The metabolic cost of walking in humans, chimpanzees, and early hominins.
ABSTRACT Bipedalism is a defining feature of the hominin lineage, but the nature and efficiency of early hominin walking remains the focus of much debate. Here, we investigate walking cost in early hominins using experimental data from humans and chimpanzees. We use gait and energetics data from humans, and from chimpanzees walking bipedally and quadrupedally, to test a new model linking locomotor anatomy and posture to walking cost. We then use this model to reconstruct locomotor cost for early, ape-like hominins and for the A.L. 288 Australopithecus afarensis specimen. Results of the model indicate that hind limb length, posture (effective mechanical advantage), and muscle fascicle length contribute nearly equally to differences in walking cost between humans and chimpanzees. Further, relatively small changes in these variables would decrease the cost of bipedalism in an early chimpanzee-like biped below that of quadrupedal apes. Estimates of walking cost in A.L. 288, over a range of hypothetical postures from crouched to fully extended, are below those of quadrupedal apes, but above those of modern humans. These results indicate that walking cost in early hominins was likely similar to or below that of their quadrupedal ape-like forebears, and that by the mid-Pliocene, hominin walking was less costly than that of other apes. This supports the hypothesis that locomotor energy economy was an important evolutionary pressure on hominin bipedalism.
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ABSTRACT: One goal of the locomotion is to move the body in the space at the most economical way possible. However, little is known about the mechanical and energetic aspects of locomotion that are affected by low back pain. And in case of occurring some damage, little is known about how the mechanical and energetic characteristics of the locomotion are manifested in functional activities, especially with respect to the energy-minimizer mechanisms during locomotion. This study aimed: a) to describe the main energy-minimizer mechanisms of locomotion; b) to check if there are signs of damage on the mechanical and energetic characteristics of the locomotion due to chronic low back pain (CLBP) which may endanger the energy-minimizer mechanisms. This study is characterized as a narrative literature review. The main theory that explains the minimization of energy expenditure during the locomotion is the inverted pendulum mechanism, by which the energy-minimizer mechanism converts kinetic energy into potential energy of the center of mass and vice-versa during the step. This mechanism is strongly influenced by spatio-temporal gait (locomotion) parameters such as step length and preferred walking speed, which, in turn, may be severely altered in patients with chronic low back pain. However, much remains to be understood about the effects of chronic low back pain on the individual's ability to practice an economic locomotion, because functional impairment may compromise the mechanical and energetic characteristics of this type of gait, making it more costly. Thus, there are indications that such changes may compromise the functional energy-minimizer mechanisms. Copyright © 2014 Elsevier Editora Ltda. All rights reserved.Revista Brasileira de Reumatologia 11/2014; 55(1). DOI:10.1016/j.rbre.2014.01.005 · 0.99 Impact Factor
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ABSTRACT: The shape of the human female pelvis is thought to reflect an evolutionary trade-off between two competing demands: a pelvis wide enough to permit the birth of large-brained infants, and narrow enough for efficient bipedal locomotion. This trade-off, known as the obstetrical dilemma, is invoked to explain the relative difficulty of human childbirth and differences in lo-comotor performance between men and women. The basis for the obstetrical dilemma is a standard static biomechanical model that predicts wider pelves in females increase the metabolic cost of locomotion by decreasing the effective mechanical advantage of the hip ab-ductor muscles for pelvic stabilization during the single-leg support phase of walking and running, requiring these muscles to produce more force. Here we experimentally test this model against a more accurate dynamic model of hip abductor mechanics in men and women. The results show that pelvic width does not predict hip abductor mechanics or loco-motor cost in either women or men, and that women and men are equally efficient at both walking and running. Since a wider birth canal does not increase a woman's locomotor cost, and because selection for successful birthing must be strong, other factors affecting maternal pelvic and fetal size should be investigated in order to help explain the prevalence of birth complications caused by a neonate too large to fit through the birth canal.PLoS ONE 03/2015; 10(3):e0118903. DOI:10.1371/journal.pone.0118903 · 3.53 Impact Factor
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ABSTRACT: Um dos objetivos da marcha é deslocar o corpo no espaço da forma mais econômica possível. Porém, pouco se sabe como os aspectos mecânicos e energéticos da caminhada são afetados pela dor lombar. Ainda, caso haja prejuízos, é pequeno o conhecimento de como as características mecânicas e energéticas da caminhada se manifestam nas atividades funcionais, principalmente nos mecanismos minimizadores de energia da locomoção. Este estudo teve por objetivos: a) descrever os principais mecanismos minimizadores de energia da locomoção; e b) verificar se há indicativos de prejuízos nas características mecânicas e energéticas da caminhada decorrentes da dor lombar crônica (DLC) que possam comprometer os mecanismos minimizadores. Estudo caracterizado como revisão narrativa de literatura. A principal teoria que explica a minimização do dispêndio energético durante a caminhada é a do pêndulo invertido pelo qual o mecanismo minimizador converte energia cinética em energia potencial do centro de massa e vice‐versa durante a passada. Esse mecanismo é fortemente influenciado por parâmetros espaços‐temporais da marcha, tais como comprimento de passo e velocidade preferida da caminhada, que, por sua vez, podem estar severamente alterados em pacientes com dor lombar crônica. Contudo ainda há muito que se entender sobre os efeitos da dor lombar crônica sobre a capacidade do indivíduo de praticar uma marcha econômica, pois os prejuízos funcionais podem comprometer características mecânicas e energéticas dessa modalidade de marcha e torná‐la mais dispendiosa. Desta forma, há indicativos de que tais mudanças funcionais possam comprometer os mecanismos minimizadores de energia.Revista Brasileira de Reumatologia 11/2014; 55(1). DOI:10.1016/j.rbr.2014.01.013 · 0.99 Impact Factor