Human Bipedal Locomotion Research Articles

Higher coactivations of lower limb muscles increase stability during walking on slippery ground in forward dynamics musculoskeletal simulation

The energy efficiency theory of human bipedal locomotion has been widely accepted as a neuro-musculoskeletal control method. However, coactivation of agonist and antagonist muscles in the lower limb has been observed during various limb movements, including walking. The emergence of this coactivation cannot be explained solely by the energy efficiency theory and remains a subject of debate. To shed light on this, we investigated the role of muscle coactivations in walking stability using a forward dynamics musculoskeletal simulation combined with neural-network-based gait controllers. Our study revealed that a gait controller with minimal muscle activations had a high probability of falls under challenging gait conditions such as slippery ground and uneven terrain. Lower limb muscle coactivations emerged in the process of gait controller training on slippery ground. Controllers with physiological coactivation levels demonstrated a significantly reduced probability of falls. Our results suggest that achieving stable walking requires muscle coactivations beyond the minimal level of muscle energy. This study implies that coactivations likely emerge to maintain gait stability under challenging conditions, and both coactivation and energy optimization of lower limb muscles should be considered when exploring the foundational control mechanisms of human walking.

INSPIIRE - A Modular and Passive Exoskeleton to Investigate Human Walking and Balance.

Powered exoskeletons for SCI patients are mainly limited by their inability to balance dynamically during walking. To investigate and understand the control strategies of human bipedal locomotion, we developed INSPIIRE, a passive exoskeleton. This device constrains the movements of able-bodied subjects to only hip and knee flexions and extensions, similar to most current active exoskeletons. In this paper, we detail the modular design and the mechanical implementation of the device. In preliminary experiments, we tested whether humans are able to handle dynamic walking without crutches, despite the limitation of lateral foot placement and locked ankles. Five healthy subjects showed the ability to stand and ambulate at an average speed of 1 m/s after 5 minutes of self-paced training. We found that while the hip abduction/adduction is constrained, the foot placement was made possible thanks to the pelvis yaw and residual flexibility of the exoskeleton segments in the lateral plan. This result points out that INSPIIRE is a reliable instrument to learn sagitally-constrained human locomotion, and the potential of investigating more dynamic walking, which is shown as possible in this implementation, even if only flexion/extension of the hip and knee are allowed.

Achilles' new heel: Shock absorbing, gait assisting and energy harvesting

Humans have evolved to walk highly efficiently to conserve energy, making it challenging to develop assistive and energy-harvesting devices for walking. Herein, we report a heel pad-based assistance device for walking that not only optimizes the energetic economy of walking and prevents plantar fasciitis but also harvests energy from heel impact. Our footwear-embedded device improves the walking economy by offering shock absorption and walking assistance, while simultaneously providing energy-harvesting functions. We demonstrate that the use of our device reduces the activation of the gastrocnemius and soleus muscles during the foot strike by 5.8 ± 1.0 % and 4.1 ± 0.6 %, respectively. The collisional energy conserved from the impact at the touchdown is transformed into 3.8 ± 0.3 watts of electrical power (mean ± SEM). Compared with walking in normal shoes, the energy savings with the device imply that walking endurance could be increased by as much as 10 % without extra effort from the wearer. Our findings demonstrate the potential of the heel pad-based device that enhances the energy economy of walking and human bipedal locomotion.

Calcaneofibular ligament may act as a tensioner of peroneal tendons as revealed by a contactless three-dimensional scan system on cadavers

The ligaments are believed to have a role in stabilizing joints and regulating joint motion. Here, we propose a novel function of the calcaneofibular ligament (CFL), which stabilizes the ankle joint. In human bipedal locomotion, the peroneal muscles maintain mediolateral stability and prevent involuntary ankle inversion. To investigate the functional relationship between the peroneal longus tendon (PLT), brevis tendon (PBT), and CFL, we quantitatively analyzed the positional changes of the tendons by using a contactless three-dimensional optical scan system. Eighteen cadaveric specimens were included in the study. Interestingly, with increased tension of the CFL, the tendons significantly moved toward the lateral direction (P < 0.001), compared with their position when the CFL was detached. The actual lift amount reached 2.0 ± 0.8 mm for the PLT and 1.9 ± 1.0 mm for the PBT. These results strongly suggest that a tensed CFL can lift the peroneal tendons and may act as a “tensioner” for the effective transmission of muscle contraction. This phenomenon contributes to postural control, especially in regaining balance on uneven terrain, and provides a new perspective for the exercise methods or understanding the ankle joint instability due to sprains.

An Evolutionary Adolescent Idiopathic Scoliosis Etiology Spine-Limbs Links, Inspiration and Laterality as Basic Factors

Moving on an evolutionary sight, this article individualizes three basic human causative factors in adolescent idiopathic scoliosis developing inspiration, bipedal locomotion and lateralities. The integrative approach considers the neuromechanical coupling in respiration, introducing the concept of pneumofascial competition (section one) as the loop that occurs between inspired air and pleural fasciae and then global myofascia. Affordances (possibilities) and constraints of respiratory system match positions and movements of whole body, where the links between spine and periphery (limbs and head) play a determinant part: these connections, the one that involves the spinal transverse plane, are worked out in section two. Therefore, section two appears a decisive step in trying to solve some questions about human bipedal locomotion and its proficiency, again in a neuromechanical coupling view, with totally original considerations about the role of scapula and about the spine as a treble torsion spring. Finally, it is possible to trace out a new adolescent idiopathic scoliosis etiology (section three), adding a third factor: laterality. What is only human is the hyper stressed lateralization (s) by means of cultural requirements. The motor hyper specialization is another form of energy saving (automatism). Thus, all the article is about the evolutionary principle of costs minimizing. Adolescent idiopathic scoliosis is here seen as an evolutionary mismatch disease between human nature and human culture and every curve can be explained in an integrative way, where causes and effects develop a mutual self-powering cycle.

Energetic costs of hindlimb‐dominated locomotion in sifakas (Propithecus verreauxi)

Human bipedal locomotion is unique, requiring a suite of musculoskeletal adaptations that were acquired gradually throughout hominin evolution. For example, lordotic lumbar spines move the center of mass over the hip joint and resists axial compression, short, laterally‐oriented iliac blades increase the leverage of the hip extensors and abductors, and the adducted hallux facilitates weight transfer during a propulsive toe‐off. Sifakas and other primates occasionally move bipedally in the wild, especially in terrestrial settings, but because they lack specialized anatomy, bipedal locomotion should be less efficient. In this study we test the hypothesis that energy costs differ among sifaka locomotor modes and predict that terrestrial bipedal locomotion is associated with greater energy expenditure than their more habitual mode of arboreal locomotion, vertical clinging and leaping. Bipedal (n=77) and vertical clinging and leaping (n=74) gait cycles were filmed in nine sifakas at the Duke Lemur Center. Locomotor data (stride length, peak body height of the cycle, and velocity) were measured from these videos using ImageJ and used to calculate energy expenditure using published equations. Linear mixed models were used to statistically test the differences in energy expenditure between locomotor modes while accounting for the effects of velocity and repeatedly measuring the same individuals. Results demonstrate that the cost of bipedalism is significantly greater than that of vertical clinging and leaping (p&lt;0.0001). This result supports the idea that the locomotor adaptations in the hominin musculoskeletal system reduce the cost of locomoting bipedally. Furthermore, because sifakas rely on bipedal locomotion in terrestrial settings, these results have conservation implications for understanding the energetic demands of sifaka locomotion in deforested habitats.

Human plantar fascial dimensions and shear wave velocity change in vivo as a function of ankle and metatarsophalangeal joint positions.

The plantar fascia (PF), a primary contributor of the foot arch elasticity, may experience slack, taut, and stretched states depending on the ankle and metatarsophalangeal (MTP) joint positions. Since PF has proximodistal site difference in its dimensions and stiffness, the response to applied tension can also be site specific. Furthermore, PF can contribute to supporting the foot arch while being stretched beyond the slack length, but it has never been quantitatively evaluated in vivo. This study investigated the effects of the ankle and MTP joint positions on PF length and localized thickness and shear wave velocity (SWV) at three different sites from its proximal to distal end using magnetic resonance and supersonic shear imaging techniques. During passive ankle dorsiflexion, rise of SWV, an indication of slack length, was observed at the proximal site when the ankle was positioned by 10°-0° ankle plantar flexion with up to 3 mm (+1.5%) increase in PF length. On the other hand, SWV increased at the distal site when MTP joint dorsiflexed 40° with the ankle 30°-20° plantar flexion, and in this position, PF was lengthened up to 4 mm (+2.3%). Beyond the slack length, SWV curvilinearly increased at all measurement sites toward the maximal dorsiflexion angle whereas PF lengthened up to 9 mm (+7.6%) without measurable changes in its thickness. This study provides evidence that the dimensions and SWV of PF change in a site-specific manner depending on the ankle and MTP joint positions, which can diversify foot arch elasticity during human locomotion.NEW & NOTEWORTHY Joint angle dependence and site specificity of the plantar fascial dimensions and SWV were examined by combining sagittal magnetic resonance and supersonic shear imaging techniques. We revealed that the site-specific changes in PF SWV were related to joint angle positions, i.e., PF slackness and elasticity changed in varying combinations of ankle and MTP angle. Our findings suggest that PF can elastically support the foot arch throughout the stance phase of human bipedal locomotion.

A mechanistic approach for the calculation of intervertebral mobility in mammals based on vertebrae osteometry.

In this paper, we develop and validate an osteometry-based mechanistic approach to calculation of available range of motion (aROM) in presacral intervertebral joints in sagittal bending (SB), lateral bending (LB), and axial rotation (AR). Our basic assumption was the existence of a mechanistic interrelation between the geometry of zygapophysial articular facets and aROM. Trigonometric formulae are developed for aROM calculation, of which the general principle is that the angle of rotation is given by the ratio of the arc length of motion to the radius of this arc. We tested a number of alternative formulae against available in vitro data to identify the most suitable geometric ratios and coefficients for accurate calculation. aROM values calculated with the developed formulae show significant correlation with in vitro data in SB, LB, and AR (Pearson r=0.900) in the reference mammals (man, sheep, pig, cow). It was found that separate formulae for different zygapophysial facet types (radial (Rf), tangential (Tf), radial with a lock (RfL)) give significantly greater accuracy in aROM calculation than the formulae for the presacral spine as a whole and greater accuracy than the separate formulae for different spine regions (cervical, thoracic, lumbar). The advantage of the facet-specific formulae over the region-specific ones shows that the facet type is a more reliable indicator of the spine mobility than the presence or absence of ribs. The greatest gain in calculation accuracy with the facet-specific formulae is characteristic in AR aROM. The most important theoretical outcome is that the evolutionary differentiation of the zygapophysial facets in mammals, that is the emergence of Tf joints in the rib cage area of the spine, was more likely associated with the development of AR rather than with SB mobility and, hence, with cornering rather than with forward galloping. The AR aROM can be calculated with the formulae common for man, sheep, pig, and cow. However, the SB aROM of the human spine is best calculated with different coefficient values in the formulae than those for studied artiodactyls. The most suitable coefficient values indicate that the zygapophysial articular facets tend to slide past each other to a greater extent in the human thoracolumbar spine rather than in artiodactyls. Due to this, artiodactyls retain relatively greater facet overlap in extremely flexed and extremely extended spine positions, which may be more crucial for their quadrupedal gallop than for human bipedal locomotion. The SB, LB, and AR aROMs are quite separate in respect of the formulae structure in the cervical region (radial facet type). However, throughout the thoracolumbar spine (tangential and radial with lock facets), the formulae for LB and AR are basically similar differing in coefficient values only. This means that, in the thoracolumbar spine, the greater the LB aROM, the greater the AR aROM, and vice versa. The approach developed promises a wide osteological screening of extant and extinct mammals to study the sex, age, geographical variations, and disorders.

Stiffness of the human foot and evolution of the transverse arch.

The stiff human foot enables an efficient push-off when walking or running, and was critical for the evolution of bipedalism1-6. The uniquely arched morphology of the human midfoot is thought to stiffen it5-9, whereas other primates have flat feet that bend severely in the midfoot7,10,11. However, the relationship between midfoot geometry and stiffness remains debated in foot biomechanics12,13, podiatry14,15 and palaeontology4-6. These debates centre on the medial longitudinal arch5,6 and have not considered whether stiffness is affected by the second, transverse tarsal arch of the human foot16. Here we show that the transverse tarsal arch, acting through the inter-metatarsal tissues, is responsible for more than 40% of the longitudinal stiffness of the foot. The underlying principle resembles a floppy currency note that stiffens considerably when it curls transversally. We derive a dimensionless curvature parameter that governs the stiffness contribution of the transverse tarsal arch, demonstrate its predictive power using mechanical models of the foot and find its skeletal correlate in hominin feet. In the foot, the material properties of the inter-metatarsal tissues and the mobility of the metatarsals may additionally influence the longitudinal stiffness of the foot and thus the curvature-stiffness relationship of the transverse tarsal arch. By analysing fossils, we track the evolution of the curvature parameter among extinct hominins and show that a human-like transverse arch was a key step in the evolution of human bipedalism that predates the genus Homo by at least 1.5million years. This renewed understanding of the foot may improve the clinical treatment of flatfoot disorders, the design of robotic feet and the study of foot function in locomotion.

Anodal transcranial patterned stimulation of the motor cortex during gait can induce activity-dependent corticospinal plasticity to alter human gait

The corticospinal system and local spinal circuits control human bipedal locomotion. The primary motor cortex is phase-dependently activated during gait; this cortical input is critical for foot flexor activity during the swing phase. We investigated whether gait-combined rhythmic brain stimulation can induce neuroplasticity in the foot area of the motor cortex and alter gait parameters. Twenty-one healthy subjects participated in the single-blinded, cross-over study. Each subject received anodal transcranial patterned direct current stimulation over the foot area of the right motor cortex during gait, sham stimulation during gait, and anodal transcranial patterned direct current stimulation during rest in a random order. Six subjects were excluded due to a failure in the experimental recording procedure. Complete-case analysis was performed using the data from the remaining 15 subjects. Self-paced gait speed and left leg stride length were significantly increased after the stimulation during gait, but not after the sham stimulation during gait or the stimulation during rest. In addition, a significant increase was found in the excitability of the corticospinal pathway of the left tibialis anterior muscle 30 min after stimulation during gait. Anodal transcranial patterned direct current stimulation during gait entrained the gait cycle to enhance motor cortical activity in some subjects. These findings suggest that the stimulation during gait induced neuroplasticity in corticospinal pathways driving flexor muscles during gait.

Earliest Known Hominin Calcar Femorale in Orrorin tugenensis Provides Further Internal Anatomical Evidence for Origin of Human Bipedal Locomotion.

The calcar femorale (CF), a plate of dense bone internal to the lesser trochanter, is visible on computed tomographic images of the 6 million-year-old femoral fragment BAR 1003'00 (from the taxon Orrorin tugenensis), among the oldest specimens relevant to reconstructing the evolution of human bipedal locomotion. A strongly expressed CF has been used previously as an indicator of bipedality. If true, then there should be a quantifiable difference in the CF among hominoids. Absolute and normalized CF lengths were measured from computed tomographic images at five anatomical locations along the proximal portion of BAR 1003'00 in addition to samples of nine H. sapiens and ten P. troglodytes femora. The span of the CF superiorly to inferiorly within the proximal femur was measured by counting the number of cross-sections on which the CF occurred. A Bayesian approach was used to classify the BAR 1003'00 sample based on normalized lengths. The P. troglodytes femora were more variable both in the occurrence of the trait and, where present, its span in the proximal femur. The H. sapiens sample exhibited CF lengths that were consistently larger at each location than the P. troglodytes in absolute terms, but the normalized lengths overlap substantially. The Bayesian posterior probability test classifies the CF of BAR 1003'00 with H. sapiens. The BAR 1003'00's calcar femorale has a strong anatomical similarity to the H. sapiens sample, supporting the conclusion that O. tugenensis is an early bipedal hominin. Anat Rec, 301:1834-1839, 2018. © 2018 Wiley Periodicals, Inc.

Bipedal gait versatility in the Japanese macaque (Macaca fuscata)

It was previously believed that, among primates, only humans run bipedally. However, there is now growing evidence that at least some non-human primates can not only run bipedally but can also generate a running gait with an aerial phase. Japanese macaques trained for bipedal performances have been known to exhibit remarkable bipedal locomotion capabilities, but no aerial-phase running has previously been reported. In the present study, we investigated whether Japanese macaques could run with an aerial phase by collecting bipedal gait sequences from three macaques on a level surface at self-selected speeds (n = 188). During our experiments, body kinematics and ground reaction forces were recorded by a motion-capture system and two force plates installed within a wooden walkway. Our results demonstrated that macaques were able to utilize a variety of bipedal gaits including grounded running, skipping, and even running with an aerial phase. The self-selected bipedal locomotion speed of the macaques was fast, with Froude speed ranging from 0.4 to 1.3. However, based on congruity, no single trial that could be categorized as a pendulum-like walking gait was observed. The parameters describing the temporal, kinematic, and dynamic characteristics of macaque bipedal running gaits follow the patterns previously documented for other non-human primates and terrestrial birds that use running gaits, but are different from those of humans and from birds' walking gaits. The present study confirmed that when a Japanese macaque engages in bipedal locomotion, even without an aerial phase, it generally utilizes a spring-like running mechanism because the animals have a limited ability to stiffen their legs. That limitation is due to anatomical restrictions determined by the morphology and structure of the macaque musculoskeletal system. The general adoption of grounded running in macaques and other non-human primates, along with its absence in human bipedal locomotion, suggests that abandonment of compliant gait was a critical transition in the evolution of human obligatory bipedalism.

Characteristics of the gait adaptation process due to split-belt treadmill walking under a wide range of right-left speed ratios in humans.

The adaptability of human bipedal locomotion has been studied using split-belt treadmill walking. Most of previous studies utilized experimental protocol under remarkably different split ratios (e.g. 1:2, 1:3, or 1:4). While, there is limited research with regard to adaptive process under the small speed ratios. It is important to know the nature of adaptive process under ratio smaller than 1:2, because systematic evaluation of the gait adaptation under small to moderate split ratios would enable us to examine relative contribution of two forms of adaptation (reactive feedback and predictive feedforward control) on gait adaptation. We therefore examined a gait behavior due to on split-belt treadmill adaptation under five belt speed difference conditions (from 1:1.2 to 1:2). Gait parameters related to reactive control (stance time) showed quick adjustments immediately after imposing the split-belt walking in all five speed ratios. Meanwhile, parameters related to predictive control (step length and anterior force) showed a clear pattern of adaptation and subsequent aftereffects except for the 1:1.2 adaptation. Additionally, the 1:1.2 ratio was distinguished from other ratios by cluster analysis based on the relationship between the size of adaptation and the aftereffect. Our findings indicate that the reactive feedback control was involved in all the speed ratios tested and that the extent of reaction was proportionally dependent on the speed ratio of the split-belt. On the contrary, predictive feedforward control was necessary when the ratio of the split-belt was greater. These results enable us to consider how a given split-belt training condition would affect the relative contribution of the two strategies on gait adaptation, which must be considered when developing rehabilitation interventions for stroke patients.

Lack of adaptation during prolonged split-belt locomotion in the intact and spinal cat.

During split-belt locomotion in humans where one leg steps faster than the other, the symmetry of step lengths and double support periods of the slow and fast legs is gradually restored. When returning to tied-belt locomotion, there is an after-effect, with a reversal in the asymmetry observed in the early split-belt period, indicating that the new pattern was stored within the central nervous system. In this study, we investigated if intact and spinal-transected cats show a similar pattern of adaptation to split-belt locomotion by measuring kinematic variables and electromyography before, during and after 10min of split-belt locomotion. The results show that cats do not adapt to prolonged split-belt locomotion. Our results suggest an important physiological difference in how cats and humans respond to prolonged asymmetric locomotion. In humans, gait adapts to prolonged walking on a split-belt treadmill, where one leg steps faster than the other, by gradually restoring the symmetry of interlimb kinematic variables, such as double support periods and step lengths, and by reducing muscle activity (EMG, electromyography). The adaptation is also characterized by reversing the asymmetry of interlimb variables observed during the early split-belt period when returning to tied-belt locomotion, termed an after-effect. To determine if cats adapt to prolonged split-belt locomotion and to assess if spinal locomotor circuits participate in the adaptation, we measured interlimb variables and EMG in intact and spinal-transected cats before, during and after 10min of split-belt locomotion. In spinal cats, only the hindlimbs performed stepping with the forelimbs stationary. In intact and spinal cats, step lengths and double support periods were, on average, symmetric, during tied-belt locomotion. They became asymmetric during split-belt locomotion and remained asymmetric throughout the split-belt period. Upon returning to tied-belt locomotion, symmetry was immediately restored. In intact cats, the mean EMG amplitude of hindlimb extensors increased during split-belt locomotion and remained increased throughout the split-belt period, whereas in spinal cats, EMG amplitude did not change. Therefore, the results indicate that the locomotor pattern of cats does not adapt to prolonged split-belt locomotion, suggesting an important physiological difference in the control of locomotion between cats and humans. We propose that restoring left-right symmetry is not required to maintain balance during prolonged asymmetric locomotion in the cat, a quadruped, as opposed to human bipedal locomotion.

Analysis of the moment arms and kinematics of ostrich (Struthio camelus) double patellar sesamoids.

The patella ("kneecap") is a biomechanically important feature of the tendinous insertion of the knee extensor muscles, able to alter the moment arm lengths between its input and output tendons, and so modify the mechanical advantage of the knee extensor muscle. However, patellar gearing function is little-explored outside of humans, and the patella is often simplified or ignored in biomechanical models. Here, we investigate patellar gearing and kinematics in the ostrich-frequently used as an animal analogue to human bipedal locomotion and unusual in its possession of two patellae at the knee joint. We use x-ray reconstruction of moving morphology (XROMM) techniques to capture the kinematics of the patellae in an adult ostrich cadaver, passively manipulated in flexion-extension. Moment arm ratios between the input and output tendons of each patella are calculated from kinematically determined centers of patellofemoral joint rotation. Both patellae are found to decrease the mechanical advantage of the extensor muscle-tendon complex, decreasing the tendon output force for a given muscle input force, but potentially increasing the relative speed of knee extension. Mechanically and kinematically, the proximal patella behaves similarly to the single patella of most other species, whereas the distal patella has properties of both a fixed retroarticular process and a moving sesamoid. It is still not clear why ostriches possess two patellae, but we suggest that the configuration in ostriches benefits their rapid locomotion and provides tendon protection.

Development and Feasibility Assessment of a Rotational Orthosis for Walking with Arm Swing.

Interlimb neural coupling might underlie human bipedal locomotion, which is reflected in the fact that people swing their arms synchronously with leg movement in normal gait. Therefore, arm swing should be included in gait training to provide coordinated interlimb performance. The present study aimed to develop a Rotational Orthosis for Walking with Arm Swing (ROWAS), and evaluate its feasibility from the perspectives of implementation, acceptability and responsiveness. We developed the mechanical structures of the ROWAS system in SolidWorks, and implemented the concept in a prototype. Normal gait data were used as the reference performance of the shoulder, hip, knee and ankle joints of the prototype. The ROWAS prototype was tested for function assessment and further evaluated using five able-bodied subjects for user feedback. The ROWAS prototype produced coordinated performance in the upper and lower limbs, with joint profiles similar to those occurring in normal gait. The subjects reported a stronger feeling of walking with arm swing than without. The ROWAS system was deemed feasible according to the formal assessment criteria.

Gait adaptation to visual kinematic perturbations using a real-time closed-loop brain–computer interface to a virtual reality avatar

Objective. The control of human bipedal locomotion is of great interest to the field of lower-body brain–computer interfaces (BCIs) for gait rehabilitation. While the feasibility of closed-loop BCI systems for the control of a lower body exoskeleton has been recently shown, multi-day closed-loop neural decoding of human gait in a BCI virtual reality (BCI-VR) environment has yet to be demonstrated. BCI-VR systems provide valuable alternatives for movement rehabilitation when wearable robots are not desirable due to medical conditions, cost, accessibility, usability, or patient preferences. Approach. In this study, we propose a real-time closed-loop BCI that decodes lower limb joint angles from scalp electroencephalography (EEG) during treadmill walking to control a walking avatar in a virtual environment. Fluctuations in the amplitude of slow cortical potentials of EEG in the delta band (0.1–3 Hz) were used for prediction; thus, the EEG features correspond to time-domain amplitude modulated potentials in the delta band. Virtual kinematic perturbations resulting in asymmetric walking gait patterns of the avatar were also introduced to investigate gait adaptation using the closed-loop BCI-VR system over a period of eight days. Main results. Our results demonstrate the feasibility of using a closed-loop BCI to learn to control a walking avatar under normal and altered visuomotor perturbations, which involved cortical adaptations. The average decoding accuracies (Pearson’s r values) in real-time BCI across all subjects increased from (Hip: 0.18 ± 0.31; Knee: 0.23 ± 0.33; Ankle: 0.14 ± 0.22) on Day 1 to (Hip: 0.40 ± 0.24; Knee: 0.55 ± 0.20; Ankle: 0.29 ± 0.22) on Day 8. Significance. These findings have implications for the development of a real-time closed-loop EEG-based BCI-VR system for gait rehabilitation after stroke and for understanding cortical plasticity induced by a closed-loop BCI-VR system.

A Closed-loop Brain Computer Interface to a Virtual Reality Avatar: Gait Adaptation to Visual Kinematic Perturbations.

The control of human bipedal locomotion is of great interest to the field of lower-body brain computer interfaces (BCIs) for rehabilitation of gait. While the feasibility of a closed-loop BCI system for the control of a lower body exoskeleton has been recently shown, multi-day closed-loop neural decoding of human gait in a virtual reality (BCI-VR) environment has yet to be demonstrated. In this study, we propose a real-time closed-loop BCI that decodes lower limb joint angles from scalp electroencephalography (EEG) during treadmill walking to control the walking movements of a virtual avatar. Moreover, virtual kinematic perturbations resulting in asymmetric walking gait patterns of the avatar were also introduced to investigate gait adaptation using the closed-loop BCI-VR system over a period of eight days. Our results demonstrate the feasibility of using a closed-loop BCI to learn to control a walking avatar under normal and altered visuomotor perturbations, which involved cortical adaptations. These findings have implications for the development of BCI-VR systems for gait rehabilitation after stroke and for understanding cortical plasticity induced by a closed-loop BCI system.

Lower extremity kinematics of athletics curve sprinting

Curve running requires the generation of centripetal force altering the movement pattern in comparison to the straight path run. The question arises which kinematic modulations emerge while bend sprinting at high velocities. It has been suggested that during curve sprints the legs fulfil different functions. A three-dimensional motion analysis (16 high-speed cameras) was conducted to compare the segmental kinematics of the lower extremity during the stance phases of linear and curve sprints (radius: 36.5 m) of six sprinters of national competitive level. Peak joint angles substantially differed in the frontal and transversal plane whereas sagittal plane kinematics remained unchanged. During the prolonged left stance phase (left: 107.5 ms, right: 95.7 ms, straight: 104.4 ms) the maximum values of ankle eversion (left: 12.7°, right: 2.6°, straight: 6.6°), hip adduction (left: 13.8°, right: 5.5°, straight: 8.8°) and hip external rotation (left: 21.6°, right: 12.9°, straight: 16.7°) were significantly higher. The inside leg seemed to stabilise the movement in the frontal plane (eversion–adduction strategy) whereas the outside leg provided and controlled the motion in the horizontal plane (rotation strategy). These results extend the principal understanding of the effects of curve sprinting on lower extremity kinematics. This helps to increase the understanding of nonlinear human bipedal locomotion, which in turn might lead to improvements in athletic performance and injury prevention.

Siblings in Kars, Turkey, with Uner Tan syndrome (quadrupedal locomotion, severe mental retardation, and no speech): a novel theory for the evolution of human bipedalism

Objective:To investigate siblings from Kars (n = 2), Turkey, with diagonal-sequence quadrupedal locomotion (QL), severe mental retardation, and no speech (Uner Tan syndrome, UTS), in relation to the evolutionary emergence of human bipedal locomotion (BL).Methods:Video recordings were made to assess gaits. Brain MRI scanning was performed to visualize the cerebro-cerebellar malformations. Genome-wide association analyses were performed in venous blood samples.Results:One of the two men with UTS showed early-onset QL and late-onset BL without infantile hypotonia, the other consistent QL with infantile hypotonia. No homozygosity was found in the genetic analysis. The family lived under extremely poor socioeconomic conditions.Conclusions:Low socioeconomic status may be a triggering factor for the epigenetic emergence of UTS. The neural networks responsible for the ancestral diagonal-sequence QL, evolutionarily preserved since about 400 MYA, may be selected during locomotor development, under the influence of self-organizing processes during pre- and postnatal periods. The diagonal-sequence QL induced ipsilateral limb interference in UTS cases as in nonhuman primates. To overcome this condition, our ancestors would prefer the attractor BL. This novel theory for the evolution of human bipedalism was evaluated in light of dynamical systems theory.