Locomotor Pattern Research Articles

Optimizing contact patterns for robot locomotion via geometric mechanics

Contact planning is crucial to the locomotion performance of robots: to properly self-propel forward, it is not only important to determine the sequence of internal shape changes (e.g., body bending and limb shoulder joint oscillation) but also the sequence by which contact is made and broken between the mechanism and its environment. Prior work observed that properly coupling contact patterns and shape changes allows for computationally tractable gait design and efficient gait performance. The state of the art, however, made assumptions, albeit motivated by biological observation, as to how contact and shape changes can be coupled. In this paper, we extend the geometric mechanics (GM) framework to design contact patterns. Specifically, we introduce the concept of “contact space” to the GM framework. By establishing the connection between velocities in shape and position spaces, we can estimate the benefits of each contact pattern change and therefore optimize the sequence of contact patterns. In doing so, we can also analyze how a contact pattern sequence will respond to perturbations. We apply our framework to sidewinding robots and enable (1) effective locomotion direction control and (2) robust locomotion performance as the spatial resolution decreases. We also apply our framework to a hexapod robot with two back-bending joints and show that we can simplify existing hexapod gaits by properly reducing the number of contact state switches (during a gait cycle) without significant loss of locomotion speed. We test our designed gaits with robophysical experiments, and we obtain good agreement between theory and experiments.

Prey-dependent feeding behavior in a kelp-forest mesopredator, the California two-spot octopus

Predators have evolved a diverse behavioral repertoire to capture and handle prey. Within coleoid cephalopods, octopuses have developed dynamic movements associated with limb hyper-redundancy. As important mesopredators in coastal marine food webs, many species of octopuses are predominantly generalists, feeding on a wide variety of invertebrate and vertebrate prey. Despite their broad diets, few studies have examined the behavioral repertoire of octopus with respect to prey type. We compare how prey type may affect octopus feeding behavior by conducting controlled feeding trials during which we recorded California two-spot octopuses (Octopus bimaculoides, Pickford & McConnaughey, 1949) predating on a sessile prey (Protothaca staminea) and an active prey (Pachygraspus crassipes). We found that prey type had no effect on octopus body orientation, arm choice, nor eye use, but did have a significant influence on the timing events within a feeding sequence, the type of attack used, and attack kinematics. When feeding on clams, octopuses exhibited a shorter latency to move towards prey and make first contact with prey, longer attack decision and prey handling times, and slower attack speed and acceleration compared to when feeding on crabs. Octopuses tended to orient their right eye towards the prey for both first touch and attack during clam trials but during crab trials there was no eye bias. In all trials, eye use appeared to influence arm choice within each prey type. Finally, we report a previously undescribed behavior in the California two-spot octopus: a sinusoidal locomotory pattern that precedes the attack and was observed more commonly for crabs.

Individual differences in response to alcohol and nicotine in zebrafish: Gene expression and behavior.

Alcohol and nicotine are psychoactive substances responsible for serious health consequences. Although the biological mechanisms of alcohol and nicotine have been studied extensively, individual differences in the response to these drugs have received little attention. Here we evaluated gene expression and behavior of bold and shy individuals after acute exposure to alcohol and nicotine. For this, zebrafish were classified as bold and shy individuals based on emergence tests, and then fish were exposed to 0.00, 0.10, and 0.50% alcohol or 0.00, 1.00, and 5.00 mg/L nicotine and their anxiety-like and locomotor behavior was observed. After behavioral assessment, brain mRNA expression (ache, bdnf, gaba1, gad1b, th1, and tph1) was evaluated. Locomotion patterns differed between profiles depending on alcohol and nicotine concentration. Anxiety increased in shy fish and decreased in bold fish after exposure to both drugs. Alcohol exposure induced an increase in tph1 mRNA expression in bold fish, while bdnf mRNA expression was increased in shy fish. Nicotine increased ache, bdnf, and tph1 mRNA levels in both profiles, but at higher levels in bold fish. Based on our research, we found that alcohol induces anxiogenic effects in both bold and shy zebrafish. Additionally, shy individuals exposed to a low concentration of nicotine exhibited stronger anxiety-like responses than their bold counterparts. These findings further support the validity of using zebrafish as a dependable tool for studying the effects of drugs and uncovering the underlying mechanisms associated with individual variations.

Peak physical demands of elite women's soccer: Assessing playing position and post-goal locomotor patterns

It has recently been identified that the assessment of peak periods of activity better considers the stochastic nature of match-play and the influence that contextual factors have on these peak periods. Limited research exists attempting to link the tactical and physical aspects of performance, especially in female players. Therefore, the current study aimed to assess post-goal locomotor patterns and positional differences on peak match demands in elite female soccer players. Using 10 Hz global positioning system units, a total of 133 player match observations were recorded from 14 matches played by an elite Scottish women's professional soccer team. The total distance (TD), high-speed running distance (>18 km/h) (HSRD) and PlayerLoad™ (PL) were assessed for 1, 3 and 5-minute peak periods using a rolling epoch approach. Playing position and post-goal activity were used as modulating factors. Linear mixed models established a main effect for playing position for the HSRD at peak 1-minute ( p<.001), 3-minute ( p < .001) and 5-minute ( p < .001) epochs. There were also main effects for the playing position for TD at peak 1-minute ( p= .001) and PL at peak-3minute ( p = .002). Team-level data showed a main effect for condition (score vs. concede) for 3-minute TD data and main effects for time (pre vs. post) for 1,3 and 5-minute epochs for PL data. The average and peak values were shown to differ across playing positions for all variables. Likewise, potentially indicative of tactical adjustments significant differences were observed at both a team and player level following scoring or conceding a goal.

Assessing the Impacts of Aquaculture Soundscapes on the Growth, Physiology and Behavior of Micropterus salmoides

Sound has a potential impact on animal welfare and production, but the impacts of soundscapes on aquaculture species in different aquaculture production systems have been rarely studied. This study investigated the impact of varying aquaculture soundscapes on largemouth bass (Micropterus salmoides). Three soundscapes were administered to replicated tanks: Recirculating Aquaculture System (RAS:107.7 dB re 1 Pa RMS), In-Pond Raceway System (IPRS:115.1 dB re 1 Pa RMS), and Ambient (70.4 dB re 1 Pa RMS) as the control. The initial weight of fish in the three groups was 3.59 ± 0.30 g. Following a 50-day experimental period, the average weight of the Ambient group (14.08 ± 0.13 g) was significantly greater than that of the IPRS group (12.79 ± 0.08 g) (p < 0.05). Examination of physiological samples revealed that the soundscape negatively impacted the fish’s immunological, anti-oxidation, and digestive enzymes. Furthermore, the external noise also influenced the locomotive patterns of the fish aggregations. Fish polarity and cohesion were significantly more discrete (p < 0.05) in both the RAS (47.79 ± 2.34° and 98.52 ± 3.22 mm) and IPRS groups (48.04 ± 0.70° and 87.70 ± 7.31 mm) compared to the Ambient group (42.76 ± 1.42° and 85.73 ± 1.57 mm). These results highlight the significant impacts of the aquaculture soundscape on the development, physiological activities, and behavioral traits of largemouth bass. Future research should focus on determining and optimizing the impact of different equipment noise to ensure optimal welfare and production performance in aquaculture systems.

Locomotor pattern generation and descending control: a historical perspective.

The ability to generate and control locomotor movements depends on complex interactions between many areas of the nervous system, the musculoskeletal system, and the environment. How the nervous system manages to accomplish this task has been the subject of investigation for more than a century. In vertebrates, locomotion is generated by neural networks located in the spinal cord referred to as central pattern generators. Descending inputs from the brain stem initiate, maintain, and stop locomotion as well as control speed and direction. Sensory inputs adapt locomotor programs to the environmental conditions. This review presents a comparative and historical overview of some of the neural mechanisms underlying the control of locomotion in vertebrates. We have put an emphasis on spinal mechanisms and descending control.

A fully automated home cage for long-term continuous phenotyping of mouse cognition and behavior

Automated home-cage monitoring systems present a valuable tool for comprehensive phenotyping of natural behaviors. However, current systems often involve complex training routines, water or food restriction, and probe a limited range of behaviors. Here, we present a fully automated home-cage monitoring system for cognitive and behavioral phenotyping in mice. The system incorporates T-maze alternation, novel object recognition, and object-in-place recognition tests combined with monitoring of locomotion, drinking, and quiescence patterns, all carried out over long periods. Mice learn the tasks rapidly without any need for water or food restrictions. Behavioral characterization employs a deep convolutional neural network image analysis. We show that combined statistical properties of multiple behaviors can be used to discriminate between mice with hippocampal, medial entorhinal, and sham lesions and predict the genotype of an Alzheimer's disease mouse model with high accuracy. This technology may enable large-scale behavioral screening for genes and neural circuits underlying spatial memory and other cognitive processes.

Early-life sleep disruption impairs subtle social behaviours in prairie voles: a pose-estimation study.

Early-life sleep disruption (ELSD) has been shown to have long-lasting effects on social behaviour in adult prairie voles (Microtus ochrogaster), including impaired expression of pair bonding during partner preference testing. However, due to the limitations of manual behaviour tracking, the effects of ELSD across the time course of pair bonding have not yet been described, hindering our ability to trace mechanisms. Here, we used pose estimation to track prairie voles during opposite-sex cohabitation, the process leading to pair bonding. Male-female pairs were allowed to interact through a mesh divider in the home cage for 72 h, providing variables of body direction, distance-to-divider and locomotion speed. We found that control males displayed periodic patterns of body orientation towards females during cohabitation. In contrast, ELSD males showed reduced duration and ultradian periodicity of these body orientation behaviours towards females. Furthermore, in both sexes, ELSD altered spatial and temporal patterns of locomotion across the light/dark cycles of the 72 h recordings. This study allows a comprehensive behavioural assessment of the effects of ELSD on later life sociality and highlights subtle prairie vole behaviours. Our findings may shed light on neurodevelopmental disorders featuring sleep disruption and social deficits, such as autism spectrum disorders.

Adaptive Threshold-Based ZUPT for Single IMU-Enabled Wearable Pedestrian Localization

Without dependence on external anchors, the Micro-Electro-Mechanical System Inertia Measurement Unit (MIMU) allowing autonomous localization has promised great potential in wearable IoT applications, including kinematic analysis in sports, medical treatment, elderly care, and disaster rescue. However, the miniaturization of devices for unobtrusive sensing, algorithms minimizing the inherent accumulative errors of inertial devices, and the adaptivity of algorithms for various motion modalities are the key challenges. The removal of accumulative error in the continuous gait cycles with adaptive algorithms is a critical issue regarding localization accuracy, especially for low-cost devices. This investigation proposes an adaptive threshold-based Zero-velocity Update (ZUPT) algorithm to separate the timing of gait cycle phases and compensate for the residual velocity with a linear fitting approximation. The key contributions include: (1) a lightweight threshold-based zero-velocity detection algorithm to split the gait cycle phases of continuous walking; (2) a quaternion-based Extended Kalman Filter (EKF) algorithm to reduce the errors of the non-linear operations for attitude prediction; (3) a linear fitting method for compensating the residual velocity in each gait cycle of continuous walking; (4) the design of a miniature single-MIMU based foot-mountable wearable device and the corresponding experimental studies to verify the proposed methods. Results show that the relative error is less than 3.0% for 2D and 3D trajectories, and the tests with different locomotion patterns demonstrate the adaptivity of the proposed algorithm compared to its peers. The results show that the presented techniques are capable of handling accumulative errors for low-cost MIMU-based systems with good adaptivity.

The influences of green light on locomotion, growth and reproduction on the brown planthopper Nilaparvata lugens.

Light stimulation at a specific wavelength triggers various responses in insects and can be used for pest control. To develop efficient and eco-friendly photophysical pest control methods, Nilaparvata lugens (Stål) (BPH), a major rice pest, was studied the effects of green light on their locomotion, growth (molting and eclosion) and reproduction. Transcriptomics and transmission electron microscopy (TEM) were used to investigate the mechanisms involved. BPH adults showed disrupted daily locomotion patterns following green light treatment at night and exhibited abnormal locomotion peaks. The total six-day locomotion of brachypterous adults was significantly higher than that in the control group. Under green light treatment, the durations of growing stage 1-4 were all shorter in the green light treatment than the control, while the duration from 4th molting to eclosion (stage 5) was significantly longer treated by green light. When the BPH adults under green light treatment laying eggs, the egg hatching ratio (36.69%) was significantly lower than the ratio in control (47.49%). Moreover, contrary to the control, BPH molting and eclosion events tended to happen more at night. Transcriptome analysis proved that green light significantly affected the expression of genes involved in cuticular proteins, chitin deacetylase and chitinase, which were related to cuticular development. TEM observations confirmed the abnormal cuticular development in nymph and adult BPHs (endocuticle，exocuticle and pore canals) under green light treatment. Green light treatment at night notably affected locomotion, growth and reproduction of BPH, thus providing a novel idea for controlling this pest. This article is protected by copyright. All rights reserved.

A mental workload and biomechanical assessment during split-belt locomotor adaptation with and without optic flow.

Adaptive human performance relies on the central nervous system to regulate the engagement of cognitive-motor resources as task demands vary. Despite numerous studies which employed a split-belt induced perturbation to examine biomechanical outcomes during locomotor adaptation, none concurrently examined the cerebral cortical dynamics to assess changes in mental workload. Additionally, while prior work suggests that optic flow provides critical information for walking regulation, a few studies have manipulated visual inputs during adaption to split-belt walking. This study aimed to examine the concurrent modulation of gait and Electroencephalography (EEG) cortical dynamics underlying mental workload during split-belt locomotor adaptation, with and without optic flow. Thirteen uninjured participants with minimal inherent walking asymmetries at baseline underwent adaptation, while temporal-spatial gait and EEG spectral metrics were recorded. The results revealed a reduction in step length and time asymmetry from early to late adaptation, accompanied by an elevated frontal and temporal theta power; the former being well corelated to biomechanical changes. While the absence of optic flow during adaptation did not affect temporal-spatial gait metrics, it led to an increase of theta and low-alpha power. Thus, as individuals adapt their locomotor patterns, the cognitive-motor resources underlying the encoding and consolidation processes of the procedural memory were recruited to acquire a new internal model of the perturbation. Also, when adaption occurs without optic flow, a further reduction of arousal is accompanied with an elevation of attentional engagement due to enhanced neurocognitive resources likely to maintain adaptive walking patterns.

Kirigami Makes a Soft Magnetic Sheet Crawl.

Limbless crawling on land requires breaking symmetry of the friction with the ground and exploiting an actuation mechanism to generate propulsive forces. Here, kirigami cuts are introduced into a soft magnetic sheet that allow to achieve effective crawling of untethered soft robots upon application of a rotating magnetic field. Bidirectional locomotion is achieved under clockwise and counterclockwise rotating magnetic fields with distinct locomotion patterns and crawling speed in forward and backward propulsions. The crawling and deformation profiles of the robot are experimentally characterized and combined with detailed multiphysics numerical simulations to extract locomotion mechanisms in both directions. It is shown that by changing the shape of the cuts and orientation of the magnet the robot can be steered, and if combined with translational motion of the magnet, complex crawling paths are programed. The proposed magnetic kirigami robot offers a simple approach to developing untethered soft robots with programmable motion.

Design of a Bio-Inspired Untethered Soft Octopodal Robot Driven by Magnetic Field.

Inspired by insects in nature, an increasing number of soft robots have been proposed to mimic their locomotion patterns. As a wireless actuation method, the magnetic actuation technique has been widely applied to drive soft magnetic robots for diverse applications. Although recent works on soft materials have stimulated the development of soft robots, it is challenging to achieve the efficient movement of soft robots for in vivo biomedical application. Inspired by centipede locomotion, a soft octopodal robot is designed in this paper. The robot is fabricated by mixing magnetic particles with silicone polymers, which is then magnetized by a specific magnetic field. The prototypes can be actuated by an external magnetic field (5-8 mT) produced by custom-made electromagnetic coils. Experimental results show that the soft robot can move at a high speed in the range of 0.536-1.604 mm/s on different surfaces, including paper, wood, and PMMA. This indicates that the soft robot can achieve comparable speeds to other robots, while being driven by a lower magnitude, resulting in energy savings. Furthermore, it achieves a high speed of 0.823 mm/s on the surface of a pig colon. The fine capabilities of the soft robot in terms of crossing uneven biological surfaces and carrying external loads are demonstrated. The results indicate that the reported soft robot exhibits promising applications in the biomedical field.

Passive Dynamics of the Head, Neck and Forelimb in Equine Foetuses-An Observational Study.

Passive dynamics is an aspect of locomotion which is entirely dependent on the mechanical configuration and linkages of adjacent body segments. Tension distribution along mechanical linkages enables the execution of movement patterns with reduced need for complex neurological pathways and may play a role in reestablishing postural stability following external disturbances. Here we demonstrate a uni-directional mechanical relationship between the equine forelimb, head and neck, which may have implications for balance and forelimb loading in the horse. These observations suggest that forelimb, head and neck movement coordination (observed in the horse during unrestrained locomotion) is significantly influenced by the mechanical linkages between body segments, rather than being entirely dependent on neurological input as previously thought. This highlights the potential significance of research directed at investigating passively induced movements in understanding common locomotory patterns. Additionally, it suggests a mode of postural control which may provide instantaneous adjustments to postural disturbances, thus promoting rapid and efficient locomotion.

Altered transposable elements expression and gene networks remodeling precede disruptions in sleep/wake cycles in a tauopathy mouse model of AD

AbstractBackgroundAlzheimer’s Disease (AD) is an widespread neurodegenerative disorder, common in elder and Veterans communities, culminating in dementia with non‐cognitive behavioral and metabolic symptoms, such as hyperactivity and altered sleep/wake patterns. In demented patients, sleep/wake cycle disruptions facilitate weight loss, which is associated with adverse outcomes like accelerated AD progression and higher institutionalization. Tg4510 mice, which express a P301L mutant variant of human tau, develop both cognitive and non‐cognitive symptoms. Several mouse models of tau deposition, including Tg4510 mice, also have negative energy balance. To identify early factors affecting AD, we measured locomotor, sleep/wake patterns in vivo, and analyzed RNA‐seq data from Tg4510 mice to identify gene and transposable elements (TE) expression changes involved in behavioral derangements in AD.MethodLocomotor activity, sleep and wake intervals and patterns were measured using in vivo metabolic cages for two weeks over 24 hr and day and night cycles from Tg4510 mice (n = 5‐7) vs. controls (n = 7‐10) before and after the onset of tauopathy (at 2 and 7 months of age respectively). In additional experiments, we analyzed RNA‐seq from hippocampi of Tg4510 mice (n = 5) vs. controls (n = 6). Using our established TTESA bioinformatics pipeline, reads were aligned to reference genome and expression of genes or TEs was measured with featureCounts. Pathway enrichment analysis using Visual Annotation Display was used to discover common functional and disease pathways using Gene Ontology, Protein Ontology, and Mammalian Phenotype Ontology.ResultWe observed altered locomotor and sleep patterns during the night phase starting in young Tg4510 vs. controls. TTESA results detected the majority of significantly differentially expressed TEs were retrotransposons (70%), which consisted mainly of long terminal repeats (LTRs; 70%) and some LINE retroelements (30%) and SINEs (<8%) in transgenic mice. VLaD pathway analysis revealed several biological processes upregulated in transgenic mice, including non‐cognitive behavioral pathways were downregulated, such as the regulation of circadian sleep/wake cycle with changes in the expression levels of Per2, Per3 (p<0.0001).ConclusionEarly dysregulation of TEs may be involved in rewiring gene expression networks underlying behavioral changes in wake and sleep cycles and other circadian patterns of behavior in this humanized mouse model of AD.

A worm-inspired robot based on origami structures driven by the magnetic field

With the rapid development of origami technology, worm-inspired origami robots have attracted tremendous interest owing to their colourful locomotion behaviours, such as creeping, rolling, climbing and obstacle crossing. In the present study, we aim to engineer a worm-inspired robot based on knitting process with paper, which could realize complicated functions associated large deformation and exquisite locomotion patterns. At first we fabricate the backbone of the robot by using the paper-knitting technique. The experiment shows that the backbone of the robot can endure significant deformation during the tension, compression and bending process, and this feature ensures it can achieve the desired targets of motion. Next, the magnetic forces and torques under the actuation of permanent magnets are analysed, which are just the driving forces of the robot. We then consider three formats of motion on the robot, i.e. the inchworm motion, the Omega motion, and the hybrid motion. Typical examples for the robot fulfil desired tasks are given, including sweeping obstacles, climbing the wall and delivering cargoes. Detailed theoretical analyses and numerical simulations are performed to illustrate these experimental phenomena. The results show that the developed origami robot is equipped with such characteristics as lightweight and great flexibility, which is sufficiently robust in various environments. These promising performances shed new light on design and fabrication of bio-inspired robots with good intelligence.

Autonomous, untethered gait-like synchronization of lobed loops made from liquid crystal elastomer fibers via spontaneous snap-through

The transition from one equilibrium state to another via rapid snap-through can store elastic energy and release it as kinetic energy for rapid motion as seen in Venus flytrap and hummingbird to catch insects mid-flight. They are explored in soft robotics for repeated and autonomous motions. In this study, we synthesize curved liquid crystal elastomer (LCE) fibers as the building blocks that can undergo buckling instability upon heated on a hot surface, leading to autonomous snap-through and rolling behaviors. When they are connected into lobed loops, where each fiber is geometrically constrained by the neighboring ones, they demonstrate autonomous, self-regulated, and repeated synchronization with a frequency of ~1.8 Hz. By adding a rigid bead on the fiber, we can fine-tune the actuation direction and speed (up to ~2.4 mm/s). Last, we demonstrate various gait-like locomotion patterns using the loops as the robot's legs.

Muscle architectural properties indicate a primary role in support for the pelvic limb of three-toed sloths (Bradypus variegatus).

Tree sloths evolved below-branch locomotion making them one of few mammalian taxa beyond primates for which suspension is nearly obligatory. Suspension requires strong limb flexor muscles that provide both propulsion and braking/support, and available locomotor kinetics data indicate that these roles differ between fore- and hindlimb pairs. Muscle structure in the pelvic limb is hypothesized to be a key anatomical correlate of function in braking/support during suspensory walking and propulsion and/or support during vertical climbing. This expectation was tested by quantifying architecture properties in the hindlimb limb musculature of brown-throated three-toed sloths (Bradypus variegatus: N = 7) to distinguish the roles of the flexor/extensor functional muscle groups at each joint. Measurements of muscle moment arm (rm ), mass, belly length, fascicle length, pennation angle, and physiological cross-sectional area (PCSA) were taken from n = 45 muscles. Overall, most muscles studied show properties for contractile excursion and fast joint rotational velocity. However, the flexor musculature is more massive (p = 0.048) and has larger PCSA (p = 0.003) than the extensors, especially at the knee joint and digits where well-developed and strong flexors are capable of applying large joint torque. Moreover, selected hip flexors/extensors and knee flexors have modified long rm that can amplify applied joint torque in muscles with otherwise long, parallel fascicles, and one muscle (m. iliopsoas) was capable of moderately high power in B. variegatus. The architectural properties observed in the hip flexors and extensors match well with roles in suspensory braking and vertical propulsion, respectively, whereas strong knee flexors and digital flexors appear to be the main muscles providing suspensory support in the pelvic limb. With aid in support by the forelimbs and the use of adaptive slow locomotion and slow muscle fiber recruitment patterns, structure-function in the tensile limb systems of sloths appears to collectively represent an additional mechanism for energy conservation.

Effects of the speed on the webbed foot kinematics of mallard (Anas platyrhynchos).

In this study, the effect of the speed on the webbed foot locomotion of the mallard was analyzed based on a considerable number of reliable indoor test data. Four adult male mallards were selected for analysis, and the locomotion speed of the mallard was controlled using the treadmill at an accurate and adjustable speed. The locomotion pattern of the webbed foot of the mallard at different speeds was recorded using a high-speed camera. The changes in the position and conformation of the webbed foot during locomotion on a treadmill were tracked and analyzed using Simi-Motion kinematics software. The results indicated that the stride length of the mallard increased, and the stance phase duration was shortened with the increase of the speed, whereas the swing phase duration did not vary significantly. The duty factor decreased with the increase of the mallard speed but not drop below to 0.5, because the mallards flew with their wings, or moved backward relative to the treadmill with the further increase of the speed. Using the energy method to further distinguish gait, and through the percentage of congruity analysis, it was found that between 0.73 and 0.93 m/s, the gait experienced a transition from walking to grounded running, with no significant changes in spatiotemporal parameters. At speeds between 0.93 and 1.6 m/s, mallards adopt a grounded running gait. The instantaneous changes of the tarsometatarso-phalangeal joint (TMTPJ) angle and the intertarsal joint (ITJ) angle at touch-down, mid-stance and lift-off concomitant with the change of the speed were examined with the TMTPJ and ITJ angle as the research objects. Moreover, the continuous changes of the joint angles were examined in a complete stride cycle. The result indicated that the increase of the speed will also make the TMTPJ and ITJ angle change ahead of time in a stride cycle, proving the shortened stance phase duration. The ITJ angle changed much more than the TMTPJ. Thus, the above result reveals that the mallard primarily responds with the increase of the speed by adjusting the ITJ, instead of the TMTPJ. The vertical displacement of the toe joint points and the toe joint angle was studied (α joint angle is between the second toe and the third toe; β joint angle is between the third toe and the fourth toe) with a complete stride cycle as the research object. The distal phalanxes of the second, third and fourth toes first contacted the ground, and the proximal phalanx touched the ground in turn during the early stance phase duration of the mallard, as indicated by the result of this study. However, the toes got off the ground in turn from the proximal phalanxes when the mallard foot got off the ground. With the decrease of the interphalangeal α and β joint angles, the foot web tended to be close and rapidly recovered before the next touch-down. The above result reveals that the webbed foot of the mallard is a coupling system that plays a role in the adjustment of speed.

Comparison of the forward and sideways locomotor patterns in children with Cerebral Palsy

Switching locomotion direction is a common task in daily life, and it has been studied extensively in healthy people. Little is known, however, about the locomotor adjustments involved in changing locomotion direction from forward (FW) to sideways (SW) in children with cerebral palsy (CP). The importance of testing the ability of children with CP in this task lies in the assessment of flexible, adaptable adjustments of locomotion as a function of the environmental context. On the one hand, the ability of a child to cope with novel task requirements may provide prognostic cues as to the chances of modifying the gait adaptively. On the other hand, challenging the child with the novel task may represent a useful rehabilitation tool to improve the locomotor performance. SW is an asymmetrical locomotor task and requires a differential control of right and left limb muscles. Here, we report the results of a cross-sectional study comparing FW and SW in 27 children with CP (17 diplegic, 10 hemiplegic, 2–10 years) and 18 age-matched typically developing (TD) children. We analyzed gait kinematics, joint moments, EMG activity of 12 pairs of bilateral muscles, and muscle modules evaluated by factorization of EMG signals. Task performance in several children with CP differed drastically from that of TD children. Only 2/3 of children with CP met the primary outcome, i.e. they succeeded to step sideways, and they often demonstrated attempts to step forward. They tended to rotate their trunk FW, cross one leg over the other, flex the knee and hip. Moreover, in contrast to TD children, children with CP often exhibited similar motor modules for FW and SW. Overall, the results reflect developmental deficits in the control of gait, bilateral coordination and adjustment of basic motor modules in children with CP. We suggest that the sideways (along with the backward) style of locomotion represents a novel rehabilitation protocol that challenges the child to cope with novel contextual requirements.