Newly Identified Gait Patterns in Patients With Multiple Sclerosis May Be Related to Push-off Quality.

Background: Limited walking ability is an important problem for patients with multiple sclerosis. A better understanding of how gait impairments lead to limited walking ability may help to develop more targeted interventions. Although gait classifications are available in cerebral palsy and stroke, relevant knowledge in MS is scarce.

Coactivation During Dynamometry Testing in Adolescents With Spastic Cerebral Palsy.

Background: Dynamometry has been used extensively to measure knee extensor strength in individuals with cerebral palsy (CP). However, increased coactivation can lead to underestimation of knee extensor strength and, therefore, reduce validity of strength measurements. It is yet unknown to what extent coactivation occurs during dynamometry testing and whether coactivation is influenced by severity of CP, load levels, and muscle fatigue.

Relations between muscle endurance and subjectively reported fatigue, walking capacity, and participation in mildly affected adolescents with cerebral palsy.

Aim: To investigate the relation between muscle endurance and subjectively reported fatigue, walking capacity, and participation in mildly affected adolescents with cerebral palsy (CP) and peers with typical development.

Method: In this case-control study, knee extensor muscle endurance was estimated from individual load-endurance curves as the load corresponding to a 15-repetition maximum in 17 adolescents with spastic CP (six males, 11 females; age 12-19y) and 18 adolescents with typical development (eight males, 10 females; age 13-19y). Questionnaires were used to assess subjectively reported fatigue (Pediatric Quality of Life Inventory Multidimensional Fatigue Scale) and participation (Life-Habits questionnaire).

Assessment of muscle endurance of the knee extensor muscles in adolescents with spastic cerebral palsy using a submaximal repetitions-to-fatigue protocol.

Objective: To compare muscle endurance in adolescents with spastic cerebral palsy (CP) with typically developing (TD) peers using a submaximal repetitions-to-fatigue (RTF) protocol.

Design: Cross sectional.

Setting: Human motion laboratory.

Muscle fatigue during repetitive voluntary contractions: a comparison between children with cerebral palsy, typically developing children and young healthy adults.

Aim: To combine peak torque and EMG analyses to investigate the hypothesis that 1) children with cerebral palsy (CP) have lower muscle fatigability than typically developing children (TD) and whether 2) muscle fatigue correlates with muscle strength.

Methods: Seven CP children, eight TD children and ten young healthy adults (YHA) performed an all-out fatigue test of 35 maximal concentric knee extension and flexion contractions on an isokinetic dynamometer. Angular velocity was set at 60°/s.

Dynamic spasticity of plantar flexor muscles in cerebral palsy gait.

Objective: To quantify dynamic spasticity, i.e. the coupling between muscle-tendon stretch velocity and muscle activity during gait, of the gastrocnemius and soleus muscles in children with spastic cerebral palsy.

Reproducibility and validity of video screen measurements of gait in children with spastic cerebral palsy.

Purpose: To determine the reproducibility and validity of video screen measurement (VSM) of sagittal plane joint angles during gait.

Methods: 17 children with spastic cerebral palsy walked on a 10m walkway. Videos were recorded and 3d-instrumented gait analysis was performed.

How crouch gait can dynamically induce stiff-knee gait.

Children with cerebral palsy frequently experience foot dragging and tripping during walking due to a lack of adequate knee flexion in swing (stiff-knee gait). Stiff-knee gait is often accompanied by an overly flexed knee during stance (crouch gait). Studies on stiff-knee gait have mostly focused on excessive knee muscle activity during (pre)swing, but the passive dynamics of the limbs may also have an important effect.

Walking speed modifies spasticity effects in gastrocnemius and soleus in cerebral palsy gait.

Background: The calf muscles of children with cerebral palsy are often spastic, which can lead to an equinus gait pattern. Although spasticity is defined as a velocity-dependent increase in muscle tone, very little is known about the effect of walking speed on muscle-tendon behavior of spastic muscles during gait. The aim of this study was to investigate gastrocnemius and soleus length and lengthening velocity during gait in spastic muscles with and without static contractures compared to non-spastic muscles, as well as the effect of walking speed, and the interacting effect of walking speed and spasticity on muscle-tendon length and lengthening velocity.

The effect of walking speed on hamstrings length and lengthening velocity in children with spastic cerebral palsy.

Children with cerebral palsy often walk with reduced knee extension in terminal swing, which can be associated with short length or slow lengthening velocity of hamstrings muscles during gait. This study investigated the role of two factors that may contribute to such short and slow hamstrings: walking speed and spasticity. 17 children with spastic cerebral palsy and 11 matched typically developing children walked at comfortable, slow, and fast walking speed.

Co-contraction in RA patients with a mobile bearing total knee prosthesis during a step-up task.

It was hypothesized that rheumatoid arthritis (RA) patients with a total knee prosthesis that allows axial rotation of the bearing (MB) will show more co-contraction to stabilize the knee joint during a step-up task than RA patients with a fixed bearing total knee prosthesis (FB) where this rotational freedom is absent while having the same articular geometry. Surface EMG, kinematics and kinetics about the knee were recorded during a step-up task of a MB group (n = 5), a FB group (n = 4) and a control group (n = 8). Surface EMG levels of thigh muscles were calibrated to either knee flexion or extension moments by means of isokinetic contractions on a dynamometer.

Validation of hamstrings musculoskeletal modeling by calculating peak hamstrings length at different hip angles.

Accurate estimates of hamstrings lengths are useful, for example, to facilitate planning for surgical lengthening of the hamstrings in patients with cerebral palsy. In this study, three models used to estimate hamstrings length (M1: Delp, M2: Klein Horsman, M3: Hawkins and Hull) were evaluated. This was done by determining whether the estimated peak semitendinosus, semimembranosus and biceps femoris long head lengths, as measured in eight healthy subjects, were constant over a range of hip and knee angles.

Effect of carbon-composite knee-ankle-foot orthoses on walking efficiency and gait in former polio patients.

Objective: To investigate the effects of total-contact fitted carbon-composite knee-ankle-foot orthoses (KAFOs) on energy cost of walking in patients with former polio who normally wear a conventional leather/metal KAFO or plastic/metal KAFO.

Design: A prospective uncontrolled study with a multiple baseline and follow-up design. Follow-up measurements continued until 26 weeks after intervention.

Complete 3D kinematics of upper extremity functional tasks.

Upper extremity (UX) movement analysis by means of 3D kinematics has the potential to become an important clinical evaluation method. However, no standardized protocol for clinical application has yet been developed, that includes the whole upper limb. Standardization problems include the lack of a single representative function, the wide range of motion of joints and the complexity of the anatomical structures.

Muscle length and lengthening velocity in voluntary crouch gait.

The purpose of this study was to explore how origin-insertion length and lengthening velocity of hamstring and psoas muscle change as a result of crouch gait. The second purpose was to study the effect of changes in walking speed, in crouch, on muscle lengths and velocities. Eight healthy female subjects walked on a treadmill both normally and in crouch.

Calibration of EMG to force for knee muscles is applicable with submaximal voluntary contractions.

Purpose: In this study, the influence of using submaximal isokinetic contractions about the knee compared to maximal voluntary contractions as input to obtain the calibration of an EMG-force model for knee muscles is investigated.

Methods: Isokinetic knee flexion and extension contractions were performed by healthy subjects at five different velocities and at three contraction levels (100%, 75% and 50% of MVC). Joint angle, angular velocity, joint moment and surface EMG of five knee muscles were recorded.

Accuracy of a practicable EMG to force model for knee muscles.

A practicable EMG-force model is evaluated for muscles about the knee. The model included envelope signal processing and a gain-dependency of knee angle and angular velocity. Six healthy subjects participated in the experiments.

The globe system: an unambiguous description of shoulder positions in daily life movements.

Positions of the shoulder joint are commonly described in terms of degrees of humeral elevation in the principal planes. This approach is inadequate for an accurate and unambiguous description of functional arm movements that are not confined to these planes. In this paper, a general unambiguous method for describing shoulder positions is adopted and visualized in globe graphs.

A clinically applicable EMG-force model to quantify active stabilization of the knee after a lesion of the anterior cruciate ligament.

Objectives: To investigate whether a simple electromyography-force (EMG-force) model can be used to measure different levels of co-contraction about the knee for healthy subjects and patients with an anterior cruciate ligament deficiency.

Design: To evaluate an EMG-to-force processing model, two groups of subjects, with and without deficiency of the anterior cruciate ligament, participated in experiments in which surface EMG, kinematics and kinetics about the knee were recorded during isokinetic and functional movements.

Background: Clinical and biomechanical evidence supports the hypothesis that higher level of co-contraction of quadriceps and hamstrings provide an active stabilization of the knee to compensate for the lost anterior cruciate ligament.

Determination of functional rotation axes during elevation of the shoulder complex.

Study Design: A cross-sectional, descriptive study of shoulder movements conducted on nonimpaired subjects.

Objective: To investigate whether a single functional rotation axis about the shoulder complex can be determined during elevation in the coronal or sagittal planes, and to identify their location.

Background: Accurate measurement of isokinetic torques about a joint requires alignment of the dynamometer axis with an assumed rotation axis of the joint.

Intermuscular co-ordination during fast contact control leg tasks in man.

From previous inverse dynamic analyses of human leg extensions, it was hypothesized that the underlying processes for the activation of mono- and biarticular muscles are different; the mono-articular muscles being activated when they shortened, whereas the biarticular muscles appeared responsible for the control of the external force direction. In the present study, experiments were performed on a dynamometer which was especially developed to test this hypothesis. Subjects had to exert different prescribed force vectors on a moving force-plate during leg extension, which they had intensively practised prior to the actual experiments.

On the effectiveness of force application in guided leg movements.

In guided leg movements (e.g., in cycling or wheelchair propulsion), the kinematics of a limb are determined by the object on which a force is applied.

Stiffness control for lower leg muscles in directing external forces.

The role of lower leg muscles is investigated during contact control tasks, in which the external force, applied by the foot on the surface, has to be controlled. Force, position and muscle activation were recorded. All subjects showed a stereotyped activation pattern to accomplish the tasks.

Two strategies of transferring from sit-to-stand; the activation of monoarticular and biarticular muscles.

In this study, two different strategies of rising from a chair were compared, using integrated biomechanical and electromyographic analyses. Nine healthy subjects were instructed to rise using two different strategies: natural sit-to-stand transfer (NSTS) and a sit-to-stand transfer with full flexion of the trunk (FSTS). Sagittal kinematics and ground reaction forces were registered.

Biomechanics and muscular activity during sit-to-stand transfer.

In the present study 10 healthy subjects were measured, performing sit-to-stand transfers in a natural way. Starting position and speed of movement were standardized. Sagittal kinematics, the ground reaction force, and muscle activity of nine leg muscles were recorded.