Amplitude Of Flexion Research Articles

A COMPARATIVE STUDY OF LUMBAR RANGE OF MOVEMENT IN HEALTHY ATHLETES AND NON-ATHLETES

Objective: To compare the amplitude of trunk flexion and extension through goniometry among athletes and non-athletes and to correlate these data with the popliteal angle and hamstring muscle tests. Methods: The amplitude of trunk flexion and extension was evaluated in 50 individuals who practiced sports on a regular basis and 50 non-athletes who did not present any painful lumber symptoms or any symptoms that could affect test performance. The measurements were made consecutively by two independent examiners by means of goniometry. The trunk flexion and extension values from the goniometry evaluation were correlated with the popliteal angle and hamstring flexibility tests, and the statistical correlation between them was analyzed. Results: The mean values obtained were 130.7 (101.9) for flexion and 40.2 (36.4) for extension. Statistically significant differences between the athletes and non-athletes were found in relation to the following parameters: goniometer in flexion with examiner 1, goniometer in flexion with examiner 2 and hamstring test. No statistically significant differences were found between the two groups in relation to the following parameters: goniometer in extension with examiner 1, goniometer in extension with examiner 2 and popliteal angle test. Conclusion: Individuals who practiced sports presented higher trunk flexion values. The use of goniometry to measure trunk amplitude showed variations in measurements between the examiners.

New fluoroscopic imaging technique for investigation of 6DOF knee kinematics during treadmill gait

IntroductionThis report presents a new imaging technique for non-invasive study of six degrees of freedom (DOF) knee kinematics during treadmill gait.Materials and methodsA treadmill was integrated into a dual fluoroscopic imaging system (DFIS) to formulate a gait analysis system. To demonstrate the application of the system, a healthy subject walked on the treadmill at four different speeds (1.5, 2.0, 2.5 and 3.0 MPH) while the DFIS captured the knee motion during three strides under each speed. Characters of knee joint motion were analyzed in 6DOF during the treadmill walking.ResultsThe speed of the knee motion was lower than that of the treadmill. Flexion amplitudes increased with increasing walking speed. Motion patterns in other DOF were not affected by increase in walking speed. The motion character was repeatable under each treadmill speed.ConclusionThe presented technique can be used to accurately measure the 6DOF knee kinematics at normal walking speeds.

Acupuncture in the Rehabilitation of Women after Breast Cancer Surgery – a Case Series

To evaluate the effect of acupuncture on rehabilitation of motor function, reduction in lymphoedema and improvement in perceived heaviness and tightness in the arms of women who had undergone breast cancer surgery. Twenty nine women who had had mastectomy or segmentectomy with axillary dissection, presenting with lymphoedema and/or a decrease in movement amplitude of the upper limb ipsilateral to surgery were studied. The patients underwent 24 acupuncture sessions once a week from February to December 2004. The movement amplitude of shoulder flexion and abduction and circumferential measurements of the arm, forearm and wrist were evaluated before and after one, three and six months of treatment. Statistical analysis was performed by Friedman's test. Significant improvements in range of movement of shoulder flexion and abduction (P<0.001), degree of lymphoedema (P=0.016), and sense of heaviness and tightening (P<0.001) in the affected limb after six months of therapy were observed. For circumferential measurements of the arm, forearm and wrist, no significant improvement between the different periods of treatment was observed. Acupuncture in rehabilitation after breast cancer surgery was shown to be associated with improvements in movement amplitude of the shoulder, symptoms of heaviness and tightness in the arm, and the degree of lymphoedema. However, controlled trials should be performed to ascertain whether the results were due to the natural history of the complaint or the acupuncture treatment.

Mucopolissacaridose tipo VI (síndrome de Maroteaux-Lamy): avaliação da mobilidade articular e das forças de garra e de pinça

OBJETIVO: Descrever o perfil de mobilidade articular e das forças de garra e de pinça de indivíduos com MPS VI, além de sua correlação com a excreção urinária de glicosaminoglicanos, atividade da ARSB e distância percorrida no teste de caminhada de 6 minutos. MÉTODOS: Estudo observacional de 28 pacientes com MPS VI, não submetidos a tratamento específico. Todos os pacientes foram avaliados em relação à amplitude da mobilidade articular, forças de garra e de pinça, excreção urinária de glicosaminoglicanos, atividade da ARSB e teste de caminhada de 6 minutos. RESULTADOS: Demonstrou-se maior comprometimento de flexão de ombro, sem correlação com a idade, e da extensão de joelho e flexão de cotovelo, estas últimas correlacionadas negativamente com a idade. A força de garra mostrou-se comprometida em todos os pacientes, e a força de pinça apresentou correlação positiva com idade. CONCLUSÕES: A restrição da flexão de ombro, sem correlação com a idade, sugere que este achado esteja presente precocemente na MPS VI e se constitua em sinal clínico importante para suspeita diagnóstica desta doença. A amplitude da extensão de joelho e da flexão de cotovelo, por sua vez, por apresentarem correlação negativa com a idade, são possíveis marcadores da evolução da doença. Estudos adicionais são necessários para confirmação dessas hipóteses.

Mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome): assessment of joint mobility and grip and pinch strength

To describe the profile of joint mobility and grip and pinch strength of MPS VI patients and to correlate this with urinary excretion of glycosaminoglycans (GAGs), ARSB activity, and the distance covered in a 6-minute walking test (6MWT). This was an observational study of 28 patients with MPS VI, who had not undergone specific treatment. All patients were assessed for amplitude of joint mobility (shoulder, elbow, and knee), grip and pinch strength and urinary GAG excretion and also performed the 6MWT. Shoulder flexion exhibited the greatest limitation, with no correlation with age, followed by knee extension and elbow flexion, both of which were correlated inversely with age. Hand grip strength was compromised in all patients, and pinch strength exhibited a positive correlation with age. The fact that restricted shoulder flexion was not correlated with age suggests that this finding is present early on in MPS VI and that it constitutes an important clinical sign that should arouse diagnostic suspicion of this disease. The amplitude of knee extension and elbow flexion, in turn, are possible markers of disease progression since they have a negative correlation with age. Further studies are needed to confirm these hypotheses.

Kinematic and electromyographic analysis of rising from a chair during a “Sit-to-Walk” task in elderly subjects: Role of strength

With aging, the deterioration of the ability to rise from a chair constitutes a major source of disability and a factor contributing to the loss of autonomy. The aim of this study was to describe kinematic and electromyographic characteristics of rising from a chair during a Sit-to-Walk task and to investigate the relationships between lower limb muscle strength and Sit-to-Walk characteristics. Twenty-four healthy elderly subjects (mean age: 73.8 (6.4) years) were included. The task analyzed consisted in standing up and taking a step. Kinematic data were obtained using a 3D motion analysis software. Surface electromyography of eight lower limb muscles was recorded. Isokinetic strength of ankle plantar flexor and knee flexors and extensors was evaluated. The Sit-to-Walk was divided into four phases. For 19 subjects, this task can be considered as a continuum with an overlap of the phases. In comparison with the Sit-to-Stand description, the Sit-to-Walk transition phase, which combined trunk flexion and knee extension, appeared longer in order to increase the body forward transfer for gait initiation. In most cases, the tibialis anterior and peroneus longus muscles were first activated. The isokinetic strength of the knee extensors was negatively correlated with the amplitude of trunk flexion and the knee flexors/extensors torque ratio was correlated with the length of this phase. Characterization of Sit-to-Walk movement provides information about the ability to rise from a chair. In the elderly, a better knowledge of its determinants could lead to improve strategies for rehabilitation of this critical task.

Transformation of the kinematic characteristics of a precise movement after a change in a spatial task

The central mechanism of motor programming was studied using a model of precise horizontal flexion of the arm at the elbow joint. Training was performed in the dark to ensure that formation of the motor program was based predominantly on the use of proprioceptive afferentation. The target was not demonstrated before training: subjects determined the angle of arm flexion during training, the moment at which the target position was reached being identified by a brief LED flash. Subjects had to perform the movement as quickly and accurately as possible. The amplitude, speed, and accuracy of the movement were measured in real time. The ten subjects were divided into two groups for initial training to precise movements, using two different protocols: flexion of the elbow to 70 degrees and to 55 degrees . At the second stage of the experiment, each subject's initial target position was suddenly changed (from 70 degrees to 55 degrees and vice versa). Training was continued until a stable accuracy in the new conditions was achieved (with errors of no more than 5% of the specified amplitude). The nature of the transformation in the kinematics of the precise movement in response to the change in the single task parameter illuminated the fundamental principle of organization of the supraspinal motor command for movements of this type. For both specified flexion amplitudes, the ratio between the acceleration and deceleration phases of the movement were identical during the period of skill fixation. On average, 70% of the total amplitude of flexion was accounted for by the acceleration phase and 30% by the deceleration phase. Adaptation of the precise movement to changes in the specified horizontal elbow flexion angle (i.e., re-achievement of the required movement accuracy in the changed conditions) during rearrangement was completed by inversion of these values. According to the results of previous studies, the most informative measure for analysis of the dynamics of the controlling central command was the acceleration of the movement. In terms of current concepts of the mechanism of motor control, the acceleration plateau can be regarded as mirroring long-term depression--the voltage plateau in Purkinje cells and motoneurons. Data processing involved calculation of the integral acceleration in both phases of the movement in relation to the angle of flexion (phase plots). These data underlie our understanding of the mechanism of transformation of movement kinematics responsible for the formation of a new central command.

An Approach to the Design of Walking Humanoid Robots with Different Leg Mechanisms or Flexible Feet and Using Dynamic Gaits

This article describes a method for designing humanoid robots and generating their dynamic gaits. Firstly, the global design process which defines structures able to carry out dynamic locomotion tasks is explained. Secondly, a set of leg and foot mechanisms are described to perform these tasks. A method of producing intrinsic smooth motions for fast walking gaits of bipedal robots with different leg mechanisms or flexible feet is then explained. Finally, some simulation results are given, showing a wide variety of possibilities for dynamic gait generation. The contribution of flexibilities in the feet of a bipedal robot during a dynamic walk can be observed. The two major effects are a diminution of the intensity of normal force when the heel touches the ground and increased length of the double support phase, allowing better stability of the system. Another notable effect is the analogy between the passive flexion amplitude of the toe tips and the measured results of human subjects.

Modifications de la cinématique du genou et des bras de levier du quadriceps et des ischio-jambiers après ostéotomie tibiale haute « curviplane » de valgisation ou de varisation: Étude in vitro

Purpose of the study Analysis of the correction or over-correction of high valgus and varus tibial osteotomies is generally limited to the frontal plane. Most likely however, the deformation observed radiographically in the frontal plane is simply a one-dimensional expression of a more complex three-dimensional deformation. This might be one of the causes for certain failures after surgery and recurrent problems which are difficult to solve. We proposed using 3D electrogoniometric to measure of the effect of a “dome” osteotomy on patellar and femoro-tibial kinematics and the changes in the moment arms of the knee muscles. Material and methods We used five lower limbs harvested from non-fixed cadavers. A “dome” osteotomy was stabilized by external fixation. Three-dimensional analysis of the femoro-tibial and femoro-patellar kinematics was performed using two electrogoniometers with six degrees of freedom. Changes in the lengths of the hamstrings and quadriceps was measured using four LVDT linear variable differential transformers. The muscles lever arms were measured with the tendon excursion method. Results At 90° flexion, varus osteotomy induced internal rotation while valgus osteotomy induced the opposite effect. Beyond 40° flexion, there was a clear internal rotation of the patella for varus and neutral corrections. Valgus corrections however induced external rotation. The peak lever arm of the quadriceps increased with valgus, while the angle of the peak was higher for varus correction. Valgus appeared to increase the lever arm of the semitendinous. Discussion Our study demonstrated that the effect of tibial osteotomy is not limited to the frontal plane. Tibial rotations are observed systematically for all corrections in the frontal plane. Varus correction tends to create internal rotation while valgus correction tends to have the opposite effect. Axial correction also affects patellar kinematics. Interanal rotation is induced by varus correction and external rotation by valgus correction. This patellar rotation could result from tibial rotations induced by the different corrections. The loss of the parallelism between the patellar crest and the trochlear groove could produce changes in femoropatellar surface contact and pressure, potentially leading to pain or cartilage degeneration. The maximal value of the quadriceps moment arm appears to increase with valgus. The efficacy of the quadriceps could thus be improved with valgus, potentially increasing extension force. Valgus increases the moment arm, improving limb flexion, while varus correction has the opposite effect. This could explain a loss in flexion amplitude in patients with varus or who underwent varus osteotomy. Tibial osteotomy is designed to correct the deviation solely in the frontal plane but also has effects in all three planes. Further 3D analyses of the morphology and physiology of the knee joint would be needed to better understand the physiological and pathological processes involved.

Perte de substance ostéo-articulaire de l’IPP des doigts longs : traitement en urgence par implant de Swanson: Étude prospective de 10 cas avec 2,7 ans de recul moyen

Purpose of the study Injury of the proximal interphalangeal joint (PIP) with loss of bone and soft tissue (joint surface, tendon, skin cover) can compromise finger vascularization. Fusion or amputation is often proposed. We report our experience with another solution, emergency implantation of the Swanson implant. Material and methods Thirteen patients, mean age 47.4 years (range 18-76) underwent emergency surgery between 1997 and 2003. In twelve patients, the finger injury occurred when working with wood. For ten of the thirteen patients, the injury occurred during recreational activity. The index was involved when only one ray was injured. The thumb was spared in all patients. Joint tissue was lost in all patients. The head of P1 was injured in all cases creating a situation incompatible with fusion without loss of finger length. All patients underwent an emergency surgery for complete reconstruction of the PIP joint with Swanson implant, tendon reconstruction or suture, and skin cover performed during the same procedure. Results Ten patients, 16 implants, were reviewed at mean 2.7 years (range 1-6 years). Mean flexion reached 41.8̊ (range 20-80̊). Maximal amplitude of flexion was achieved at one year and remained unchanged thereafter. There were no cases of infection, or secondary amputation. Two implant fractures were noted with no functional impact at six years. There were four cases of instability. Discussion Most reports in the literature concern composite blast or firearm injuries. Ours appears to be the first series involving injuries occurring while working with wood. Most of the lesions caused by the circular saw were tangential, damaging the dorsal aspect of several PIP joints. Classically, it would be logical to propose arthrodesis if the bone and cartilage loss is not excessive, but with the loss of joint motion provided by implants. Like Nagle, we propose emergency implantation of a Swanson prosthesis if soft tissue and tendon reconstruction can be achieved, avoiding amputation. Conclusion Although the technique is relatively simple, implantation of a Swanson prosthesis implies certain prerequisites, particularly ligament repair and correct alignment. Oversized implants appear to be better. We did not have to perform any secondary arthrodesis.

Limb joints kinematics and their relation to increasing speed in the guinea pig Cavia porcellus (Mammalia: Rodentia)

The kinematics of each joint of the guinea pig Cavia porcellus were studied during the locomotor cycle at increasing speed by high-speed cinefluorography. The main objective was to reveal the functional specific features of these structural elements in each dynamic phase of the cycle and also which limb joints are important during the increase of animal speed. Most of the analysed angles in C. porcellus were affected as the speed increased, both in trot and gallop. However, only a few of them were correlated with speed. There were also differences with respect to symmetrical or asymmetrical gaits. Both pairs of limbs responded differently to the increase of speed; while the forelimb joints modified the duration of their action (frequency) more than the amplitude (stride length), the hindlimbs acted inversely. The movements of the joints during the stance phase changed dramatically with speed, particularly in the hindlimb. At knee level, the flexion amplitude increases to maintain the stiffness of the leg spring, a principle previously discussed as essential for the running process. In the swing phase, inertial effects are the main constraints and, as in the stance phase, the knee joint in the swing phase is correlated with speed both during trot and gallop, confirming the major importance of this joint to increasing speed.

Modifications de la marche associées à la présence d’une prothèse totale de genou conservant ou sacrifiant le ligament croisé postérieur

Purpose of the study We wanted to check whether the differences in joint kinematics between the normal and prosthesis knee, with or without preservation of the posterior cruciate ligament, have an effect on knee flexion-extension during gait and on gait performance. Material and methods A control group of nine subjects was compared with two groups of subjects with total knee prostheses, with (n = 10 patients) or without (n = 6 patients) preservation of the posterior cruciate ligament. Gait was studied on flat ground at three different walking speeds. We measured the principal temporospatial gait parameters as well as knee flexion and extension angles using continuous electrogoniometry. Non-parametric statistical tests were used to analyze data due to the small number of subjects in each group. Results The flexion-extension cycles were different between the control group and the prostheses groups, but there was no difference between the two prostheses groups. Measurements made during gait confirmed this result, demonstrating a modification of the temporospatial parameters and a decrease in knee flexion during weight bearing in the prostheses groups compared with the control group. The statistical analysis demonstrated a correlation between these two results. Discussion The individual nature of gait parameters hindered data analysis. Indeed, there are many different ways to walk “normally”. We were however able to demonstrate the following points. The theoretical differences in joint kinematics between prostheses with or without preservation of the posterior cruciate ligament did not have any effect on gait. There were however significant differences between the control group and the prostheses groups, and these differences depended on walking speed. The most interesting results concerned the changes in the weight-bearing phase. Flexion during this phase was related to walking speed and was decreased in amplitude in both prostheses groups. This lesser amplitude in knee flexion probably affected the quality of gait because it was correlated with decreased temporospatial parameters related to gait performance. Conclusion This decreased amplitude of flexion during gait, which cannot be expected from motion measurements without weight bearing, can be explained by an interaction between joint kinematics, the musculoligamentary system and the locomotor schema.

The value of adding sciatic block to continuous femoral block for analgesia after total knee replacement

The benefit of adding a sciatic nerve block to the femoral block to improve analgesia after total knee replacement is controversial. The aim of this study is to address this controversy in a prospective, comparative, and randomized study. Patients were allocated randomly to receive a continuous femoral nerve block or continuous blocks of both the femoral and sciatic nerves. Stimulating catheters were used in all cases. A loading dose of 15 mL ropivacaine 0.75% was injected into each catheter, followed by administration of ropivacaine 0.2% (2-5 mL/h infusion via the femoral catheter; bolus 10 mL repeated every 12 hours in the sciatic catheter). The primary outcome was visual analog scale (VAS) scores (0 = no pain, 100 mm = worst pain) in postanesthesia care unit and in the 48-hour period after surgery. The secondary outcomes were amplitude of knee flexion, morphine consumption, and occurrence of postoperative nausea and vomiting (PONV). The VAS scores at rest were significantly higher when there was only continuous femoral nerve block than when there was both continuous femoral and sciatic nerve blocks. This difference progressively decreased and disappeared at 36 hours after surgery. The combined femoral and sciatic blocks decreased the morphine consumption by 81% and significantly decreased the occurrence of PONV. During the 36 hours immediately after total knee replacement, the combination of continuous femoral and sciatic nerve blocks improves analgesia while decreasing morphine consumption and PONV.

Dynamic analysis of trunk flexion after stroke

Messier S, Bourbonnais D, Desrosiers J, Roy Y. Dynamic analysis of trunk flexion after stroke. Arch Phys Med Rehabil 2004;85:1619–24. Objective To quantify trunk movement and lower-extremity weight bearing in patients with stroke-associated hemiparesis compared with healthy subjects. Design Controlled study with 2 groups: persons with hemiparesis and healthy controls. Setting Geriatric center offering rehabilitation services. Participants A convenience sample of 15 persons with poststroke hemiparesis (age, 69.4±12.0y; ≥3mo poststroke; total motor function range, 63–95/100) on the Fugl-Meyer Assessment and of 13 healthy persons (age, 67.8±7.5y). Interventions Subjects were seated on a chair placed on a forceplate with their feet on 2 additional forceplates. A target was placed directly in front of or at a 45° angle from the midline at 66% of the nonparetic/dominant arm length. Subjects’ task was to touch the target with their forehead. Main outcome measures Amplitude and speed of trunk movements, displacement of the global center of pressure (COP), and percentage of body weight distributed on the buttocks and the feet. Results Despite speed and amplitude comparable to that of the healthy subjects (NS), subjects with hemiparesis (HS) had less COP displacement (HS, 33.7±6.9; NS, 40.5±9.2), resulting in a lower weight-bearing value on the feet (HS for the paretic foot, 2.3%±3.6%; HS for the nonparetic foot, 2.2%±2.9%; NS for the nondominant foot, 5.4%±3.4%; NS for the dominant foot, 5.2%±4.0%). Conclusions The similar amplitude of trunk flexion with a decreased displacement of COP and a lower weight bearing on the feet suggest smaller anterior displacement of the body mass. It is possible that trunk movements in persons with hemiparesis are executed by the upper trunk with very little anterior tilt of the pelvis.

Knee angular displacement and extensor muscle activity in telemark skiing and in ski-specific strength exercises

Much of the training of competitive telemark skiers is performed as dry-land exercises. The specificity of these exercises is important for optimizing the training effect. Our aim here was to study the activation of the knee extensor musculature and knee angular displacement during competitive telemark skiing and during dry-land strength training exercises to determine the specificity of the latter. Specificity was analysed with respect to angular amplitude, angular velocity, muscle action and electromyographic (EMG) activity. Five male telemark skiers of national and international standard volunteered to participate in the study, which consisted of two parts: (1) skiing a telemark ski course and (2) specific dry-land strength training exercises for telemark skiing (telemark jumps and barbell squats). The angular displacement of the right knee joint was recorded with an electrogoniometer. A tape pressure sensor was used to measure pressure between the sole of the foot and the bottom of the right ski boot. Electromyographic activity in the right vastus lateralis was recorded with surface electrodes. The EMG activity recorded during maximum countermovement jumps was used to normalize the EMG activity during telemark skiing, telemark jumps and barbell squats. The results showed that knee angular displacement during telemark skiing and dry-land telemark jumps had four distinct phases: a flexion (F1) and extension (E1) phase during the thrust phase of the outside ski/leg in the turn/jump and a flexion (F2) and extension (E2) phase when the leg was on the inside of the turn/jump. The vastus lateralis muscle was activated during F1 and E1 in the thrust phase during telemark skiing and telemark jumps. The overall net knee angular amplitude was significantly greater (P<0.05) for telemark jumps than for telemark skiing. Barbell squats showed a knee angular amplitude significantly greater than that in telemark skiing (P<0.05). The mean knee angular velocity of the F1 and E1 phases during telemark skiing was about 0.47 rad · s−1; during barbell squats, it was about 1.22 rad · s−1. The angular velocity during telemark jumps was 2.34 and 1.59 rad · s−1 in the F1 and E1 phase, respectively. The normalized activation level of the EMG bursts during telemark skiing, telemark jumps and barbell squats was 70–80%. In conclusion, the muscle action and level of activation in the vastus lateralis during the F1 and E1 phases were similar during telemark skiing and dry-land exercises. However, the dry-land exercises showed a larger knee extension and flexion amplitude and angular velocity compared with telemark skiing. It appears that an adjustment of knee angular velocity during barbell squats and an adjustment of knee angle amplitude during both telemark jumps and barbell squats will improve specificity during training.

Performing the vertical jump: Movement adaptations for submaximal jumping

The purpose of this study was to gain insight into the kinematics and kinetics of the vertical jump when jumping for different heights and to investigate movement effectiveness as a criterion for movement control in submaximal jumping. In order to jump high a countermovement is used and large body segments are rotated, both of which consume energy which is not directly used to gain extra jump height. It was hypothesized that the energy used to reach a specified jump height is minimized by limiting the non-effective energy consumed. Standing vertical jumps attempting 100%, 75%, 50%, and 25% of maximal height were performed by a group of 10 subjects. Force and motion data were recorded simultaneously during each performance. We found that jump height increased due to increasing vertical velocity at take off. This was primarily related to an increase in countermovement amplitude. As such, flexion amplitude of the hip joint increased with jump height whereas the ankle and knee joint flexion did not. These findings revealed that for submaximal jumping a consistent strategy was used of maximizing the contribution of distal joints and minimizing the contribution of proximal joints. Taking into account the high inertia of proximal segments, the potential energy deficit due to countermovement prior to joint extension, the advantageous horizontal orientation of the foot segment during stance and the tendon lengths in distal muscles, it was concluded that movement effectiveness is a likely candidate for the driving criterion of this strategy.

Kinematics of wrist joint flexion in overarm throws made by skilled subjects.

Previous studies of multijoint arm movements have shown that the CNS holds arm kinematics constant in different situations by predictively compensating for the effects of interaction torques. We determined whether this was also the case for wrist joint flexion in natural overarm throws performed by skilled subjects in 3D, a situation where large passive torques can occur at the wrist. Specifically, we investigated whether wrist flexion amplitudes are held constant in throws of different speeds. Joint rotations were recorded at 1,000 Hz with the search-coil technique. Contrary to a previous study on constrained 2D throwing, indirect evidence was found that in fast throws passive torques associated with forearm deceleration were exploited to increase wrist flexion velocity. This increase in wrist flexion velocity was associated with constant wrist flexion amplitudes at ball release (mean 27 degrees) for throws of different speeds. Furthermore, final wrist flexion positions after ball release were similar for a particular subject irrespective of the speed of the throw. This was associated in faster throws with increased magnitudes of wrist flexor and wrist extensor EMG activity which damped passive torques associated with forearm angular deceleration. It is concluded that wrist flexion in overarm throws of different speeds is produced by central signals which precisely control net joint torque by both exploiting and damping passive torques during different parts of the throw to keep wrist joint angular position parameters constant. As such the results show that control strategies for natural 3D throwing are different from those for constrained 2D throwing.

Some biomechanical characteristics of standing up at three different speeds: implications for functional training

Individuals with motor disability typically stand up (STS) more slowly than able-bodied subjects, and are at risk of falling. The purpose of this study was to examine the effects of varying movement speed on angular displacement and velocity of trunk flexion at the hips and on extensor force production through the lower limbs. Able-bodied subjects were videotaped as they stood up at three different speeds (fast, slow, preferred) with feet on a force plate. Amplitude of hip flexion was greater but velocity was less when subjects moved slowly compared with fast. Moving slowly was also characterized by a decrease in peak support moment, an increase in time spent sustaining an overall extensor force of three times body weight, and a reversal in sequencing of joint movement onsets. The force-time trade-offs and variations in the basic motor pattern associated with differences in speed suggest that training to increase muscle strength and intersegmental coordination in STS should involve practising standing up at a range of speeds since the ability to control speed variation is critical to independence.

Use-dependent gain change in the reflex contribution to extensor activity in walking cats

Denervation of the synergists of the medial gastrocnemius (MG) muscle in the cat hind leg results in a progressive increase in the magnitude of burst activity in the MG muscle during walking. The increase in burst magnitude is associated with an increase in the slope of the relationship between the magnitude of individual MG bursts and the amplitude of ankle flexion during stance. This finding is consistent with the hypothesis that the increase in MG burst magnitude is due to an increase in gain of reflex pathways reinforcing the activation of MG. The increase in slope is use-dependent since it was not observed when the leg was released from a cast that immobilized the leg for 6 days.

Effects of inactivation of the anterior interpositus nucleus on the kinematic and dynamic control of multijoint movement.

We previously showed that inactivating the anterior interpositus nucleus in cats disrupts prehension; paw paths, normally straight and accurate, become curved, hypometric, and more variable. In the present study, we determined the joint kinematic and dynamic origins of this impairment. Animals were restrained in a hammock and trained to reach and grasp a cube of meat from a narrow food well at varied heights; movements were monitored using the MacReflex analysis system. The anterior interpositus nucleus was inactivated by microinjection of the GABA agonist muscimol (0.25-0.5 microgram in 0.5 microliter saline). For each joint, we computed the torque due to gravity, inertial resistance (termed self torque), interjoint interactions (termed interaction torque), and the combined effects of active muscle contraction and passive soft tissue stretch (termed generalized muscle torque). Inactivation produced significant reductions in the amplitude, velocity, and acceleration of elbow flexion. However, these movements continued to scale normally with target height. Shoulder extension was reduced by inactivation but wrist angular displacement and velocity were not. Inactivation also produced changes in the temporal coordination between elbow, shoulder, and wrist kinematics. Dynamic analysis showed that elbow flexion both before and during inactivation was produced by the combined action of muscle and interaction torque, but that the timing depended on muscle torque. Elbow interaction and muscle torques were scaled to target height both before and during inactivation. Inactivation produced significant reductions in elbow flexor interaction and muscle torques. The duration of elbow flexor muscle torque was prolonged to compensate for the reduction in flexor interaction torque. Shoulder extension was produced by extensor interaction and muscle torques both before and during inactivation. Inactivation produced a reduction in shoulder extension, primarily by reduced interaction torque, but without compensation. Wrist plantarflexion, which occurred during elbow flexion, was driven by plantarflexor interaction and gravitational torques both before and during inactivation. Muscle torque acted in the opposite direction with a phase lead to restrain the plantarflexor interaction torque. During inactivation, there was a reduction in plantarflexor interaction torque and a loss of the phase lead of the muscle torque. Our findings implicate the C1/C3 anterior interpositus zone of the cerebellum in the anticipatory control of intersegmental dynamics during reaching, which zone is required for coordinating the motions of the shoulder and wrist with those of the elbow. In contrast, this cerebellar zone does not play a role in scaling the movement to match a target.