The effect of branch diameter on primate gait sequence pattern

Most mammals use lateral sequence gaits during quadrupedal locomotion, a pattern characterized by the touchdown of a forelimb directly following the ipsilateral hind limb in a given stride cycle. Primates, however, tend to use diagonal sequence (DS) gaits, whereby it is the touchdown of a contralateral forelimb that follows that of a given hind limb most closely in time. A number of scenarios have been offered to explain why primates favor DS gaits, most of them relating to the use of the arboreal habitat and, in particular, the exploitation of a narrow branch niche. This experimental study explores the potential explanation for the use of DS gaits by examining the relationship between branch diameter and gait patterns in 360 strides collected from six species of quadrupedal strepsirrhine primates on broad and narrow diameter supports. Gait sequence is quantified using limb phase, or the percentage of time during a stride cycle that a forelimb touchdown follows an ipsilateral hind limb touchdown. Although Loris, Nycticebus and Eulemur rubriventer individuals in this study did exhibit significantly lower locomotor velocities on narrower supports (P<0.01 in all three species), analyses of covariance showed no significant differences in limb phase values between broad and narrow diameter supports. Hence, results indicate surprisingly little evidence to suggest that alterations in gait sequence pattern provide a specific advantage for negotiating narrow supports.     

Estimation of stride length in level walking using an inertial measurement unit attached to the foot: a validation of the zero velocity assumption during stance

In a variety of applications, inertial sensors are used to estimate spatial parameters by double integrating over time their coordinate acceleration components. In human movement applications, the drift inherent to the accelerometer signals is often reduced by exploiting the cyclical nature of gait and under the hypothesis that the velocity of the sensor is zero at some point in stance. In this study, the validity of the latter hypothesis was investigated by determining the minimum velocity of progression of selected points of the foot and shank during the stance phase of the gait cycle while walking at three different speeds on level ground. The errors affecting the accuracy of the stride length estimation resulting from assuming a zero velocity at the beginning of the integration interval were evaluated on twenty healthy subjects. Results showed that the minimum velocity of the selected points on the foot and shank increased as gait speed increased. Whereas the average minimum velocity of the foot locations was lower than 0.011 m/s, the velocity of the shank locations were up to 0.049 m/s corresponding to a percent error of the stride length equal to 3.3%. The preferable foot locations for an inertial sensor resulted to be the calcaneus and the lateral aspect of the rearfoot. In estimating the stride length, the hypothesis that the velocity of the sensor can be set to zero sometimes during stance is acceptable only if the sensor is attached to the foot.     

Cineradiographic study of forelimb movements during quadrupedal walking in the brown lemur (Eulemur fulvus, Primates: Lemuridae)

Movements of forelimb joints and segments during walking in the brown lemur (Eulemur fulvus) were analyzed using cineradiography (150 frames/sec). Metric gait parameters, forelimb kinematics, and intralimb coordination are described. Calculation of contribution of segment displacements to stance propulsion shows that scapular retroversion in a fulcrum near the vertebral border causes more than 60% of propulsion. The contribution by the shoulder joint is 30%, elbow joint 5%, and wrist joint 1%. Correlation analysis was applied to reveal the interdependency between metric and kinematic parameters. Only the effective angular movement of the elbow joint during stance is speed-dependent. Movements of all other forelimb joints and segments are independent of speed and influence, mainly, linear gait parameters (stride length, stance length). Perhaps the most important result is the hitherto unknown and unexpected degree of scapular mobility. Scapular movements consist of ante-/retroversion, adduction/abduction, and scapular rotation about the longitudinal axis. Inside rotation of the scapula (60 degrees -70 degrees ), together with flexion in the shoulder joint, mediates abduction of the humerus, which is not achieved in the shoulder joint, and is therefore strikingly different from humeral abduction in man. Movements of the shoulder joint are restricted to flexion and extension. At touch down, the shoulder joint of the brown lemur is more extended compared to that of other small mammals. The relatively long humerus and forearm, characteristic for primates, are thus effectively converted into stride length. Observed asymmetries in metric and kinematic behavior of the left and right forelimb are caused by an unequal lateral bending of the spinal column.     

3D gait assessment in young and elderly subjects using foot-worn inertial sensors

This study describes the validation of a new wearable system for assessment of 3D spatial parameters of gait. The new method is based on the detection of temporal parameters, coupled to optimized fusion and de-drifted integration of inertial signals. Composed of two wirelesses inertial modules attached on feet, the system provides stride length, stride velocity, foot clearance, and turning angle parameters at each gait cycle, based on the computation of 3D foot kinematics. Accuracy and precision of the proposed system were compared to an optical motion capture system as reference. Its repeatability across measurements (test-retest reliability) was also evaluated. Measurements were performed in 10 young (mean age 26.1±2.8 years) and 10 elderly volunteers (mean age 71.6±4.6 years) who were asked to perform U-shaped and 8-shaped walking trials, and then a 6-min walking test (6 MWT). A total of 974 gait cycles were used to compare gait parameters with the reference system. Mean accuracy±precision was 1.5±6.8 cm for stride length, 1.4±5.6 cm/s for stride velocity, 1.9±2.0 cm for foot clearance, and 1.6±6.1° for turning angle. Difference in gait performance was observed between young and elderly volunteers during the 6 MWT particularly in foot clearance. The proposed method allows to analyze various aspects of gait, including turns, gait initiation and termination, or inter-cycle variability. The system is lightweight, easy to wear and use, and suitable for clinical application requiring objective evaluation of gait outside of the lab environment.     

The techniques of elite male long jumpers

A model was developed to identify the characteristics of long jumping technique that determine the distance of the jump. The performances of the finalists in the TAC (U.S. national) Championships were recorded cinematographically and the best trials analyzed. The results indicated that the relative lengths of the last two strides of the approach are poor indicators of success in the event. Maximum horizontal velocities were usually attained at takeoff into the third- or second-last stride and not exclusively during the second-last stride, as previously reported. None of the subjects had either a zero or upward vertical velocity of the center of gravity at touchdown of the foot for takeoff into the jump, contrary to an argument occasionally advanced. The greatest percentages of the variance in the distance of the jump were accounted for by the horizontal velocity at takeoff into the fourth-last stride, the change in horizontal velocity during the next support phase, the horizontal and resultant velocities at takeoff and the flight distance.     

Gait stride-to-stride variability and foot clearance pattern analysis in Idiopathic Parkinson’s Disease and Vascular Parkinsonism

The literature on gait analysis in Vascular Parkinsonism (VaP), addressing issues such as variability, foot clearance patterns, and the effect of levodopa, is scarce. This study investigates whether spatiotemporal, foot clearance and stride-to-stride variability analysis can discriminate VaP, and responsiveness to levodopa.Fifteen healthy subjects, 15 Idiopathic Parkinson's Disease (IPD) patients and 15 VaP patients, were assessed in two phases: before (Off-state), and one hour after (On-state) the acute administration of a suprathreshold (1.5 times the usual) levodopa dose. Participants were asked to walk a 30-meter continuous course at a self-selected walking speed while wearing foot-worn inertial sensors. For each gait variable, mean, coefficient of variation (CV), and standard deviations SD1 and SD2 obtained by Poincaré analysis were calculated. General linear models (GLMs) were used to identify group differences. Patients were subject to neuropsychological evaluation (MoCA test) and Brain MRI.VaP patients presented lower mean stride velocity, stride length, lift-off and strike angle, and height of maximum toe (later swing) (p < .05), and higher %gait cycle in double support, with only the latter unresponsive to levodopa. VaP patients also presented higher CV, significantly reduced after levodopa. Yet, all VaP versus IPD differences lost significance when accounting for mean stride length as a covariate.In conclusion, VaP patients presented a unique gait with reduced degrees of foot clearance, probably correlated to vascular lesioning in dopaminergic/non-dopaminergic cortical and subcortical non-dopaminergic networks, still amenable to benefit from levodopa. The dependency of gait and foot clearance and variability deficits from stride length deserves future clarification.     

The effect of three-dimensional geometrical changes during adolescent growth on the biomechanics of a spinal motion segment

During adolescent growth, vertebrae and intervertebral discs undergo various geometrical changes. Although such changes in geometry are well known, their effects on spinal stiffness remains poorly understood. However, this understanding is essential in the treatment of spinal abnormalities during growth, such as scoliosis.A finite element model of an L3–L4 motion segment was developed, validated and applied to study the quantitative effects of changing geometry during adolescent growth on spinal stiffness in flexion, extension, lateral bending and axial rotation. Height, width and depth of the vertebrae and intervertebral disc were varied, as were the width of the transverse processes, the length of the spinous process, the size of the nucleus, facet joint areas and ligament size. These variations were based on average growth data for girls, as reported in literature.Overall, adolescent growth increases the stiffness with 36% (lateral bending and extension) to 44% (flexion). Two thirds of this increase occurs between 10 and 14 years of age and the last third between 14 years of age and maturity.Although the height is the largest geometrical change during adolescent growth, its effect on the biomechanics is small. The depth increase of the disc and vertebrae significantly affects the stiffness in all directions, while the width increase mainly affects the lateral bending stiffness. Hence, when analysing the biomechanics of the growing adolescent spine (for instance in scoliosis research), the inclusion of depth and width changes, in addition to the usually implemented height change, is essential.     

Influence of gait parameters on the loading of the lower limb

The ground reaction force which acts on the foot during normal walking consists of the sum of two components: the support of the weight of the body and the acceleration of the body. The relationships between the initial loading rate of the lower limb (ignoring the contribution of the heelstrike transient) and the general gait parameters — cadence, stride length, and velocity — have been examined. Plots of the resultant ground reaction force were used to calculate the loading rate of the limb. A sample of 13 normal male subjects, aged from 18 to 63 years, walked at five different self-selected speeds. Velocity showed the highest correlation with loading rate (r = 0.95) and stride length the lowest (r = 0.85). The relationship between cadence and loading rate was non-linear.     

Symmetrical gaits of Cebus apella: implications for the functional significance of diagonal sequence gait in primates

Quadrupedal locomotion of primates is distinguished from the quadrupedalism of many other mammals by several features, including a diagonal sequence (DS) footfall used in symmetrical gaits. This presumably unique feature of primate locomotion has been attributed to an ancestral adaptation for cautious arboreal quadrupedalism on thin, flexible branches. However, the functional significance of DS gait remains largely hypothetical. The study presented here tests hypotheses about the functional significance of DS gait by analyzing the gait mechanics of a primate that alternates between DS and lateral sequence (LS) gaits, Cebus apella. Kinematic and kinetic data were gathered from two subjects as they moved across both terrestrial and simulated arboreal substrates. These data were used to test four hypotheses: (1) locomotion on arboreal supports is associated with increased use of DS gait, (2) DS gait is associated with lower peak vertical substrate reaction forces than LS gait, (3) DS gait is associated with greater forelimb/hind limb differentiation in force magnitudes, and (4) DS gait offers increased stability. Our results indicate that animals preferred DS gait on the arboreal substrate, and LS gait while on the ground. Peak vertical substrate reaction forces showed a tendency to be lower in DS gait, but not consistently so. Pole ("arboreal") forces were lower than ground forces in DS gait, but not in LS gait. The preferred symmetrical gait on both substrates was a grounded run or amble, with the body supported by only one limb throughout most of the stride. During periods of bilateral support, the DS gait had predominantly diagonal support couplets. This benefit for stability on an arboreal substrate is potentially outweighed by overstriding, its associated ipsilateral limb interference in DS gait and hind foot positioning in front of the hand on untested territory. DS gait also did not result in an optimal anchoring position of the hind foot under the center of mass of the body at forelimb touchdown. In sum, the results are mixed regarding the superiority of DS gait in an arboreal setting. Consequently, the notion that DS gait is an ancestral adaptation of primates, conditioned by the selection demands of an arboreal environment, remains largely hypothetical.     

Spatio-temporal parameters of gait measured by an ambulatory system using miniature gyroscopes

In this study we describe an ambulatory system for estimation of spatio-temporal parameters during long periods of walking. This original method based on wavelet analysis is proposed to compute the values of temporal gait parameters from the angular velocity of lower limbs. Based on a mechanical model, the medio-lateral rotation of the lower limbs during stance and swing, the stride length and velocity are estimated by integration of the angular velocity. Measurement's accuracy was assessed using as a criterion standard the information provided by foot pressure sensors. To assess the accuracy of the method on a broad range of performance for each gait parameter, we gathered data from young and elderly subjects. No significant error was observed for toe-off detection, while a slight systematic delay (10 ms on average) existed between heelstrike obtained from gyroscopes and footswitch. There was no significant difference between actual spatial parameters (stride length and velocity) and their estimated values. Errors for velocity and stride length estimations were 0.06 m/s and 0.07 m, respectively. This system is light, portable, inexpensive and does not provoke any discomfort to subjects. It can be carried for long periods of time, thus providing new longitudinal information such as stride-to-stride variability of gait. Several clinical applications can be proposed such as outcome evaluation after total knee or hip replacement, external prosthesis adjustment for amputees, monitoring of rehabilitation progress, gait analysis in neurological diseases, and fall risk estimation in elderly.     

Body temperature and oxygen consumption of two malaysian prosimians

The body temperature and oxygen consumption of freshly trapped Slow Loris (Nycticebus coucang) and Common Tree Shrews (Tupaia glis) were measured in Malaysia. The Slow Loris had a low body temperature and oxygen consumption, while the values for the Common Tree Shrew were relatively high. The data are discussed in relation to information obtained from captive animals. The importance of the Slow Loris is stressed because it represents one of the few natural hypometabolic states in primates.     

Functional differentiation of long bones in lorises

The external dimensions of the limb bones and the geometry of their midshaft cross-sections were determined for Loris tardigradus and Nycticebus coucang. Relative cortical thickness, cortical area, and second moment of area were calculated and contrasted with locomotor stresses. The difference in shape-related strength of the bones between the smaller- and the larger-bodied species is more pronounced than can be expected from stresses acting during normal locomotion. The Nycticebus skeleton has a much higher safety margin overall and seems to be dimensioned for infrequent but critical stresses of high magnitude. Lorisine gaits in general are characterized by low ground reaction forces, great mobility in all joints, and a nearly equal share in propulsion and weight-bearing by the fore- and hindlimb. Accordingly, the long bones of lorises (especially those of L. tardigradus) tend to be less rigid than those of other mammalian species (including other primates), they lack a preferential plane of higher bending strength, and femur and humerus do not differ markedly in their capacity to withstand mechanical stresses. External dimensions of the humerus and femur of the two African lorisine species parallel and corroborate these results. Some more general implications for the relationships between bone shape and locomotor stresses are also discussed.     

Interactive rhythmic auditory stimulation reinstates natural 1/f timing in gait of Parkinson's patients

Parkinson's disease (PD) and basal ganglia dysfunction impair movement timing, which leads to gait instability and falls. Parkinsonian gait consists of random, disconnected stride times--rather than the 1/f structure observed in healthy gait--and this randomness of stride times (low fractal scaling) predicts falling. Walking with fixed-tempo Rhythmic Auditory Stimulation (RAS) can improve many aspects of gait timing; however, it lowers fractal scaling (away from healthy 1/f structure) and requires attention. Here we show that interactive rhythmic auditory stimulation reestablishes healthy gait dynamics in PD patients. In the experiment, PD patients and healthy participants walked with a) no auditory stimulation, b) fixed-tempo RAS, and c) interactive rhythmic auditory stimulation. The interactive system used foot sensors and nonlinear oscillators to track and mutually entrain with the human's step timing. Patients consistently synchronized with the interactive system, their fractal scaling returned to levels of healthy participants, and their gait felt more stable to them. Patients and healthy participants rarely synchronized with fixed-tempo RAS, and when they did synchronize their fractal scaling declined from healthy 1/f levels. Five minutes after removing the interactive rhythmic stimulation, the PD patients' gait retained high fractal scaling, suggesting that the interaction stabilized the internal rhythm generating system and reintegrated timing networks. The experiment demonstrates that complex interaction is important in the (re)emergence of 1/f structure in human behavior and that interactive rhythmic auditory stimulation is a promising therapeutic tool for improving gait of PD patients.     

笼养间蜂猴的繁殖

1989年至今,对15只（10,5）成年间蜂猴在人工饲养条件下的繁殖进行观察,结果为：1．间蜂猴的繁殖有明显的季节性;2．发情周期为49．67d(SD=1.25),在此期间,雌性外生殖器红肿,变大;雄性阴囊胀大;3．交配以背腹相贴为主;4．怀孕期为188d;5．哺乳期为108d(SD=4.12);6．均为一胎二仔。     

The importance of swing-phase initial conditions in stiff-knee gait

The diminished knee flexion associated with stiff-knee gait, a movement abnormality commonly observed in persons with cerebral palsy, is thought to be caused by an over-active rectus femoris muscle producing an excessive knee extension moment during the swing phase of gait. As a result, treatment for stiff-knee gait is aimed at altering swing-phase muscle function. Unfortunately, this treatment strategy does not consistently result in improved knee flexion. We believe this is because multiple factors contribute to stiff-knee gait. Specifically, we hypothesize that many individuals with stiff-knee gait exhibit diminished knee flexion not because they have an excessive knee extension moment during swing, but because they walk with insufficient knee flexion velocity at toe-off. We measured the knee flexion velocity at toe-off and computed the average knee extension moment from toe-off to peak flexion in 17 subjects (18 limbs) with stiff-knee gait and 15 subjects (15 limbs) without movement abnormalities. We used forward dynamic simulation to determine how adjusting each stiff-knee subject's knee flexion velocity at toe-off to normal levels would affect knee flexion during swing. We found that only one of the 18 stiff-knee limbs exhibited an average knee extension moment from toe-off to peak flexion that was larger than normal. However, 15 of the 18 limbs exhibited a knee flexion velocity at toe-off that was below normal. Simulating an increase in the knee flexion velocity at toe-off to normal levels resulted in a normal or greater than normal range of knee flexion for each of these limbs. These results suggest that the diminished knee flexion of many persons with stiff-knee gait may be caused by abnormally low knee flexion velocity at toe-off as opposed to excessive knee extension moments during swing.     

Muscles that influence knee flexion velocity in double support: implications for stiff-knee gait

Adequate knee flexion velocity at toe-off is important for achieving normal swing-phase knee flexion during gait. Consequently, insufficient knee flexion velocity at toe-off can contribute to stiff-knee gait, a movement abnormality in which swing-phase knee flexion is diminished. This work aims to identify the muscles that contribute to knee flexion velocity during double support in normal gait and the muscles that have the most potential to alter this velocity. This objective was achieved by perturbing the forces generated by individual muscles during double support in a forward dynamic simulation of normal gait and observing the effects of the perturbations on peak knee flexion velocity. Iliopsoas and gastrocnemius were identified as the muscles that contribute most to increasing knee flexion velocity during double support. Increased forces in vasti, rectus femoris, and soleus were found to decrease knee flexion velocity. Vasti, rectus femoris, gastrocnemius, and iliopsoas were all found to have large potentials to influence peak knee flexion velocity during double support. The results of this work indicate which muscles likely contribute to the diminished knee flexion velocity at toe-off observed in stiff-knee gait, and identify the treatment strategies that have the most potential to increase this velocity in persons with stiff-knee gait.     

Patterns of axial and appendicular movements during aquatic walking in the salamander Siren lacertina

Most studies of salamander locomotion have focused either on swimming or terrestrial walking, but some salamanders also use limb-based locomotion while submerged under water (aquatic walking). In this study we used video motion analysis to describe the aquatic walking gait of Siren lacertina, an elongate salamander with reduced forelimbs and no hindlimbs. We found that S. lacertina uses a bipedal-undulatory gait, which combines alternating use of the forelimbs with a traveling undulatory wave. Each forelimb is in contact with the substrate for about 50% of the stride cycle and forelimbs have little temporal overlap in contact intervals. We quantified the relative timing and frequency of limb and tail movements and found that, unlike the terrestrial gaits of most salamanders, axial and appendicular movements are decoupled during aquatic walking. We found no significant relationship between stride frequency and aquatic walking velocity, but we did find a statistically significant relationship between tailbeat frequency and aquatic walking velocity, which suggests that aquatic walking speed is mainly modulated by axial movements. By comparing axial wavespeed and distance traveled per tailbeat during swimming (forelimbs not used) and aquatic walking (forelimbs used), we found lower wavespeed and greater distance traveled per tailbeat during aquatic walking. These findings suggest that the reduced forelimbs of S. lacertina contribute to forward propulsion during aquatic walking.     

Dynamic Biomechanical Examination of the Lumbar Spine with Implanted Total Spinal Segment Replacement (TSSR) Utilizing a Pendulum Testing System

Background

Biomechanical investigations of spinal motion preserving implants help in the understanding of their in vivo behavior. In this study, we hypothesized that the lumbar spine with implanted total spinal segment replacement (TSSR) would exhibit decreased dynamic stiffness and more rapid energy absorption compared to native functional spinal units under simulated physiologic motion when tested with the pendulum system.

Methods

Five unembalmed, frozen human lumbar functional spinal units were tested on the pendulum system with axial compressive loads of 181 N, 282 N, 385 N, and 488 N before and after Flexuspine total spinal segment replacement implantation. Testing in flexion, extension, and lateral bending began by rotating the pendulum to 5°; resulting in unconstrained oscillatory motion. The number of rotations to equilibrium was recorded and bending stiffness (N-m/°) was calculated and compared for each testing mode.

Results

The total spinal segment replacement reached equilibrium with significantly fewer cycles to equilibrium compared to the intact functional spinal unit at all loads in flexion (p<0.011), and at loads of 385 N and 488 N in lateral bending (p<0.020). Mean bending stiffness in flexion, extension, and lateral bending increased with increasing load for both the intact functional spinal unit and total spinal segment replacement constructs (p<0.001), with no significant differences in stiffness between the intact functional spinal unit and total spinal segment replacement in any of the test modes (p>0.18).

Conclusions

Lumbar functional spinal units with implanted total spinal segment replacement were found to have similar dynamic bending stiffness, but absorbed energy at a more rapid rate than intact functional spinal units during cyclic loading with an unconstrained pendulum system. Although the effects on clinical performance of motion preserving devices is not fully known, these results provide further insight into the biomechanical behavior of this device under approximated physiologic loading conditions.     

How to measure responses of the knee to lateral perturbations during gait? A proof-of-principle for quantification of knee instability

Knee instability is a major problem in patients with anterior cruciate ligament injury or knee osteoarthritis. A valid and clinically meaningful measure for functional knee instability is lacking. The concept of the gait sensitivity norm, the normalized perturbation response of a walking system to external perturbations, could be a sensible way to quantify knee instability. The aim of this study is to explore the feasibility of this concept for measurement of knee responses, using controlled external perturbations during walking in healthy subjects.Nine young healthy participants walked on a treadmill, while three dimensional kinematics were measured. Sudden lateral translations of the treadmill were applied at five different intensities during stance. Right knee kinematic responses and spatio-temporal parameters were tracked for the perturbed stride and following four cycles, to calculate perturbation response and gait sensitivity norm values (i.e. response/perturbation) in various ways.The perturbation response values in terms of knee flexion and abduction increased with perturbation intensity and decreased with an increased number of steps after perturbation. For flexion and ab/adduction during midswing, the gait sensitivity norm values were shown to be constant over perturbation intensities, demonstrating the potential of the gait sensitivity norm as a robust measure of knee responses to perturbations.These results show the feasibility of using the gait sensitivity norm concept for certain gait indicators based on kinematics of the knee, as a measure of responses during perturbed gait. The current findings in healthy subjects could serve as reference-data to quantify pathological knee instability.     

Microcomputer-based low-cost method for measurement of spatial and temporal parameters of gait

The instantaneous velocity of the forward-going foot is measured throughout the swing phase during several successive gait cycles using punched paper tapes attached to the feet. The velocity profiles thus obtained show clearly any asymmetry or departure from the normal walking pattern. The data are processed to provide the spatial and temporal parameters of gait, i.e. step lengths, stride times, double-support times, cadence and walking speed. The equipment is low-cost, easy to set up and use, and the results, which are presented on the VDU or as hard copy, are readily interpreted and related to the underlying pathology.