Sagittal Motion Research Articles

Proportional lumbar spine inter-vertebral motion patterns: a comparison of patients with chronic, non-specific low back pain and healthy controls

Identifying biomechanical subgroups in chronic, non-specific low back pain (CNSLBP) populations from inter-vertebral displacements has proven elusive. Quantitative fluoroscopy (QF) has excellent repeatability and provides continuous standardised inter-vertebral kinematic data from fluoroscopic sequences allowing assessment of mid-range motion. The aim of this study was to determine whether proportional continuous IV rotational patterns were different in patients and controls. A secondary aim was to update the repeatability of QF measurement of range of motion (RoM) for inter-vertebral (IV) rotation. Fluoroscopic sequences were recorded of passive, recumbent coronal and sagittal motion, which was controlled for range and velocity. Segments L2-5 in 40 primary care CNSLBP patients and 40 matched controls were compared. Patients also completed the von Korff Chronic Pain Grade and Roland and Morris Disability Questionnaire. Sequences were processed using automated image tracking algorithms to extract continuous inter-vertebral rotation data. These were converted to continuous proportional ranges of rotation (PR). The continuous proportional range variances were calculated for each direction and combined to produce a single variable representing their fluctuation (CPRV). Inter- and intra-rater repeatability were also calculated for the maximum IV-RoM measurements obtained during controlled trunk motion to provide an updated indication of the reliability and agreement of QF for measuring spine kinematics. CPRV was significantly higher in patients (0.011 vs. 0.008, Mann-Whitney two-sided p = 0.008), implying a mechanical subgroup. Receiver operating characteristic curve analysis found its sensitivity and specificity to be 0.78 % (60-90) and 0.55 % (37-73), respectively (area under the curve 0.672). CPRV was not correlated with pain severity or disability. The repeatability of maximum inter-vertebral range was excellent, but range was only significantly greater in patients at L4-5 in right side bending (p = 0.03). The variation in proportional motion between lumbar vertebrae during passive recumbent trunk motion was greater in patients with CNSLBP than in matched healthy controls, indicating that biomechanical factors in passive structures play a part.

ARE TWO-DIMENSIONAL MEASURED SAGITTAL PLANE KINEMATICS RELATED TO THREE-DIMENSIONAL JOINT LOADING DURING THE DROP VERTICAL JUMP TEST?

BackgroundAcute and overuse knee injuries are common in sports involving jump-landing movements, especially in female athletes. More erect sagittal plane movement patterns are believed to increase injury risk. Whilst three-dimensional...

Post-traumatic elbow rotational stiffness.

The elbow is an important but complex structure, with movement in both the sagittal plane in flexion and extension, as well as the rotational plane in forearm supination and pronation. Trauma is a common cause of elbow stiffness, which significantly hampers daily function. There are currently no gold-standard management guidelines for post-traumatic elbow stiffness, and most of the published literature focuses solely on the sagittal plane of motion. This is a retrospective case series reviewing all patients who underwent a surgical release for treatment of post-traumatic elbow stiffness during a 36-month period. Motion range and the shortened version of the Disabilities of the Arm, Shoulder and Hand scores were serially measured and analyzed. The results obtained showed that both the sagittal and rotational range of motion directly influenced upper limb function; however, the relationship between these two motion planes was weak, meaning that both sagittal and rotational motion in the elbow need be addressed individually. Post-traumatic elbow stiffness could be aptly managed by various surgical approaches, including arthroscopic-assisted procedures; these were all effective in increasing both the sagittal and rotational range of motion. More importantly, this gain in range translated to a statistically significant improvement in upper limb function. Management of elbow stiffness needs to be tackled in both the sagittal and rotational motion planes.

Amputation effects on the underlying complexity within transtibial amputee ankle motion

The presence of chaos in walking is considered to provide a stable, yet adaptable means for locomotion. This study examined whether lower limb amputation and subsequent prosthetic rehabilitation resulted in a loss of complexity in amputee gait. Twenty-eight individuals with transtibial amputation participated in a 6 week, randomized cross-over design study in which they underwent a 3 week adaptation period to two separate prostheses. One prosthesis was deemed "more appropriate" and the other "less appropriate" based on matching/mismatching activity levels of the person and the prosthesis. Subjects performed a treadmill walking trial at self-selected walking speed at multiple points of the adaptation period, while kinematics of the ankle were recorded. Bilateral sagittal plane ankle motion was analyzed for underlying complexity through the pseudoperiodic surrogation analysis technique. Results revealed the presence of underlying deterministic structure in both prostheses and both the prosthetic and sound leg ankle (discriminant measure largest Lyapunov exponent). Results also revealed that the prosthetic ankle may be more likely to suffer loss of complexity than the sound ankle, and a "more appropriate" prosthesis may be better suited to help restore a healthy complexity of movement within the prosthetic ankle motion compared to a "less appropriate" prosthesis (discriminant measure sample entropy). Results from sample entropy results are less likely to be affected by the intracycle periodic dynamics as compared to the largest Lyapunov exponent. Adaptation does not seem to influence complexity in the system for experienced prosthesis users.

Load sharing in lumbar spinal segment as a function of location of center of rotation

The center (axis) of rotation (COR) in the lumbar spine has been studied well. However, there is limited information on the kinetic and kinematic consequences of imposed shift in the location of the COR, although this type of shift can be seen after surgeries using motion preservation or dynamic stabilization devices. The objective of this study was to assess the kinetic and kinematic changes in the lumbar spinal segment due to various imposed CORs. A 3D finite element model of the L4-5 segment was constructed and validated. The segment was loaded under a 7.5-Nm bending moment while constrained to rotate about various imposed CORs in the sagittal and axial motion planes. Range of motion, ligament forces, facet loads, and disc stresses were measured. The present model showed an agreement with previous in vitro and finite element studies under the same load and boundary conditions. Range of motion, facet forces, disc stresses, and ligament loads showed a strong association with the location of the COR. Acute alterations in the location of the COR can significantly change the load sharing characteristics within the spine segment. The normal location of the COR is a result of the tendency of the vertebra to move in the path of least cumulative resistance.

Unilateral ankle immobilization alters the kinematics and kinetics of lifting

Theoretical and empirical data support the notion that distal lower extremity joint dysfunction could influence the low-back injury potential of workers, but the impact of unilateral ankle immobilization on low-back loading during lifting has yet to be examined. To examine the influence of unilateral ankle immobilization on the kinematics and kinetics of lifting. With and without their right ankle immobilized, 10 men performed laboratory-simulated occupational lifting tasks. Together with force platform data, three-dimensional kinematics of the lumbar spine, pelvis, and lower extremities were collected, and a dynamic biomechanical model was used to calculate peak compressive and shear loads imposed on the L4/L5 intervertebral joint. In comparison to the unaffected conditions, ankle immobilization generally resulted in less knee (0.001 ≤ p ≤ 0.07) and greater lumbar spine (0.001 ≤ p ≤ 0.35) sagittal motion when lifting. Associated with this compensatory movement strategy were greater L4/L5 anterior/posterior reaction shear forces (0.001 ≤ p ≤ 0.25). However, there were cases when individual compensatory movement strategies differed from the "group" response (i.e., subjects increased their sagittal knee motion on the affected side about 8% of the time); this resulted in increased peak L4/L5 joint compression forces without changing the peak L4/L5 anterior-posterior shear forces. Ankle dysfunction can alter the way in which individuals move and load their low-backs when lifting. The different ways in which individuals compensate for personal movement constraints could alter the potential site and mechanism of occupational low-back injury.

Sagittal joint instability in the cranial cruciate ligament insufficient canine stifle

This in vivo study qualitatively describes the sagittal motion pattern of the cranial cruciate ligament (CrCL) insufficient canine stifle in operated and unoperated joints with cranio-caudal laxity on palpation. Sagittal stifle kinematics were recorded in vivo in dogs (> 15 kg BW) with unilateral (n = 7) or bilateral (n = 6) complete CrCL rupture and positive cranial drawer test as well as two sound control dogs using uniplanar fluoroscopic kinematography with the dogs walking on a treadmill. Stifle stability and sagittal motion pattern of the femur and the tibia were determined by visual inspection of the fluoroscopic video sequences. Control dogs showed no cranio-caudal instability, identical to the contralateral stifles of the dogs with unilateral rupture. All unoperated stifles with CrCL rupture (n = 6) showed caudal slippage of the femur at the beginning of the stance phase. Of the 13 operated stifles (TightRope: n = 1, tibial tuberosity advancement, TTA: n = 6, tibial plateau leveling osteotomy, TPLO: n = 5, cranial closing wedge osteotomy, CCWO: n = 1) nine were unstable, showing the same motion pattern as the unoperated stifles. In the CrCL insufficient stifle with in vivo cranio-caudal instability caudal slippage of the distal femur at tow touch is the predominant motion pattern. The discrepancy between in vivo motion pattern and in vitro simulation of CrCL insufficiency in which cranial tibial subluxation is the predominant sagittal motion pattern warrants further studies.

Sagittal and axial mobility of 1st ray in hallux valgus

Hypermobility of the first ray is one causative factor in development and recurrence of Hallux valgus[1],[2],[3]. so treated as an important factor in hallux valgus. While most discussions of 1st ray instability refer to sagittal motion [4],[5], [6],[7]. Increased motion may also be present in the axial plan. However, there is no known way of measuring motion of axial plan. In this study, we assessed the axial plan mobility by means of measuring the difference between weight bearing IMA and non-weight bearing IMA from foot AP radiograph. This study investigated the difference between the axial motion of the first ray of the symptomatic hallux valgus patients group and that of the normal group.

Temporal pattern in segmental motions of the foot in healthy senile adults: comparison between young and senile healthy adults

The incidence of foot and ankle disease increases as the age increases [1,2]. However, there was no report about differences of foot motion between senile person and young adults. The purpose of this study is to analyze distinctions according to age in segmental foot motion using 3D multi-foot model from healthy senior and young adults. One hundred senile (50 males, 50 females) and young adults (50 males, 50 females) were tested by 3D multi-foot model with 15-markers. The cadence, speed, stride length, step width, step time, and stance phase were analyzed. The maximum and minimal values and motions of 3-planes of hallux, forefoot, hindfoot, and arch were compared between senile and young adults. The cadence, speed, stride length, and step width were lower in senior. The stance phase was longer (Table​(Table1).1). In female, sagittal motion of all segment were more limited and hindfoot was more unstable in senior (Figure ​(Figure1).1). In male, sagittal motion of hallux and forefoot were lower in senior (Figure ​(Figure2).2). Hallux valgus of male and female was more severe in senior during gait. Arch height was no difference (Figure ​(Figure3).3). In 3D foot gait analysis, the differences between senior and young adults were apparent. In summary, foot motion in senior had limited range of motion during gait. And hallux valgus in senior was more severe. But arch height was not diminished. The understanding about changes of foot segmental motion depending on age will suggest more correct approach in degenerative foot and ankle disease. Table 1 Basic gait parameters in senile adults Figure 1 Comparison of the mean foot segmental motion between senile and young adults in female. Figure 2 Comparison of the mean foot segmental motion between senile and young adults in male. Figure 3 Comparison of the mean foot segmental motion between male and female in senior.

Gender differences in segmental foot motions during gait using 3D multi‐segment foot model

in female than in male. The stride length, the step width, and the step time were significantly longer in male. The speed and the proportion of stance phase were not significantly different (Table 1). The range of segmental motion (hallux, forefoot, hindfoot) and arch data were recorded during the gait and compared between male and female. The both genders had similar patterns of segmental foot motions. The range of sagittal motion and coronal angulation of the hallux was greater during gait in females. The range of motion on the hindfoot was also greater in females. The male had higher adjusted arch height and arch index. However, the range of adjusted arch height was larger in females (Figure 1). We demonstrated that there was a substantial temporal pattern of the foot segmental motion in normal adults. We also presented that

Effects of supramalleolar osteotomies for ankle osteoarthritis on foot kinematics and lower leg muscle activation during walking

BackgroundEarly stages of asymmetric ankle osteoarthritis can be treated by joint preserving supramalleolar osteotomies that surgically realign the ankle and unload degenerated cartilage. While studies have already shown pain relief and functional improvements, the effects on gait biomechanics are largely unknown. This study investigated patients' gait pattern after supramalleolar osteotomies by focusing on foot kinematics and lower leg muscle activation. MethodsAn instrumented three-dimensional gait analysis with simultaneous electromyography of gastrocnemius medialis and lateralis, soleus, peroneus longus, and tibialis anterior muscles was performed on 12 patients with ankle osteoarthritis, seven of which were followed up 12–18months postoperatively. Additionally, seven different long-term follow-up patients (8–9years postoperatively) and 15 healthy control subjects were measured. The waveforms of the foot kinematics and muscle activation were analyzed using principal component analysis. FindingsCompared to healthy controls, principal component scores that affected the sagittal range of motion of the hindfoot and hallux were lower in all patient groups, while scores that affected the timing of the peaks in the sagittal forefoot motion were mainly altered in short-term follow-up patients. Lower principal component scores in patients with ankle osteoarthritis and short-term follow-up patients resulted in a less pronounced peak activation of gastrocnemius medialis and soleus. InterpretationBoth postoperative patient groups showed similar adaptations in their gait pattern as those observed in patients with ankle osteoarthritis. These changes are probably related to the lower ankle mobility. However, the reduced mobility seems to affect the patients' well-being less than a painful joint.

The Six Degrees of Freedom Motion of the Human Head, Spine, and Pelvis in a Frontal Impact

Objective: The goal of this study is to characterize the in situ 6-degree-of-freedom kinematics of the head, 3 vertebrae (T1, T8, and L2), and the pelvis in a 40 km/h frontal impact. Methods: Three postmortem human surrogates (PMHS) were exposed to a deceleration of 15 g over 125 ms and the motion of selected anatomical structures (head, T1, T8, L2, and pelvis) was tracked at 1000 Hz using an optoelectric stereophotogrammetric system. Displacements of the analyzed structures are reported in the sagittal and the transverse planes. Rotations of the structures are described using the finite helical axis of the motion. Results: Anterior displacements were 530.5 ± 39.4 mm (head), 434.7 ± 20.0 mm (T1), 353.3 ± 29.6 mm (T8), 219.9 ± 19.3 mm (L2), and 78.9 ± 22.1 mm (pelvis). The ratio between peak anterior and lateral displacement was up to 19 percent (T1) and 26 percent (head). Magnitudes of the rotation of the head (69.9 ± 1.5°), lumbar (66.5 ± 9.1°), and pelvis (63.8 ± 11.8°) were greater than that of the thoracic vertebrae (T1: 49.1 ± 7.8°; T8: 47.7 ± 6.3°). Thoracic vertebrae exhibited a complex rotation behavior caused by the asymmetric loading of the shoulder belt. Rotation of the lumbar vertebra and pelvis occurred primarily within the sagittal plane (flexion). Conclusion: Despite the predominance of the sagittal motion of the occupant in a pure (12 o’clock) frontal impact, the asymmetry of belt loading induced other relevant displacements and rotations of the head and thoracic spine. Attempts to model occupant kinematics in a frontal impact should consider these results to biofidelically describe the interaction of the torso with the belt.

Foot and ankle joint movements inside orthoses for children with spastic CP

We compared the ankle joint and foot segment kinematics of pediatric cerebral palsy (CP) participants walking with and without orthoses. A six segment foot model (6SF) was used to track foot motion. Holes were cut in the study orthoses so that electromagnetic markers could be directly placed on the skin. The Hinged Ankle Foot Orthoses (HAFO) allowed a significant increase in ankle dorsiflexion as compared to the barefoot condition during gait, but significantly constrained sagittal forefoot motion and forefoot sagittal range of motion (ROM) (p < 0.01), which may be detrimental. The Solid Ankle Foot Orthoses (SAFO) constrained forefoot ROM as compared to barefoot gait (p < 0.01). The 6SF model did not confirm that the SAFO can control excessive plantarflexion for those with severe plantarflexor spasticity. The supramalleolar orthosis (SMO) significantly (p < 0.01) constrained forefoot ROM as compared to barefoot gait at the beginning and end of the stance phase, which could be detrimental. The SMO had no effects observed in the coronal plane.

Trunk bend and twist coordination is affected by low back pain status during running

Recent literature has related differences in pelvis–trunk coordination to low back pain (LBP) status. In addition, repetitive motions involving bending and twisting have been linked to high incidence of LBP. The purpose of this study was to examine trunk sagittal motion – axial rotation (‘bend and twist’) coordination during locomotion in three groups of runners classified by LBP status (LBP: current low back pain; RES: resolved low back pain and CTR: control group with no history of LBP). Trunk kinematic data were collected as running speed was systematically increased on a treadmill. Within-segment coordination between trunk sagittal and transverse planes of motion (trunk lean and axial rotation, respectively) was calculated using continuous relative phase (CRP), and coordination variability was defined as the between stride cycle standard deviation of CRP (CRPvar). Bend–twist coordination was more in-phase for the LBP group than CTR (p = 0.010) regardless of running speed. No differences in CRPvar were found between the groups. The results from our coordination (CRP) analysis were sensitive to LBP status and suggest that multi-plane interactions of the trunk should be considered in the assessment of LBP. This analysis also has potential for athletically oriented tasks that involve multi-plane interactions of the trunk, particularly ones that contain asymmetric action, such as sweep rowing or a shot on goal in field hockey or ice hockey.

Reliability and measurement error of sagittal spinal motion parameters in 220 patients with chronic low back pain using a three-dimensional measurement device

Background contextA basic premise for any instrument measuring spinal motion is that reliable outcomes can be obtained on a relevant sample under standardized conditions. PurposeThe purpose of this study was to assess the overall reliability and measurement error of regional spinal sagittal plane motion in patients with chronic low back pain (LBP), and then to evaluate the influence of body mass index, examiner, gender, stability of pain, and pain distribution on reliability and measurement error. Study design/settingThis study comprises a test-retest design separated by 7 to 14 days. Patient sampleThe patient cohort consisted of 220 individuals with chronic LBP. Outcome measuresKinematics of the lumbar spine were sampled during standardized spinal extension-flexion testing using a 6-df instrumented spatial linkage system. MethodsTest-retest reliability and measurement error were evaluated using interclass correlation coefficients (ICC1,1) and Bland-Altman limits of agreement (LOAs). ResultsThe overall test-retest reliability (ICC1,1) for various motion parameters ranged from 0.51 to 0.70, and relatively wide LOAs were observed for all parameters. Reliability measures in patient subgroups (ICC1,1) ranged between 0.34 and 0.77. In general, greater (ICC1,1) coefficients and smaller LOAs were found in subgroups with patients examined by the same examiner, patients with a stable pain level, patients with a body mass index less than below 30 kg/m2, patients who were men, and patients in the Quebec Task Force classifications Group 1. ConclusionsThis study shows that sagittal plane kinematic data from patients with chronic LBP may be sufficiently reliable in measurements of groups of patients. However, because of the large LOAs, this test procedure appears unusable at the individual patient level. Furthermore, reliability and measurement error varies substantially among subgroups of patients.

Modeling and Control of Passive Dynamic Walking Robot with Humanoid Gait

Considering the sagittal movement and the lateral swing in the humanoid practical walking, a new humanoid passive dynamic bipedal robot with the lateral movable upper body is proposed in this paper. The finite state machine (FSM) theory is adopted to control the robot, which changes agilely the control strategy according to the practical states of the humanoid gait. In the method, the torque compensation adaptive excitation control strategy is used for sagittal control and PID is applied to the upper body for the robots lateral stability. It is verified by the co-simulation based on ADAMS and MATLAB that the bipedal robot can reach the stable humanoid gait with the high energy efficiency.

Lumbopelvic rhythm during forward and backward sagittal trunk rotations: Combined in vivo measurement with inertial tracking device and biomechanical modeling

BackgroundThe ratio of total lumbar rotation over pelvic rotation (lumbopelvic rhythm) during trunk sagittal movement is essential to evaluate spinal loads and discriminate between low back pain and asymptomatic population. MethodsAngular rotations of the pelvis and lumbar spine as well as their sagittal rhythm during forward flexion and backward extension in upright standing of eight asymptomatic males are measured using an inertial tracking device. The effect of variations in the lumbopelvic ratio during trunk flexion on spinal loads is quantified using a detailed musculoskeletal model. FindingsThe mean of peak voluntary flexion rotations of the thorax, pelvis, and lumbar was 121° (SD 9.9), 53.0° (SD 5.2), and 60.2° (SD 8.6), respectively. The mean lumbopelvic ratios decreased from 2.51 in 0–30° of trunk flexion to 1.34 in 90–120° range during forward bending while it increased from 1.23 in 90–120° range to 2.86 in 0–30° range during backward extension. Variations in the lumbopelvic ratio from 0.5 to 3 (with an interval of 0.25) at any trunk flexion angle generally reduced the L5–S1 compression and shear forces by up to 21 and 45%, respectively. The measured lumbopelvic ratios resulted overall in near-optimal (minimal) L5–S1 compression forces. InterpretationA simultaneous rhythm between the lumbar and pelvis movements was found during both forward and backward trunk movements. While the lumbar spine contributed more to the trunk rotation during early and final stages of forward flexion and backward extension, respectively, the pelvis contributed more during final and early stages of forward flexion and backward extension, respectively. Our healthy subjects adapted a lumbopelvic coordination that diminished L5–S1 compression force.

Comparison of cervical kinematics between patients with cervical artificial disc replacement and anterior cervical discectomy and fusion for cervical disc herniation

Background contextAlthough anterior cervical discectomy and fusion (ACDF) is an effective treatment option for patients with cervical disc herniation, it limits cervical range of motion, which sometimes causes discomfort and leads to biomechanical stress at neighboring segments. In contrast, cervical artificial disc replacement (ADR) is supposed to preserve normal cervical range of motion than ACDF. A biomechanical measurement is necessary to identify the advantages and clinical implications of ADR. However, literature is scarce about this topic and in those available studies, authors used the static radiological method, which cannot identify three-dimensional motion and coupled movement during motion of one axis. PurposeThe purpose of this study was to compare the clinical parameters and cervical motion by three-dimensional motion analysis between ACDF and ADR and to investigate the ability of ADR to maintain cervical kinematics. Study designThis was a prospective case control study. Patient samplePatients who underwent ADR or ACDF for the treatment of single-level cervical disc herniation. Outcome measuresVisual analog scale (VAS), Korean version of Neck Disability Index (NDI, %), and three-dimensional motion analysis were used. MethodsThe patients were evaluated by VAS and the Korean version of the NDI (%) to assess pain degree and functional status. Cervical motions were assessed by three-dimensional motion analysis in terms of sagittal, coronal, and horizontal planes. Markers of 2.5 cm in diameter were attached at frontal polar (Fpz), center (Cz), and occipital (Oz) of 10–20 system of electroencephalography, C7 spinous process, and both acromions. These evaluations were performed preoperatively and 1 month and 6 months after surgery. ResultsThe ACDF and ADR groups revealed no significant difference in VAS, NDI (%), and cervical range of motion preoperatively. After surgery, both groups showed no significant difference in VAS and NDI (%). In motion analysis, significantly more range of motion was retained in flexion and extension in the ADR group than the ACDF group at 1 month and 6 months. There was no significant difference in lateral tilt and rotation angle. In terms of coupled motion, ADR group exhibited significantly more preserved sagittal plane motion during right and left rotation and also showed significantly more preserved right lateral bending angle during right rotation than ACDF group at 1 month and 6 months. There was no significant difference in other coupled motions. ConclusionThree-dimensional motion analysis could provide useful information in an objective and quantitative way about cervical motion after surgery. In addition, it allowed us to measure not only main motion but also coupled motion in three planes. ADR demonstrated better retained cervical motion mainly in sagittal plane (flexion and extension) and better preserved coupled sagittal and coronal motion during transverse plane motion than ACDF. ADR had the advantage in that it had the ability to preserve more cervical motions after surgery than ACDF.

Walking at the preferred stride frequency maximizes local dynamic stability of knee motion

Healthy humans display a preference for walking at a stride frequency dependent on the inertial properties of their legs. Walking at preferred stride frequency (PSF) is predicted to maximize local dynamic stability, whereby sensitivity to intrinsic perturbations arising from natural variability inherent in biological motion is minimized. Previous studies testing this prediction have employed different variability measures, but none have directly quantified local dynamic stability by computing maximum finite-time Lyapunov exponent (λMax), which quantifies the rate of divergence of nearby trajectories in state space. Here, ten healthy adults walked 45m overground while sagittal motion of both knees was recorded via electrogoniometers. An auditory metronome prescribed 7 different frequencies relative to each individual's PSF (PSF; ±5, ±10, ±15strides/min). Stride frequencies were performed under both freely adopted speed (FS) and controlled speed (CS: set at the speed of PSF trials) conditions. Local dynamic stability was maximal (λMax was minimal) at the PSF, becoming less stable for higher and lower stride frequencies. This occurred under both FS and CS conditions, although controlling speed further reduced local dynamic stability at non-preferred stride frequencies. In contrast, measures of variability revealed effects of stride frequency and speed conditions that were distinct from λMax. In particular, movement regularity computed by approximate entropy (ApEn) increased for slower walking speeds, appearing to depend on speed rather than stride frequency. The cadence freely adopted by humans has the benefit of maximizing local dynamic stability, which can be interpreted as humans tuning to their resonant frequency of walking.

Locomotor Anatomy and Behavior of Patas Monkeys (Erythrocebus patas) with Comparison to Vervet Monkeys (Cercopithecus aethiops).

Patas monkeys (Erythrocebus patas) living in African savanna woodlands and grassland habitats have a locomotor system that allows them to run fast, presumably to avoid predators. Long fore- and hindlimbs, long foot bones, short toes, and a digitigrade foot posture were proposed as anatomical correlates with speed. In addition to skeletal proportions, soft tissue and whole body proportions are important components of the locomotor system. To further distinguish patas anatomy from other Old World monkeys, a comparative study based on dissection of skin, muscle, and bone from complete individuals of patas and vervet monkeys (Cercopithecus aethiops) was undertaken. Analysis reveals that small adjustments in patas skeletal proportions, relative mass of limbs and tail, and specific muscle groups promote efficient sagittal limb motion. The ability to run fast is based on a locomotor system adapted for long distance walking. The patas' larger home range and longer daily range than those of vervets give them access to highly dispersed, nutritious foods, water, and sleeping trees. Furthermore, patas monkeys have physiological adaptations that enable them to tolerate and dissipate heat. These features all contribute to the distinct adaptation that is the patas monkeys' basis for survival in grassland and savanna woodland areas.