Knee Flexion-extension Movements Research Articles

Cortical activation changes induced by visual biofeedback tracking training in chronic stroke patients

We tried to examine whether visual biofeedback tracking training (VBTT) can improve both the gait performance and cortical activation pattern in chronic stroke patients. We enrolled 10 chronic hemiparetic patients with stroke(mean age 46.3 +/- 5.19 years). The patients were randomly assigned to the training group (5 patients) or the control group (5 patients). VBTT was to follow the PC-generated sine waves with the knee joint electrogoniometer, and the two sine waves should appear as close to overlapping as possible on the PC monitor. The training was performed for 39 minutes/day, 5 days/week, for 4 weeks. Pre-training and post-training accuracy of tracking, functional status of gait, and functional MRI (fMRI) were measured. fMRI was performed at 1.5 T in parallel with timed knee flexion-extension movements at a fixed rate. The accuracy of the tracking performance, walking speed, and motor scale for gait improved in the training group. Primary sensorimotor cortex (SM1) cortical activation shifted significantly from the unaffected to the affected hemisphere in the training group. We demonstrated that cortical activation changes occurred with gait function improvement in chronic stroke patients throughout the 4-week VBTT program. It seems that the cortical reorganization was induced by VBTT.

Electrical Manifestations of Muscle Fatigue During Concentric and Eccentric Isokinetic Knee Flexion-Extension Movements

The quantification of the progression of muscle fatigue during a sustained contraction is a valuable tool in several clinical applications, ranging from the evaluation of functional impairment to the development of specific rehabilitative and training protocols. In these fields, great importance is given to isokinetic contractions. The aim of this paper was twofold: first, to propose signal processing methods for assessing the spectral changes of the surface myoelectric signal due to fatigue during isokinetic concentric and eccentric knee flexion-extension movements at a given angular velocity (60 degrees/s); second, to analyze the electrical manifestations of muscle fatigue of four thigh muscles (vastus lateralis, vastus medialis, rectus femoris, and biceps femoris) in the two contraction modalities (i.e. concentric versus eccentric). We demonstrated that, when considering concentric contractions, localized muscle fatigue can be assessed by computing the mean frequency of the frequency marginal of the time-frequency distribution derived from the surface myoelectric signal collected during each contraction cycle. Stronger nonstationarities were observed in the surface myoelectric data recorded within each cyclical movement of the studied eccentric exercise. Thus we propose the computation of the instantaneous mean frequency of the signal based on an original cross-time-frequency algorithm, which proved more sensitive than the frequency marginal in tracking the spectral changes associated with localized muscle fatigue. We derived the average fatigue pattern of the investigated muscles from experimental data recorded from a sample population consisting of twenty healthy subjects and we statistically compared the two contraction modalities. Our results showed that the electrical manifestations of muscle fatigue during concentric contractions were higher than those found during eccentric contractions, although in the latter modality the torque exerted and the mechanical work produced by the subjects were larger than those recorded during the concentric exercise. The results presented in this paper have potential clinical application and they could play an important future role in investigations of muscle behavior during dynamic, highly fatiguing contractions.

A walking assistance equipment providing knee flexion-extension movement in the orthotic gait for spinal cord injued patients

A walking assistance equipment providing knee flexion-extension movement in the orthotic gait for spinal cord injued patients

Extensor mechanism of the knee

Knee flexion-extension movements are an integral part of daily activity, not only in occasional large movements such as sitting or rising from a chair, but also as an integral part of normal locomotion. A stifflegged gait would cause the centre of gravity to rise and fallwith every stride, which would waste energy and thus be very tiring. As the foot is projected forwards to meet the ground with each step in normal gait, the knee is extended; after heel strike, the knee flexes and tension in the knee extensors arrests the fall of the body during the stance phase; the extensors plus gastrocnemius then help to propel the body forward for the next step. This cyclic action allows the centre of gravity of the trunk to progress at approximately a constant height. During the swing phase, as the leg is brought forwards, the knee is flexed approximately 70”. lm3 Although the patellofemoral joint (PFJ) is not obviously interposed into the weight-bearing column of the lower limb, and thus may be perceived as not being ‘weight bearing’, the PFJ is in fact subjected to joint contact forces and stresses that may actually be higher than in the tibiofemoral joint. This is not surprising if it is noted that the small patella is the focus for the insertions of the large quadriceps muscles. The combined actions of the muscles converging onto the patella normally ensure a smooth and stable movement along the patellar groove as the knee extends: it is easy to imagine that any imbalance in their action will lead to maltracking, excessive pressure on one side of the groove, or even subluxation out of the groove.4 It follows that the first thought of the physician faced with a PFJ problem will often be

Calf muscle work and segment energy changes in human treadmill walking

The relation between changes in potential and kinetic energy in a seven-segment model of the human body and the work of m. triceps surae was investigated in four subjects walking on a treadmill at speeds between 0.5 and 2.0 m/s. Segment energy levels were determined by means of tachometers attached with strings to various points on the subject's body. Muscle work was assessed by electromyogram to force processing. M. triceps surae is active during stance, first doing negative (eccentric) work and ending with a short period of positive (concentric) work at “push-off”. It turned out that in normal walking these muscles provide the major part of positive work for the initiation of swing at push-off. Only at large step lengths, when push-off starts well before contralateral heel contact, is there a minor pushing forward of the trunk. In the negative work phase, m. triceps surae seem to check the forward speed of the trunk. A related decrease of trunk kinetic energy is not present, however, but this may be obscured by the simultaneous action of m. quadriceps femoris and, in a later stage, by a transfer of energy from the decelerating contralateral (swing) leg to the trunk. Energy of the trunk segment shows a sharp decline in double stance and a more gradual increase in the first half of single stance. Evidence is given that this effect is due to quadriceps action in the knee flexion-extension movement during stance. The presented results are incorporated in a general picture of energy flows in human walking.

Factors affecting selected reciprocal muscle group ratios in preadolescents.

This study examines the influence of limb velocity and lateral dominance on the relationship between the knee flexors and extensors. Thirty preadolescents, 18 male and 12 female, performed a series of reciprocal knee flexion-extension movements on the Cybex II isokinetic system. The tests were performed at a range of selected velocities and on both dominant and nondominant limbs. The agonist-antagonist ratios considered were the peak torque ratios, the torque ratio produced at specific angles, and the ratio comparing the total work performed by the hamstrings with that of the quadriceps. The results showed that an increased limb velocity produces a significant increase in the peak torque and work ratios (P less than 0.05), limb velocity has no significant effect on the torque ratio produced at 30 degrees and 60 degrees in the preadolescents, and lower limb lateral dominance has no significant effect on the three ratios examined.