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Biomedical subjects

A J Spaepen

Publications and source records attributed to A J Spaepen.

13 recordsLinked to original sources
PubMed2004

A new method for semiautomatic analysis of surface EMG in patients with oral parafunctions.

Sleep-related phenomena or disorders, including snoring and tooth grinding, can be investigated using polysomnography. This method, however, generates large amounts of synchronically recorded data that are often analyzed visually with subjective interpretation. The purpose of this study was to minimize the need for subjective evaluation by developing a computer program for analysis of EMG data linked with polysomnographic recordings in a standardized and semi-automatic way. The selected algorithm differs from the Root Mean Square (RMS) method by being based on the theory of "differentiated EMG" (DIFEMG), which relies on two principles. The first says that the activation of a larger number of motor units results in a greater force production. The second principle says that the force production will continue for some time after the muscle is no longer stimulated. After a visual check for artifacts in the basic EMG recordings, the computer program is used to analyze the corrected basic EMG signal. The results were that both methods yield identical results as far as the detected number of events is concerned. There is, however, a significant difference when the duration of the events is considered, because the start and end of an event can be more accurately determined with the new method presented here. The computer program described will make comparison of data from different studies easier.

Algorithms↗
PubMed1999

Lipoatrophia semicircularis and the relation with office work.

The relation between lipoatrophia semicircularis (LS--band-like circular depressions and isolated atrophy of the subcutaneous fatty tissue on the anterior thighs and sitting posture or pressure on the seat surface of office chairs was investigated in an office environment. A questionnaire was presented to 21 subjects and electromyographic measurements, video analysis and pressure measurements were performed. Remarkable posture differences between the LS group and the group without LS were found: less use of the lumbar support of the chair, static sitting postures and a too high seat surface of the office chair were characteristics of the subjects with LS. These observations were confirmed by higher pressure measurements for the subjects with LS. In addition, highly significant pressure differences were found between different chairs.

Adipose Tissue↗
PubMed1999

Measuring small linear displacements with a three-dimensional video motion analysis system: determining its accuracy and precision.

OBJECTIVES: To determine accuracy, precision, and smallest detectable difference for a three-dimensional (3D) video motion analysis system specifically configured for measuring small and slow displacements within a small measurement volume (0.7 x 0.5 x 0.3 m). DESIGN: Repeated measurements with random sequence of conditions. SETTING: Rehabilitation research laboratory. INTERVENTION: A reference sliding device was used to control cyclic displacements of two reflective markers over 5 calibrated ranges (1, 3, 10, 30, and 60 mm). Nine cycles were performed for each of 9 conditions (3 directions x 3 zones). Four cameras recorded all trials on tapes, which were digitized with a Kinemetrix system. MAIN OUTCOME MEASURES: Change in distance of the moving markers relative to a third static marker was averaged over 50 frames per trial. Mean error, mean absolute error, and intertrial and intratrial standard deviations (SDs) were calculated for each zone and direction. RESULTS: For 810 trials, mean error and absolute error were, respectively, .034 mm and .094 mm. The mean intertrial and intratrial SDs and 99% confidence interval were .047 mm (CI = +/- .121 mm) and .030 mm (CI = +/- .077 mm). The corresponding smallest detectable differences were .171 mm and .109 mm. CONCLUSION: Motion analysis configured for registration within small volumes allows measurement of minuscule displacements with great accuracy and may therefore be suitable for many applications in rehabilitation research other than gait analysis.

Equipment Design↗
PubMed1999

Relation between differences in electromyographic adaptations during static contractions and the muscle function.

This study determines whether changes in the EMG values of two important muscles of the shoulder and neck region, the anterior deltoid and the upper trapezius, are due to changes in torque production or due to fatigue processes during sustained activity. Contractions at 20, 40, 60, 80 and 100% MVC were performed during a flexion of the arm in the sagittal plane at 90 degrees, to examine the relation between torque and EMG. A sustained contraction at 20% MVC was performed to endurance point in the same position. RMS, a new parameter called activity, (ACT), and MPF of the deltoid anterior and the upper trapezius were analysed. The amplitude values correlated highly with increasing torque production, both for the deltoid muscle (range r = 0.95-0.96), and the trapezius muscle (range r = 0.83-0.87), whereas no significant difference was found for MPF. For the endurance task, the decrease in MPF was far more pronounced for the deltoid than for the trapezius, whereas the opposite occurred with RMS (P < or = 0.01). Furthermore, there was no significant difference over time for the ACT values of the deltoid, whereas there were significant increases in ACT for the trapezius (P < or = 0.01). The RMS/ACT ratio correlated highly (r = 0.81) with the MPF. Regression coefficients of these parameters differed significantly for the trapezius muscle but not for the deltoid muscle. Therefore, the RMS/ACT ratio may be extremely important in analysing the fatigue effects during sustained efforts, independent of torque variations, which can influence indicators of fatigue.

Adult↗
PubMed1998

Hierarchical control of different elbow-wrist coordination patterns.

The present paper focused on the role of mechanical factors arising from the multijoint structure of the musculoskeletal system and their use in the control of different patterns of cyclical elbow-wrist movements. Across five levels of cycling frequency (from 0.45 Hz up to 3.05 Hz), three movement patterns were analyzed: (1) unidirectional, including rotations at the elbow and wrist in the same direction; (2) bidirectional, with rotation at the joints in opposite directions, and (3) free-wrist pattern, which is characterized by alternating flexions and extensions at the elbow with the wrist relaxed. Angular position of both joints and electromyographic activity of biceps, triceps, the wrist flexor, and the wrist extensor were recorded. It was demonstrated that control at the elbow was principally different from control at the wrist. Elbow control in all three patterns was similar to that typically observed during single-joint movements: elbow accelerations-decelerations resulted from alternating activity of the elbow flexor and extensor and were largely independent of wrist motion at all frequency plateaus. The elbow muscles were responsible not only for the elbow movement, but also for the generation of interactive torques that played an important role in wrist control. There were two types of interactive torques exerted at the wrist: inertial torque arising from elbow motion and restraining torque arising from physical limits imposed on wrist rotation. These interactive torques were the primary source of wrist motion, whereas the main function of wrist-muscle activity was to intervene with the interactive effects and to adjust the wrist movement to comply with the required coordination pattern. The unidirectional pattern was more in agreement with interactive effects than the bidirectional pattern, thus causing their differential difficulty at moderate cycle frequencies. When cycling frequency was further increased, both the unidirectional and bidirectional movements lost their individual features and acquired features of the free-wrist pattern. The deterioration of the controlled patterns at high cycling frequencies suggests a crucial role for proprioceptive information in wrist control. These results are supportive of a hierarchical organization of control with respect to elbow-wrist coordination, during which the functions of control at the elbow and wrist are principally different: the elbow muscles generate movement of the whole linkage and the wrist muscles produce corrections of the movement necessary to fulfill the task.

Elbow Joint↗
PubMed1998

Evaluation of stroke performance in tennis.

In the present studies, the Leuven Tennis Performance Test (LTPT), a newly developed test procedure to measure stroke performance in match-like conditions in elite tennis players, was evaluated as to its value for research purposes. The LTPT is enacted on a regular tennis court. It consists of first and second services, and of returning balls projected by a machine to target zones indicated by a lighted sign. Neutral, defensive, and offensive tactical situations are elicited by appropriately programming the machine. Stroke quality is determined from simultaneous measurements of error rate, ball velocity, and precision of ball placement. A velocity/precision (VP) an a velocity/precision/error (VPE) index are also calculated. The validity and sensitivity of the LTPT were determined by verifying whether LTPT scores reflect minor differences in tennis ranking on the one hand and the effects of fatigue on the other hand. Compared with lower ranked players, higher ones made fewer errors (P < 0.05). In addition, stroke velocity was higher (P < 0.05), and lateral stroke precision, VP, and VPE scores were better (P < 0.05) in the latter. Furthermore, fatigue induced by a prolonged tennis load increased (P < 0.05) error rate and decreased (P < 0.05) stroke velocity and the VP and VPE indices. It is concluded that the LTPT is an accurate, reliable, and valid instrument for the evaluation of stroke quality in high-level tennis players.

Adult↗
PubMed1997

Influence of electrode position on changes in electromyograph parameters of the upper trapezius muscle during submaximal sustained contractions.

The purpose of the present study was to evaluate whether differences could be found in the changes in mean power frequency (MPF) and root-mean-square (rms) due to electrode positions on the upper trapezius muscle during a sustained submaximal task. A group of 25 healthy subjects performed a continuous forward flexion of the right arm at 20% of their maximal voluntary contraction (MVC). Three pairs of bipolar surface electrodes were positioned on a straight line between the spine of the seventh cervical vertebra (C7) and the lateral edge of the acromion. The fourth pair (the caudal position) was placed 2 cm below the midpoint of this line. The analysis of variance revealed significant differences between the electrode positions during the short 20% MVC and during MVC (P < or = 0.01). Furthermore, lower rms values were found when the electrodes were placed symmetrically around the midpoint of the reference line, which confirms previous studies. A statistical model has been developed to discriminate additionally the very small changes in the electromyogram parameters due to electrode position during the sustained 20% MVC. It was found that the slope coefficients of rms and MPF were significantly different from 0 (P < or = 0.01), although to a lesser degree for rms and more clearly for MPF of the caudal position (P < or = 0.05). Furthermore, significant differences were found between several combinations of the uppermost electrodes and the caudal position (P < or = 0.01). From this study, it is concluded that it is important to evaluate several electrode positions on the upper trapezius muscle to be able to represent the behaviour of this muscle accurately during a sustained contraction.

Adult↗
PubMed1997

Muscular activity of the shoulder and neck region during sustained and intermittent exercise.

Sustained isometric contractions of the neck and shoulder muscles in laboratory conditions are often assumed to be representative of muscular load in occupational tasks. The present study aims to investigate whether differences can be found between these contractions and those in intermittent tasks. Ten subjects performed forward flexions of the right arm during three tests to the limit of endurance: (1) a sustained contraction; (2) an intermittent contraction with a cycle time of 10 s and a duty cycle of 0.7; and (3) the same intermittent contraction with the possibility of changing the shoulder angle during relaxation. Muscular activities of the upper trapezius, deltoid pars anterior and medialis and infraspinatus were registered using surface electromyography, and changes in the signal were quantified by root mean square (RMS) and mean power frequency (MPF) values. During the continuous test, highly significant changes in both parameters were found for the four muscles. Significant changes were found during both intermittent conditions, although to a lesser degree than in the continuous test. Significant differences between the regression coefficients of the sustained test and the two intermittent tests were found on all occasions: for RMS and MPF of the four muscles. Significant differences were also found regarding the intermittent tests. The test in which no variation in limb position was allowed during relaxation caused a more pronounced MPF decrease for the trapezius (P < or = 0.01), which was confirmed by the subjective scores of perceived exertion and a higher RMS increase (P < or = 0.01) for the middle part of the deltoid. The intermittent condition with changes in shoulder angle showed more MPF decrease for the deltoid, significant for the middle part (P < or = 0.05), not significant for the anterior part and a larger RMS increase for infraspinatus (P < or = 0.05). It can be concluded that the latter condition represents more the trapezius and deltoid activity as in occupational tasks.

Adolescent↗
PubMed1994

Wheelchair propulsion efficiency: movement pattern adaptations to speed changes.

Low mechanical efficiency values in wheelchair propulsion are usually explained on the basis of the supply of force and power generated during the push phase. The purpose of this study is to analyze the movement and muscular activity pattern in handrim wheelchair propulsion, focusing on both the push and recovery phases. Data on cardiorespiratory and propulsion technique parameters were obtained from 40 wheelchair basketball players with extensive experience in wheelchair propulsion in six situations: two exercise levels (60% and 80% of individual VO2peak), and three velocities (1.11, 1.67, and 2.22 m.s-1) with constant power output on a treadmill. A two-factor analysis of variance with repeated measurements was applied with "exercise level" and "speed" as the main factors. A significant effect on gross mechanical efficiency was found when the velocity was increased from 1.67 to 2.22 m.s-1. Decreased mechanical efficiency could be explained by a significant change in the acceleration of the wheelchair-user system during recovery, caused by arm and trunk movements, inducing inertial forces to act on the wheelchair. Consequently, mechanical work increased significantly during the recovery phase. These findings indicate that studies on mechanical efficiency in wheelchair propulsion should not only be focussed on power supply during the push phase, but also on the movement pattern during recovery.

Adaptation, Physiological↗
PubMed1994

Wheelchair propulsion: functional ability dependent factors in wheelchair basketball players.

The aim of this study was to examine the user-related parameters, 1) force generation 2) maximal aerobic power and 3) propulsion technique, in respect to functional ability level [ISMWSF] wheelchair basketball classification: groups 1, 2 and 3) of 40 elite wheelchair basketball players. Isometric (position on the handrims = -30, 0 degrees, +30 degrees and +60 degrees) and dynamic force application (velocities = 0.56, 0.83 and 1.11 m.s-1) on the handrims (test 1) was measured by means of a computerised wheelchair simulator, with the subjects sitting in a standardised position. Each subject performed a maximal exercise test (test 2) on a motor driven treadmill at 1.67 m.s-1 and four subsequent submaximal tests (test 3) at two exercise levels (60 and 80% of individual VO2) and two velocities (1.11 and 2.22 m.s-1) with constant power output. In tests 2 and 3, cardiorespiratory and kinematic data were recorded simultaneously. Although no significant differences between functional ability groups were found in relation to force application on the handrims, three different force application strategies were observed (test 1). Maximal aerobic capacity and power output (test 2) differed significantly (p < 0.05) between groups 1 and 2 and between groups 1 and 3. No differences in mechanical efficiency were observed between the three functional ability groups, irrespective of changes in wheelchair velocity and external load (test 3). Propulsion technique was not proven to be functional ability dependent although remarkable differences in movement pattern were observed, especially during the recovery phase.

Activities of Daily Living↗