Late Stance Research Articles

The effect of modifying foot progression angle on the knee loading parameters in healthy participants with different static foot postures

BackgroundStudies have found that toe-in gait reduced the peak knee adduction moment (KAM) during early stance, while toe-out gait reduced the peak KAM during late stance. However, some other studies found that toe-in or toe-out gait could reduce the KAM throughout stance phase. There is still a divergence of opinion on the use of toe-in or toe-out gait for reducing the KAM. Research questionThis study aimed to investigate whether static foot posture affected participants’ biomechanical responses to three self-selected foot progression angles (FPA): neutral, toe-out and toe-in. MethodsTwenty-seven healthy participants were recruited for this FPA gait modification experiment and classified into three groups: neutral (n = 8), supination (n = 9) and pronation (n = 10), based on the Foot Posture Index (FPI). The kinematic and kinetic data were recorded with Vicon motion capture system and three force plates. The knee adduction moment and ankle eversion moment were calculated using an inverse dynamics model. The effect of the FPA modification on the knee loading parameters was analysed by the Friedman non-parametric test. ResultsThe KAM results in the neutral group showed that the toe-in gait modification reduced the first peak of the KAM (KAM1), while the KAM1 was increased in the supination group. The effect of the FPA modification on the KAM1 did not reach significance in the pronation group. The toe-out gait modification reduced the second peak (KAM2) regardless of the static posture. SignificanceDifferent static foot postures were correlated with different peak KAM during the early stance phase due to FPA modification. These data suggest that the assessment of static foot posture provides a reference on how to offer adequate FPA modification for knee OA patients with different foot postures.

Walking with added mass magnifies salient features of human foot energetics.

The human foot serves numerous functional roles during walking, including shock absorption and energy return. Here, we investigated walking with added mass to determine how the foot would alter its mechanical work production in response to a greater force demand. Twenty-one healthy young adults walked with varying levels of added body mass: 0%, +15% and +30% (relative to their body mass). We quantified mechanical work performed by the foot using a unified deformable segment analysis and a multi-segment foot model. We found that walking with added mass tended to magnify certain features of the foot's functions. Magnitudes of both positive and negative mechanical work, during stance in the foot, increased when walking with added mass. Yet, the foot preserved similar amounts of net negative work, indicating that the foot dissipates energy overall. Furthermore, walking with added mass increased the foot's negative work during early stance phase, highlighting the foot's role as a shock-absorber. During mid to late stance, the foot produced greater positive work when walking with added mass, which coincided with greater work from the structures spanning the midtarsal joint (i.e. arch). While this study captured the overall behavior of the foot when walking with varying force demands, future studies are needed to further determine the relative contribution of active muscles and elastic tissues to the foot's overall energy.

Treatment Response to Botulinum Neurotoxin-A in Children With Cerebral Palsy Categorized by the Type of Stretch Reflex Muscle Activation.

While Botulinum NeuroToxin-A (BoNT-A) injections are frequently used to reduce the effects of hyperactive stretch reflexes in children with cerebral palsy (CP), the effects of this treatment vary strongly. Previous research, combining electromyography (EMG) with motion analysis, defined different patterns of stretch reflex muscle activation in muscles, those that reacted more to a change in velocity (velocity dependent –VD), and those that reacted more to a change in length (length dependent –LD). The aim of this study was to investigate the relation between the types of stretch reflex muscle activation in the semitendinosus with post-BoNT-A outcome as assessed passively and with 3D gait analysis in children with spastic CP. Eighteen children with spastic CP (10 bilaterally involved) between the ages of 12 and 18 years were assessed before and on average, 8 weeks post-treatment. EMG and motion analysis were used to assess the degree and type of muscle activation dependency in the semitendinosus during passive knee extensions performed at different joint angular velocities. Three-dimensional gait analysis was used to assess knee gait kinematics as a measure of functional outcome. Pre-treatment, 9 muscles were classified as VD and 9 as LD, but no differences between the groups were evident in the baseline knee gait kinematics. Post-treatment, stretch reflex muscle activation decreased significantly in both groups but the reduction was more pronounced in those muscles classified pre-treatment as VD (−72% vs. −50%, p = 0.005). In the VD group, these changes were accompanied by greater knee extension at initial contact and during the swing phase of gait. In the LD group, there was significantly increased post-treatment knee hyperextension in late stance. Although results vary between patients, the reduction of stretch reflex muscle activation in the semitendinosus generally translated to an improved functional outcome, as assessed with 3D gait analysis. However, results were less positive for those muscles with pre-treatment length-dependent type of stretch reflex muscle activation. The study demonstrates the relevance of categorizing the type of stretch reflex muscle activation as a possible predictor of treatment response.

How does normal variability in trunk flexion affect lower limb muscle activity during walking?

A large proportion of the mass of the body is contained within the trunk segment. Therefore, small changes in the inclination of this segment have the potential to influence the direction of the ground reaction force and alter lower limb joint moments and muscle activation patterns during walking. The aim of this study was to investigate if variability in sagittal trunk inclination in healthy participants is associated with differences in lower limb biomechanics. Gait analysis data was collected on 41 healthy participants during walking. Two groups were defined based on habitual trunk flexion angle during normal walking, a forward lean group (n=18) and a backward lean group (n=17). Lower limb moments, muscle activation patterns and co-contraction levels were compared between the two groups using independent t-tests. The forward lean group walked with 5° more trunk flexion than the backward lean group. This difference was associated with a larger peak hip moment (effect size=0.7) and higher activation of the lateral gastrocnemius (effect size =0.6) and the biceps femoris (effect size =0.7) muscles. The forward lean group also exhibited greater co-contraction in late stance (effect size =0.7). This is the first study to demonstrate that small differences in trunk flexion are associated with pronounced alterations in the activation of the lateral knee flexor muscles. This is important because people with knee osteoarthritis have been observed to walk with increased trunk flexion. It is possible that increased sagittal trunk inclination may be associated with elevated joint loads in people with knee osteoarthritis.

Effective Mechanical Advantage About the Ankle Joint and the Effect of Achilles Tendon Curvature During Toe-Walking.

Aim: To study the causes of locomotor dysfunction, estimate muscle forces, or understand the influence of altered sarcomere and muscle properties and behaviours on whole body function, it is necessary to examine the leverage with which contractile forces operate. At the ankle joint, current methods to quantify this leverage for the plantarflexors do not account for curvature of the Achilles tendon, and so may not be appropriate when studying equinus gait. Thus, novel methodologies need to be developed and implemented to quantify the Achilles tendon moment arm length during locomotion.Methods: Plantarflexor internal moment arm length and effective mechanical advantage of 11 typically developed young adults were calculated throughout stance, while heel-toe walking and voluntarily toe-walking on an instrumented treadmill. Achilles tendon moment arm was defined in two-ways: (1) assuming a straight tendon, defined between the gastrocnemius medialis myotendinous junction and Achilles tendon insertion point, and (2) accounting for tendon curvature, by tracking the initial path of the Achilles tendon from the calcaneal insertion.Results: When accounting for tendon curvature, Achilles tendon moment arm length and plantarflexor effective mechanical advantage did not differ between walking conditions (p > 0.05). In contrast, when assuming a straight tendon, Achilles tendon moment arm length (p = 0.043) and plantarflexor effective mechanical advantage (p = 0.007) were significantly greater when voluntary toe-walking than heel-toe walking in late stance.Discussion: Assuming a straight Achilles tendon led to a greater Achilles tendon moment arm length and plantarflexor effective mechanical advantage during late stance, compared to accounting for tendon curvature. Consequently, plantarflexor muscle force would appear smaller when assuming a straight tendon. This could lead to erroneous interpretations of muscular function and fascicle force-length-velocity behaviour in vivo, and potentially inappropriate and ineffective clinical interventions for equinus gait.

Biomechanical responses of young adults with unilateral transfemoral amputation using two types of mechanical stance control prosthetic knee joints.

Prosthetic knee joint function is important in the rehabilitation of individuals with transfemoral amputation. The objective of this study was to assess the gait patterns associated with two types of mechanical stance control prosthetic knee joints-weight-activated braking knee and automatic stance-phase lock knee. It was hypothesized that biomechanical differences exist between the two knee types, including a prolonged swing-phase duration and exaggerated pelvic movements for the weight-activated braking knee during gait. Prospective crossover study. Spatiotemporal, kinematic, and kinetic parameters were obtained via instrumented gait analysis for 10 young adults with a unilateral transfemoral amputation. Discrete gait parameters were extracted based on their magnitudes and timing. A 1.01% ± 1.14% longer swing-phase was found for the weight-activated braking knee (p < 0.05). The prosthetic ankle push-off also occurred earlier in the gait cycle for the weight-activated braking knee. Anterior pelvic tilt was 3.3 ± 3.0 degrees greater for the weight-activated braking knee. This range of motion was also higher (p < 0.05) and associated with greater hip flexion angles. Stance control affects biomechanics primarily in the early and late stance associated with prosthetic limb loading and unloading. The prolonged swing-phase time for the weight-activated braking knee may be associated with the need for knee unloading to initiate knee flexion during gait. The differences in pelvic tilt may be related to knee stability and possibly the different knee joint stance control mechanisms. Understanding the influence of knee function on gait biomechanics is important in selecting and improving treatments and outcomes for individuals with lower-limb amputations. Weight-activated knee joints may result in undesired gait deviations associated with stability in early stance-phase, and swing-phase initiation in the late stance-phase of gait.

A Lower Limb Exoskeleton Recycling Energy From Knee and Ankle Joints to Assist Push-Off

Abstract This paper presents the design and preliminary evaluation of a quasi-passive lower limb exoskeleton for walking efficiency improvements. The exoskeleton recycles the negative work performed by the knee joint in late swing phase and the ankle joint in mid-stance phase, to assist ankle push-off in late-stance phase when a burst of positive power is needed. The exoskeleton consists of a torsion spring as an energy storage element, and two clutches attached to both ends of the spring to control the timing of recycling and releasing energy in a gait cycle. The two clutches are actively controlled by two small servo motors with very low power consumption based on the plantar pressure. The novelty of this exoskeleton is it makes the extra kinetic energy dissipated at the knee joint reusable, by transferring it to the ankle joint to assist positive power generation during push-off, for the first time. Eight male subjects walked with the exoskeleton engaged (EXO_ON), disengaged (EXO_OFF), and without the exoskeleton (NO_EXO). Inverse dynamics analysis demonstrated reduced negative biological work at the knee joint during late swing and at the ankle joint during mid stance, as well as reduced positive biological work at the ankle joint during late stance comparing the EXO_ON to EXO_OFF conditions. These results prove the effectiveness of the exoskeleton at joint level.

A comparison of coordination and its variability in lower extremity segments during treadmill and overground running at different speeds

BackgroundRecently, the use of treadmills for walking and running has increased due to lifestyle changes. However, biomechanical differences in coordination between running on a treadmill or overground have not been adequately addressed. Research questionThe purpose of this study was to compare coordination and its variability in lower limb segments during treadmill and overground running at different speeds. MethodsTwenty physically active university undergraduate students participated in this study. Each participant ran trials for both overground and treadmill running at slow and fast speeds. Three-dimensional kinematic data of the lower limb segments were captured. The continuous relative phase (CRP) was used to compute coordination and its variability (VCRP) for foot, shank, and thigh segments of the dominant side of the participants. ResultsA vector analysis using statistical parametric mapping (SPM) revealed that there were statistically significant differences in the calculated CRPs for treadmill and overground running in the stance phase of running and for different running speeds in the late stance and swing phases. However, the VCRPs calculated for the two locations and speeds did not exhibit any statistically significant differences. ConclusionThe findings of this study suggest differences in segment coupling between treadmill and overground running may affect lower extremity biomechanics. In addition, changes in the coupling patterns for different running speeds suggest that segment coordination is not stable in the range of training speeds used by runners. Finally, the lack of differences in the variability of segment couplings during treadmill and overground conditions at different speeds potentially demonstrates similar dynamic neuromuscular control and degrees of freedom at these different running locations and speeds.

Biomechanical effects of manipulating peak vertical ground reaction force throughout gait in individuals 6–12 months after anterior cruciate ligament reconstruction

BackgroundWe aimed to determine the effect of cueing an increase or decrease in the vertical ground reaction force impact peak (peak in the first 50% of stance) on vertical ground reaction force, knee flexion angle, internal knee extension moment, and internal knee abduction moment waveforms throughout stance in individuals 6–12 months after an anterior cruciate ligament reconstruction. MethodsTwelve individuals completed 3 conditions (High, Low, and Control) where High and Low Conditions cue a 5% body weight increase or decrease, respectively, in the vertical ground reaction force impact peak compared to usual walking. Biomechanics during High and Low Conditions were compared to the Control Condition throughout stance. FindingsThe High Condition resulted in: (a) increased vertical ground reaction forces at each peak and decreased during mid-stance, (b) greater knee excursion (i.e., greater knee flexion angle in early stance and a more extended knee in late stance), (c) greater internal extension moment for the majority of stance, and (d) lesser second internal knee abduction moment peak. The Low Condition resulted in: (a) vertical ground reaction forces decreased during early stance and increased during mid-stance, (b) decreased knee excursion, (c) increased internal extension moment throughout stance, and (d) decreased internal knee abduction moment peaks. InterpretationCueing a 5% body weight increase in vertical ground reaction force impact peak resulted in a more dynamic vertical ground reaction force loading pattern, increased knee excursion, and a greater internal extension moment during stance which may be useful in restoring gait patterns following anterior cruciate ligament reconstruction.

Transspinal stimulation downregulates activity of flexor locomotor networks during walking in humans

The objective of this study was to establish the effects of transspinal stimulation on short-latency tibialis anterior (TA) flexion reflex during walking in healthy humans. Single pulse transspinal stimulation was delivered at a conditioning-test (C-T) interval either after (~20 ms) or simultaneously with the last pulse of the pulse train (0 ms) delivered to the medial arch of the right foot. Transspinal stimulation was delivered at sub- and supra-threshold intensities of the spinally-mediated TA transspinal evoked potential. Stimulation was delivered randomly at different phases of the step cycle, based on the foot switch threshold signal, which was divided into 16 equal bins. The TA flexion reflex facilitation under control conditions occurred at heel contact and then progressively from late stance phase reaching its peak at early and late swing phases. Transspinal stimulation at a negative and suprathreshold 0 ms C-T interval depressed flexion reflex excitability at all phases of the step cycle. The short-latency TA flexion reflex depression was possibly mediated through spinal inhibitory interneurons acting at both pre- and post- motoneuronal sites or by transspinal stimulation affecting directly the activity of the flexor half spinal center. These results reveal direct actions of transspinal stimulation on human spinal locomotor networks.

Joint coordination when running in minimalist, neutral, and ultra-cushioning shoes

ABSTRACTUltra-cushioning (ULTRA) shoes are new to the running shoe market. Several studies have evaluated kinematics and kinetics while running in ULTRA shoes, however it remains unknown how such shoes influence joint coordination. Therefore, the purpose of this study was to evaluate lower extremity coordination and coordination variability when running in minimalist (MIN), traditional (NEUT) and ULTRA shoes. Fifteen runners ran for ten minutes in each shoe type. Coordination patterns and coordination variability were assessed for rearfoot-tibia, rearfoot-knee, and tibia-knee couplings using a modified vector coding method during early, mid, and late stance periods. During late stance ULTRA shoes resulted in more antiphase coordination than MIN (p =.036) or NEUT (p =.047) shoes and less in-phase coordination than MIN (p =.048) or NEUT (p =.013) shoes. During late stance there was also more proximal phase rearfoot-knee coordination in ULTRA shoes than in either MIN (p =.039) or NEUT (p =.005) shoes and less in-phase coordination in ULTRA shoes than in NEUT shoes (p =.006). There were no differences in coordination variability between shoes during any phase. The differences in coordination may have implications for tissue loading and injury development when running in ULTRA shoes..

Ultrasound imaging links soleus muscle neuromechanics and energetics during human walking with elastic ankle exoskeletons

Unpowered exoskeletons with springs in parallel to human plantar flexor muscle-tendons can reduce the metabolic cost of walking. We used ultrasound imaging to look ‘under the skin’ and measure how exoskeleton stiffness alters soleus muscle contractile dynamics and shapes the user’s metabolic rate during walking. Eleven participants (4F, 7M; age: 27.7 ± 3.3 years) walked on a treadmill at 1.25 m s−1 and 0% grade with elastic ankle exoskeletons (rotational stiffness: 0–250 Nm rad−1) in one training and two testing days. Metabolic savings were maximized (4.2%) at a stiffness of 50 Nm rad−1. As exoskeleton stiffness increased, the soleus muscle operated at longer lengths and improved economy (force/activation) during early stance, but this benefit was offset by faster shortening velocity and poorer economy in late stance. Changes in soleus activation rate correlated with changes in users’ metabolic rate (p = 0.038, R2 = 0.44), highlighting a crucial link between muscle neuromechanics and exoskeleton performance; perhaps informing future ‘muscle-in-the loop’ exoskeleton controllers designed to steer contractile dynamics toward more economical force production.

Monocular 3D Sway Tracking for Assessing Postural Instability in Cerebral Hypoperfusion During Quiet Standing.

Postural instability is prevalent in aging and neurodegenerative disease, decreasing quality of life and independence. Quantitatively monitoring balance control is important for assessing treatment efficacy and rehabilitation progress. However, existing technologies for assessing postural sway are complex and expensive, limiting their widespread utility. Here, we propose a monocular imaging system capable of assessing sub-millimeter 3D sway dynamics during quiet standing. Two anatomical targets with known feature geometries were placed on the lumbar and shoulder. Upper and lower trunk 3D kinematic motion were automatically assessed from a set of 2D frames through geometric feature tracking and an inverse motion model. Sway was tracked in 3D and compared between control and hypoperfusion conditions in 14 healthy young adults. The proposed system demonstrated high agreement with a commercial motion capture system (error [Formula: see text], [-0.52, 0.52]). Between-condition differences in sway dynamics were observed in anterior-posterior sway during early and mid stance, and medial-lateral sway during mid stance commensurate with decreased cerebral perfusion, followed by recovered sway dynamics during late stance with cerebral perfusion recovery. This inexpensive single-camera system enables quantitative 3D sway monitoring for assessing neuromuscular balance control in weakly constrained environments.

Redistribution of joint moments and work in older women with and without hallux valgus at two walking speeds

BackgroundHallux valgus (HV) is a highly prevalent foot deformity in older women. Differences in lower extremity joint function of older women with and without HV during walking at slower and faster speeds are unknown. Research questionDoes walking speed affect lower extremity joint range of motion (ROM) and net extensor joint moment and associated work in older women with and without HV? MethodsThirteen older women with HV and 13 controls completed five walking trials at 1.1 and 1.3 m·s−1 as kinematic marker position and ground reaction force data were collected. Net ankle, knee, and hip joint moments were computed using inverse dynamics during the stance phase. Positive joint work was calculated by integrating hip power in early stance, knee power in mid stance, and ankle power in late stance. ResultsAverage ankle ROM and plantarflexor moment did not increase with walking speed in the HV group, while in the control group these variables were greater for the faster compared to the slower speed (p < 0.05). The magnitude of increase in ankle joint work with speed was 12 % lesser in the HV compared to the control group (p = 0.008). The hip ROM, extensor moment, and associated work was greater in the HV compared to the control group (p < 0.05). Knee and hip joint ROM, extensor moments, and work increased with walking speed in both groups (p < 0.05). SignificanceOlder women with HV compared to older women without HV demonstrate a distal-to-proximal redistribution by increasing hip motion and effort to compensate for reduced ankle contribution during walking.

Flip-flops do not alter the neuromuscular function of the gastrocnemius muscle and tendon during walking in children

Introduction/Aim: Flip-flops are a popular choice of footwear for children. However, their inherent design provides minimal support to the foot and ankle and has been suggested to increase the work performed by muscle and tendon structures, potentially predisposing them to injury. Therefore, the aim of this study was to compare the length change behaviour of the medial gastrocnemius (MG) muscle fascicles and muscle tendon unit (MTU) and their mechanical function at the ankle and subtalar joints in children during walking with and without flip-flop. Methods: Eight healthy children walked barefoot and with flip-flops whilst 3D gait analysis and simultaneous B-mode ultrasound images of the MG fascicles during level walking were collected. Joint kinematics, kinetics and MTU lengths were analysed using musculoskeletal modelling and fascicle lengths using a semi-automated tracking algorithm. Results: The muscles and tendons across the ankle absorbed greater amounts of power during barefoot walking compared to flip-flop walking. The muscle activations of the lateral gastrocnemius, soleus and tibialis anterior remained invariant across the conditions as did the activation, and fascicle length change behaviour of the medial gastrocnemius. In the barefoot condition, there was a trend of greater MTU lengthening, to potentially absorb greater amounts of power, although no differences in shortening was observed during late stance. Conclusion: Walking with flip-flops does not increase the mechanical work performed by the MG muscle at the ankle and subtalar joints, suggesting that flip-flops do not increase the stresses and strains of the Achilles tendon and hence its predisposition to strain induced injury. Instead, our results suggest that flip-flops, act as a compliant surface and absorb energy during contact and hence the strain experienced by the Achilles tendon.

Gait training facilitates push-off and improves gait symmetry in children with cerebral palsy

BackgroundHuman walking involves a rapid and powerful contraction of ankle plantar flexors during push-off in late stance. ObjectiveHere we investigated whether impaired push-off force contributes to gait problems in children with cerebral palsy (CP) and whether it may be improved by intensive gait training. MethodsSixteen children with CP (6–15 years) and fourteen typically developing (TD) children (4–15 years) were recruited. Foot pressure was measured by insoles and gait kinematics were recorded by 3-dimensional video analysis during treadmill and overground walking. The peak derivative of ground reaction force at push off (dPF) was calculated from the foot pressure measurements. Maximal voluntary plantar flexion (MVC) was measured while seated. Measurements were performed before and after a control period and after 4 weeks of 30 minutes daily inclined treadmill training. ResultsdPF and MVC were significantly lower in children with CP on the most affected (MA) as compared to TD children (p < .001). dPF was lower on the MA leg as compared to the less affected (LA) leg in children with CP (p < .05). Following gait training, increases in dPF (p < .001) and MVC (p < .01) were observed for the MA leg. Following gait training children with CP showed similar timing of dPF and similar stance phase duration on both legs indicating improved symmetry of gait. These effects were also shown during overground walking. ConclusionImpaired ability to voluntarily activate ankle plantar flexors and produce a rapid and powerful push-off during late stance are of importance for impaired gait function in children with CP. Intensive treadmill training may facilitate the drive to ankle plantar flexors and reduce gait asymmetry during both treadmill and overground walking.

Contribution of hip and knee muscles to lateral knee stability during gait.

[Purpose] Lateral knee instability is frequently observed in patients with knee injury or risk factors associated with knee osteoarthritis. Physical exercises can strengthen muscles that stabilize the knee joint. The purpose of this study was to define the contribution of the knee and hip muscles to lateral knee stability by comparing the muscle forces, as assessed by musculoskeletal simulation using one or two degrees-of-freedom (1-DOF and 2-DOF) knee models. [Participants and Methods] We evaluated the normal gait of 15 healthy subjects. We conducted a three-dimensional gait analysis using a motion analysis system and a force plate. We considered a muscle as a lateral knee stabilizer when the calculated muscle force was greater with the 2-DOF model than with the 1-DOF model. [Results] During early and late stance, the muscle forces of the lateral knee and hip joint increased in the 2-DOF model as opposed to in the 1-DOF model. In contrast, the forces of the medial knee muscles decreased. Furthermore, hip muscle forces increased during the late stance. [Conclusion] Our results show that the lateral knee and hip muscles contribute to lateral knee stability. Thus, exercises to strengthen these muscles could improve lateral knee stability.

Modeling of pneumatic controlled bio mimetic articulated passive prosthetic spring loaded knee mechanism for transfemoral amputees

Lower limb amputation causes many changes and associated adjustments, which not only relates the damaged limb but also to the entire body. Today, the development of prosthetic devices for transfemoral amputation witness continual growth in medical applications. In India, an estimated 2.68 crore people have movement disability according to disability census 2011. At present 230,000 transfemoral amputees are in need of prosthetic devices to be facilitated for the better living style and standards, but low cost devices are yet to touch the market. And also, the amputee must endure to function in society uncomplaining that his disability may utterly inhibit or even prohibit the performance of various activities to which he has long been habituated. When compared to other disabilities, above knee amputation deprive a human to perform his activities and earn livelihood becomes an arduous task. Regardless of the developments in technology, above-knee amputees still indicates significant deficiencies in walking patterns, speed in walking. In this paper, a novel modelling of a pneumatic controlled bio mimetic articulated passive prosthetic spring loaded knee system for early and late swing and stance control has been presented. This work establishes a functional knee model developed by Catia software for various activities. The proposed model contemplates user needs and provides a low cost alternative with high stability and more durability to enable flexion-extension of prosthetic leg during the gait cycle.

Forefoot Injuries in Sports

Forefoot injuries are common injuries in high-impact sports. The forefoot experiences a large amount of stress during the late stance phase of the gait cycle. Repetitive load applied to the forefoot without adequate rest can lead to tissue breakdown, resulting in injury. Forefoot sporting injuries can deteriorate gait function, sporting performance, and quality of life. In this article, we review the typical presentation, approach, and treatment modalities of the commonest forefoot sporting injuries. These include metatarsal stress fractures, second metatarsophalangeal joint (MTPJ) instability, turf toe injury, sesamoid pathologies, as well as hallux valgus and rigidus. Metatarsal stress fractures are frequent overuse injuries. They can be managed conservatively with activity modification and protected weight-bearing or surgically with open internal fixation. Second MTPJ instability typically involves disruption of the second MTPJ ligamentous joint capsule. Management of this condition includes customized orthotics, physiotherapy, hydrocortisone and lignocaine (HL7(2):50–56.

Modeling and Control of Knee-Ankle-Toe Active Transfemoral Prosthesis

The main joints of lower limb are hip, knee, ankle, and toe. Because of accidents or diseases, some people have to amputate. Wearing prosthesis can help them return to normal life. In the past, Active Knee joint and Active Knee-Ankle transfemoral prosthesis are studied. While in the stance phase, toe joint play an important role. In this article, the dynamic model and control method of Knee-Ankle-Toe Active Transfemoral Prosthesis are studied. The main contents are as follows: Firstly, according to the ground reaction force, the gait cycle is divided into three phases, Early and Middle Stance Phase (E&MSP), Late Stance Phase (LSP) and Swing Phase (SP), and the mechanical model of Knee-Ankle-Toe Active Transfemoral Prosthesis (KATATP) is established. Secondly, consider the cooperative movement of amputee and prosthesis, the kinematics model of prosthesis is established by Lie Groups and Lie Algebras, and the dynamic model of prosthesis is established by Lagrange equation. Thirdly, the whole gait cycle is a complete system and each phase is a different subsystem, switching rules and controllers of different subsystems are designed. Finally, experiments show that KATAP with the switching control enables amputee to have a biomechanically appropriate walking gait and achieve smooth transition between different gait phases.