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      Stroller running: Energetic and kinematic changes across pushing methods

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      PLoS ONE
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          Abstract

          Objective

          Running with a stroller provides an opportunity for parents to exercise near their child and counteract health declines experienced during early parenthood. Understanding biomechanical and physiological changes that occur when stroller running is needed to evaluate its health impact, yet the effects of stroller running have not been clearly presented. Here, three commonly used stroller pushing methods were investigated to detect potential changes in energetic cost and lower-limb kinematics.

          Methods

          Sixteen individuals (M/F: 10/6) ran at self-selected speeds for 800m under three stroller conditions (2-Hands, 1-Hand, and Push/Chase) and an independent running control.

          Results

          A significant decrease in speed (p = 0.001) and stride length (p<0.001) was observed between the control and stroller conditions, however no significant change in energetic cost (p = 0.080) or heart rate (p = 0.393) was observed. Additionally, pushing method had a significant effect on speed (p = 0.001) and stride length (p<0.001).

          Conclusions

          These findings suggest that pushing technique influences stroller running speed and kinematics. These findings suggest specific fitness effects may be achieved through the implementation of different pushing methods.

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          Most cited references17

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          Humans Can Continuously Optimize Energetic Cost during Walking.

          People prefer to move in ways that minimize their energetic cost. For example, people tend to walk at a speed that minimizes energy use per unit distance and, for that speed, they select a step frequency that makes walking less costly. Although aspects of this preference appear to be established over both evolutionary and developmental timescales, it remains unclear whether people can also optimize energetic cost in real time. Here we show that during walking, people readily adapt established motor programs to minimize energy use. To accomplish this, we used robotic exoskeletons to shift people's energetically optimal step frequency to frequencies higher and lower than normally preferred. In response, we found that subjects adapted their step frequency to converge on the new energetic optima within minutes and in response to relatively small savings in cost (<5%). When transiently perturbed from their new optimal gait, subjects relied on an updated prediction to rapidly re-converge within seconds. Our collective findings indicate that energetic cost is not just an outcome of movement, but also plays a central role in continuously shaping it.
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            Optimal running speed and the evolution of hominin hunting strategies.

            Recent discussion of the selective pressures leading to the evolution of modern human postcranial morphology, seen as early as Homo erectus, has focused on the relative importance of walking versus running. Specifically, these conversations have centered on which gait may have been used by early Homo to acquire prey. An element of the debate is the widespread belief that quadrupeds are constrained to run at optimally efficient speeds within each gait, whereas humans are equally efficient at all running speeds. The belief in the lack of optimal running speeds in humans is based, however, on a number of early studies with experimental designs inadequate for the purpose of evaluating optimality. Here we measured the energetic cost of human running (n=9) at six different speeds for five minutes at each speed, with careful replicates and controls. We then compared the fit of linear versus curvilinear models to the data within each subject. We found that individual humans do, in fact, have speeds at which running is significantly less costly than at other speeds (i.e., an optimal running speed). In addition, we demonstrate that the use of persistence hunting methods to gain access to prey at any running speed, even the optimum, would be extremely costly energetically, more so than a persistence hunt at optimal walking speed. We argue that neither extinct nor extant hominin populations are as flexible in the chosen speeds of persistence hunting pursuits as other researchers have suggested. Variations in the efficiency of human locomotion appear to be similar to those of terrestrial quadrupeds.
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              Reproductive costs for everyone: how female loads impact human mobility strategies.

              While mobility strategies are considered important in understanding selection pressures on individuals, testing hypotheses of such strategies requires high resolution datasets, particularly at intersections between morphology, ecology and energetics. Here we present data on interactions between morphology and energetics in regards to the cost of walking for reproductive women and place these data into a specific ecological context of time and heat load. Frontal loads (up to 16% of body mass), as during pregnancy and child-carrying, significantly slow the optimal and preferred walking speed of women, significantly increase cost at the optimal speed, and make it significantly more costly for women to walk with other people. We further show for the first time significant changes in the curvature in the Cost of Transport curve for human walking, as driven by frontal loads. The impact of these frontal loads on females, and the populations to which they belong, would have been magnified by time constraints due to seasonal changes in day length at high latitudes and thermoregulatory limitations at low latitudes. However, wider pelves increase both stride length and speed flexibility, providing a morphological offset for load-related costs. Longer lower limbs also increase stride length. Observed differences between preferred and energetically optimal speeds with frontal loading suggest that speed choices of women carrying reproductive loads might be particularly sensitive to changes in heat load. Our findings show that female reproductive costs, particularly those related to locomotion, would have meaningfully shaped the mobility strategies of the hominin lineage, as well as modern foraging populations. Copyright © 2013 Elsevier Ltd. All rights reserved.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                3 July 2017
                2017
                : 12
                : 7
                : e0180575
                Affiliations
                [1 ]Department of Biology, Seattle Pacific University, Seattle, Washington, United States of America
                [2 ]Department of Anthropology, University of Washington, Seattle, Washington, United States of America
                Norwegian University of Science and Technology, NORWAY
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                • Conceptualization: RA CW.

                • Data curation: RA CW.

                • Formal analysis: RA CW.

                • Investigation: RA CW.

                • Methodology: RA CW.

                • Project administration: RA CW.

                • Resources: RA CW.

                • Software: RA CW.

                • Supervision: CW.

                • Validation: RA CW.

                • Visualization: RA CW.

                • Writing – original draft: RA.

                • Writing – review & editing: RA CW.

                Author information
                http://orcid.org/0000-0002-8539-711X
                Article
                PONE-D-16-44360
                10.1371/journal.pone.0180575
                5495480
                28672004
                18aae055-0cf4-49fe-b865-e7e75acb7590
                © 2017 Alcantara, Wall-Scheffler

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 7 November 2016
                : 16 June 2017
                Page count
                Figures: 0, Tables: 3, Pages: 9
                Funding
                The authors received no specific funding for this work.
                Categories
                Research Article
                Biology and Life Sciences
                Physiology
                Biological Locomotion
                Running
                Medicine and Health Sciences
                Physiology
                Biological Locomotion
                Running
                Physical Sciences
                Physics
                Classical Mechanics
                Kinematics
                Medicine and Health Sciences
                Public and Occupational Health
                Physical Activity
                Medicine and Health Sciences
                Cardiology
                Heart Rate
                Biology and Life Sciences
                Biochemistry
                Bioenergetics
                Biology and Life Sciences
                Physiology
                Biological Locomotion
                Medicine and Health Sciences
                Physiology
                Biological Locomotion
                Medicine and Health Sciences
                Pediatrics
                Child Health
                Medicine and Health Sciences
                Public and Occupational Health
                Child Health
                Medicine and Health Sciences
                Public and Occupational Health
                Physical Activity
                Physical Fitness
                Exercise
                Medicine and Health Sciences
                Sports and Exercise Medicine
                Exercise
                Biology and Life Sciences
                Sports Science
                Sports and Exercise Medicine
                Exercise
                Custom metadata
                All relevant data are within the paper and its Supporting Information files.

                Uncategorized
                Uncategorized

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