Journal of Human Evolution

Washington University, Department of Anthropology, St. Louis, MO 63130, USA.
Journal of Human Evolution (Impact Factor: 3.73). 12/2008; 56(1):43-54. DOI: 10.1016/j.jhevol.2008.09.001
Source: PubMed


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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Available from: Herman Pontzer, Oct 09, 2015
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    • "Although the selective factors underlying the evolution of both walking and running are debated, it is likely that locomotor economy played a key role. Hypothesized energysaving features for walking include long legs and dorsally oriented ischia (Crompton et al., 1998; Pontzer et al., 2009; Robinson, 1972; Sockol et al., 2007). Energy saving features for running in the genus Homo include a long, compliant Achilles tendon and a spring-like median longitudinal arch, which are known to store and recover elastic energy during running in other vertebrates (Biewener, 2003; Ker et al., 1987; Roberts, 2002). "
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    ABSTRACT: The human iliotibial band (ITB) is a poorly understood fascial structure that may contribute to energy savings during locomotion. This study evaluated the capacity of the ITB to store and release elastic energy during running, at speeds ranging from 2-5m/s, using a model that characterizes the three-dimensional musculoskeletal geometry of the human lower limb and the force-length properties of the ITB, tensor fascia lata (TFL), and gluteus maximus (GMax). The model was based on detailed analyses of muscle architecture, dissections of 3-D anatomy, and measurements of the muscles' moment arms about the hip and knee in five cadaveric specimens. The model was used, in combination with measured joint kinematics and published EMG recordings, to estimate the forces and corresponding strains in the ITB during running. We found that forces generated by TFL and GMax during running stretch the ITB substantially, resulting in energy storage. Anterior and posterior regions of the ITB muscle-tendon units (MTUs) show distinct length change patterns, in part due to different moment arms at the hip and knee. The posterior ITB MTU likely stores more energy than the anterior ITB MTU because it transmits larger muscle forces. We estimate that the ITB stores about 1J of energy per stride during slow running and 7J during fast running, which represents approximately 14% of the energy stored in the Achilles tendon at a comparable speed. This previously unrecognized mechanism for storing elastic energy may be an adaptation to increase human locomotor economy. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Journal of Biomechanics 06/2015; 265. DOI:10.1016/j.jbiomech.2015.06.017 · 2.75 Impact Factor
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    • "Although human walking has been extensively investigated in its multifaceted biomechanical, physiological, and pathological aspects [13] [14], little is known on whether lower limb length and body proportions affect the efficiency of overground walking in older persons. In fact, those studies that have addressed the issue [5] [6] [7] have assessed energy expenditure in contemporary children and younger adults walking on a treadmill, which has been shown to be significantly higher and not applicable to overground walking in older persons [15] [16]. Further, overground walking is a more natural task when compared to treadmill walking, particularly for older persons, and, contrary to treadmill walking, individuals self-select their own walking speed. "
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    ABSTRACT: Background: Although walking has been extensively investigated in its biomechanical and physiological aspects, little is known on whether lower limb length and body proportions affect the energy cost of overground walking in older persons. Methods: We enrolled 50 men and 12 women aged 65 years and over, mean 69.1 ± SD 5.4, who at the end of their cardiac rehabilitation program performed the six-minute walk test while wearing a portable device for direct calorimetry and who walked a distance comparable to that of nondisabled community-dwelling older persons. Results: In the multivariable regression model (F = 12.75, P < 0.001, adjusted R(2) = 0.278) the energy cost of overground walking, expressed as the net energy expenditure, in kg(-1) sec(-1), needed to provide own body mass with 1 joule kinetic energy, was inversely related to lower limb length and directly related to lower limb length to height ratio (β ± SE(β) = -3.72 × 10(-3) ± 0.74 × 10(-3), P < 0.001, and 6.61 × 10(-3) ± 2.14 × 10(-3), P = 0.003, resp.). Ancillary analyses also showed that, altogether, 1 cm increase in lower limb length reduced the energy cost of overground walking by 2.57% (95%CI 2.35-2.79). Conclusions: Lower limb length and body proportions actually affect the energy cost of overground walking in older persons.
    06/2014; 2014:318204. DOI:10.1155/2014/318204
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    • "The energetic demand is not only related to walking but also to posture. Even though bipedalism can be seen as being economical concerning locomotor energy (Pontzer et al., 2009), the effect of load-carrying, such as carrying a child, adds a further dimension into the energetic needs of women. Watson et al. (2008) showed that one sided load carrying , e.g. a mannequin on one hip (similar to carrying a child), was coupled with higher energy requirement. "
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    ABSTRACT: Patients with hypothyroidism can present a series of so-called residual symptoms which are said to be without physical pathology. These symptoms, however, affect negatively the well-being state of these patients. Currently there are no explanations for this situation. Based on previous investigations done with thyroid disease patients we have carried out a clinical examination which is centered on musculoskeletal features together with a simple evaluation of psychological stressors (scaled 1–3). Laboratory diagnosis was focused on serum magnesium. This report includes the data from 166 women including 58 euthyroid controls (six males) and 108 patients with hypothyroidism (eight males). The most common complaints seen in our patients included fatigue, being easily tired, concentration deficit, ankle instability, and gait insecurity, giving way of the ankle, muscle cramps in the shanks, visual disturbances, irritability, and vertigo sensation. Besides this symptomatology a great majority of the patients (89.5%) presented musculoskeletal alterations. The main finding was that of lateral tension which entails an eccentric muscle action of the affected lower extremity. Lateral tension was always accompanied by (forward) rotation of the hemi-pelvis of the affected side. Idiopathic moving toes were found to be independent of lateral tension. Stress scores in patients were higher in patients than in the control group. Serum magnesium levels were significantly lower in patients (0.87 ± 0.1 mmol/l vs. 0.92 ± 0.07 mmol/l, p = 0.041) and showed a trend toward an inverse correlation to the intensity of lateral tension as well as to the stress score. Patients having magnesium levels below 0.9 mmol/l received 3× 1.4 mmol daily of elemental magnesium in the form of 400 mg of magnesium citrate. In cases presenting stress scores of 2 or 3 a relaxation treatment procedure was included in the treatment. This treatment was extended to the use of acupuncture on points of the Triple Burner meridian. Treatment success was observed in 90% of cases, i.e. residual symptoms were no longer present and patients reported an improved feeling of well-being. We hypothesize that magnesium deficit is facilitated by the presence of physical and psychological stressors. This condition has the potential to negatively influence the function of Complex V of oxidative phosphorylation which relies on magnesium-ATP. Reproductive processes, which have high energetic requirements in women, could thus be affected. The disappearance of the so-called psychosomatic symptoms after our therapeutic scheme brings a new light into this field of medicine and it stresses the importance of holistic handling. Understanding of body–mind interactions is explained by discussing thermodynamics, noesis, Salutogenesis and Resilience, and shamanism.
    03/2014; 1. DOI:10.1016/j.woman.2014.02.001
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