Biomedical subjects

B Maton

Publications and source records attributed to B Maton.

At least 19 recordsLinked to original sources

PubMed2006

Human muscle fatigue and elastic compressive stockings.

The present study was performed to test if elastic compressive stockings (ECSs) increase muscle fatigability during sustained muscle contraction or if it improves the recovery after fatigue. Surface electromyograms (EMGs) were recorded on 4 leg and thigh muscles, and static ankle dorsal flexion force levels were measured in the right limb of 15 healthy subjects. The subjects maintained a 50% maximum ankle dorsal flexion force (MVF) for as long as possible without and, after a 30 min rest, with a European class I ECS. Finally, after another 30 mn rest, the pressure exerted by the ECS on the skin was measured at standard points on the limb, using a Salzmann apparatus. During the first 10 min of both rest periods, the subjects performed brief static maximum ankle dorsal flexions every 30 s. ECS exerted a 14.3 mm Hg mean pressure at tibial level C. Linear relationships, whose slopes were not influenced by ECS, existed between the maintenance time and both the mean power frequency and the logarithm of the total power of the tibialis anterior and gastrocnemius lateralis EMGs. The endurance times, the force recovery times after fatigue and the linear relationships between the logarithm of the time elapsing after exhaustion and the MVF reached during the recovery period were also independent of ECS. The results show that class I ECSs are not responsible for greater muscle fatigability; but they do not improve force recovery during rest following static fatiguing voluntary contractions.

Adult↗

PubMed2006

Adaptation of gait initiation in children with unilateral idiopathic clubfoot following conservative treatment.

Children with unilateral clubfoot (CF) treated conservatively have residual foot deformities and triceps surae m. atrophy. Using surface electromyography of tibialis anterior (TA), gastrocnemius (GA), and peroneus longus muscles, simultaneously with ground reaction forces recordings, the present work assesses the influence of this pathology on the gait initiation process. Ten children with CF and 10 healthy children were investigated. In children with CF, the velocity of the centre of gravity (CG) at the end of gait initiation did not differ from that of healthy children, because of adaptations of anticipation and execution phases. CG velocity at the end of anticipation was lower in children with CF than in healthy children when the swing foot was the affected one, indicating that propulsion was less efficient in this condition. It is shown that this resulted from alterations in anticipation duration, initial centre of pressure position and TA and PL excitations. Execution was shortened when support was provided by the pathological foot: the motor program was adapted to shorten the phase during which equilibrium control might be deficient. Biomechanical characteristics of the execution phase of children with CF did not depend on the swing foot. This indicated that the sound foot cannot be used as a control for accessing residual deficiencies.

Acceleration↗

PubMed2006

[Electromyographic study of stretch reflexes in the normal and prosthetic hip].

PURPOSE OF THE STUDY: Several studies have been devoted to the effect of proprioception on joint function. Modifications in feedback control from the cord have been observed in unstable joints due to capsule and ligament laxity. A few studies have examined the effect of knee and hip arthroplasty on proprioception, but none have established whether stretch reflexes affect function of a prosthetic joint. The purpose of the present study was to demonstrate the electromyographic characteristics of stretch reflexes of the normal hip joint and to compare them with those observed in the prosthetic hip. MATERIAL AND METHODS: Two groups of patients were studied. The first included eleven subjects free of neurological disorders whose studied limb was healthy. The second group included ten subjects with a total hip prosthesis who had undergone extensive capsulectomy during the arthroplasty. Voluntary muscle contraction was noted in each subject. In addition, electromyographic recordings were made to note response of the ipsilateral and contralateral quadriceps crural and tensor of the fascia lata during changes in joint position. Recordings were made with the subject in the supine position, the limb suspended, hip flexed at 45 degrees and knee extended. Three series of ten recordings were made in random order to measure the latency of muscle response to free fall of the limb, accelerated fall of the relaxed limb, and accelerated fall associated with calibrated contraction of the quadriceps. Mean latency of muscle response was calculated for each trial. RESULTS: In the conditions of this study, there was no statistically significant difference (p = 0.05) in the reflex time course between natural and prosthetic hips. DISCUSSION: Changes due to joint replacement and capsulectomy do not appear to affect the stretch reflexes of the hip joint.

Aged↗

PubMed2005

Intramuscular pressure and surface EMG in voluntary ankle dorsal flexion: Influence of elastic compressive stockings.

Intramuscular pressure (IMP) is of major importance in blood flow and is often taken as a good estimate of muscular tension. However, its measurement remains invasive. The aims of the present work were: (1) to re-examine the possibility of evaluating IMP and muscular tension changes by means of surface electromyographic recordings, and (2) to clarify the influence of elastic compressive stockings (ECS). Surface EMG of muscles tibialis anterior (TA), soleus, gastrocnemius, and IMP from the anterior tibial compartment (ATC), deep posterior compartment (DPC), superficial posterior compartment (SPC) of the right leg, were simultaneously recorded in nine healthy subjects. Subjects performed series of voluntary concentric TA contractions (right ankle dorsal flexions) and TA isometric contractions, with or without elastic ECS, in a decubitus posture. Rest IMP mean values, measured over 60 s, ranged between 12.3 and 26.6 mmHg, i.e. in the range or slightly higher than those reported in the literature. When ECS were applied, mean IMP increase was 6.4 mmHg in ATC, 8.7 mmHg in DPC and 21.0 mmHg in SPC, while the corresponding EMG amplitude decreased. In ankle dorsal flexion movements, instantaneous values of TA-EMG amplitudes were linearly correlated to ATC-IMP instantaneous values, over the whole of the EMG rising part of every movement. When ECS were applied, the relationships between TA-EMG amplitude and ATC-IMP amplitude remained linear but where shifted towards higher IMP, in agreement with the increase in rest IMP. Because of antagonist co-contractions, IMP from DPC and SPC were also linearly correlated with ATC-IMP but with low coefficients of proportionality. As in TA concentric contractions, TA-EMG amplitudes were linearly correlated to ATC-IMP instantaneous values in isometric contractions, but the slopes of the latter were always greater. This result is explained by the relationship between muscle tension and shortening velocity. Al the results showed that: (1) instantaneous changes in surface EMG amplitude may provide a good estimate of IMP changes during the rising part of isometric, but also of concentric voluntary contractions; (2) elastic compressive stockings do not impair subjects relaxation capacity but actually increase the ratio IMP/muscle activation. As a consequence, ECS may actually increase the venous return during voluntary contractions.

Adaptation, Physiological↗

PubMed2005

[Effects of elastic stockings on venous flow during simple movements and muscular contractions of lower limb in healthy volunteers. Pilot study].

AIM: To study common femoral vein flow during simple movements and voluntary contractions of muscles of lower limbs in healthy volunteers and to evaluate the effects of elastic stocking on venous flow. METHODOLOGY: Experimental study. Ten subjects, aged 21 to 25 years, underwent duplex ultrasound to examine venous flow, the lower limb being fitted with sensors to characterize kinematics and of muscle activity. MOVEMENTS STUDIED: In supine position: thigh muscles contraction. forefoot dorsal flexion. Standing on both feet: thigh muscles contraction, tip-toe, front load transfer, extension of the leg on the knee, loading on one limb, forefoot back flexion. Data were recorded with a computerised system for secondary analysis. A mean venous velocity was calculated after elimination of parasite signals. Venous velocity was correlated with muscle signals. The procedure was repeated with the patient wearing a thigh-length class II elastic stockings (Varisma Innothera Ltd). RESULTS, CONCLUSION: All movements increased venous flow. Wearing elastic stockings increased the venous flush due to movements or muscle contractions. The level of muscle activity during the same movement or the same muscle contraction varied from one subject to the other.

Adult↗

PubMed2004

Centrally adaptations in unilateral idiopathic clubfoot children following conservative treatment.

Adaptations in tiptoe rising were studied in unilateral idiopathic clubfoot (ICF) children, who underwent conservative treatment. The current study concerned 10 ICF children and 10 healthy children of the same range of ages (8-12 year). All ICF children were rated "good" or "very good" treatment results, but showed residual m. Triceps surae atrophy and mild foot alignment flaws. Tiptoe rising task was performed with subjects standing quietly with the feet on separate force platforms. Subjects were instructed to rise onto tiptoes as fast as possible and to maintain the tiptoe erect posture for a few seconds. Surface EMG of muscles Gastrocnemius, Tibialis anterior, Peroneus longus were recorded on both sides, simultaneously with vertical reaction forces (RZ) and centres of pressure (CP) displacements, during a series of 10-15 trials. Foot preferentiality was without influence on the EMG and biomechanical activities of the control group. Although not aware of a deficit in performance, ICF children show less vertical acceleration than healthy children. Timing and magnitude of muscular activities, and Cp and RZ variables of ICF children, evidenced alterations in both affected and sound side, when compared to healthy subjects. Alterations in the affected side activities were well explained by Triceps surae atrophy. Alterations in the sound side were considered as adaptations of central nervous system (CNS), preserving a global symmetry of the task. These results highlight the CNS capacity to adapt even for mild deficiencies. They stressed that it is mandatory to follow ICF children, even if they recovered a normal life.

Acceleration↗

PubMed2003

Body equilibrium at the end of gait initiation: importance of ankle muscular force as evidenced in clubfoot children.

This study investigates the importance of ankle muscular force and foot shape on body equilibrium at the end of a first step by means of a comparison between healthy children and children with unilateral clubfoot who showed Triceps surae atrophy. Subjects were asked to initiate gait at different velocities and to perform a few forward-oriented steps. In healthy children, there was a significant increase in the number of positive values of the centre of gravity vertical acceleration at foot contact (Z"HC) as velocity increased without any difference between the preferred and non-preferred stepping foot. These results indicated that ankle muscular forces from the leg of support intervene in braking the downfall of the body, as velocity and step length increase, and that this function does not depend on the subject's lateralization. In comparison with healthy children, clubfoot subjects showed a greater occurrence of low or negative Z"HC values when gait was initiated at a velocity greater than 0.8 m/s. However, except for two of them, there was no difference in Z"HC control between the steps initiated with the sound leg and those initiated with the affected leg. These results indicate that in unilateral clubfoot children, residual musculoskeletal impairment of one leg induces a deficit in equilibrium control as soon as step length needs a significant braking of the body's vertical fall. It is also shown that equilibrium is not limited to the gait period where the affected leg is the body's supporting leg but also when it is the stepping one. This could reflect a global alteration of the body scheme preserving symmetry in the control of both legs.

Ankle↗

PubMed2002

Effects of postural muscle fatigue on the relation between segmental posture and movement.

The purpose of this study was to examine whether fatigue of postural muscles might influence the coordination between segmental posture and movement. Seven healthy adults performed series of fifteen fast wrist flexions and extensions while being instructed to keep a dominant upper limb posture as constant as possible. These series of voluntary movements were performed before and after a fatiguing submaximal isometric elbow flexion, and also with or without the help of an elbow support. Surface EMG from muscles Deltoïdeus anterior, Biceps brachii, Triceps brachii, Flexor carpi ulnaris, Extensor carpi radialis were recorded simultaneously with wrist, elbow and shoulder accelerations and wrist and elbow displacements. Fatigue was evidenced by a shift of the elbow and shoulder muscles EMG spectra towards low frequencies. Kinematics of wrist movements and corresponding activations of wrist prime-movers, as well as the background of postural muscle activation before wrist movement were not modified. There were only slight changes in timing of postural muscle activations. These data indicate that postural fatigue induced by a low-level isometric contraction has no effect on voluntary movement and requires no dramatic adaptation in postural control.

Adult↗

PubMed2001

Postictal stability of proton magnetic resonance spectroscopy imaging (1H-MRSI) ratios in temporal lobe epilepsy.

Interictal proton (1H) MRS is increasingly used for seizure lateralization in patients with temporal lobe epilepsy (TLE). Studies reporting postictal 1H-MRS metabolite changes in patients with TLE are few and contradictory. The authors prospectively performed interictal and postictal proton magnetic resonance spectroscopy imaging (1H-MRSI) studies in seven patients with TLE. The authors found no consistent changes in metabolite peak area ratios between studies, suggesting that 1H-MRS ratios remain stable between interictal and postictal state in TLE.

Adolescent↗

PubMed2001

Electromyographic and biomechanical characteristics of segmental postural adjustments associated with voluntary wrist movements. Influence of an elbow support.

This study re-investigates the characteristics of segmental postural adjustments associated with rapid mono-articular movements and analyses their dependence on initial postural conditions. Subjects performed rapid voluntary wrist flexions and extensions while maintaining their upper limb posture as stable as possible, with or without an elbow support. Surface electromyographic activity (EMG) was recorded from Flexor carpi ulnaris, Extensor carpi radialis, Biceps brachii, Triceps brachii and Deltoideus anterior. The kinematics of the three joints and kinetics in the support condition were also recorded. A planar mechanical model was used to determine the muscle torque required to keep the upper limb posture constant while performing wrist movements. All subjects showed anticipatory postural adjustments (APA) which, unlike those described for whole-body postural control, could not counteract in advance the perturbing inter-segmental forces created by the movement. Postural muscles were activated before the wrist movement with a chronology specific to the direction of the wrist movement. Some postural muscular activities anticipated that of the prime-movers in accordance with muscle torque, which had to be applied to the joints to keep the upper limb posture constant. These results reveal that the central nervous system (CNS) uses the same organization of the motor command for the control of both segmental and whole-body posture: APA and corrective postural adjustments (CPA), which are based on well-organized anticipatory postural muscle activities (APMA), except that APA can be non-efficient in segmental postural control. The presence or absence of an elbow support influenced the level of activation of postural muscle but not their chronology. This result suggests that the CNS uses a sequence of APMA: a postural muscle synergy which is predetermined as a function of the intended direction of the movements and modulates the gain towards certain muscles, in accordance with the gravitational effects, and supports reaction changes.

Action Potentials↗

PubMed2001

Correlation of scalp EEG and 1H-MRS metabolic abnormalities in temporal lobe epilepsy.

PURPOSE: To correlate the interictal spike field and region of seizure onset with the distribution of 1H-MRS abnormalities in temporal lobe epilepsy (TLE) and improve our understanding of the clinical significance of 1H-MRS abnormalities. METHODS: Scalp electroencephalogram (EEG) monitoring and proton magnetic resonance spectroscopy (1H-MRS) results were correlated in 31 consecutive patients with TLE. RESULTS: Lateralized 1H-MRS-based hippocampal abnormalities were recorded in 95% of the patients with unilateral interictal spikes, with a high degree of concordance for the lateralization side (90%). In 64% of the patients with normal or bilateral interictal EEG spikes, 1H-MRS provided lateralizing information. Bilateral 1H-MRS abnormalities, with or without lateralization, were 3 times more frequent than bitemporal EEG spikes. Anterior predominance of the 1H-MRS abnormalities was more frequent in patients with anterior temporal EEG spiking (50%), than in patients without this EEG distribution (18%). Similar association was noted between distribution of 1H-MRS abnormalities and region of EEG seizure onset. CONCLUSIONS: Our results show a moderate level of concordance between the distribution of 1H-MRS and EEG abnormalities. 1H-MRS identifies abnormalities contralateral to the predominant seizure focus more often than does EEG and may provide lateralizing information in patients with nonlateralizing interictal EEG.

Adult↗

PubMed2001

Reproducibility of proton magnetic resonance spectroscopy imaging measurements of normal human hippocampus at 1.5 T: clinical implications.

The authors investigate the reproducibility of metabolite signals measured with proton magnetic resonance spectroscopy (1H-MRS) acquired from the human hippocampus in controls and in a phantom. Two 1H-MRS studies separated by 3 weeks were performed in 8 healthy volunteers and in a phantom. N-acetyl compounds (NA), choline (Ch), and creatine (Cr) peak areas and ratios were measured and compared using percentage variation, and Pearson Correlation Coefficient at the level of every voxel, the level of 1 hippocampus (5 voxels), and the level of 2 hippocampi (10 voxels). Sensitivity for observing clinically significant between-session 1H-MRS changes was evaluated using the reliable change index. Reproducibility measures for metabolite peak areas were only moderately concordant with percentage variation ranging from 14% to 20% for NA, Cho, and Cr. Stability was much improved when NA ratios and sum of multiple voxels were considered. Between-session NA/(Cho + Cr) changes greater than 22%, 12%, and 10% in one given participant can be detected with a 90% confidence interval when considered at the single-voxel level, the level of a single hippocampus, or the level of both hippocampi, respectively. Left-right asymmetry indices showed similar and limited inter-hemispheric asymmetry in repeated examination. This study suggests that 1H-MRS reproducibility performance is adequate for the study and monitoring of human hippocampus function when NA ratios and the sum of multiple voxels are considered. Individual metabolite peaks and single-voxel measurements have low reproducibility at 1.5 T and should be used only with clearly established statistical parameters.

Adult↗

PubMed2000

Is human gait initiation program affected by a reduction of the postural basis?

The aim of this study was to access the adaptability of the gait initiation program by imposing before and during gait a posture that partially prevents the backward shift of the center of foot pressure. Six healthy subjects performed normal gait in the control situation (CS) and gait in the absence of heel ground contact in the test situation (TS) on a force platform at three different speed conditions. It is shown that an increase in the duration of the anticipation phase in TS is necessary to create conditions for progression which allow the subjects to reach a gait velocity similar to the one obtained in CS at the end of the anticipatory movements and also at the end of the first step. Modifications of the gait initiation program occur in order to fulfil the performance in terms of gait velocity.

Adaptation, Physiological↗

PubMed2000

Anticipatory postural adjustments depend on final equilibrium and task complexity in vertical high jump movements.

Anticipatory postural adjustments (APA) associated with high vertical jumping were studied in five normal men. The dependence of APA on final equilibrium and task complexity was studied by analyzing the characteristics of single versus repetitive jumps. Subjects performed series of 25 single jumps and 25 repetitive jumps on a force platform, in response to a Go signal. Surface EMG from the Soleus (SO), Tibialis anterior (TA), Vastus lateralis (VL) and Biceps femoris (BF) muscles were recorded simultaneously with the three components of the ground reaction forces. The existence of APA associated with both single and repetitive jumps was evidenced by a backward shift of the center of pressure, an SO deactivation, and a TA activation which preceded the onset of movement by hundreds of milliseconds. In repetitive jumps, SO deactivation occurred later than in single jump, whereas the center of pressure shift started earlier, lasted longer and had a greater amplitude. Moreover, repetitive jumps were initiated later with respect to the Go signal. These data show that the central nervous system anticipates not only the equilibrium disturbance caused by an initial movement but that caused by a whole sequence of movements. They also show that the corresponding APA are based heavily on a single functional ankle synergy.

Adaptation, Physiological↗

PubMed2000

Visual confrontation naming and hippocampal function: A neural network study using quantitative (1)H magnetic resonance spectroscopy.

Prior research on the relationship between visual confrontation naming and hippocampal function has been inconclusive. The present study examined this relationship using quantitative (1)H magnetic resonance spectroscopy ((1)H-MRS) to operationalize the function of the left and right hippocampi. The 60-item Boston Naming Test (BNT) was used to measure naming. Our sample included 46 patients with medically intractable, focal mesial temporal lobe epilepsy who had been screened for all pathology other than mesial temporal sclerosis. Statistics included Pearson correlations and neural network analysis (multilayer perceptron and radial basis function). Baseline BNT performance correlated significantly with left (1)H-MRS hippocampal ratios. Thirty-six per cent of the variance in baseline BNT performance was explained by a neural network model using left and right (1)H-MRS ratios(creatine/N-acetylaspartate) as input. This was elevated to 49% when input from the right hippocampus was lesioned mathematically. In a second model, left (1)H-MRS hippocampal ratios were modelled using measures of semantic and episodic memory as input (including the BNT). Explained variance in left (1)H-MRS hippocampal ratios fell from 60.8 to 3.6% when input from BNT and another semantic memory measure was degraded mathematically. These results provide evidence that the speech-dominant hippocampus is a significant component of the overall neuroanatomical network of visual confrontation naming. Clinical and theoretical implications are explored.

Adult↗

PubMed2000

Encephalopathy with epileptic spasms resolved with corticoids in a 69 year-old patient.

A 69 year-old man with a history of recent temporal lobe seizures, presented with progressive coma and frequent epileptic spasms. Ictal EEG, PET and SPECT alterations were strikingly similar to those described in infantile spasms. Conventional antiepileptic drugs were ineffective but the introduction of corticoids induced a dramatic improvement with disappearance of the spasms. The etiology remains unknown. Epileptic spasms may occur in the elderly. If conventional antiepileptic drugs are ineffective, corticoids should be tried immediately.

Aged↗

PubMed1999

Chronology of upper limb anticipatory postural adjustments associated with voluntary wrist flexions and extensions in humans.

Six sitting healthy subjects were instructed to keep a constant upper limb posture while performing wrist flexions and extensions. Acceleration of the wrist, elbow and shoulder joints, and surface electromyograms (EMGs) of the upper limb's main flexors and extensors were studied. Results indicated the existence of anticipatory (APA) and corrective postural adjustments. The APAs were based on a reproducible directional chronology of postural muscle activations. As shown by a simple mechanical model, this chronology was in accordance with the muscular torque which should be applied to the joints to keep the upper limb posture constant. All these data indicate that APA are involved in segmental posture, where their general organization is similar to those of APA associated with whole-body movements. The use of constant directional postural synergies well agrees with a simplification of the motor control according to Bernstein's theory.

Arm↗

PubMed1999

Changes to the gait initiation programme following a running exercise in human subjects.

The question addressed by the present study was whether the programme for gait initiation is fully invariant or can be modified by a prior long duration running exercise. Eight subjects performed a series of gait initiation movements on a force platform in three different speed conditions before and after running on a treadmill (3.3 m/s, 0% slope). Following the running exercise, the first step length and velocity were greater and the double stance phase duration was shorter, while the relationships between the temporal parameters of gait initiation and the velocity of the centre of gravity at the end of the first step were not significantly different. During the anticipation phase, the maximal variation of the ankle joints moment remained significantly correlated with the integrated EMG activity of the Tibialis Anterior after the run. However the displacement of the centre of foot pressure, displayed some post-exercise changes, indicating a modification to the postural part of the gait initiation programme. The greater velocities reached after the running exercise could be explained by a recalibration of gravitational force control, while the invariance of time necessary to reach these velocities showed the rigidity of the initiation gait.

Adaptation, Physiological↗