankle moment of ~12% and reduced soleus muscle activity of ~10%. We found no spring stiffness that could reduce the metabolic cost of walking at 1.5 m s -1 . Across all speeds, the non-weighted sum of soleus and tibialis anterior activation rate explained the change metabolic rate due to exoskeleton assistance ( p < .05; R 2 > 0.56)). Conclusions: Elastic ankle exoskeletons with low rotational stiffness reduce users’ metabolic cost of walking at slow and fast walking speeds but not at intermediate walking speed. The relationship between the non-weighted sum of soleus and tibialis activation rate and metabolic cost (R 2 > 0.56) indicates that muscle activation may drive metabolic demand. Future work using computer simulations and ultrasound imaging will get ‘under the skin’ and examine the interaction between exoskeleton stiffness and plantarflexor muscle dynamics to better inform stiffness selection in human-machine systems.

Energetics of ascent: insects on inclines

1990 ◽  
Vol 149 (1) ◽  
pp. 307-317 ◽  
Author(s):  
R. J. Full ◽  
A. Tullis
Keyword(s):  
Oxygen Consumption ◽  
Minimum Cost ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Stride Frequency ◽  
Energetic Cost ◽  
Incline Angle ◽  
Small Animals ◽  
Cost Of Locomotion ◽  
The Cost

Small animals use more metabolic energy per unit mass than large animals to run on a level surface. If the cost to lift one gram of mass one vertical meter is constant, small animals should require proportionally smaller increases in metabolic cost to run uphill. To test this hypothesis on very small animals possessing an exceptional capacity for ascending steep gradients, we measured the metabolic cost of locomotion in the cockroach, Periplaneta americana, running at angles of 0, 45 and 90 degrees to the horizontal. Resting oxygen consumption (VO2rest) was not affected by incline angle. Steady-state oxygen consumption (VO2ss) increased linearly with speed at all angles of ascent. The minimum cost of locomotion (the slope of the VO2ss versus speed function) increased with increasing angle of ascent. The minimum cost of locomotion on 45 and 90 degrees inclines was two and three times greater, respectively, than the cost during horizontal running. The cockroach's metabolic cost of ascent greatly exceeds that predicted from the hypothesis of a constant efficiency for vertical work. Variations in stride frequency and contact time cannot account for the high metabolic cost, because they were independent of incline angle. An increase in the metabolic cost or amount of force production may best explain the increase in metabolic cost. Small animals, such as P. americana, can easily scale vertical surfaces, but the energetic cost is considerable.

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