Article

Endurance Running and the Evolution of Homo

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Abstract

Striding bipedalism is a key derived behaviour of hominids that possibly originated soon after the divergence of the chimpanzee and human lineages. Although bipedal gaits include walking and running, running is generally considered to have played no major role in human evolution because humans, like apes, are poor sprinters compared to most quadrupeds. Here we assess how well humans perform at sustained long-distance running, and review the physiological and anatomical bases of endurance running capabilities in humans and other mammals. Judged by several criteria, humans perform remarkably well at endurance running, thanks to a diverse array of features, many of which leave traces in the skeleton. The fossil evidence of these features suggests that endurance running is a derived capability of the genus Homo, originating about 2 million years ago, and may have been instrumental in the evolution of the human body form.

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... Humans are the only extant primates fully committed to terrestrial bipedalism, with concomitant loss of some morphological adaptations for climbing and arboreal locomotion (Harcourt-Smith, 2007; Harcourt- Smith & Aiello, 2004). The emergence of obligate bipedalism may date back to the early Pleistocene as anatomical features which have been associated with energetically efficient bipedalism (often referred to as striding bipedalism) such as long lower limbs, enlarged hindlimb joint surfaces, and elastic strain-storage mechanisms in the foot and possibly ankle appear to have been present in Homo erectus, (Bramble & Lieberman, 2004;DeSilva et al., 2019;Pontzer, 2017;Steudel-Numbers, 2006;Steudel-Numbers & Tilkens, 2004), but see (Antón et al., 2014;Pontzer et al., 2010). Most later members of the genus Homo, such as Homo neanderthalensis, Homo antecessor, and Homo heidelbergensis, are conventionally thought to have been full striding, obligate bipeds (Aiello & Wells, 2002;Harcourt-Smith & Aiello, 2004;Lorenzo et al., 1999). ...
... Numerous authors suggest that Australopithecus may have had a fundamentally human-like gait (Kozma et al., 2018;Kramer & Eck, 2000;Nagano et al., 2005;Sellers et al., 2004;Ward, 2013;Wang et al., 2004;Wiseman et al., 2023), while others infer important differences in the form of bipedalism practiced between different australopith species or in the genus as a whole (see DeSilva et al., 2013;Ruff et al., 2016;Stern Jr & Susman, 1983). Either way, they were most likely limited in their endurance ability due to their lack of other skeletal features that have been argued to be important to endurance running, such as a mediolaterally narrow thorax and pelvis, a shortened femoral neck, and a lowered shoulder complex with laterally-oriented glenoid fossae (Bramble & Lieberman, 2004;Pontzer, 2017). Longer legs and expanded hind limb joint areas are further associated with endurance running, although are often difficult to assess in earlier hominins given the fragmentary nature of fossils. ...
... Our finding of relatively small knee joints in H. naledi do not seem to be compatible with the high loading and repetitive impact associated with running. Bramble and Lieberman (2004) detail how the enlargement of the joints in the lower body (including the knee joint) helps to lower stress generated from heel strike during walking but more importantly would dissipate the higher impact loads generated in running. Larger joint surfaces in the lower limb further reduce stresses on those joints by spreading forces over a larger articular area (Jungers, 1988). ...
Article
The lower limb of Homo naledi presents a suite of primitive, derived and unique morphological features that pose interesting questions about the nature of bipedal movement in this species. The exceptional representation of all skeletal elements in H. naledi makes it an excellent candidate for biomechanical analysis of gait dynamics using modern kinematic software. However, virtual gait analysis software requires 3D models of the entire lower limb kinematic chain. No single H. naledi individual preserves all lower limb elements, and what material is preserved is fragmentary. As an antecedent to future kinematic analysis, a 3D lower limb skeleton was reconstructed from the most complete fossil bones of different H. naledi individuals. As both juvenile and adult H. naledi were used, we tested if the knee joint remained congruent throughout ontogeny in a sample of great apes ( N = 143) and modern humans ( N = 70). The reconstruction and subsequent comparative analysis reveal that H. naledi had remarkably small joint sizes for their body size, a hyper‐elongated tibia, and a high crural index (90.2). We consider that the lower limb morphology of H. naledi could have improved locomotor economy, but the exceptionally small joints cast doubt on its capabilities for long distance travel, including endurance running. The unusual mixture of primitive and derived traits in H. naledi remains intriguing and might indicate that this hominin engaged both in bipedal walking and climbing, demonstrating that kinematic diversity in hominins persisted well into the Middle Pleistocene.
... The evolution of bipedal gait is a key adaptive feature in hominids, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] but the running abilities of early hominins have not been extensively studied. 2 Here, we present physics simulations of Australopithecus afarensis that demonstrate this genus was mechanically capable of bipedal running but with absolute and relative (size-normalized) maximum speeds considerably inferior to modern humans. Simulations predicted running energetics for Australopithecus that are generally consistent with values for mammals and birds of similar body size, therefore suggesting relatively low cost of transport across a limited speed range. ...
... The evolution of bipedal gait is a key adaptive feature in hominids, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] but the running abilities of early hominins have not been extensively studied. 2 Here, we present physics simulations of Australopithecus afarensis that demonstrate this genus was mechanically capable of bipedal running but with absolute and relative (size-normalized) maximum speeds considerably inferior to modern humans. Simulations predicted running energetics for Australopithecus that are generally consistent with values for mammals and birds of similar body size, therefore suggesting relatively low cost of transport across a limited speed range. ...
... Overview of approach The evolution of a low-cost bipedal gait is a key adaptive feature in hominins. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Due to its somewhat ''intermediate'' body plan and near-complete osteology, Australopithecus afarensis has often been identified as a key fossil taxon for understanding the evolution of bipedalism in our lineage 2,3,8-16 ( Figure 1A). Analyses of fossilized skeletons 7,16 and footprints 8 have provided convincing evidence that australopithecines adopted mechanically efficient, upright (''human-like'') bipedal walking gaits by at least 3.7 Ma. ...
Article
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The evolution of bipedal gait is a key adaptive feature in hominids, but the running abilities of early hominins have not been extensively studied. Here, we present physics simulations of Australopithecus afarensis that demonstrate this genus was mechanically capable of bipedal running but with absolute and relative (size-normalized) maximum speeds considerably inferior to modern humans. Simulations predicted running energetics for Australopithecus that are generally consistent with values for mammals and birds of similar body size, therefore suggesting relatively low cost of transport across a limited speed range. Through model parameterization, we demonstrate the key role of ankle extensor muscle architecture (e.g., the Achilles tendon) in the evolution of hominin running energetics and indeed in an increase in speed range, which may have been intrinsically coupled with enhanced endurance running capacity. We show that skeletal strength was unlikely to have been a limiting factor in the evolution of enhanced running ability, which instead resulted from changes to muscle anatomy and particularly overall body proportions. These findings support the hypothesis that key features in the human body plan evolved specifically for improved running performance and not merely as a byproduct of selection for enhanced walking capabilities.
... Throughout the last three decades, a comparative description of the Australopithecus and Homo ribcages has elucidated differences among the species that might be intimately linked to variation in their ecosystems (Bastir et al., 2022). Hence, it has been proposed that the narrow upper thorax of Australopithecus was suitable for arboreality (Schmid et al., 2013), the stocky lower thorax of Neanderthals was helpful to avoid heat loss (Franciscus and Churchill, 2002;Weinstein, 2008;G omez-Olivencia et al., 2009) or even to support an enlarged liver for protein processing (Ben-Dor et al., 2016), and the slender ribcage of Homo sapiens was highly efficient in the context of endurance running during persistence hunting (Bramble and Lieberman, 2004;Lieberman and Bramble, 2007;Pomeroy, 2023). However, the study of the ribcage in the fossil record is limited by the fact that vertebrae, and mainly ribs, are numerous and fragile. ...
... Other authors state that these features could also have been involved in thermoregulation, given the cold climate conditions in which Neanderthals supposedly lived during the Upper Pleistocene (Churchill, 2006;Weinstein, 2008;Ocobock et al., 2021). Additionally, higher activity rates proposed for Neanderthals have been tentatively linked to ambush hunting strategies, where explosive strength (e.g., Ayalon et al., 1974) is required, rather than the endurance proposed for H. sapiens hunter-gatherers (Bramble and Lieberman, 2004;Lieberman and Bramble, 2007;Raichlen et al., 2011;Stewart et al., 2019;Pomeroy, 2023). However, it has been argued that the robust bauplan proposed for Neanderthals 1) could not have been strictly adapted to climate or diet (Weaver et al., 2007;Weaver, 2009;Henry et al., 2011;Hardy et al., 2022) and 2) might be included in the recent H. sapiens range of variation (Arensburg, 1991), given the worldwide distribution of the latter and their ecogeographic adaptations to different environments (L opez-Rey et al., 2024a). ...
... Also, in vivo kinematic simulations have shown that volumetric variations in the lower thorax produce much greater variations in lung volumes than those produced in the upper thorax (Bastir et al., 2017b), which would provide further support for the idea of a larger respiratory system in Neanderthals (Franciscus and Churchill, 2002;Bastir, 2008Bastir, , 2019bGarcía-Martínez et al., 2018b). Thus, the Neanderthal respiratory system would allow greater oxygen supply, leading to higher activity rates that would tentatively be suitable to ambush hunting strategies where explosive strength is required, rather than the endurance proposed for H. sapiens hunter-gatherers (Bramble and Lieberman, 2004;Lieberman and Bramble, 2007;Raichlen et al., 2011;Stewart et al., 2019;Pomeroy, 2023). Our results, however, have limitations related to the nature of geometric morphometric studies. ...
Article
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The study of the ribcage is fundamental to understanding hominin evolution. However, ribs and vertebrae are scarce in the fossil record. Although Neanderthals are one of the most represented and, therefore, one of the most studied fossil Homo species, it is controversial whether there is a standardized Neanderthal ribcage morphotype that could differ from modern humans. Hence, we used three-dimensional geometric morphometrics to reconstruct and compare the Neanderthal ribcage of Shani-dar 3 with another Neanderthal specimen, Kebara 2, and with 58 Homo sapiens individuals of worldwide distribution. Shape differences among the Neanderthal and H. sapiens ribcages were analyzed by a hierarchical cluster using the Euclidean distances among the permuted Procrustes distances between groups. Size differences between the Neanderthal and H. sapiens ribcages were examined using a permutation test on centroid size. To examine the potential for allometry, we performed a linear regression of Procrustes coordinates on centroid size of the sample, followed by a principal component analysis in form space. Our results show that Shanidar 3 has the 'bell-shaped' thorax typically described for Ne-anderthals. In fact, the shapes of both Shanidar 3 and Kebara 2 ribcages cluster apart from that of H. sapiens, being closer to cold-adapted individuals. The study of the centroid size supports similarities between Neanderthals and cold-adapted H. sapiens since significant size differences were found only between Neanderthals and temperate/tropical recent humans. The linear regression and principal component analysis showed an allometric relationship between ribcage size and shape, suggesting Neanderthals had larger and stockier ribcages than most H. sapiens, although they fall within the H. sapiens range of variation. Finally, ribcage similarities found between Shanidar 3 and Kebara 2, both inhabiting warm Levantine locations during the Upper Pleistocene, could challenge the conventional idea of a cold-adapted bauplan in Neanderthals.
... Much work has focused on hypothesized dietary differences (9)(10)(11)(12) because most fossils confidently attributed to these taxa are cranial and dental remains (7). One hypothesis posits that H. erectus was the earliest hominin to practice fully modern human-like bipedal walking and endurance running, and that this adaptation set them on a different evolutionary trajectory (13). With a sparse record of postcranial fossils that are mostly isolated, fragmentary, and/or difficult to attribute taxonomically, there is little skeletal evidence allowing direct comparisons of bipedalism in H. erectus and P. boisei (14,15). ...
... Ma (46), we hypothesize low to neutral competition between these genera. This scenario seems plausible given their apparent adaptations for consuming different dietary resources (9)(10)(11)(12)(13). Later, climate-caused environmental shifts could have changed the balance of resource availability (3), leading to increased competition and potentially driving adaptive shifts toward the riskier, higher-reward food acquisition strategies that later defined our genus (13,47,48). ...
... This scenario seems plausible given their apparent adaptations for consuming different dietary resources (9)(10)(11)(12)(13). Later, climate-caused environmental shifts could have changed the balance of resource availability (3), leading to increased competition and potentially driving adaptive shifts toward the riskier, higher-reward food acquisition strategies that later defined our genus (13,47,48). Testing such hypotheses will require detailed analyses of multiple environmental and behavioral data sources and will benefit from integrating fossil footprints with other fossil and archaeological evidence. ...
Article
For much of the Pliocene and Pleistocene, multiple hominin species coexisted in the same regions of eastern and southern Africa. Due to the limitations of the skeletal fossil record, questions regarding their interspecific interactions remain unanswered. We report the discovery of footprints (~1.5 million years old) from Koobi Fora, Kenya, that provide the first evidence of two different patterns of Pleistocene hominin bipedalism appearing on the same footprint surface. New analyses show that this is observed repeatedly across multiple contemporaneous sites in the eastern Turkana Basin. These data indicate a sympatric relationship between Homo erectus and Paranthropus boisei , suggesting that lake margin habitats were important to both species and highlighting the possible influence of varying levels of coexistence, competition, and niche partitioning in human evolution.
... In Homo ergaster, with complete adaptations to arboreal life gone, the glenoid cavity oriented laterally (Bramble and Lieberman, 2004) and probably decreased muscular connections between the shoulder girdle and the cervical spine and skull (with the muscle rhomboid origin varying and the atlantoclavicular muscle disappearing), shifting the shoulders sideways, increasing shoulder and arm movement range, and thus throwing speed, making it more powerful (Arbeit, 1988). These adaptations, along with adopting anthropometric measures similar to current high-competition javelin throwers, with a height and weight surpassing 1.80 m and 85 kg respectively (http://www2.webpark.cz/booboo/Athletics.htm.), likely made H. ergaster/erectus true throwing specialists, acquiring the optimal size and shape to perform this activity most effectively. ...
... Bramble and Lieberman (Bramble & Lieberman, 2004) argue that the anatomical modifications previously described in the locomotor apparatus, along with other changes in Homo compared to chimpanzees, such as the expansion of the area of origin of the gluteus maximus muscle and the erector spinae muscles, the greater separation between the thorax and pelvis (Aiello & Dean, 1990; Bramble & Lieberman, 2004), and the longer lengths of the Achilles tendon, iliotibial tract, and peroneus longus muscle (Swindler & Wood, 1973) are a result of adaptation to long-distance endurance running that uses aerobic metabolism as an energy source. This is because these modifications involve a more pronounced trunk rotation relative to the head or hips, facilitating balance while running, greater stabilization of the trunk or head, a reduction in stress during the action, and lower energy consumption. ...
... Bramble and Lieberman (Bramble & Lieberman, 2004) argue that the anatomical modifications previously described in the locomotor apparatus, along with other changes in Homo compared to chimpanzees, such as the expansion of the area of origin of the gluteus maximus muscle and the erector spinae muscles, the greater separation between the thorax and pelvis (Aiello & Dean, 1990; Bramble & Lieberman, 2004), and the longer lengths of the Achilles tendon, iliotibial tract, and peroneus longus muscle (Swindler & Wood, 1973) are a result of adaptation to long-distance endurance running that uses aerobic metabolism as an energy source. This is because these modifications involve a more pronounced trunk rotation relative to the head or hips, facilitating balance while running, greater stabilization of the trunk or head, a reduction in stress during the action, and lower energy consumption. ...
... We focused on the human Gmax, a typical end-divergent muscle having broad attachment on the pelvis and femur, crossing the hip joint. The Gmax is well-known to be evolutionary distinct in humans as compared to apes (Bramble and Lieberman, 2004), playing a critical role in our upright bipedal locomotion (Lieberman et al., 2006). Therefore, understanding human Gmax architecture would provide some perspectives into our evolution as well as the fundamental structure-function relationship of skeletal muscle. ...
... Then, why does the human Gmax have opposing torque? It is well known that human Gmax differs from that in chimpanzees (our closest relatives), reflecting our adaptation from quadruped to bipedal locomotion (Bramble and Lieberman, 2004;Lieberman et al., 2006). Specifically, humans substantially developed the cranial part of Gmax but lost the caudal compartment that appears in chimpanzees (Lieberman et al., 2006). ...
... Lower limbs, in contrast, have experienced selective pressure for bipedal locomotion, which may have favored similar neuromuscular properties in both sexes. This interpretation is supported by studies showing consistent patterns of muscle activation and force production in lower limbs across sexes during locomotion [31]. ...
... Similarly, peripheral nerve development may exhibit region-specific patterns, which could explain the differences in nerve characteristics between upper and lower limbs. The evolution of obligate bipedalism, a uniquely human characteristic, appears to have shaped lower limb neuromuscular function differently from upper limbs [31]. The evolutionary pressure for efficient bipedal locomotion has likely led to a convergence of lower limb nerve characteristics between males and females, effectively overriding the inherent sex-specific differences observed in the upper limbs. ...
Article
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Background/Objectives: Peripheral nerve conduction velocity (NCV) and nerve cross-sectional area (nCSA) are crucial parameters in neurophysiological assessments, yet their sex-specific differences are not fully understood. This study investigated sex-based variations in NCV and nCSA between upper and lower limbs. Methods: Twenty participants (ten males and ten females) were recruited for this study. The NCV and nCSA of the ulnar and tibial nerves were measured in both the upper and lower limbs. NCV was measured using supramaximal electric stimulation, and nCSA was assessed using peripheral nerve ultrasonography at three regions for each nerve. Supramaximal electric stimulations were applied superficially to the ulnar and tibial nerves at each measurement point. Action potentials were recorded from the abductor digiti minimi and soleus muscles for the ulnar and tibial nerves, respectively. Results: The ulnar nCSA of the upper limbs was significantly greater in males than in females (p < 0.05). However, ulnar NCV was significantly higher in females than in males (p < 0.05). In the lower limbs, no sex differences were observed in tibial NCV or nCSA. Conclusions: These findings reveal sex-specific differences in upper limb peripheral nerve characteristics that may have important implications for clinical assessments and treatment strategies. The contrasting patterns between upper and lower limbs suggest that both developmental and functional factors influence peripheral nerve properties.
... Running has evolved, through a complex interplay of biomechanical adaptations, from a crucial survival skill in our ancestors to a modern form of athletic performance, recreation, and social engagement [1], [2], [3], [4]. Many individuals, particularly those involved in athletics, aspire to enhance this human ability as they continually strive to surpass their limits. ...
... The analysis exclusively focuses on second-lap data for each experimental repetition, ensuring a stable and consistent metabolic response and minimizing transient effects. The justification for using this metric while considering self-selected speed as an uncontrolled variable in the experimental design is well-supported, as research indicates that the energy cost of transport for human running is essentially independent of speed [3], [38]. ...
Article
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Over the past decade, considerable steps have been made in designing wearable assistive devices that reduce the metabolic cost of walking. As the field continues to advance, a growing emphasis is extending to human running, driven by the goal of improving efficiency and reducing metabolic strain. In our study, we developed a portable active exosuit to support hip extension during endurance running. The exosuit, featuring custom linear actuators and a control system synchronous with the wearer’s kinematics, initially underwent bench testing and, finally, a field evaluation with users running at their self-selected pace on an athletics track. Results from seven participants showed a significant reduction in the metabolic cost of transport when the exosuit was active. Specifically, we observed a 9.6% decrease with respect to the unpowered condition, with a 4.3% net saving compared to not wearing the device. Additionally, kinematic assessments revealed no alteration of the participants’ motion after toe-off, indicating transparency to physiological movement pattern during hip flexion. These findings highlight the potential of the exosuit to enhance athletic performance, opening new possibilities for running assistance in real-world scenarios.
... Generally, body mass has increased over time, though often displaying a high degree of variability for each group of hominins ( Supplementary Fig. 1a, b) [9][10][11][12][13][14] . For example, the isolated small-bodied individuals of Homo naledi (~0.3 Ma,~37 kg) and Homo floresiensis (~0.1 Ma,~27 kg) represent important exceptions to this general growth rule 15,16 . The reasons for the rise and fall of body size over time are not clear but have overall resulted in a mean body mass among modern humans of~62 kg 16 . ...
... The reasons for the rise and fall of body size over time are not clear but have overall resulted in a mean body mass among modern humans of~62 kg 16 . Previous studies have even argued that locomotor capacity, particularly endurance running, has been instrumental in the evolution of the human body form 15 . Thus, hominins represent an important group for understanding how body size might influence locomotor performance, not only to explore the extent to which this might have influenced hominin evolution, but also as a unique phenotype to explore the detailed patterns between size, speed, and movement economy. ...
Article
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An unusual pattern among the scaling laws in nature is that the fastest animals are neither the largest, nor the smallest, but rather intermediately sized. Because of the enormous diversity in animal shape, the mechanisms underlying this have long been difficult to determine. To address this, we challenge predictive human musculoskeletal simulations, scaled in mass from the size of a mouse (0.1 kg) to the size of an elephant (2000 kg), to move as fast as possible. Our models replicate patterns observed across extant animals including: (i) an intermediate optimal body mass for speed; (ii) a reduction in the cost of transport with increasing size; and (iii) crouched postures at smaller body masses and upright postures at larger body masses. Finally, we use our models to determine the mechanical limitations of speed with size, showing larger animals may be limited by their ability to produce muscular force while smaller animals are likely limited by their ability to produce larger ground reaction forces. Despite their bipedal gait, our models replicate patterns observed across quadrupedal animals, suggesting these biological phenomena likely represent general rules and are not the result of phylogenetic or other ecological factors that typically hinder comparative studies.
... A defining activity of Homo is the capability to hunt which is thought to have originated some two million years ago (Liebenberg, 2013). However, it is now recognised that running and chasing an animal until it overheats and drops from hyperthermia represents a transition from predation to hunting (Liebenberg, 2006;Bramble and Lieberman, 2004). Since it has been observed that tracking and hunting takes place during the warmest part of the day, it has been termed persistence hunting which has been posited as an evolutionary advantage for Homo (Carrier, 1984;Liebenberg, 2006). ...
... Moreover, there is now compelling evidence that humans can, with a sampling of a single unique odour be able to identify a location and then return to that location using only the olfactory information to inform their positioning (Jacobs et al., 2015). A key point these authors make is that if humans are indeed specialised for walking and running long distances (Bramble and Lieberman, 2004;Liebenberg, 2006;Hora et al., 2020) then it would make intuitive sense to employ olfaction in navigation, especially if sourcing water was a key survival strategy. Although speculative to suggest that humans might have used petrichor as a strategy to search for and find water, this environmental cue, and our olfactory sensitivity for it could have been one method our ancestors used to sense rain and find water sources to enhance their survival. ...
... Humans exhibit a distinctive muscle morphology in primates (Bramble and Lieberman, 2004). The relatively longer legs of humans have a larger muscle mass than those of the apes (Zihlman and Bolter, 2015). ...
... Although human muscle enlargement is known to reflect adaptation to mechanical demands in upright bipedalism (Bramble and Lieberman, 2004), its relevance to the ease of limb motion, which affects motor performance, has not been acknowledged. Specifically, the ease of limb motion can limit the maximal speed of movements by regulating the capacity to move fast. ...
... The biomechanics underpinning the acceleration of jointed body segments, alongside the physiological processes of energy generation by skeletal muscle, predicts that locomotor costs may be reduced through the possession of certain anatomical traits and the use of specific movement patterns [2][3][4][5][6][7][8] . Indeed, this has led many to infer that the evolution of locomotor morphology, mechanics and energetics are often causatively linked [9][10][11][12] . For example, the trunk and limb proportions, relatively muscular lower limbs and stiff plantigrade foot of humans have been mechanistically linked to lower energy costs and greater endurance in an upright bipedal gait when compared to the more energetically costly arboreally adapted morphologies and flexed limb postures of non-human apes 10,[13][14][15] . ...
... Indeed, this has led many to infer that the evolution of locomotor morphology, mechanics and energetics are often causatively linked [9][10][11][12] . For example, the trunk and limb proportions, relatively muscular lower limbs and stiff plantigrade foot of humans have been mechanistically linked to lower energy costs and greater endurance in an upright bipedal gait when compared to the more energetically costly arboreally adapted morphologies and flexed limb postures of non-human apes 10,[13][14][15] . In addition, a more general example can be found in terms of the hypothesised influence of body size upon causal relationships between morphology, kinematics and locomotor efficiency. ...
Article
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A central concept of evolutionary biology, supported by broad scale allometric analyses, asserts that changing morphology should induce downstream changes in locomotor kinematics and energetics, and by inference selective fitness. However, if these mechanistic relationships exist at local intraspecific scales, where they could provide substrate for fundamental microevolutionary processes, is unknown. Here, analyses of selectively-bred duck breeds demonstrate that distinct body shapes incur kinematic shifts during walking, but these do not translate into differences in energetics. A combination of modular relationships between anatomical regions, and a trade-off between limb flexion and trunk pitching, are shown to homogenise potential functional differences between the breeds, accounting for this discrepancy between form and function. This complex interplay between morphology, motion and physiology indicates that understanding evolutionary links between the avian body plan and locomotor diversity requires studying locomotion as an integrated whole and not key anatomical innovations in isolation.
... 1. L'ultra-trail : 1 [8] . ...
Research
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The chronic lateral ankle instability is the main complication of lateral ankle sprain which is the most recurrent trauma during ultra-trail running. Nowadays, the two used roads to treat this instability are conservative functional rehabilitation and surgery. However, even if these treatments have proven effective, they can extend on periods ranging from a few weeks to several years, leaving the patient during this time interval vulnerable to the consequences of his instability. The purpose of this study is to understand if the insoles with a posterior pronator wedge (or lateral wedge) can be part of this multidisciplinary therapeutic circuit in order to improve the treatment conditions of these ultra-trailers patients. Thanks to an experimentation using the Star Excursion Balance Test, the Emery’s test and the Side Hop Test, it was discovered that insoles make it possible to increase significantly of 24 % the dynamic stability of the patient (p < 0,01). Thus, the results of this research work indicate that the utilisation of insoles with posterior pronator wedge constitutes an additional lever which can be offered to the patient while awaiting the recovery of his physiological balance functions. Withal, given to the low number of patients (one patient) for this study, it would be relevant to carry out further researches on larger controlled and randomized samples in order to clarify the conclusions observed in this dissertation.
... Running is regarded as a critical aspect of human evolutionary history. Around 2 million years ago, humans began to track their prey over long distances by running (Bramble & Lieberman, 2004). In early civilizations, running also held significant importance. ...
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The Ottoman Empire covered a vast surface area. From this perspective, a reliable and fast communication network was considered one of the most important elements for the smooth functioning of the military and administrative structure. Messenger runner peyks were one of the most important building blocks of this element. Despite the long distances and harsh natural conditions, peyks were tasked with delivering strategically important messages to strengthen state authority. Thanks to their running skills, administrative and military decision-making mechanisms were carried out quickly, contributing greatly to the operational efficiency of the state. Notable for their high level of endurance and speed, peyks were also noteworthy for their performance, as well as their ability to perform under difficult conditions and training activities involving strict discipline. Peyks were also an important figure that symbolized discipline and power. In this context, they took part in ceremonies. Running was historically used as a means of communication rather than a sport, and in this direction, the role of Peyks in the Ottoman Empire in the communication network is discussed. Thus, this research examines the benefits they had for the administrative and military structure of the state within the scope of the source scans of the period.
... The lower limbs of the human body have a high degree of flexibility, and people can independently and flexibly switch between various gaits and locomotion speeds to adapt to different terrains and accomplish a variety of mobility tasks [1][2][3][4]. Since the early 2000s, researchers have been trying to develop robotic exoskeletons to comply with human lower limbs to complete various movements and provide effective assistance in the process of movement, with the goal of enhancing human locomotor performance [5,6]. ...
Article
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Researchers have been trying to develop lower-limb exoskeletons to reduce the metabolic cost for human augmentation. The research on (quasi-)passive exoskeletons has gained more widespread attention since the first passive ankle exoskeleton was demonstrated to reduce the metabolic cost of human walking in 2015. Here, we reviewed studies on lower-limb (quasi-)passive exoskeletons for human performance augmentation in the past decade and highlighted key innovations and techniques to enable some of these exoskeletons to achieve the goal of reducing metabolic cost. We reviewed the (quasi-)passive exoskeleton research from three aspects including biological fundamentals for exoskeleton design, assistive principle and mechanical design of exoskeleton, which are the primary considerations of designing and evaluating (quasi-)passive exoskeletons. Lastly, we underlined some practical challenges and emerging trends of (quasi-)passive exoskeleton technology for further enhancing human mobility performance in the future.
... To prevent these injuries, understanding the correct running pattern is key [4]. Therefore, the biomechanics of running has been a major interest for researchers in human locomotion sciences due to its uniqueness and complexity [5,6]. ...
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Background:Running is one of the simplest and most popular forms of exercise. Biomechanical evaluation of running is one of the elements of evaluating running technique and, consequently, improving sports performance. Running uphill and downhill is one of the components of daily running but also an element of training used by recreational runners. The aim of this study is to optimize running training and minimize the risk of injury by identifying changes in the spatiotemporal structure of running at different inclinations. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. The protocol has been registered on the international platform INPLASY under the number INPLASY202430094U2. The search was conducted up to 30 March 2024 using the Scopus, PubMed, and Web of Science databases. Results: Spatiotemporal parameters were most frequently analyzed at 2.8–3.35 m/s velocities and inclinations in the range of −11% to 11%. Decreases in stride length (SL) and flight time (FT), and increases in step frequency (SF) were the most frequently reported changes from all parameters analyzed as a function of inclination and velocity. Significant increases or decreases in individual parameters were more often observed for positive inclination values than negative ones. Conclusions: The heterogeneous results of the study limit the possibility of determining the changes that occur in the spatiotemporal structure of the run under the impact of different inclinations. The variation in the results for negative inclination values indicates the different characteristics of running uphill and downhill. However, for uphill running, SF, SL, and FT are closely related to the increase in inclination.
... Since then, humans have spread across the globe, but as Figs. 1B and 2F show, mass-corrected AEEs from diverse human populations in a wide range of environments diverge from the TMQ gradient between AMQ and RMQ, and 116 human sample means of mass-corrected AEEs (from ref. 34 ), see Materials and Methods ) are independent of Te unlike the observed negative trend with Te across mammals. While most mammals are less active in the higher T e ( 12 ), humans have adaptations to overcome this constraint; similarly, while most animals are more active in lower T e , humans do not need to elevate their metabolisms as much in colder environments because of technologies such as clothing and fire ( 35 ). ...
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All organisms use limited energy to grow, survive, and reproduce, necessitating energy allocation tradeoffs, but there is debate over how selection impacted metabolic budgets and tradeoffs in primates, including humans. Here, we develop a method to compare metabolic rates as quotients of observed relative to expected values for mammals corrected for size, body composition, environmental temperature, and phylogenetic relatedness. Contrary to previous analyses, these quotients reveal that nonhuman primates have total metabolic rates expected for similar-sized mammals in similar environments. In addition, data from several small-scale societies show that humans evolved exceptionally high resting, activity, and total metabolic rates apparently by overcoming tradeoffs between resting and active energy expenditures that constrain other primates. Enhanced metabolic rates help humans fuel expanded brains, faster reproductive rates, extended longevity, and high percentage of body fat.
... The increase in body size in Homo erectus was accompanied by an increase in relative LLL (Pontzer, 2012;Pontzer et al., 2010;Steudel-Numbers, 2006). The changes in the morphology of Homo erectus might have been an adaptation to a new foraging regime, which is thought to bring about increased locomotion distances (Bramble & Lieberman, 2004;Isbell et al., 1998). Relatively long lower limbs of Homo erectus might have decreased cost of locomotion Steudel-Numbers & Tilkens, 2004) and thermal strain (Longman et al., 2021) created by locomotion used for hunting and scavenging (Lieberman, 2015;Pontzer et al., 2010) or plant gathering (Isbell et al., 1998). ...
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Objectives Long lower limbs relative to body size are thought to be an adaptation to prevent excessive increases in body temperature during running in hot climate. The advantage of long lower limbs relative to body size is usually explained by an increase in body surface area relative to mass; however, the influence of limb length on relative body surface area was shown to be minor. We aimed to experimentally test the effect of relative lower‐limb length (LLL) on body temperature changes during running. Furthermore, we tested the effect of relative LLL on relative body surface area. Materials and Methods Adult men ( n = 37) ran for 40 min on a treadmill, while their core temperature (ingestible thermometer), skin temperature (infrared thermography), and oxygen consumption (indirect calorimetry) were measured. Relative LLL was calculated as residuals from linear regression of LLL on stature. Linear regression was used to test the effect of relative LLL on standardized heat loss (heat loss/heat production), mean body temperature (weighted mean of skin and core temperatures), and body surface area. Results Relative LLL had a positive effect on standardized heat loss and a negative effect on mean body temperature change during running. Relative LLL had a positive effect on the proportion of body surface area allocated to the lower limbs but not on the relative body surface area. Discussion The reduced increase in mean body temperature associated with long lower limbs suggests an advantage of relatively long lower limbs for greater endurance and speed during persistence hunting or contemporary running events.
... From a psychophysiological point of view, physical activity with slight to moderate intensity (technically, below the so-called aerobic threshold) evokes pleasure, whereas vigorous exercise (above the threshold) leads to displeasure, an aversive psychological state (Ekkekakis, 2009). Below-threshold physical activity is sustainable in the long run (Bramble & Lieberman, 2004;Raichlen & Alexander, 2017) and leads to improved cardiovascular fitness. Therefore, it shows disproportional health benefits compared to above-threshold exercise (American College of Sports Medicine, 2017). ...
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Background: Feelings and emotions during sports and exercise determine commitment, adherence, and enjoyment of the activity. The Physical Activity Affect Scale (PAAS) combined two earlier instruments, the Exercise-Induced Feelings Inventory and the Subjective Exercise Experiences Scale, to investigate affective states generally characterizing post-exercise feelings based on the circumplex model of affect. Therefore, the PAAS measures positive affect, negative affect, fatigue, and tranquility on a five-point Likert scale having only 12 items. Aim: Its ease of administration and interpretation renders the PAAS a valuable tool in both research and practice, but it is unavailable to Hungarian scholars and sports and exercise professionals due to the lack of adaptation. Hence, this work aimed to develop and validate the Hungarian version of the PAAS. Methods: Three hundred sixty-two recreational exercisers (64.1% women), aged from 18 to 62 (mean of age: 27.0 [SD = 10.0]) years completed the questionnaires before and during their exercise (briefly interrupting activity). Measures: PAAS was used to measure positive affect, negative affect, fatigue and tranquility aspects of internal affective experience. Positive and Negative Affect Schedule (PANAS) was utilized to assess the actual mood state, consisting of positive affect and negative affect subscales. Arousal was measured with Felt Arousal Scale (FAS), while the pleasure–displeasure affective valence was assessed with the Feeling Scale (FS). Results: A confirmatory factor analysis indicated good fit of the four-factor model. The results also revealed configural, metric, and scalar measurement invariance between sexes. The internal reliabilities of the scales varied between (Cronbach’s α ) .73 and .85 before and during exercise. PAAS scales largely showed the expected associations with other measures of positive and negative affect and activation. The lowest association was between Tranquility (PAAS) and Felt arousal ( r = .14), followed by Tranquility and Feeling ( r = .27). Feeling and Felt arousal correlated negatively with Fatigue (PAAS, r = –.42 and r = –.44), as well as with the Negative affect (PAAS, r = –.61 and r = –.40). Positive affect from PAAS (PAAS PA) had a positive correlation with Feeling and Felt arousal ( r = .64, r = .54). PAAS PA and Positive affect from PANAS (PANAS PA) correlated strongly ( r = .77), similar to the Negative affect from both inventories ( r = .78; p < .01 for all cases). Conclusion: Therefore, the Hungarian PAAS could assess exercise-induced affect in a reliable and valid way in recreational exercisers. However, its validity in competitive sports remains to be tested.
... Ribcage types have been used to infer the organ size in extinct hominins, such as in Australopithecus afarensis, Homo erectus, Homo naledi, and Neandertals [1][2][3][4][5]. The idea that the size of the intestines ("gut") or the liver have changed in the hominin lineage informs narratives about the evolution of diet, locomotion, and the brain, and underlying these narratives is an assumption that a relationship exists between these organs and the torso skeleton [1,2,[6][7][8]. The present study directly examines the gut-ribcage and liver-ribcage relationship in humans, offering a quantitative exploration of the conventional wisdom that the torso skeleton reflects the abdominal organ size. ...
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Organ–skeleton relationships are understudied in biological anthropology. The torso skeleton is often used to infer the organ size and evolution in hominins; ribcage “types”, in particular, are used to infer the abdominal organ size in hominins. This study is a quantitative examination of the relationship between the lower ribcage and two organs: the liver and the intestines (“gut”) in humans. Specifically, we test whether the ribcage breadth, shape, and “flare”, at the level of rib 10, covaries with the liver volume and gut volume in Homo sapiens. Liver size, gut size, and ribcage measurements are taken from CT scans (N = 61). The results show sex differences in the gut–ribcage relationship. The gut volume is associated with ribcage breadth and flare in both sexes. The liver volume is not associated with any ribcage measurements. We conclude that sex differences in the organ–skeleton relationship complicate the previous simplistic view that the size of the liver or the gut could be inferred through a fossil’s ribcage type. Biological anthropologists should continue to explore sex differences in organ–skeleton relationships, when attempting to understand the evolution of visceral organs and the torso.
... This bio-cultural feedback loop allowed humans to accumulate diverse and complex skill sets more efficiently and reallocate energy to other energy budget components, such as the metabolic costs of a large brain and a high rate of reproduction (Aiello & Wheeler, 1995;Kaplan et al., 2000;Key & Lycett, 2023;Leonard & Robertson, 1994;Pontzer, 2012). Improvements in diet quality were critical for the evolution of an expanded human energy budget (Leonard & Robertson, 1994;Marean, 2016;Pontzer, 2012); however, anthropologists continue to debate the cultural shifts and corresponding foraging behaviors that may have facilitated the evolution of human energy allocation strategies (Aiello & Wheeler, 1995;Bramble & Lieberman, 2004;Kaplan et al., 2000;Wrangham et al., 1999). ...
Article
Objectives This study investigates the energetic costs associated with Oldowan‐style flake production and how skill differences influence these costs. Materials and Methods Nine adult participants, including novice and expert toolmakers, underwent a 2‐h experimental session where we measured energy expenditure and flaking outcomes. We measured body mass (kg), percent body fat, and fat‐free mass (kg) and used open‐circuit indirect calorimetry to quantify energy expenditure. The lithic analysis used standard linear and mass measurements on the resulting cores and flakes. Qualitative observations from the video recordings provide insight into the subject's body positions and hand grips. Results Results reveal significant differences in energy expenditure between novice and expert toolmakers, with experts demonstrating lower overall energy expenditure. Additionally, experts produced more flakes, reduced greater core mass per unit of energy expenditure, and exhibited distinct body positions, hand grips, and core/flake morphologies compared with novices. Discussion The study provides novel insights into the bio‐cultural impacts of stone toolmaking skill acquisition, suggesting that skilled performance reduces the metabolic costs of stone tool production. These findings contribute to debates surrounding the origins of human cultural capacities and highlight the importance of including energy expenditure measures in knapping experiments. Moreover, the results suggest that the presence or absence of expertise in the Paleolithic would have fundamentally altered selective pressures and the reliability of skill reproduction. This study enhances our understanding of differences in stone toolmaking skill and their implications for human energy allocation strategies during early technological evolution.
... It is yet unclear to what extent cognitive and motor creativity are driven by similar mechanisms. Movement is an intrinsic part of infants' and children's brain and cognitive development, as it allows exploration of, and interaction with, the environment (Bramble & Lieberman, 2004;Campos et al., 2000;Hillman et al., 2019). Children have prior experience of acquiring movement skills through exploration and trial and error, gradually supporting their learning to play and complete tasks independently. ...
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Movement is an intrinsic part of infants’ and children’s brain and cognitive development. Creativity theories and models have mainly focused on cognitive creativity, assessed for example with the alternative uses test in adults. More recently, researchers have proposed an embodied model of creativity. The present study investigated the relationship between personality traits, self-regulation, cognitive abilities, and both cognitive and motor creativity in 6- to 7-year-old primary school pupils (n = 152). We assessed cognitive creativity with a drawing task and motor creativity with Bertsch’s test. We hypothesized that better emotional regulation skills, and self-regulation more broadly, would allow individuals to harness their creative potential for creative achievement and that fluid intelligence and inhibitory control, measured by a delayed reward task, would predict cognitive creativity and motor creativity, respectively. Our results showed that motor and cognitive aspects of creativity were associated with both common and specific individual differences in cognition, self-regulation, and personality traits. Fluid intelligence, the ability to wait for a reward, and strengths for creativity showed positive associations of similar size with motor and cognitive creativity. Higher cognitive and motor creativity were associated with fewer emotional problems. Motor creativity showed a greater positive relationship with cognitive and affective self-regulation responses to a physical challenge than cognitive creativity, which mediated the association between strengths for creativity and motor creativity. Our research highlights the relevance of movement in the development of cognition in childhood and invites further study of an embodied approach to creativity.
... For example, physical effort is inherent to PA and is processed as a cost and an aversive experience to be avoided Maltagliati et al., 2022). Thus, from an evolutionary biological perspective (Bramble & Lieberman, 2004), one might wonder whether it is possible to develop a true dependence to behaviours that have an aversive value. Similarly, unlike gambling or pornography, PA behaviours are generally associated with delayed, not immediate, reward. ...
Article
While physical activity (PA) has numerous health benefits, in rare cases it can become addictive and lead to adverse health effects. Automatic reactions to addiction-related cues are a hallmark of addiction, however, their association with exercise dependence (ED) remains unknown. This research examined the links between ED and automatic reactions to PA-related cues in physically active individuals with low-to-moderate levels of ED through two studies. Study 1 (N = 65) used a dot-probe task with eye-tracking to assess the association between attentional bias toward PA and ED scores measured by the Exercise Dependence Scale-Revised. Study 2 (N = 125) used a manikin task and a single-category implicit association test to examine the association of approach-avoidance tendencies and implicit affective attitudes toward PA with ED scores. Results revealed ED scores were positively associated with behavioral indicators of attentional bias (i.e., reaction times), but not with eye-tracking indicators (i.e., first-gaze localization, gaze duration). Similarly, ED scores were unrelated to approach-avoidance tendencies or implicit affective attitudes toward PA. Therefore, our research provides limited evidence supporting the hypothesis that automatic reactions to PA may reflect a “signature” of ED. Our findings do not robustly support the link between automatic processes and ED, raising questions about whether the psychological mechanisms involved in ED might differ from those observed in other addictive behaviors where automatic processes are key. However, due to our sample's low-to-moderate levels of ED, definitive conclusions cannot be drawn. Further research with individuals exhibiting addiction-related dependence, personalized stimuli, and neurophysiological methods is needed.
... As we noted above, the human spinal maps of activation ( Figure 2B) have some specific features related to the idiosyncratic gait style involving erect bipedalism. Humans have many musculoskeletal specializations for bipedalism (Bramble and Lieberman, 2004), with walking and running being the most common forms of human locomotion. They show highly automated rhythmic movements with a relatively stereotyped pattern of muscle activation, which most likely reflects both the activity of underlying pattern generators and proprioceptive feedback. ...
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The spatial segmental location of motoneurons in the human spinal cord is influenced by both evolutionary and functional principles tending to optimize motor control, reflex integration, and adaptation to the demands of movement. Bearing in mind the biomechanics of limb muscles, it is logical to examine how motoneuron activity clusters functionally during typical daily activities like walking. This article provides a summary of advancements in the study of spinal maps of motoneuron activation during human locomotion by reviewing data gathered over ∼20 years. The effects of child development, aging, and neurological disorders show the salient characteristics of spinal segmental activity during different human locomotor tasks and conditions. By exploiting the neuromechanics of the spinal motor circuits, that is, the link between motoneuron activity and gait mechanics, neuroprosthetics and other focused treatments may better help individuals with locomotor impairments.
... Musculoskeletal adaptations of early hominins suggest they balanced an arboreal lifestyle, including climbing, with a terrestrial lifestyle, featuring bipedalism (Carlson et al., 2021;Prang, 2019;Sorrentino et al., 2023;Williams et al., 2023). While there are undoubtedly multiple adaptive solutions for achieving this balance, bipedalism eventually became the predominant hominin locomotor mode after the emergence of genus Homo (Bramble and Lieberman, 2004;Pontzer, 2017). Variations in morphology and bipedal gait mechanics can be heavily influenced by mobility, which in humans is partly a function of subsistence economy, substrate use, choice of footwear, and other biological factors (e.g., sex, age, and body mass) (Carlson and Marchi, 2014;Chirchir et al., 2015;Saers et al., 2019;Sorrentino et al., 2020;Trinkaus, 2005). ...
... In various human physical activities including walking, running, jumping, and other sports, the foot serves as the terminal point of movement. It functions to attenuate the impact forces from ground contact during landing (Chan and Rudins, 1994;Pan et al., 2023), generate propulsive force for the body during push-off (Bramble and Lieberman, 2004;Takahashi et al., 2016;Xu et al., 2024), and optimize energy conversion efficiency (Kuo et al., 2005;Zelik and Kuo, 2010;Khuyagbaatar et al., 2024). To accommodate the multifunctional demands placed upon them, humans have evolved a pair of remarkably flexible feet capable of modulating stiffness to suit various requirements across different athletic endeavors (Bojsen-Møller, 1979;Ker et al., 1987;Kuo et al., 2005;Zelik and Kuo, 2010). ...
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Background The plantar vault, comprising the transverse and longitudinal arches of the human foot, is essential for impact absorption, elastic energy storage, and propulsion. Recent research underscores the importance of the transverse arch, contributing over 40% to midfoot stiffness. This study aimed to quantify biomechanical responses in the ankle-foot complex by varying the stiffness of the deep metatarsal transverse ligament (DTML). Methods Using CT image reconstruction, we constructed a complex three-dimensional finite element model of the foot and ankle joint complex, accounting for geometric complexity and nonlinear characteristics. The focus of our study was to evaluate the effect of different forefoot transverse arch stiffness, that is, different Young’s modulus values of DTML (from 135 MPa to 405 MPa), on different biomechanical aspects of the foot and ankle complex. Notably, we analyzed their effects on plantar pressure distribution, metatarsal stress patterns, navicular subsidence, and plantar fascial strain. Results Increasing the stiffness of the DTML has significant effects on foot biomechanics. Specifically, higher DTML stiffness leads to elevate von Mises stress in the 1st, 2nd, and 3rd metatarsals, while concurrently reducing plantar pressure by 14.2% when the Young’s modulus is doubled. This stiffening also impedes navicular bone subsidence and foot lengthening. Notably, a 100% increase in the Young’s modulus of DTML results in a 54.1% decrease in scaphoid subsidence and a 2.5% decrease in foot lengthening, which collectively contribute to a 33.1% enhancement in foot longitudinal stiffness. Additionally, doubling the Young’s modulus of DTML can reduce the strain stretch of the plantar fascia by 38.5%. Conclusion Preserving DTML integrity sustains the transverse arch, enhancing foot longitudinal stiffness and elastic responsiveness. These findings have implications for treating arch dysfunction and provide insights for shoe developers seeking to enhance propulsion.
... However, with the surge in running trends, running-related injuries also demonstrate an increase that cannot be ignored, contradicting the theoretical health benefits of active exercise [1]. Over millions of years, humans have evolved features related to energy efficiency, strength, stability, and temperature regulation, enabling exceptional performance in long-distance running [2]. However, reports indicate that the injury rates for long-distance runners range from 30% to 80% annually, with foot and ankle injuries constituting approximately one-fourth of these injuries [3]. ...
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Previous research has predominantly focused on the biomechanical effects of anterior–posterior foot motion during running, with comparatively less attention given to medial–lateral foot motion and its impact on lower limb biomechanical characteristics. We recruited 18 healthy runners who wore five different types of running shoes: regular shoes (NS), those with a 6 mm and 9 mm medial–lateral height difference in the forefoot (M6, M9), and those with a 6 mm and 9 mm lateral–medial height difference (L6, L9). Biomechanical parameters of lower limb joints during the stance phase of running, including range of motion, peak angular velocity, peak moment, power, and work, were analyzed. We used paired-sample t-tests and one-dimensional statistical parametric mapping (SPM1D) to compare joint biomechanics between shoes with varying height differences and NS. Under the L6 condition, notable differences occurred in the hip and knee flexion–extension moments during landing and push-off, accompanied by a significant increase in ankle dorsiflexion work and a significant decrease in inversion–eversion work. In contrast, the M9 condition resulted in decreased hip flexion–extension peak moment, power, and work in the sagittal plane. These findings indicate that varying forefoot medial–lateral height differences in running shoes significantly impact lower limb joint dynamics during the stance phase, particularly the L6 condition, potentially reducing knee injury risk and aiding gait improvement for overpronators. The findings offer valuable insights for sports injury prevention and athletic footwear design. However, further research is needed to understand the underlying mechanisms and practical implications for sports injury prevention and performance enhancement
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The origin of animal tissue consumption within the hominin lineage remains a central question in palaeoanthropology and taphonomy. This question is mostly addressed through the study of bone surface modifications (e.g., butchery marks) observed on fossils from East African sites. Albeit somewhat overlooked compared to East Africa, South Africa provides an additional body of evidence regarding the evolution of hominin behaviours. Here, we provide a comprehensive description and analysis of a butchered bone assemblage from the Sterkfontein Name Chamber and Member 5 East Oldowan infill in South Africa, dated conservatively to between 1.4 and 2.18 Ma. Based on the anatomical location and morphology of the bone surface modifications, we demonstrate that hominins using Oldowan tools were capable of performing a complete butchery sequence that included skinning, disarticulation, defleshing and marrow extraction. Furthermore, comparison with the butchered bones from the neighbouring sites of Cooper’s D and Swartkrans shows a continuity, or the repeated emergence, of similar butchery patterns through the Early Pleistocene. The identification of distinct butchery patterns, the range of exploited animals, as well as the presence of bone tools in many sites highlight the diversity of hominin subsistence behaviours during the Early Pleistocene, which we interpret as a reflection of the likely non-linear evolution of such behaviours. Finally, we argue that the research focus of taphonomic analyses should address how hominins processed carcasses in addition to how and when these were acquired. Such analyses would help identifying the development of complex butchery practices in the archaeological record.
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Shared intentionality is the derived hominin motivation and skills to align mental states. Research on the role of interdependence in the phylogeny of shared intentionality has only considered the archeological record of Homo heidelbergensis . But ethnographic and fossil data must be considered, too. Doing so suggests that shared intentionality may have been favored in Homo erectus to support persistence hunting.
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Nuchal ligaments are relatively well understood and have venerable histories of recognition in extant euungulates, canids, elephants, and humans, but whether any anatomical structures in other taxa, both extant and extinct, qualify as nuchal ligaments is unclear because the term ‘nuchal ligament’ lacks a clear, narrow, consistently applied definition. Possible definitions of the term could be etymological, taxonomic, compositional, or morphological/topological, or a combination thereof. Currently, a de facto morphological/topological definition of ‘nuchal ligament’ sensu stricto seems most common: a nuchal ligament is an epaxial, cervical ligament with a funiculus that is elevated above the cervical spinous processes and connected to them only via laminae. However, many references to ‘nuchal ligaments’ in both extant and extinct taxa instead seem to employ a broader, etymological definition that encompasses numerous different compositions, morphologies and topologies. Several, largely untested assumptions have been made about functional and osteological correlates of a nuchal ligament, such as possessing a ‘large’ or ‘heavy’ head and/or a ‘long’ neck, possessing specific features on the occipital region of the skull, and possessing specific morphologies or dimensions of the cervical and cranial thoracic spinous processes. These assumptions have led to corollary assumptions that many extinct tetrapods—particularly those phylogenetically far removed from taxa known to possess them—had nuchal ligaments, but until these presumed correlates are tested and demonstrated in extant taxa, such assumptions remain purely speculative, and alternative cranio-cervical support mechanisms also must be considered. Depending on the definition applied, attributions of nuchal ligaments to extinct taxa, and even to some extant taxa (including humans), may be references to other sorts of morphologically and topologically distinct epaxial structures such as supraspinous ligaments and fibrous septa/raphes that occupy similar anatomical positions as nuchal ligaments sensu stricto. ‘Nuchal ligament’ requires a narrow definition to understand what, if any, features correlate with the presence of the ligament, as well as what taxa have convergently evolved the structure.
Article
Human proficiency for bipedal locomotion relies on the structure and function of our feet, including the interplay between active muscles and passive structures acting on the toes during the propulsive phase of gait. However, our understanding of the relative contributions of these different structures remains incomplete. We aimed to determine the distinct toe-flexion torque-angle relationships of the plantar intrinsic muscles (PIMs), extrinsic muscles, and passive structures, therefore offering insight into their force-generating capabilities and importance for walking and running. Torque-angle data were twice collected from nine healthy individuals (6 males, 3 females; 28±5 years) using supramaximal transcutaneous electrical stimuli applied at two tibial nerve sites to distinguish between muscle-driven and passive toe-flexion torque about the metatarsophalangeal (MTP) joint. Innervating extrinsic muscles and PIMs concurrently produced peak torques (Hallux=3.05±0.70 Nm, MTP angle=48.0°±13.6°; Lesser Digits=3.19±0.98 Nm, MTP angle=42.6°±13.4°) exceeding by 208% (Hallux) and 150% (Lesser Digits), respectively, those from PIM stimulation alone. Notably, MTP joint angles pertinent to gait corresponded to the ascending limb of the active torque-angle relationship, with active muscle joint torques the dominant contributor over passive torques. The latter finding suggests that human toe flexors are well-adapted to generate the MTP joint torques that are necessary for walking and running. This further supports the notion that muscles acting within the foot play an important role in the foot's mechanical function and our ability to walk and run in an upright posture.
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Les recherches sur les courses à pied d’ultra-endurance se multiplient, et témoignent de la popularité de ce sport. Quelles places occupent les sciences humaines et sociales dans la compréhension de cette pratique ? Cet article contribue à préciser la compréhension d’un véritable phénomène de société à partir d’une revue de littérature pluridisciplinaire dans le domaine des sciences humaines et sociales sur l’ultra-trail. Une analyse qualitative systémique de leur contenu permet d’identifier trois thèmes majeurs : 1) Engagement et profils des coureurs d’ultra-trail ; 2) Motivations et expériences de ses participants ; 3) Territoires et événements du trail running. Ces résultats ont permis de synthétiser les travaux réalisés à ce jour et constituent un point de départ pour développer d’autres approches. Il apparaît qu’au-delà des ancrages disciplinaires, les résultats présentés résonnent entre eux autant qu’ils mettent en évidence un certain nombre de paradoxes, ce qui est représentatif de la discipline elle-même. Au vu de ces observations, certaines pistes peuvent être explorées pour approfondir ces approches et ces études.
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The late Early Pleistocene archaeological site of Fuente Nueva-3 (FN3), which lies in the Guadix-Baza Depression (SE Spain) and is dated to ~ 1.4 Ma, contributes some of the oldest evidence of hominin presence in Western Europe, including a huge tool assemblage of Oldowan tradition, manuports (i.e., unmodified stones used as percussion tools) and abundant fossils of large mammals, some of which preserve anthropogenic marks related to defleshing, butchering and marrow processing. In addition, there are bones with tooth marks produced by scavenging carnivores. The fertile layers of the FN3 section have been grouped in a lower archaeological level (LAL) and an upper archaeological level (UAL). Both levels preserve abundant skeletal remains and lithic tools. However, the LAL shows a high density of manuports, which suggests that hominin activity was more intense at this level, while the UAL preserves many remains of megaherbivores, particularly proboscideans (Mammuthus meridionalis), and almost all coprolites unearthed from the site, which points to a greater involvement of the giant hyenas (Pachycrocuta brevirostris). In this paper, we (i) test for statistical differences in the composition of the faunal assemblages preserved in the UAL and LAL; and (ii) analyze particle size in the fertile layers of both archaeological levels. Our results show that megaherbivores are comparatively overrepresented in the UAL, specially by young elephants, while other medium-to-large and large-sized ungulates, particularly equids, are more abundant in the LAL, showing a predominance of adult individuals. Concerning the sedimentology, layers 2-3 of the LAL show a predominance of silts and clays, with sands representing a minor fraction. In contrast, layer 5 of the UAL is composed of two-thirds of fine and very fine sands, with the remaining third consisting of silts and clays. These data and the paleoenvironmental reconstruction of layer 5 suggest that it may be interpreted as a paleo-quicksand in which megaherbivores were trapped due to the elevated weight per unit area supported by their feet, and their half-sunken carcasses attracted the scavengers, particularly the hyenas, which fed on these carcasses and defecated in their surroundings. El yacimiento del Pleistoceno inferior de Fuente Nueva-3 (depresión de Guadix-Baza, sureste deEspaña): ¿Una letrina de hienas desarrollada en una trampa de arenas movedizas para la megafauna? Resumen El yacimiento arqueológico de Fuente Nueva-3 (FN3), de finales del Pleistoceno temprano, se sitúa en la Depresión de Guadix-Baza (SE de España) y ha sido datado en ~1,4 Ma. Aporta algunas de las evidencias más antiguas de la presencia de homininos en Europa occidental, incluyendo un amplio conjunto de herramientas de tradición olduvayense, manuports Extended author information available on the last page of the article Journal of Iberian Geology (es decir, piedras no modificadas utilizadas como herramientas de percusión) y abundantes fósiles de grandes mamíferos, algunos de los cuales conservan marcas antropogénicas relacionadas con el desollamiento, la carnicería y el procesamiento del tuétano. Además, hay huesos con marcas de dientes producidas por carnívoros carroñeros. Las capas fértiles de la sec-ción de FN3 se agrupan en un nivel arqueológico inferior (LAL) y un nivel arqueológico superior (UAL). Ambos niveles conservan abundantes restos óseos y herramientas líticas. Sin embargo, el LAL presenta una alta densidad de manuports, lo que sugiere que la actividad de los homininos fue más intensa en este nivel, mientras que el UAL conserva muchos restos de megaherbívoros, en particular proboscídeos (Mammuthus meridionalis), y casi todos los coprolitos exhumados del yacimiento, lo que apunta a una mayor participación de las hienas gigantes (Pachycrocuta brevirostris). En este tra-bajo (i) comprobamos si existen diferencias estadísticas en la composición de los conjuntos faunísticosconservados en el UAL y el LAL; y (ii) analizamos el tamaño de las partículas en las capas fértiles de ambos niveles arqueológicos. Nuestros resultados muestran que los megaherbívoros están comparativamente sobrerrepresentados en el UAL, especialmente por elefantes jóvenes, mientras que otros ungulados de tamaño medio-grande y grande, particularmente los équidos, son más abundantes en el LAL, mostrando un predominio de individuos adultos. En cuanto a la sedimentología, las capas 2-3 del LAL muestran un predominio de limos y arcillas, representando las arenas una fracción reducida. Por el contrario, la capa 5 de la UAL está compuesta en dos tercios por arenas finas y muy finas, y el tercio restante por limos y arcillas. Estos datos y la reconstrucción paleoambiental de la capa 5 sugieren que se puede interpretar como una paleoarena movediza en la que los megaherbívoros quedaban atrapados debido al elevado peso por unidad de superficie que soportaban sus extremidades, atrayendo sus cadáveres a medio hundir a los carroñeros, en particular a las hienas, que se alimentaron de estos cadáveres y defecaron en sus alrededores. Palabras clave Orce · Pleistoceno inferior · Tafonomía · Paleoecología · Proboscidios · Coprolitos
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Although anxiety is a common psychological condition, its symptoms are related to a cardiopulmonary strain which can cause palpitation, dyspnea, dizziness, and syncope. Severe anxiety can be disabling and lead to cardiac events such as those seen in Takotsubo cardiomyopathy. Since torso stiffness is a stress response to unpredictable situations or unexpected outcomes, studying the biomechanics behind it may provide a better understanding of the pathophysiology of anxiety on circulation, especially on venous impedance. Any degree of torso stiffness related to anxiety would limit venous return, which in turn drops cardiac output because the heart can pump only what it receives. Various methods and habits used to relieve stress seem to reduce torso stiffness. Humans are large obligatory bipedal upright primates and thus need to use the torso carefully for smooth upright activities with an accurate prediction. The upright nature of human activity itself seems to contribute to anxiety due to the needed torso stiffness using the very unstable spine. Proper planning of actions with an accurate prediction of outcomes of self and non-self would be critical to achieving motor control and ventilation in bipedal activities. Many conditions linked to prediction errors are likely to cause various degrees of torso stiffness due to incomplete learning and unsatisfactory execution of actions, which will ultimately contribute to anxiety. Modifying environmental factors to improve predictability seems to be an important step in treating anxiety. The benefit of playful aerobic activity and proper breathing on anxiety may be from the modulation of torso stiffness and enhancement of central circulation resulting in prevention of the negative effect on the cardiopulmonary system.
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This article argues that understanding the primary functions of cognitive processes in our evolutionary past can help to develop effective cognitive enhancement methods. The adaptive problems our ancestors faced forged interconnected cognitive and motor mechanisms supporting various movement-based problem-solving processes. However, the physical and social challenges these cognitive-motor capacities originally evolved to address are no longer prevalent in modern societies. Consequently, many adaptive problem-solving mechanisms linked to a wide range of body movements are often underused and insufficiently developed in modern contexts, contributing to age-related cognitive decline. From this view, and considering current cognitive enhancement techniques such as cognitive training, neurostimulation, physical exercise, and combined cognitive and physical training, the present article introduces an evolutionary-inspired cognitive enhancement framework. This framework advocates for developing strategies and training methods that stimulate our evolved cognitive-motor adaptations. In particular, therapeutic interventions should incorporate adaptive problems and whole-body movement solutions into modern technologies and computer-based tasks.
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It seems reasonable that quadrupeds should change gait from a walk to a trot to a gallop in such a way as to minimize their energy consumption, as human beings are known to change from a walk to a run at a particular speed (2.4 m s -1) below which walking requires less energy than running and above which the opposite is true. Thus by changing gait, human beings keep the energy cost of locomotion to a minimum as their speed increases. One reason this relation holds is that in humans, metabolic rate increases curvilinearly with walking speed. If metabolism were a curvilinear function of speed within each of the gaits used by quadrupeds, it would support the hypothesis that they also change gait to minimize energetic cost. There is an old controversy about whether metabolic rate increases linearly or curvilinearly in running humans but all previous reports have suggested that metabolic rate increases linearly with speed in quadrupeds. Extended gaits were an important experimental tool in the study of human gait changes; thus we have trained three small horses (110-170 kg) to walk, trot and gallop on a motorized treadmill, and to extend their gaits on command. We report here that, using measurements of rates of oxygen consumption as an indicator of rates of energy consumption, we have confirmed that the natural gait at any speed indeed entails the smallest possible energy expenditure.
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1. The technique of perceptual rating of thermal stimuli was used, in eight human subjects immersed in warm water, in order to appreciate whether they were hypo-, normo- or hyperthermic. Oesophageal, tympanic and forehead skin temperatures were recorded, as also was the temperature of the skin above the angularis oculi vein. Once the subjects gave clearly hyperthermic ratings, one arm was exposed to a 6 m/s wind. After 5--10 min the arm was re-immersed and the face was fanned. 2. Fanning of the arm resulted in lowering of body core temperature. However ratings of thermal stimuli remained hyperthermic. 3. Face fanning decreased forehead skin, angularis oculi vein and tympanic temperatures. Hyperthermic ratings were replaced by normothermic ratings, although oesophageal temperature continued to rise. 4. The upper limit of oesophageal temperature for normothermic ratings was 37.o6 +/- 0.09 degrees C during the control period without fanning. This temperature rose to 37.91 +/- 0.09 degrees C during facial ventilation. 5. These results suggest a selective cerebral cooling due to venous blood returning from facial skin via the ophthalmic vein to the cavernous sinus, where a cooling of arterial blood ascending to the brain can take place.
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The amount of energy used to run a mile is nearly the same whether it is run at top speed or at a leisurely pace (although it is used more rapidly at the higher speed). This puzzling independence of energy cost and speed is found generally among running animals, although, on a per gram basis, cost is much higher for smaller animals. Running involves little work against the environment; work is done by muscles and tendons to lift and accelerate the body and limbs. Some of the work is recovered from muscle-tendon springs without metabolic cost and work rate does not parallel metabolic rate with either speed or size. Regardless of the amount of work muscles do, they must be activated and develop force to support the weight of the body. Load-carrying experiments have shown that the cost of supporting an extra newton of load is the same as the weight-specific cost of running. Size differences in cost are proportional to stride frequency at equivalent speeds, suggesting that the time available for developing force is important in determining cost. We report a simple inverse relationship between the rate of energy used for running and the time the foot applies force to the ground during each stride. These results support the hypothesis that it is primarily the cost of supporting the animal's weight and the time course of generating this force that determines the cost of running.
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The preferred stride frequency (SF) and stride length (SL) of male recreational distance runners were measured on a level treadmill under a variety of conditions over the typical distance running speed range of 3.15-4.12 m.s-1. At a given speed, the correlation coefficients between the subjects' anthropometric variables (APV) (such as stature, leg length, and limb segment mass) and their preferred stride variables were consistently low (less than or equal to 0.36) and not significantly different from zero. As speed increased through the experimental range, SF remained nearly constant (only a 4% increase) while SL increased by 28%. The use of dimensionless velocity was shown to be no more effective than conventional methods in the prediction of a SL vs velocity relationship, but the dimensionless form of the relationship was remarkably similar to those observed for other animal species and other forms of gait. The addition of masses up to 1.1 kg at each ankle produced no significant change in SF or SL. The results indicate that factors other than APV are the primary determinants of preferred SF and SL. Since it has been shown previously that the preferred SL is usually the most economical, APV cannot be used to accurately predict or prescribe SF or SL on an individual basis.
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Principal strains were recorded in vivo from the radial and tibial midshafts of three goats as they increased speed and changed gait. These data were compared with strain data measured for the radius and tibia of the dog (Rubin & Lanyon, 1982) and the horse (Biewener, Thomason & Lanyon, 1983b) in order to test the hypothesis that similar peak bone strains (stresses) occur at functionally equivalent points in the gaits of different species. Multiple recordings of in vivo strain along the caudal diaphyses of the radius and tibia of one goat were made to test the validity of this technique for measuring peak locomotor stress. Measured strains were extremely consistent over the animal's full range of speed (coefficient of variation for the radius 0.05-0.08, and for the tibia 0.06-0.11). The data from the three gauges, which were spaced 15 mm apart, demonstrated that maximal strains act at the midshaft, substantiating the use of this technique to measure peak locomotor bone strains. Strain levels recorded at the trot-gallop transition and top galloping speeds of the goat were similar to the values reported for the dog and horse, despite large differences in absolute speed (goat, 4.3 ms-1; dog, 6.9 ms-1; horse, 7.5 ms-1 at maximum gallop). The second moments of area of the tibia and radius (+ ulna) of the dog are 29% and 113% greater than for goats of equal size, explaining how similar strains are achieved in the dog at higher speeds than the goat. Furthermore, peak bone strains recorded at the fastest trotting speed were similar to those recorded at the fastest galloping speed for each species. Peak strains recorded for the goat at a maximum gallop correspond to stresses of +37.9 MPa (cranial) and -47.7 MPa (caudal) in the radius and +36.3 MPa (cranial) and -50.3 MPa (caudal) in the tibia, representing a safety factor to yield failure of three.
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Large mammals, including humans, save much of the energy needed for running by means of elastic structures in their legs and feet. Kinetic and potential energy removed from the body in the first half of the stance phase is stored briefly as elastic strain energy and then returned in the second half by elastic recoil. Thus the animal runs in an analogous fashion to a rubber ball bouncing along. Among the elastic structures involved, the tendons of distal leg muscles have been shown to be important. Here we show that the elastic properties of the arch of the human foot are also important.
Thesis
This thesis explores form variation in the adult tarsal skeleton of extant and fossil hominoids. Three dimensional coordinate data were obtained from five bones of the foot: the calcaneus, talus, cuboid, navicular and medial cuneiform. The comparative sample was made up of Homo sapiens, Pan troglodytes troglodytes, Pan paniscus, Gorilla gorilla gorilla and Pongo pygmaeus. The fossil sample consisted of tarsal remains assigned to a number of Late Pliocene taxa: Australopithecus afarensis, Australopithecus africanus, Paranthropus robustus and Homo habilis. Statistical shape analysis was conducted using geometric morphometric techniques. The first section of analysis explores sexual dimorphism in the extant hominoid foot. It is found that there is no shape dimorphism in the forefoot, and a marginal amount in the hindfoot of Gorilla and Pongo only. Such differences are likely to be linked to high degrees of body mass dimorphism in those taxa. The section concludes that shape dimorphism is unlikely to be an important factor in explaining differences between fossil hominin pedal remains. The second section explores the inter-specific relationship between the tarsals of the extant hominoids. It is found that shape differences between taxa closely mirror those differences already described in the literature. However, it is found that the phenetic relationship between the taxa varies from bone to bone, and, furthermore, does not match the consensus molecular phylogeny. The section concludes that some tarsals are more specialised and remodelled than others, and thus great caution should be taken when considering isolated fossil pedal specimens. The third section incorporates the fossil specimens into the study. It is found that the morphology of the A. africanus and H. habilis tarsals are very similar, and fall within extant hominoid intra-specific ranges of variation. However, the morphology of the A. afarensis tarsals are considerably distinct, and show a different overall pattern to those of A. africanus and H. habilis. The section concludes that all taxa were mosaic in their affinities, but were mosaic in different ways. This thesis concludes that it is likely that there were at least two distinct ways in which the tarsals of different hominin taxa had adapted to bipedal locomotion. This finding supports recent new discoveries suggesting a far wider degree of taxonomic diversity in the African fossil hominin record than had previously been thought.
Chapter
The morphology of the hip region, and its functional implications, have figured prominently in discussions of the origin and nature of hominid bipedality (Dart, 1949; Broom and Robinson, 1950; Washburn, 1950; Le Gros Clark, 1955; Mednick, 1955; Napier, 1964, 1967; Day, 1969, 1973; Robinson, 1972; Lovejoy et al., 1973; McHenry, 1975; Wood, 1976; McHenry and Corruccini, 1978; Stern and Susman, 1983, 1991; Susman et al., 1984; Lovejoy, 1988; Berge, 1991; Jungers, 1991). During most of human bipedal gait, the body is balanced over one lower limb (Inman et al., 1981), a biomechanical problem not faced by quadrupeds. The solution to this problem has involved major changes in the form of the human pelvis and proximal femur (as well as structures more distal in the lower limb) from that of our primate quadrupedal contemporaries, and presumably ancestors (Le Gros Clark, 1959).
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The "radiator" theory of brain evolution is proposed to account for "mosaic evolution" whereby brain size began to increase rapidly in the genus Homo well over a million years after bipedalism had been selected for in early hominids. Because hydrostatic pressures differ across columns of fluid depending on orientation (posture), vascular systems of early bipeds became reoriented so that cranial blood flowed preferentially to the vertebral plexus instead of the internal jugular vein in response to gravity. The Hadar early hominids and robust australopithecines partly achieved this reorientation with a dramatically enlarged occipital/marginal sinus system. On the other hand, hominids in the gracile australopithecine through Homo lineage delivered blood to the vertebral plexus via a widespread network of veins that became more elaborate through time. Mastoid and parietal emissary veins are representatives of this network, and increases in their frequencies during hominid evolution are indicative of its development. Brain size increased with increased frequencies of mastoid and parietal emissary veins in the ineage leading to and including Homo, but remained conservative in the robust australopithecine lineage that lacked the network of veins. The brain is an extremely heat-sensitive organ and emissary veins in humans have been shown to cool the brain under conditions of hyperthermia. Thus, the network of veins in the lineage leading to Homo acted as a radiator that released a thermal constraint on brain size. The radiator theory is in keeping with the belief that basal gracile and basal robust australopithecines occupied distinct niches, with the former living in savanna mosaic habitats that were subject to hot temperatures and intense solar radiation during the day.
Article
The relationship between relative joint size and locomotor adaptations in living hominoids is examined using a variety of analytical strategies: narrow allometry, a priori geometrical adjustments, and empirical regression (allometric) adjustments. Regardless of method, the observation that emerges conspicuously is that modern humans possess exceptionally large hindlimb and lumbo-sacral joints for their body size. Full-time terrestrial bipedality precludes the sharing of weight support and propulsion with the forelimbs, and this fundamental difference from the other hominoids is reflected in the relative size of human hindlimb joints. Similar analyses including “Lucy” (A.L. 288-1, Australopithecus afarensis) suggest that a modest degree of hindlimb joint enlargement had already taken place at this point in hominid evolution, but that the highly-derived relative joint size characteristic of modern humans had not yet been achieved. This implies that the adaptation to terrestrial bipedalism in early hominids was far from complete and not functionally equivalent to the modern human condition. It is speculated that later enlargement of the hindlimb joints and elongation of the lower extremity represent a major adaptive shift linked to the advent of longer distance travel in human evolution.
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Brain tissue is metabolically expensive, but there is no significant correlation between relative basal metabolic rate and relative brain size in humans and other encephalized mammals. The expensive-tissue suggests that the metabolic requirements of relatively large brains are offset by a corresponding reduction of the gut. The splanchnic organs (liver and gastro-intestinal tract) are as metabolically expensive organs in the human body that is markedly small in relation to body size. Gut size is highly correlated with diet, and relatively small guts are compatible only with high-quality, easy-to-digest food. The often -cited relationship between diet and relative brain size is more properly viewed as a relationship between relative brain size and relative gut size, the latter being determined by dietary quality. No matter what is selecting for relatively large brains in humans and other primates, they cannot be achieved without a shift to a high-quality diet unless there is a rise in the metabolic rate. Therefore the incorporation of increasingly greater amounts of animal products into the diet was essential in the evolution of the large human brain.
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Numerous studies of the locomotor skeleton of the Hadar hominids have revealed traits indicative of both arboreal climbing/suspension and terrestrial bipedalism. These earliest known hominids must have devoted part of their activities to feeding, sleeping and/or predator avoidance in trees, while also spending time on the ground where they moved bipedally. In this paper we offer new data on phalangeal length and curvature, moφhology of the tarsus and metatarsophalangeal joints, and body proportions that further strengthen the argument for arboreality in the Hadar hominids. We also provide additional evidence on limb and pedal proportions and on the functional anatomy of the hip, knee and foot, indicating that the bipedality practiced at Hadar differed from that of modern humans. Consideration of the ecology at Hadar, in conjunction with modern primate models, supports the notion of arboreality in these earliest australopithecines. We speculate that selection for terrestrial bipedality may have intensified through the Plio-Pleistocene as forests and woodland patches shrunk and the need arose to move increasingly longer distances on the ground. Only with Homo erectus might body size, culture and other factors have combined to ‘release’ hominids from their dependence on trees.
Article
The “radiator” theory of brain evolution is proposed to account for “mosaic evolution” whereby brain size began to increase rapidly in the genus Homo well over a million years after bipedalism had been selected for in early hominids. Because hydrostatic pressures differ across columns of fluid depending on orientation (posture), vascular systems of early bipeds became reoriented so that cranial blood flowed preferentially to the vertebral plexus instead of the internal jugular vein in response to gravity. The Hadar early hominids and robust australopithecines partly achieved this reorientation with a dramatically enlarged occipital/marginal sinus system. On the other hand, hominids in the gracile australopithecine through Homo lineage delivered blood to the vertebral plexus via a widespread network of veins that became more elaborate through time. Mastoid and parietal emissary veins are representatives of this network, and increases in their frequencies during hominid evolution are indicative of its development. Brain size increased with increased frequencies of mastoid and parietal emissary veins in the lineage leading to and including Homo, but remained conservative in the robust australopithecine lineage that lacked the network of veins. The brain is an extremely heatsensitive organ and emissary veins in humans have been shown to cool the brain under conditions of hyperthermia. Thus, the network of veins in the lineage leading to Homo acted as a radiator that released a thermal constraint on brain size. The radiator theory is in keeping with the belief that basal gracile and basal robust australopithecines occupied distinct niches, with the former living in savanna mosaic habitats that were subject to hot temperatures and intense solar radiation during the day.
Article
A group of mathematical models has been devised to estimate the metabolic power requirement for any quadrupedal running gait. A previous model was restricted to bipedal running because extension to the quadrupedal case would have made the mathematics cumbersome. This has been avoided in the new models by using Fourier series to represent forces on the feet. In the previous model power requirements were inferred from fluctuations of kinetic and potential energy but this gave rise to ambiguities which are avoided in the new models by direct calculation of the power outputs of individual legs. The possible roles of tendon and muscle elasticity are explored by considering inelastic, perfectly elastic and imperfectly elastic models in turn. The power which would be required if the legs had n o mass, and the additional power required to swing the legs because they have mass, are considered separately. The models indicate that at low running speeds the amble and its reverse in time are the most economical gaits, the trot is rather more expensive and gallops are still more expensive. However, the models are restricted to two dimensions, and a three-dimensional model might show that the trot was the most economical gait. Most mammals trot at low running speeds. At high speeds gallops and most other asymmetrical gaits can be made as economical as the symmetrical gaits, by exerting appropriate patterns of force on the feet. The gallop is no more economical than most other gaits but it enables the muscles of the back and abdomen to contribute to the power needed for swinging the legs, which is large at high speeds. The predictions of the elastic models agree well with published observations of the oxygen consumption during trotting of fairly large mammals, but they are too low for small mammals.
Article
Primate stride lengths during quadrupedal locomotion are very long when compared to those of nonprimate quadrupedal mammals at the speed of trot/gallop transition. These exceptional lengths are a consequence of the relatively long limbs of primates and the large angular excursions of their limbs during quadrupedalism. When quadrupedal primates employ bipedal gaits they exhibit much lower angular excursions. Consequently their bipedal stride lengths do not appear to be exceptional in length when compared to other mammals. Angular excursions of the lower limbs of modern humans are not exceptionally large. However, when running, humans exhibit relatively long periods of flight (i.e., they have low duty factors) when compared to other mammals including primates. Because of these long periods of flight and their relative long lower limbs, humans have running stride lengths that are at the lower end of the range of stride lengths of quadrupedal primates. The stride length of the Laetoli hominid trails are evaluated in this context.
Article
A new theory is presented which describes quadrupedal as well as bipedal walking. It avoids errors which occurred in previous theories by evaluating separately the work done by each leg instead of deriving net work from mechanical energy fluctuations. It takes particular account of two parameters, the duty factor β (the fraction of the stride for which each foot is on the ground) and a parameter q which defines the time course of the force on each foot. It shows that for any given speed there is an optimum (β,q) which minimizes the energy cost of locomotion. These (β,q) are only a little different for bipeds and quadrupeds except near the critical speed at which the optimum moves abruptly from walking (high β) to running (low β). Walking men use (β, q) close to the theoretical optima, but with slightly higher q. Walking dogs and sheep use q which are lower than the optimum values except at very low speeds. Some of the energy which would otherwise be required for locomotion may be saved by storage of elastic strain energy in tendons etc. This mechanism is more effective in running than in fast walking, which may be why men change from walking to running at lower speeds than the inelastic theory suggests.
Article
The very broad pelvis of small early hominids (AL 288-1, STS 14, etc.) has previously been interpreted in obstetrical and biomechanical terms. However, neither of these considerations can explain the subsequent decrease in maximum pelvic breadth relative to stature in larger more recent hominids. It is shown here that this increase in relative linearity of the body with an increase in body size is consistent with basic thermoregulatory principles. Specifically, to maintain a constant surface area/body mass ratio, absolute body breadth should remain constant despite differences in body height. Variation among modern humans supports the prediction: populations living in the tropics vary greatly in stature, but show little variation in body breadth. In contrast, populations living in colder climates have absolutely wider bodies, and thus lower surface area/body mass, regardless of stature. All African early hominids—small australopithecines as well as the very tallHomo erectus KNM-WT 15000—have absolute body breadths within the modern human tropical-subtropical range; variations in relative body linearity are due almost entirely to variations in stature. A later hominid from a cold temperate climate (the Kebara 2 Neandertal) has an absolutely wide body, similar to living higher latitude populations. Thermoregulatory constraints on absolute body breadth, together with obstetric and biomechanical factors, may have contributed to the evolution of the rotational birth process and secondary altriciality with increased body and brain size inHomo erectus. Thermoregulatory considerations also suggest that AfricanH. erectus would most likely have been limited to relatively open/dry environments, while australopithecines could have inhabited either open/dry or closed/wet environments.
Article
The thermoregulatory advantages conferred by bipedalism to a large-brained primate on the African savannah could have been significant factors contributing to the adoption of this unusual mode of terrestrial locomotion. Although the major benefit is a dramatic reduction in direct solar radiation exposure, additional advantages also result from the higher distribution of the body surfaces. Windspeeds are higher and air temperatures lower away from the ground, both factors increasing the rate at which a biped dissipates heat by convection. The greater airflow and low relative humidity above any surface vegetation present will also increase the rate at which sweat can be evaporated from the skin.
Article
Homo erectus is notable for its taller stature and longer lower limbs relative to earlier hominids, but the selective pressures favoring such long limbs are unclear. Among anthropoid primates, patas monkeys (Erythrocebus patas) and extant hominids share several extreme characteristics involved with foraging and movement, including the relatively longest lower limb proportions, longest daily travel distances and largest home ranges for their body or group size, occupancy of some of the driest habitats, and very efficient thermoregulatory systems. We suggest that patas monkeys are an appropriate behavioral model with which to speculate on the selective pressures that might have operated on H. erectus to increase lower limb length. Here, in a comparison of the locomotor activities of patas monkeys and sympatric, closely related vervet monkeys (Cercopithecus aethiops), we provide evidence for the hypothesis that patas use their long stride more to increase foraging efficiency while walking than to run, either from predators or otherwise.
Article
The work done at each step during level walking and running to lift the centre of mass of the body, Wv, and to increase its forward speed, Wf, and the total mechanical energy involved (potential + kinetic) Wext, have been measured at various 'constant' speeds (2-32 km/hr) with the technique described by Cavagna (1975). 2. At intermediate speeds of walking (about 4 km/hr) Wv = Wf and Wext/km is at a minimum, as is the energy cost. At lower speeds Wv greater than Wf whereas at higher speeds Wf greather than Wv: in both cases Wext/km increases. 3. The recovery of mechanical energy, through the pendular motion characteristic of walking, was measured as (/Wv/ + /Wf/ - Wext)/(/Wv/ + /Wf/): it attains a maximum (about 65%) at intermediate speeds. 4. A simple model, assuming that in walking the body rotates as an inverted pendulum over the foot in contact with the ground, fits the experimental data better at intermediate speeds but is no longer tenable above 7 km/hr. 5. In running the recovery defined above is minimal (0-4% independent of speed), i.e. Wext congruent to /Wv/ + /Wf/: potential and kinetic energy of the body do not interchange but are simultaneously taken up and released by the muscles with a rate increasing markedly with the speed (from about 1 to 4 h.p.). 6. Wext increases linearly with the running speed Vf from a positive y intercept owing to the fact that Wv is practically constant independent of Vf. On the contrary, Wf = aVf2/(1 + bVf), where b is the ratio between the time spent in the air and the forward distance covered while on the ground during each step.
Article
Mechanical hypotheses concerning the function of chimpanzee anatomical specializations are examined in light of recent positional behavior data. Arm-hanging was the only common chimpanzee positional behavior that required full abduction of the humerus, and vertical climbing was the only distinctive chimpanzee positional behavior that required forceful retraction of the humerus and flexion of the elbow. Some elements of the chimpanzee anatomy, including an abductible humerus, a broad thorax, a cone-shaped torso, and a long, narrow scapula, are hypothesized to be a coadapted functional complex that reduces muscle action and structural fatigue during arm-hanging. Large muscles that retract the humerus (latissimus dorsi and probably sternocostal pectoralis major and posterior deltoid) and flex the elbow (biceps brachii, probably brachialis and brachioradialis) are argued to be adaptations to vertical climbing alone. A large ulnar excursion of the manus and long, curved metacarpals and phalanges are interpreted as adaptations to gripping vertical weight-bearing structures during vertical climbing and arm-hanging. A short torso, an iliac origin of the latissimus dorsi, and large muscles for arm-raising (caudal serratus, teres minor, cranial trapezius, and probably anterior deltoid and clavicular pectoralis major) are interpreted as adaptations to both climbing and unimanual suspension.
Article
The relationships between muscle fibre characteristics and the physical performance capacity of trained athletic boys (aged 11-13 years) were studied over 2 days. The subjects were divided into two groups according to muscle fibre distribution. The 'fast' group (FG) comprised 10 subjects (sprinters, weightlifters, tennis players) with more than 50% fast-twitch fibres (type II), and the 'slow' group (SG) comprised 8 subjects (endurance runners, tennis players, one weightlifter) with more than 50% slow-twitch fibres (type I) in their vastus lateralis muscle. The 'fast' group had 59.2 +/- 6.3% and the 'slow' group had 39.4 +/- 9.8% type II fibres. Other clear differences (P less than 0.05-0.01) between the groups were observed as regards reaction time, rate of force development and rise of the body's centre of gravity in the squatting jump. For these variables, the 'fast' group was superior to the 'slow' group. Muscle fibre distribution (% type II) correlated (P less than 0.05-0.01) negatively with reaction time. Muscle fibre area (% type II) correlated negatively with reaction time (P less than 0.05-0.001) and positively with chronological age (P less than 0.05) height (P less than 0.05), mass (P less than 0.001), serum testosterone (P less than 0.05), force production (P less than 0.05-0.01) and blood lactate (P less than 0.05) in the 60-s maximal anaerobic test. There were no significant correlations between muscle fibre characteristics and maximal oxygen uptake. The present study assumes that heredity partly affects the selection of sporting event. Growth, development and training are associated with muscle fibre area, which affects the physical performance capacity of the neuromuscular system in trained young boys.
Article
Energy can be saved in terrestrial locomotion in many different ways. The maximum shortening speeds (Vmax) of the muscles can be adjusted to their optimum values for the tasks required of them. The moments exerted by the muscles at different joints can be adjusted to keep the ground force in line with the leg so that muscles do not work against each other. The joints of the legs can be kept as straight as possible, minimizing muscle forces and work requirements. Walking gaits should be selected at low Froude numbers (a dimensionless speed parameter) and running gaits at high Froude numbers. Tendon and other springs can be used to store elastic strain energy and to return it by elastic recoil. This paper aims to show how these energy-saving mechanisms work and to what extent mammals exploit them. Arguments based on our rather limited knowledge of the relationship between the mechanical performance of muscle and its metabolic energy consumption are used throughout. They suggest that muscles that are optimally adapted for their tasks in running should do positive work with constant efficiency.
Article
As shown by statistical evaluation carried out within various animal species (e.g. ruminants, equids, carnivores and proboscidates) the thickness of elastic fibres of the nuchal ligament is a specific character, i.e. unrelated to the somatic size of taxonomically different specimens. On the whole, ruminants are characterized by thicker elastic fibres than those from equids and carnivores. Moreover, within ruminants a correlation between the thickness of elastic fibres and body size has consistently been found. However, this condition occurs only when comparison between zoologically related species is drawn. During postnatal growth clearcut structural changes were brought to light, represented by the following phenomena simultaneously taking place: a) increase in thickness and lenght of preexisting elastic fibres; b) a progressive increase in the number of fibre splittings as well as of collaterals given off by individual fibres along their extension; c) neoformation of elastic fibres, and their addition to preexisting ones. In the bovines, already at six months of postnatal life, the elastic fibres of larger caliber have attained their full size.
Article
Calcanei from African apes, modern humans, and Australopithecus afarensis are compared to investigate the anatomical and mechanical changes that occurred in this bone as a result of the transition to terrestrial bipedality. Features analyzed include the cross-sectional area and volume of the calcaneal tuber, the geometry and orientation of the articular surfaces, and the surface topography of the calcaneal corpus. Calcaneal morphology is unequivocal in its partitioning of quadrupedal pongids and bipedal hominids.
Article
In this study we investigate how speed and stride frequency change with body size. We use this information to define 'equivalent speeds' for animals of different size and to explore the factors underlying the six-fold difference in mass-specific energy cost of locomotion between mouse- and horse-sized animals at these speeds. Speeds and stride frequencies within a trot and a gallop were measured on a treadmill in 16 species of wild and domestic quadrupeds, ranging in body size from 30 g mice to 200 kg horses. We found that the minimum, preferred and maximum sustained speeds within a trot and a gallop all change in the same rather dramatic manner with body size, differing by nine-fold between mice and horses (i.e. all three speeds scale with about the 0.2 power of body mass). Although the absolute speeds differ greatly, the maximum sustainable speed was about 2.6-fold greater than the minimum within a trot, and 2.1-fold greater within a gallop. The frequencies used to sustain the equivalent speeds (with the exception of the minimum trotting speed) scale with about the same factor, the -0.15 power of body mass. Combining this speed and frequency data with previously published data on the energetic cost of locomotion, we find that the mass-specific energetic cost of locomotion is almost directly proportional to the stride frequency used to sustain a constant speed at all the equivalent speeds within a trot and a gallop, except for the minimum trotting speed (where it changes by a factor of two over the size range of animals studied). Thus the energy cost per kilogram per stride at five of the six equivalent speeds is about the same for all animals, independent of body size, but increases with speed: 5.0 J kg-1 stride-1 at the preferred trotting speed; 5.3 J kg-1 stride-1 at the trot-gallop transition speed; 7.5 J kg-1 stride-1 at the preferred galloping speed; and 9.4 J kg-1 stride-1 at the maximum sustained galloping speed. The cost of locomotion is determined primarily by the cost of activating muscles and of generating a unit of force for a unit of time. Our data show that both these costs increase directly with the stride frequency used at equivalent speeds by different-sized animals. The increase in cost per stride with muscles (necessitating higher muscle forces for the same ground reaction force) as stride length increases both in the trot and in the gallop.
Article
Functional morphologists have traditionally regarded cost of locomotion as an important influence on the design of locomotor structures. If cost of locomotion is an important constraint in the natural selection of these structures, it should be possible to show that animals differing in limb morphology also differ in their locomotor costs. In previous experiments on three species of cursorial mammals differing considerably in limb structure, no such differences were detected. Since the factors that determine the rate of energy consumption of a running animal are not well understood, we felt that the effect of limb morphology on cost could best be examined in a system in which only the inertial properties of limbs were varied while other factors remained constant. Consequently, we have measured changes in the rate of energy consumption of running human subjects produced by artificial alterations in limb inertial properties. Other variables that might influence cost have been controlled. We found that the cost of adding a given mass to the limbs is significantly greater than adding it to the centre of mass and that this effect becomes more pronounced as the limb loads are moved distally. Thus a clear effect of limb mass and its distribution on cost of locomotion has been demonstrated.
Article
Disagreement exists over whether man's bipedal form of locomotion evolved as an economical means for covering long distances. There is also some disagreement about the energetic price man had to pay to free his hands. In an investigation of the relative energetic cost of bipedal and quadrupedal locomotion in primates, chimpanzees (Pan troglodytes) and capuchin monkeys (Cebus capucinus) were trained to run on a treadmill either on two or on four legs while their oxygen consumption was being measured. Both primates expend the same amount of energy whether running on two or on four legs. The relative energy cost of bipedal versus quadrupedal running should not be used in arguments about the evolution of bipedal locomotion in man.
Article
The postcranial skeleton of Australopithecus afarensis from the Hadar Formation, Ethiopia, and the footprints from the Laetoli Beds of northern Tanzania, are analyzed with the goal of determining (1) the extent to which this ancient hominid practiced forms of locomotion other than terrestrial bipedality, and (2) whether or not the terrestrial bipedalism of A. afarensis was notably different from that of modern humans. It is demonstrated that A. afarensis possessed anatomic characteristics that indicate a significant adaptation for movement in the trees. Other structural features point to a mode of terrestrial bipedality that involved less extension at the hip and knee than occurs in modern humans, and only limited transfer of weight onto the medial part of the ball of the foot, but such conclusions remain more tentative than that asserting substantive arboreality. A comparison of the specimens representing smaller individuals, presumably female, to those of larger individuals, presumably male, suggests sexual differences in locomotor behavior linked to marked size dimorphism. The males were probably less arboreal and engaged more frequently in terrestrial bipedalism. In our opinion, A. afarensis from Hadar is very close to what can be called a "missing link." We speculate that earlier representatives of the A. afarensis lineage will present not a combination of arboreal and bipedal traits, but rather the anatomy of a generalized ape.
Article
A male hominine partial hip bone, KNM -ER 3228, from East Lake Turkana , Kenya is described. In most of its features this specimen resembles modern human male hip bones. This is especially true for functional features related to weight transfer from the trunk to the pelvis and within the pelvis, and to the effective action of musculature arising from the pelvis during the performance of the modern human type of bipedalism . KNM -ER 3228 is very similar to the Olduvai Hominid 28 and the Arago XLIV hip bones, both attributed to Homo erectus .
Article
This series of four papers investigates the link between the energetics and the mechanics of terrestrial locomotion. Two experimental variables are used throughout the study : speed and body size. Mass-specific metabolic rates of running animals can be varied by about tenfold using either variable. This first paper considers metabolic energy consumed during terrestrial locomotion. New data relating rate of oxygen consumption and speed are reported for: eight species of wild and domestic artiodactyls; seven species of carnivores ; four species of primates ; and one species of rodent. These are combined with previously published data to formulate a new allometric equation relating mass-specific rates of oxygen consumed during locomotion at a constant speed to speed and body mass (based on data from 62 avian and mammalian species): where has the units ml O2 s−1 kg−1; Mb is in kg; and vg is in m s−1. This equation can be expressed in terms of mass-specific rates of energy consumption (Ėmetab/Mb) using the energetic equivalent of 1 ml O2 = 20·1 J because the contribution of anaerobic glycolysis was negligible : where Ėmetab/Mb has the units watts/kg. This new relationship applies equally well to bipeds and quadrupeds and differs little from the allometric equation reported 12 years ago by Taylor, Schmid-Nielsen & Raab (1970). Ninety per cent of the values calculated from this general equation for the diverse assortment of avian and mammalian species included in this regression fall within 25 % of the observed values at the middle of the speed range where measurements were made. This agreement is impressive when one considers that mass-specific rates of oxygen consumption differed by more than 1400% over this size range of animals.
Article
The switching point from nasal to oronasal breathing during incrementally graded submaximal exercise was determined in 30 (14 M, 16 F) healthy adult volunteers. Nasal airflow was measured by a pneumotachograph attached to a nasal mask. Oral airflow was determined as the difference between nasal airflow and total pulmonary airflow, the latter being measured by a head-out exercise body plethysmograph. The airflow and pressure signals were sampled every 20 msec by a micropressor, which calculated respiratory volumes and nasal work of breathing, and produced an on-line print-out. Twenty of the 30 subjects (normal augmenters) switched from nasal to oronasal breathing at submaximal exercise of 105.0 W (SD = 30.1), four subjects (mouth breathers) breathed habitually oronasally, five subjects (nose breathers) persistently breathed through the nose only, and one subject showed no consistent nose/mouth breathing pattern. In normal augmenters, the onset of oronasal breathing (VE 35.3 +/- 10.81 . min-1) was quite consistent individually, but varied considerably between inividuals without showing a significant sex difference. The factors most closely related to the switching point were rating of perceived exertion of breathing and nasal work of breathing.
Article
Four articulating hominid foot bones have been recovered from Sterkfontein Member 2, near Johannesburg, South Africa. They have human features in the hindfoot and strikingly apelike traits in the forefoot. While the foot is manifestly adapted for bipedalism, its most remarkable characteristic is that the great toe (hallux) is appreciably medially diverged (varus) and strongly mobile, as in apes. Possibly as old as 3.5 million years, the foot provides the first evidence that bipedal hominids were in southern Africa more than 3.0 million years ago. The bones probably belonged to an early member of Australopithecus africanus or another early hominid species.