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Human Foot (human + foot)
Selected AbstractsA new family of hybrid 4-DOF parallel mechanisms with two platforms and its application to a footpad deviceJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 5 2005Jungwon Yoon This paper proposes a new family of 4-degrees-of-freedom (DOF) parallel mechanisms with two platforms and its application to a footpad device that can simulate the spatial motions of the human foot. The new mechanism consists of front and rear platforms, and three limbs. Two limbs with 6-DOF serial joints (P -S-P-P) are attached to each platform and are perpendicular to the base plate, while the middle limb is attached to the revolute joint that connects the front and rear platforms. The middle limb is driven by the 2-DOF driving mechanism that is equivalent to active serial prismatic and revolute joints (Pe - Re), or prismatic and prismatic joints (Pe - Pe) with two base-fixed prismatic actuators. Since the middle limb perpendicular to the base plate has 3-DOF serial joints (Pe - Re -R or Pe - Pe -R), two new 4-DOF parallel mechanisms with two platforms can generate pitch motion of each platform, and roll and heave motions (1T-3R) or pitch motion of each platform and two translational motions (2T-2R) at both platforms, according to the type of the 2-DOF driving mechanism. Kinematic analyses of the 1T-3R mechanism were performed, including inverse and forward kinematics and velocity analysis. Based on the 1T-3R mechanism, a footpad device was designed to generate foot trajectories for natural walking. © 2005 Wiley Periodicals, Inc. [source] Apparent density of the primate calcaneo-cuboid joint and its association with locomotor mode, foot posture, and the "midtarsal break"AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Matthew G. Nowak Abstract Primates use a range of locomotor modes during which they incorporate various foot postures. Humans are unique compared with other primates in that humans lack a mobile fore- and midfoot. Rigidity in the human foot is often attributed to increased propulsive and stability requirements during bipedalism. Conversely, fore- and midfoot mobility in nonhuman primates facilitates locomotion in arboreal settings. Here, we evaluated apparent density (AD) in the subchondral bone of human, ape, and monkey calcanei exhibiting different types of foot loading. We used computed tomography osteoabsorptiometry and maximum intensity projection (MIP) maps to visualize AD in subchondral bone at the cuboid articular surface of calcanei. MIPs represent 3D volumes (of subchondral bone) condensed into 2D images by extracting AD maxima from columns of voxels comprising the volumes. False-color maps are assigned to MIPs by binning pixels in the 2D images according to brightness values. We compared quantities and distributions of AD pixels in the highest bin to test predictions relating AD patterns to habitual locomotor modes and foot posture categories of humans and several nonhuman primates. Nonhuman primates exhibit dorsally positioned high AD concentrations, where maximum compressive loading between the calcaneus and cuboid likely occurs during "midtarsal break" of support. Humans exhibit less widespread areas of high AD, which could reflect reduced fore- and midfoot mobility. Analysis of the internal morphology of the tarsus, such as subchondral bone AD, potentially offers new insights for evaluating primate foot function during locomotion. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] Brief communication: Dynamic plantar pressure distribution during locomotion in Japanese macaques (Macaca fuscata)AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Eishi Hirasaki Abstract To better place the form and motion of the human foot in an evolutionary context, understanding how foot motions change when quadrupeds walk bipedally can be informative. For this purpose, we compared the pressures beneath the foot during bipedal and quadrupedal walking in Japanese macaques (Macaca fuscata). The pressure at nine plantar regions was recorded using a pressure mat (120 Hz), while the animals walked on a level walkway at their preferred speeds. The results revealed substantial differences in foot use between the two modes of locomotion, and some features observed during bipedal walking resembled human gait, such as the medial transfer of the center of pressure (COP), abrupt declines in forefoot pressures, and the increased pressure beneath the hallux, all occurring during the late-stance phase. In particular, the medial transfer of the COP, which is also observed in bonobos (Vereecke et al.: Am J Phys Anthropol 120 (2003) 373,383), was due to a biomechanical requirement for a hind limb dominant gait, such as bipedal walking. Features shared by bipedal and quadrupedal locomotion that were quite different from human locomotion were also observed: the heel never contacted the ground, a foot longitudinal arch was absent, the hallux was widely abducted, and the functional axis was on the third digit, not the second. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] On the nature and evolution of the neural bases of human languageAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue S35 2002Philip Lieberman Abstract The traditional theory equating the brain bases of language with Broca's and Wernicke's neocortical areas is wrong. Neural circuits linking activity in anatomically segregated populations of neurons in subcortical structures and the neocortex throughout the human brain regulate complex behaviors such as walking, talking, and comprehending the meaning of sentences. When we hear or read a word, neural structures involved in the perception or real-world associations of the word are activated as well as posterior cortical regions adjacent to Wernicke's area. Many areas of the neocortex and subcortical structures support the cortical-striatal-cortical circuits that confer complex syntactic ability, speech production, and a large vocabulary. However, many of these structures also form part of the neural circuits regulating other aspects of behavior. For example, the basal ganglia, which regulate motor control, are also crucial elements in the circuits that confer human linguistic ability andreasoning. The cerebellum, traditionally associated with motor control, is active in motor learning. The basal ganglia are also key elements in reward-based learning. Data from studies of Broca's aphasia, Parkinson's disease, hypoxia, focal brain damage, and a genetically transmitted brain anomaly (the putative "language gene," family KE), and from comparative studies of the brains and behavior of other species, demonstrate that the basal ganglia sequence the discrete elements that constitute a complete motor act, syntactic process, or thought process. Imaging studies of intact human subjects and electrophysiologic and tracer studies of the brains and behavior of other species confirm these findings. As Dobzansky put it, "Nothing in biology makes sense except in the light of evolution" (cited in Mayr, 1982). That applies with as much force to the human brain and the neural bases of language as it does to the human foot or jaw. The converse follows: the mark of evolution on the brains of human beings and other species provides insight into the evolution of the brain bases of human language. The neural substrate that regulated motor control in the common ancestor of apes and humans most likely was modified to enhance cognitive and linguistic ability. Speech communication played a central role in this process. However, the process that ultimately resulted in the human brain may have started when our earliest hominid ancestors began to walk. Yrbk Phys Anthropol 45:36,62, 2002. © 2002 Wiley-Liss, Inc. [source] Visual guidance of the human foot during a stepTHE JOURNAL OF PHYSIOLOGY, Issue 2 2005Raymond F. Reynolds When the intended foot placement changes during a step, either due to an obstacle appearing in our path or the sudden shift of a target, visual input can rapidly alter foot trajectory. However, previous studies suggest that when intended foot placement does not change, the path of the foot is fixed after it leaves the floor and vision has no further influence. Here we ask whether visual feedback can be used to improve the accuracy of foot placement during a normal, unperturbed step. To investigate this we measured foot trajectory when subjects made accurate steps, at fast and slow speeds, to stationary floor-mounted targets. Vision was randomly occluded in 50% of trials at the point of foot-off. This caused an increase in foot placement error, reflecting lower accuracy and higher variability. This effect was greatest for slow steps. Trajectory heading analysis revealed that visually guided corrections occurred as the foot neared the target (on average 64 mm away). They occurred closer to the target for the faster movements thus allowing less time and space to execute corrections. However, allowing for a fixed reaction time of 120 ms, movement errors were detected when the foot was approximately halfway to the target. These results suggest that visual information can be used to adjust foot trajectory during the swing phase of a step when stepping onto a stationary target, even for fast movements. Such fine control would be advantageous when environmental constraints place limitations on foot placement, for example when hiking over rough terrain. [source] | ||||||||||