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A Plamondon

Publications and source records attributed to A Plamondon.

At least 19 recordsLinked to original sources
PubMed2006

Analysis of self-reported problematic tasks for pregnant women.

The objective of this study was to identify major components of, and influential factors in, problematic tasks performed by pregnant women employed in education, health care and service areas. Seventy-two pregnant women were surveyed using specially designed questionnaires consisting of an Initial Survey, a Job Analysis Questionnaire and a Task Description Questionnaire. Forty-four subjects (60%) had difficulty performing at least one work task and reported 105 tasks that were problematic at work. Reaching above the head, bending forward, bending and twisting, pushing, repeating actions and working at a fast pace were identified as the task components requiring the greatest level of effort. Excessive effort, excessive time, getting tired, repetitive actions, stress and fear of injury were identified as factors that had strong associations with the six major task components. Findings of this study suggest that these task components and factors should be considered when designing, assigning or analysing tasks for working pregnant women.

Activities of Daily Living↗
PubMed2006

Reproducibility of a task description questionnaire for working pregnant women.

The objective of this study was to evaluate the reproducibility of a Task Description Questionnaire that was designed to investigate exposures to, and influential factors for, problematic tasks experienced by working pregnant women. The questionnaire comprised questions concerning 22 task components (covering working posture, manual material handling, work pace, prolonged postures and others), eight influential factors contributing to problematic tasks, discomfort (measured using a body map) and level of effort to perform the tasks. Reproducibility of the questionnaire was assessed by interviewing participants on two occasions one week apart for interviews at both 20 and 34 weeks of pregnancy. Eleven and 13 problematic tasks were reported by 21 working pregnant women at 20 and 34 weeks of pregnancy, respectively. These tasks were surveyed using the Task Description Questionnaire. Kappa statistics and correlation coefficients (supplemented by paired t-tests) were used to examine the reproducibility of responses to the questionnaire. The results showed that most of the variables were measured with very good or satisfactory reproducibility. The reproducibility of exposure to work posture was higher than that of exposure to manual material handling. There was no significant difference between test and retest means for the discomfort scores measured on the body map, except for the maximum discomfort score for the whole body in the 34 weeks survey. The study suggests that the questionnaire can be reliably used in the study of problematic tasks experienced by pregnant women. But an initial preview of the questions by the subjects and explanation of the questions given to the subjects by the interviewer may help to produce more reliable results.

Female↗
PubMed2004

Back muscle fatigue during intermittent prone back extension exercise.

UNLABELLED: The purpose of this study was to estimate the level of muscular activation and muscle fatigue of the low back muscles during the performance of an intermittent prone back extension (PBE) exercise. Forty-one healthy students (24 males and 17 females) lying prone on a bench with the legs fixed performed two maximal voluntary contractions (MVC) in extension, a maximum of 100 repetitions of an intermittent PBE exercise immediately followed by a final MVC in extension. In addition, 12 subjects (11 males and one female) repeated the PBE exercise but with the addition of a 45-N weight on the back. The PBE exercise consisted of a task broken into four 1-s segments, while lying prone on a bench (10 degrees below horizontal): (1) raising the trunk to a horizontal position; (2) holding the trunk in the static phase (10 degrees above horizontal); (3) returning to the original position; and (4) resting on the bench. Electromyography (EMG) was used to measure the level of muscle activity (erector spinae (ES), gluteus maximus (GM), hamstrings (HA)) relative to the maximum voluntary EMG (MVE). RESULTS: Most of the subjects (34 out of 41) completed the 100 repetitions without excessive muscle fatigue according to the post-exercise MVC values. The intermittent PBE increased fatigue in the lumbar and hip extensor muscles in terms of: (1) a decrease in the MVC; (2) an increase in the level of muscle activation; and (3) a decline of the median frequency (MF). There was no gender difference in all EMG measurements. The level of muscle activation in the hip extensors (GM and HA) was associated with task failure (number of repetitions <100) for some subjects and the addition of a weight of 45 N had more impact on HA than ES. In conclusion, the PBE exercise as performed in the present study (including rest intervals), although not very strenuous for our healthy subjects, seems an adequate exercise to measure and train the aerobic capacity of the back muscles. However, to train specifically the back muscles, the exercise must be adjusted to avoid task failure due to possible hip extensor fatigue.

Adult↗
PubMed2002

Assessment of a three-dimensional robotic model for biomechanical-data acquisition of human movement.

The use of a kinematic robotic model has not been implemented in the biomechanical-data acquisition protocol, as it has in workplace analysis, ergonomics and design. The purpose of this paper was to assess the use of a kinematic model to retrieve frames of human movements from data obtained at a low sampling frequency. From experimental trials with an original sampling frequency of 60 Hz, the data were sampled again at two lower frequencies, 5 Hz and 10 Hz. The model was then used to reconstitute the data to its original frequency (60 Hz). The results demonstrated that it was possible to retrieve a full 3-D human movement from a sampling rate lower than normal without sacrificing accuracy. It was observed from both reduced sampling frequencies that the error level was comparable to the usual accuracy of a DLT 3-D reconstruction technique. It was therefore concluded that the data retrieved from these two frequencies were very similar to the original data sampled at 60 Hz.

Activities of Daily Living↗
PubMed2002

Handling missing marker coordinates in 3D analysis.

The use of mathematical formulations to retrieve missing data is not usually implemented as an automated computer procedure. The purpose of this paper is to present a simple mathematical formulation that can be used to retrieve the coordinates of markers hidden during a task. A strategy based on the smoothness of the variation of distance between points is devised, which leads to an automated computer procedure for retrieving hidden skin markers or missing joint coordinates (missing 3D points). This approach has the advantage of not being restricted to the usual rigid-body assumption.

Algorithms↗
PubMed2002

Estimated moments at L5/S1 level and muscular activation of back extensors for six prone back extension exercises in healthy individuals.

The purpose of this study was to identify the prone back extension (PBE) exercises that offer the most resistance to the back extensor muscles. Twenty males with no previous history of low back injury performed two repetitions of eight exercises. These consisted of two maximal isometric voluntary activations (MVA) and six different PBE exercises. The participants, while lying prone on a bench, were asked to raise either their trunk or legs to the horizontal position and hold for one second (static phase) before returning to the original position. The exercises differed according to the particular segments that were raised into extension. To assess the PBE exercises, a biomechanical model was used to estimate the level of load resistance (%MVA) relative to the maximum voluntary activation strength (MVA). In addition, electromyography (EMG) was included to measure the level of muscle activity (%MVE) relative to the maximum voluntary activation EMG (MVE) value reached during the MVA. A significant relationship of 0.86 was found between the mass of the subject and the peak reaction moment during the MVA. Peak level of load resistance averaged around 50% MVA with the exception of exercise no. 5 where the subject had to raise in extension his trunk, legs and arms (65% MVA). The erector spinae (ES) activity level reached a peak value of 61% MVE for exercise no. 5. In the exercises where only the trunk was lifted, the peak level of ES was below 47% MVE and the average activity during the static phase reached approximately 26% MVE. For healthy individuals PBE exercises can be considered low intensity exercises (< 50% MVA; except exercise no. 5) and can be used to improve the endurance of the back muscles.

Adolescent↗
PubMed1999

Toward a better prescription of the prone back extension exercise to strengthen the back muscles.

This study investigated the level of resistance and the level of muscle activation of the prone back exercise. Fifteen male subjects with no previous history of low back injury performed two repetitions of seven exercises. These consisted of four maximal isometric voluntary contractions (MVC) and three prone back extension (PBE) exercises. The subject was lying prone on a table, the upper body was suspended off the end of the table and the legs and thighs were secured to the table with straps. Three starting positions from the horizontal were investigated, 0 degree, 30 degrees and 60 degrees, and were compared with MVC to quantify the level of effort needed to perform the task. The results showed that the three PBE exercises require a level of resistance and a level of muscle activation generally under 40% of the maximum capacity of healthy subjects. Muscle activity of the erector spinae (ES) was slightly greater when the exercise started at 60 degrees, compared to 0 degree and 30 degrees. During the static phase of the PBE exercises, the level of resistance remained at 40% relative to the peak reaction moment of the MVC, but muscular activity of ES tended to work at a lower activity level. In conclusion, since for healthy subjects PBE exercises are low resistance exercises, they seem to be more specifically designed to develop muscular endurance of the back muscles.

Adult↗
PubMed1998

Sensitivity analysis of segment models to estimate the net reaction moments at the L5/S1 joint in lifting.

This paper deals with the mathematics of inverse dynamic analysis for calculating the net reaction moments; the sensitivity of the net reaction moments to nine experimental values is quantified and two dynamic models are compared. The results indicate that, among all terms, the external forces in the case of a lower body model and the segment masses in the case of an upper body model contributed the most to differences in the sensitivity of the lumbosacral reaction moment about the transverse axis. About the other axes there was no clear difference between the two body models.

Adult↗
PubMed1997

Development and application of predictive equations of maximal static moments generated by the trunk musculature.

OBJECTIVE: To develop and apply regression equations that predict the maximal static moments generated by the extensor, axial rotator and lateral flexor muscles of the trunk as a function of forward bending angles and asymmetrical positions of the torso in human subjects. DESIGN: Using experimental data, polynomial predictive equations were developed. The equations were applied in an algorithm to estimate the maximal moment generated by individual subjects. METHODS: Three groups of male subjects participated in the evaluation of the effect of forward bending and trunk asymmetry on the static moment of the extensor, right axial rotator, and right lateral flexor muscles of the trunk, respectively. Two other groups of male subjects were evaluated to test the validity of the algorithm. During the dynamometric tests, the three-dimensional position of the trunk was determined using cinematography techniques. RESULTS: For the extensor muscles, a curvilinear increase of the maximal moment was observed with forward bending, with a slight decrease of the moment on each side of the neutral position. For the right axial rotator muscles, both forward bending and left asymmetrical position of the trunk increased the maximal moments generated by these muscles. The right lateral flexors were stronger in the standing and mid-flexion positions than in other positions. First-order, second-order and interaction terms appear in the regression equations to account for the effect of forward bending and asymmetrical positions. The regression equation for the extensors and right axial rotator muscles have R(2) coefficients (range 0.56-0.76) higher than those of the lateral flexor regression equations (range 0.09-0.12). The algorithm results in an average error of 13% in predicting the strength of extensor and axial rotator muscles of individual subjects. CONCLUSION: The results have shown that strength of the extensor and axial rotator muscles is affected by forward bending and the asymmetry of the trunk, while strength of the lateral flexor muscles is only dependent on the forward bending position. The regression equations and the corresponding algorithm are applicable for the range of positions used in the study.

Journal Article↗
PubMed1996

Knee movement strategies differentiate expert from novice workers in asymmetrical manual materials handling.

One way to generate hypotheses on appropriate handling principles is to compare the strategies of highly skilled workers (experts) with those of novice workers (novices). This study was conducted to determine whether experts differ from novices in their handling strategies and to determine the effects of these differences in joint motions and net reaction moments at the trunk (L5/S1) and knees. Six experts and five novices were compared transferring two loads (12 and 22 kg) from four different initial low positions to a standardized low position on a trolley. The external forces were obtained from two AMTI force platforms, and two 16 mm Locam cameras coupled with two mirrors were used to obtain the three-dimensional kinematic data. An inverse dynamic analysis was performed on each segment and the net reaction moments were evaluated at L5/S1 and the knees; trunk posture, knee flexion angles and feet spacings were also calculated. Results showed that both groups minimized trunk asymmetries of posture and efforts; however, the experts were characterized by reduced knee flexion (31 degrees vs 53 degrees) and total knee excursion (20 degrees vs 38 degrees), increased flexion moments (72 vs 58 Nm) but reduced extension moments (4 vs 26 Nm) and valgus moments (30 vs 54 Nm). The experts' strategies appear safer overall because they reduce trunk asymmetry, asymmetrical efforts on the knee and stress on the femoropatellar joint. Moreover, these strategies present a potential for reduced mechanical energy expenditure due to lower knee excursions and increased knee stability due to reduced knee flexion.

Adult↗
PubMed1996

Validation of two 3-D segment models to calculate the net reaction forces and moments at the L(5)/S(1) joint in lifting.

The purpose of this study was to examine the validity and sensitivity of two three-dimensional segment models to estimate the net reaction forces and moments at the L(5)/S(1) joint. The two dynamic three-dimensional multisegment models, applied to lifting activities, were a lower body model and an upper body model. Three healthy male subjects participated in this study. The asymmetrical task consisted of lifting a load of 9.6 kg in a normal speed condition and in a fast condition. Results from the two models in terms of joint reaction forces and joint reaction moments at L(5)/S(1) were compared and were then used to validate them. The correlation between the reaction moments from both models were generally above 0.95 and the root mean square (RMS) differences were generally below 10 Nm but could reach 38 Nm. Similar trends were observed in the sensitivity analysis. A proportion of the error was attributable to errors in the segment accelerations because of an increase in the RMS differences between the models with an increase in lifting speed. The use of the lower body model seemed to present some advantages over the upper body model because of the nature of the task analysed which did not require large accelerations from the lower part of the body.

Journal Article↗
PubMed1995

Moments at the L(5)/S(1) joint during asymmetrical lifting: effects of different load trajectories and initial load positions.

The purpose of this study was to examine the reaction moments at L(5)/S(1) about the three orthogonal orthopaedic axes on the trunk when performing asymmetrical lifting tasks under six experimental conditions. The first three conditions were three lifting modes referring to different load trajectories (diagonal, extension then twisting, twisting then extension). The next three conditions were three lifts referring to different initial load positions (90 degrees, 45 degrees, 0 degrees ). Ten male volunteers (mean age 23.4 years) participated in the study. The mass of the load was 11.6 kg and two shelves were used: a low shelf of 22 cm from which the load was removed and a high shelf of 80 cm onto which the load was laid down following the manoeuvre. A dynamic 3D multisegment model was used to compute spinal loadings. The maximum reaction moments generated at the joint for the three load trajectories and for the three initial load positions were approximately of the same magnitude. On the other hand, significant differences were observed in the trunk orientation when the maximal moment was generated. Symmetrical trunk positions appeared to be more advantageous because of the reduction in the capability of maximal extension force in asymmetric trunk posture. A possible alternative for avoiding excessive stress on the back in asymmetric trunk posture may be to keep the shoulders parallel to the ground. RELEVANCE: Three-dimensional studies of the resulting moments at L(5)/S(1) when performing lifting activities are not common, particularly when the tasks include muscular exertions in trunk flexion combined with either twisting or lateral bending. This type of analysis is particularly important since asymmetries have been identified as risk factors for low back disorders. The knowledge of reaction moments in relation to postures are essential to understand the mechanism of low back pain.

Journal Article↗
PubMed1995

Effects of symmetry and load absorption of a falling load on 3D trunk muscular moments.

Some epidemiological data have suggested that many physical causes of low back pain such as bending and twisting were, in fact, sudden maximal efforts incidentally carried out at the moment of accident. Sudden loading conditions may be encountered in several circumstances, one of them being the recuperation of a falling load. Such conditions are more likely to occur in conditions of trunk asymmetry. The objective of this study was to determine spinal loadings associated with the reception of a falling box symmetrically and asymmetrically for two mechanisms of load absorption, one limited to the elbows and the other including full absorption with the elbows and lower limbs. It was hypothesized that asymmetrical receptions would be more strenuous for the spine; it was further hypothesized that the full absorption to decelerate the load might be more efficient in reducing the strain in the trunk muscular moments. Nine students in physical education with limited experience in manual materials handling were the subjects of the study. The tasks consisted of receiving a 6.6 kg load falling from a height of 50 cm above the flexed forearms when in a standing position. The subjects were tested with two AMTI force plates and two Locam cameras coupled with two mirrors; dynamic 3D multi-segment models were constructed and the net muscular moments as well as the angular velocities of the trunk relative to pelvis were determined about the three orthogonal axes of the trunk at L5/S1, in twisting, lateral bending, and flexion/extension. The dependent variables included maximal moments, maximal rates of loading for these moments, and the integration of these moments. Statistical analyses were performed to test the main effects of symmetry and absorption and their interaction. The results showed that asymmetrical conditions impose supplementary muscular exertions for trunk muscles, especially the trunk extensors and lateral flexors. Contrary to the proposed hypothesis, full absorption as used in the present study was a condition leading to considerably larger muscular exertions, especially for the loading rates. Thus it was concluded that the process of training for load absorption is essential to effectively decrease the risks of injuries. This factor would merit full consideration in future studies.

Absorption↗
PubMed1993

Pivoting with the load. An alternative for protecting the back in asymmetrical lifting.

The purpose of this study was to examine different lifting conditions with combined flexion and twisting of the trunk relative to the pelvis (full twist and half-twist techniques) and to compare them to a situation using feet pivoting with minimization of trunk motions relative to the pelvis. Nine subjects with limited experience were tested with two force platforms and two 16-mm cameras coupled with two mirrors; dynamic three-dimensional multisegment models were constructed and the net muscular moments as well as the angular velocities of the trunk relative to pelvis were determined about the three orthogonal orthopaedic axes of the trunk at L5-S1 in flexion-extension, lateral bending, and twisting. The results showed that pivoting required larger extension moments but considerably smaller twisting moments and that these moments were exerted from a safer trunk posture. Pivoting appears to be a good compromise to avoid or minimize complex trunk postures and loadings.

Adult↗
PubMed1990

Evaluation of Euler's angles with a least squares method for the study of lumbar spine motion.

To analyse intervertebral movements, methods with a high level of accuracy are required. Stereoradiographic methods have been used for a number of years to describe intervertebral movements, but their major problem is to identify the same anatomical landmarks, not only on the pair of radiographs used for three-dimensional reconstruction, but also on all the pairs used to analyse the displacements. To minimize the errors due to the incorrect identification of anatomical landmarks, a least squares method to resolve the parameters of Euler's angles was validated by means of measurements made on a spine obtained from a cadaver. The accuracy of this method varied between 0.69 degrees and 0.71 degrees in rotation and between 0.28 mm and 0.77 mm in translation. In addition, this method significantly corrected the position of the anatomical landmarks. Euler's angles, used with a least squares estimate, can provide accurate and precise results.

Aged↗