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Biomedical subjects

A B Arsenault

Publications and source records attributed to A B Arsenault.

At least 37 records · Page 2Linked to original sources
PubMed1992

Characterization of contralateral torques during static hip efforts in healthy subjects and subjects with hemiparesis.

Contralateral torques exerted at the hip were measured in healthy subjects and subjects with hemiparesis performing unilateral static hip efforts in abduction, adduction, flexion and extension, in a sitting position, at two torque levels. In general, the ipsilateral hip efforts were accompanied by mirrored contralateral torques in both groups of subjects. The directionality of these contralateral torques indicates that their action at the pelvis is mechanically opposite to the ipsilateral efforts, suggesting that they ensure the stabilization of the pelvis. In healthy subjects, analyses of variance showed no difference in the magnitude of the contralateral torques with regard to which limb was used to perform the task. However, a significant increase in magnitude was demonstrated in the contralateral torques concurrent with the increasing level of effort requested ipsilaterally. In hemiparetic subjects, when performing the tasks with their paretic limb, the magnitude of the contralateral torques was significantly increased in the non-paretic limb when compared with those measured in the paretic limb during non-paretic limb efforts. Based on the present results, a model of postural control is presented to explain the relationship between the ipsilateral and contralateral torques. Using this model, it is hypothesized that the increased contralateral torques observed in hemiparetic subjects when performing the tasks with their paretic limb is related to the weakness of the paretic muscles. The clinical importance of exercises used for the re-education of the paretic lower limb in this population, which consist of resisting the non-paretic hip movements in order to strengthen the paretic hip muscles, is discussed in light of these results.

Adult↗
PubMed1991

EMG power spectra of elbow extensors during ramp and step isometric contractions.

The goal of the present study was to compare electromyogram (EMG) power spectra obtained from step (constant force level) and ramp (progressive increase in the force level) isometric contractions. Data windows of different durations were also analysed for the step contractions, in order to evaluate the stability of EMG power spectrum statistics. Fourteen normal subjects performed (1) five ramp elbow extensions ranging from 0 to 100% of the maximum voluntary contraction (MVC) and (2) three stepwise elbow extensions maintained at five different levels of MVC. Spectral analysis of surface EMG signals obtained from triceps brachii and anconeus was performed. The mean power frequency (MPF) and the median frequency (MF) of each power spectrum were obtained from 256-ms windows taken at 10, 20, 40, 60 and 80% MVC for each type of contraction and in addition on 512-, 1024- and 2048-ms windows for the step contractions. No significant differences (P greater than 0.05) were found in the values of both spectral statistics between the different window lengths. Even though no significant differences (P greater than 0.05) were found between the ramp and the step contractions, significant interactions (P less than 0.05) between these two types of contraction and the force level were found for both the MPF and the MF data. These interactions point out the existence of different behaviours for both the MPF and the MF across force levels between the two types of contraction.

Adult↗
PubMed1991

Clinical significance of the V-shaped space in the subluxed shoulder of hemiplegics.

Recently, it has been proposed that shoulder subluxation in hemiplegia is accompanied by 1) the appearance of a V-shaped articular configuration occurring between the humeral head and glenoid fossa and 2) the presence of chronic pain. The main purpose of this study was to investigate the validity of these statements. We evaluated 40 hemiplegic subjects over 3 months. Radiographs of the affected and nonaffected shoulders were taken at both a frontal plane (0 degree) and a 45 degree incidence. From these patients, subluxed (n = 19) and nonsubluxed (n = 21) groups were formed. Pain was evaluated using the Present Pain Intensity index of the McGill Pain Questionnaire. On these x-ray films, measurements were taken of the V-shaped space, abduction of the arm, and rotation of the scapula. The statistical analysis (analysis of variance for repeated measures) contrasted the results obtained from the nonaffected side with those from the affected side over the 3 months studied. At the 45 degree angle, which better exposes the articular configuration of the shoulder, the difference in the V angle between the affected and nonaffected shoulders was significant for the subluxed group (p less than 0.01), indicating that such a V-shaped space can be identified. The measures taken also indicate that a downward subluxation of the humeral head occurs relative to the scapula without any systematic abduction of the humerus or downward rotation of the scapula. None of the results obtained from the frontal plane x-ray films was significant. Finally, no significant relation was found between subluxation and shoulder pain.

Adult↗
PubMed1991

Motor function and activities of daily living assessments: a study of three tests for persons with hemiplegia.

The relationship between upper extremity motor function and independence in basic activities of daily living in subjects with hemiplegia was explored. The Barthel Index (Mahoney & Barthel, 1965) and the Fugl-Meyer Test (Fugl-Meyer, Jääskö, Leyman, Olsson, & Steglind, 1975) were selected as the standard instruments for the evaluation of activities of daily living and upper extremity motor function, respectively, because their validity and reliability have been demonstrated many times. The Functional Test for the Hemiplegic/Paretic Upper Extremity (Wilson, Baker, & Craddock, 1984a, 1984b) was also used for the evaluation of upper extremity motor function. The results obtained in 18 subjects with hemiplegia indicate that the scores on the Barthel Index are poorly correlated with both the Fugl-Meyer Test and the Functional Test for the Hemiplegic/Paretic Upper Extremity scores. It is suggested that variables other than motor function, such as the learning of compensatory techniques and perceptual-cognitive status, are responsible for this discrepancy because they can influence activities of daily living performance in persons with hemiplegia. The high correlation between the scores on the Fugl-Meyer Test and the Functional Test for the Hemiplegic/Paretic Upper Extremity indicates that either test may be used for the assessment of upper extremity motor function.

Activities of Daily Living↗
PubMed1991

Cocontraction of the elbow muscles during combined tasks of pronation-flexion and supination-flexion.

The aim of this study was to determine if the antagonist activity of the triceps brachii (TB) and anconeus (AN) muscles is modulated when the activity of the biceps brachii (BB) and brachioradialis (BR) is modulated by the performance of combined tasks and to verify if this behavior is similar at different elbow angles. Electromyographic (EMG) activity of BB, BR, AN and TB was recorded for normal subjects (N = 6) with surface electrodes during a ramp isometric contraction in elbow flexion (F) which was performed alone or combined with 20% of maximal voluntary contraction (MVC) in pronation (P) or in supination (S). Two cocontraction ratios, using the EMG root mean square (rms) values of each muscle and identified as BB/TB and BR/AN were calculated. The results indicate that for low flexion torque levels, the BB/TB ratio is higher for the S-F condition while the BR/AN ratio is higher during the pure flexion task. Variations of the EMG activity across tasks were significant only for BB (Friedman ANOVA, p less than .01) whereas there was no significant change in EMG activity (rms) for TB, BR and AN (Friedman ANOVA, p greater than .01). Furthermore, the behavior of both ratios across tasks was similar at 50 degrees, 90 degrees and 130 degrees of elbow flexion. Thus, for isometric conditions, there appears to be no evidence of modulation of EMG activity of elbow extensors while performing combined tasks of S-F and P-F. In addition, cocontraction activity during these tasks tends to be similar across elbow angles.

Elbow↗
PubMed1991

Changes in hip position modulate soleus H-reflex excitability in man.

The effects of hip flexion and extension on the ipsilateral soleus Hoffmann (H) reflex recruitment curve were studied in 11 healthy subjects. Hip flexion (50 degrees), but not hip extension (15-20 degrees), produced changes in the H-reflex. A maintained facilitation, peaking at intensities of stimulation producing a maximal H-reflex (Hmax), was observed in 6/18 sessions. Inhibition, peaking at intensities submaximal for Hmax, was seen in 7/18 sessions. In some of the latter experiments, there was also a facilitation at high intensities of stimulation (greater than Hmax). The remaining experiments were classified as showing no effect: 3 were unmodulated but 2 showed a facilitation at high intensities of stimulation (greater than Hmax). Since the knee was extended in the test position, a second series of experiments (n = 7) were carried out to determine the possible influence of stretch of the biarticular hamstrings muscle group on the soleus H-reflex by comparing the effects of hip flexion with the knee extended with those obtained when the knee was flexed, thereby relaxing the hamstrings. The results provided no evidence that the variability could be explained by differences in the relative degree of stretch on the hamstrings muscle group. There were, however, systematic variations in the shape of the corresponding control H-reflex recruitment curves between subjects: the mean slope of the rising limb of the recruitment curve was highest in those experiments showing an inhibition, intermediate in the ineffective experiments and lowest in those showing a maintained facilitation. These observations indicate that the reflex output studied was different in the three groups, possibly reflecting differences in the relative proportions of slow- and fast-twitch motor units contributing to the reflex response.

Achilles Tendon↗
PubMed1990

The influence of an increase in the level of force on the EMG power spectrum of elbow extensors.

It has been proposed that the mean power frequency (MPF) of the electromyogram (EMG) power spectrum increases gradually with force of contraction and that this increase is a function of the fiber-type content of the muscle investigated and the inter-electrode distance (IED) used when recording the EMG signals. In order to test these hypotheses, the values of the MPF of two elbow extensor muscles, triceps brachii (TB, 65% fast twitch fibers) and anconeus (AN, 65% slow twitch fibers), were compared at different levels of contraction. Subjects (n = 13) produced ten static ramp elbow extensions [0-100% maximum voluntary contraction (MVC)]. EMG signals of each muscle were recorded with two pairs of surface miniature electrodes having IEDs of 6 mm and 30 mm respectively. MPFs were obtained at each of the following levels: 10, 20, 40, 60, 80 and 100% MVC. Statistical analyses indicated that the MPF of AN increased significantly (P less than 0.05) up to 60% MVC. In contrast, the MPF values for TB showed no significant change across different levels of contraction (P greater than 0.05). Since skinfold was on average 3.2 times thicker over TB than over AN it is suggested that the low-pass filtering effect of the skin could have prevented the observation of an increase of the MPF for TB. It thus appears that changes of the MPF with the level of force, as disclosed by surface electrode recordings, is specific to each muscle. Consequently one has to account for factors such as thickness of the skinfold when it comes to the determination of the fiber-type content of different muscles within a subject.

Adult↗
PubMed1990

EMG power spectrum as a measure of muscular fatigue at different levels of contraction.

The shift in the power spectrum resulting from a 5-7 min fatigue-inducing effort followed by a 1-2 min recovery period of two elbow flexors, the biceps brachii (BB) and the brachio-radialis (BR), was assessed using two variables, the mean frequency Fm and the median or central frequency Fmd. These two variables were calculated in pre- and post-fatigue conditions and following a brief recovery, at four levels, namely 20, 40, 60 and 80 per cent of maximum voluntary contraction (MVC). These were taken from a ramped isometric effort that is from 0 to 100 per cent MVC. The EMG activity of the two flexors was recorded with bipolar surface electrodes from a group of ten volunteers. Following muscle fatigue, induced with a maintained 60 per cent MVC isometric contraction, a statistically significant (p less than 0.05) shift towards the lower frequencies was observed for both Fm and Fmd for both muscles. Following a brief recovery, a shift towards the pre-fatigue higher frequencies was statistically significant (p less than 0.05). These two synergists responded to muscle fatigue and recovery similarly, as they both demonstrated parallel shifts in power spectrum. The power spectrum is consequently a reliable measure of muscular fatigue. It is also complementary to the net articular moment results.

Adult↗
PubMed1988

An evaluation of the hemiplegic subject based on the Bobath approach. Part I: The model.

An evaluation, based on the Bobath approach to treatment has been developed. A model, substantiating this evaluation is presented. In this model, the three stages of motor recovery presented by Bobath have been extended to six, to better follow the progression of the patient. Six parameters have also been identified. These are the elements to be quantified so that the progress of the patient through the stages of motor recovery can be followed. Four of these parameters are borrowed from the Bobath approach, that is: postural reaction, muscle tone, reflex activity and active movement. Two have been added: sensorium and pain. An accompanying paper presents the evaluation protocol along with the operational definition of each of these parameters.

Disability Evaluation↗
PubMed1988

An evaluation of the hemiplegic subject based on the Bobath approach. Part III. A validation study.

Sixty-two hemiplegic subjects were treated with the Bobath approach for a period of three months. During this time they were evaluated on three occasions. The testing battery consisted of a Bobath evaluation, the Brunnstrom scale, the Fugl-Meyer test, the Upper Extremity Functional Test (UEFT) and the Present Pain Intensity (PPI) of the McGill pain questionnaire. A Friedman analysis of variance showed that, except for pain, all the protocols used disclosed significant progress (p less than 0.001) over time in terms of motor recovery. Except for pain, the results of the Bobath evaluation were significantly correlated (Spearman's Rho, p less than 0.001) with the results of the other testing procedures. It is concluded that the new Bobath evaluation proposed in a previous paper is as sensitive in depicting progress in motor recovery over time as are the other testing procedures used. Furthermore, this new evaluation seems to be measuring similar properties to the other tests. However, pain (PPI) appears not to be an important dependent variable.

Adult↗
PubMed1988

An evaluation of the hemiplegic subject based on the Bobath approach. Part II: The evaluation protocol.

A protocol of evaluation of the hemiplegic patient based on the Bobath approach to treatment is presented. Six parameters are evaluated: sensorium, muscle tone, reflex activity, active movement, postural reactions and pain. The first and last of these are included because of their possible effects on the motor recovery process of the hemiplegic patient. The other four are directly borrowed from the Bobath modality of treatment. For each of these parameters, the procedures are given for its evaluation along with its respective rating scales. These scales are of an ordinal nature ranging from 0 to 3. It is suggested that this new evaluation protocol is fully compatible with the therapeutic modality developed by Bobath and as well is adequate to quantify patient progress in the principle aspects treated by this well used rehabilitation approach.

Disability Evaluation↗
PubMed1987

Muscular compensatory mechanism in the presence of a tendinitis of the supraspinatus.

The aim of this study was to assess the electromyographic (EMG) activity of the middle part of the deltoid and of the supraspinatus muscles in subjects suffering from supraspinatus tendinitis. This experimental group (N = 10) was compared to a control group (N = 10). Each subject performed three isometric contractions for each of four pre- determined levels (5, 20, 35 and 50%) of their maximal voluntary contraction (MVC) during shoulder abduction. These contractions were carried out at angles of 0 degree and 45 degrees of abduction. The EMG signals obtained for each subject were integrated and normalized in a Z score form. Trend analysis, performed on the data of each of the two groups, revealed the existence of a significant (p less than 0.001) linear relationship between the integrated EMG (IEMG) and torque levels for each muscle investigated, at both angles of abduction. Furthermore, in the control group, similar EMG amplitudes were obtained for each muscle at these two angles of abduction. However, in the experimental group, the IEMG of the deltoid muscle showed a significant decrease in activity relative to the activity of the supraspinatus at an angle of 45 degrees of abduction (ANOVA, p less than 0.05). It is suggested that this inhibition of the deltoid reflects a compensatory mechanism. The purpose of this mechanism could be to prevent the compression of the affected supraspinatus tendon between the humeral head and the acromion that could occur while abducting the arm.

Adult↗
PubMed1987

Shoulder subluxation in hemiplegia: a radiologic correlational study.

A tridimensional (3-D) x-ray method of evaluation of the shoulder was contrasted with six clinical and radiologic techniques used to evaluate shoulder subluxation, in 50 hemiplegic subjects. The 3-D evaluation is obtained through a mathematical computation associating two x-rays of the same shoulder, one taken at 0 degree (anteroposterior) and the other at a 45 degrees oblique view. A vector is thus obtained quantifying the separation from the apex of the humeral head to the inferior border of the glenoid fossa. The Y component (cephalocaudal) of this vector is used to represent the inferior displacement of the humeral head. The six other techniques of evaluation were: a) palpation, or the number of finger breadths inserted between the acromial process and the head of the humerus; b) anthropometry, or the distance between the acromial process and the lateral epicondyle of the humerus; c) templates, or the use of four schemas representing different degrees of separation of the humeral head from the glenoid fossa; d) a measure of the relation of the center of the humeral head to the center of the glenoid fossa; e) the vertical distance between the center of the humeral head and the center of the glenoid fossa; and f) the vertical distance between the apex of the humeral head and the inferior border of the glenoid fossa. Correlation coefficients contrasting the 3-D x-ray technique and the six other measures ranged from .738 to .995. The high level of precision and reliability of the 3-D measure indirectly validated the other measurement techniques.

Female↗
PubMed1987

Rotation of the scapula and shoulder subluxation in hemiplegia.

Inferior subluxation of the shoulder in hemiplegia was measured using a tridimensional (3-D) x-ray technique. This technique gave the true vertical distance separating the apex of the humeral head and the inferior margin of the glenoid cavity. Both shoulders of each subject were evaluated and the difference used as a measure of subluxation. This measure was then compared to the orientation of the scapula relative to the vertical, to the abduction, and to the relative abduction of the arm. Relative abduction is defined as the angle between the humerus and the glenoid fossa. It has been suggested that these factors are associated with inferior subluxation in hemiplegia. Results of this study of 50 volunteer stroke patients indicated that the affected and nonaffected shoulders were different (subluxed) in terms of the vertical position of the humerus vis-à-vis the scapula. The orientation of the glenoid cavities was also different, the subluxed one facing less downward. The angle of abduction of the arm of the affected side was significantly greater than on the nonaffected side, but the relative abduction of the arm was on the same order of magnitude for both sides. There was no significant relationship between the orientation of the scapula and the severity of the subluxation. The abduction of the humerus was weakly (r = .24) related to the subluxation, which partly explained the weak association found between the relative abduction of the arm and the subluxation. It was concluded that the position of the scapula and the relative abduction of the arm cannot be considered important factors in the occurrence of inferior subluxation in hemiplegia.

Female↗
PubMed1986

How many strides are required for the analysis of electromyographic data in gait?

This study was conducted to obtain information on the number of strides of EMG data needed per subject in a gait study. Ten strides of EMG data were cumulated on eight subjects for each of the soleus, rectus femoris, biceps femoris, vastus medialis and tibialis anterior muscles. The linear envelope of the EMG, normalized in time and amplitude, demonstrated a very high level of stability for a given subject, relative to the variability that was found across subjects. It was concluded that three strides of EMG data per subject provides information as reliable as that obtained from twelve strides.

Adult↗