Biomedical subjects

M R Drost

Publications and source records attributed to M R Drost.

36 records · Page 2Linked to original sources

PubMed2000

Effect of immobilization on ankle dorsiflexion strength.

This study was performed in order to determine the loss of strength of the dorsiflexors in healthy persons after immobilization of the ankle, and the ability of these muscles to regain strength. First, isometric ankle dorsiflexion strength was measured in 33 healthy male and 39 female subjects in age categories 20-40 and 40-80 years, in order to obtain reference data and to determine the reproducibility of the measurement protocol. Gender, age and ankle position had a significant influence on the ankle dorsiflexion torque. Secondly, torque was measured in 15 patients after 4-6 weeks' immobilization of the ankle due to a fracture. A 28% decrease in dorsiflexion torque was seen. Strength reduction in neutral position and in 30 degrees plantar flexion was not significantly different. Without specific therapy restoration of torque was almost complete 6 weeks after cast removal.

Adult↗

PubMed1999

Enzyme activity of rat tibialis anterior muscle differs between treatment with triamcinolone and prednisolone and nutritional deprivation.

The maximal activity of a selection of enzymes involved in muscle carbohydrate handling, citric acid cycle and fatty acyl beta-oxidation were studied after treatment with the fluorinated corticosteroid triamcinolone and compared to a similar treatment of the non-fluorinated corticosteroid prednisolone in an equipotent anti-inflammatory dose. Furthermore, because triamcinolone causes loss of body mass and muscle wasting, the effects of triamcinolone were investigated relative to a control group, with the same loss of body mass, due to nutritional deprivation. The study was performed in male Wistar rats in the following treatment groups: TR, triamcinolone treatment (0.25 mg x kg(-1) x day(-1) for 2 weeks), which resulted in a reduction of body mass (24%); ND, nutritional deprivation (30% of normal daily food intake for 2 weeks) resulting in a similar (24%) decrease of body mass as TR; PR, prednisolone treatment (0.31 mg x kg(-1) x day(-1) for 2 weeks), with a 10% increase in body mass; FF, free-fed control group, with a 12% increase in body mass in 2 weeks. Compared to FF, TR induced an increase in phosphofructokinase (PFK) activity (P < 0.01), glycogen synthase [GS(i + d)] activity (P < 0.05) and glycogen content (P < 0.01) in the tibialis anterior muscle. The PR and ND caused no alterations in PFK or citrate synthase (CS) activity compared to FF. Compared to PR, TR induced an increase in PFK (P < 0.01), CS (P < 0.05) and GS(i + d) activity (P < 0.01). Both TR and PR caused an increased muscle glycogen content, being more pronounced in TR (P < 0.05). Compared to ND, TR induced an increased CS (P < 0.05) and GS(i + d) activity (P < 0.01) and glycogen content (P < 0.01). The ND resulted in a decreased glycogen content compared to FF (P < 0.05). None of the treatments affected the activity of glycogen phosphorylase, beta-hydroxyacyl coenzyme A dehydrogenase and lactate dehydrogenase. It was concluded that corticosteroids led to an increased muscle glycogen content; however, the changes in the enzymes of carbohydrate metabolism were corticosteroid type specific and did not relate to undernutrition, which accompanied the triamcinolone treatment.

Animals↗

PubMed1999

Skeletal muscle transverse strain during isometric contraction at different lengths.

An important assumption in 2D numerical models of skeletal muscle contraction involves deformation in the third dimension of the included muscle section. The present paper studies the often used plane strain description. Therefore, 3D muscle surface deformation is measured from marker displacements during isometric contractions at various muscle lengths. Longitudinal strains at superficial muscle fibers ( - 14 +/- 2.6% at L0, n = 57) and aponeurosis (0.8 +/- 0.9% at L0) decrease with increasing muscle length. The same holds for transverse muscle surface strains in superficial muscle fibers and aponeurosis, which are comparable at intermediate muscle length, but differ at long and short muscle length. Because transverse strains during isometric contraction change with initial muscle length, it is concluded that the effect of muscle length on muscle deformation cannot be studied in plane strain models. These results do not counteract the use of these models to study deformation in contractions with approximately - 9 % longitudinal muscle fiber strain, as transverse strain in superficial muscle fibers and in aponeurosis tissue is minimal in that case. Aponeurosis surface area change decreases with increasing initial muscle length, but muscle fiber surface area change is - 11%, independent of muscle length. Assuming incompressible muscle material, this means that strain perpendicular to the muscle surface equals 11%. Taking the relationship between transverse and longitudinal muscle fiber strain into account, it is hypothesized that superficial muscle fibers flatten during isometric contractions.

Animals↗

PubMed1999

Diffusion tensor imaging in biomechanical studies of skeletal muscle function.

In numerical simulations of skeletal muscle contractions, geometric information is of major importance. The aim of the present study was to determine whether the diffusion tensor imaging (DTI) technique is suitable to obtain valid input with regard to skeletal muscle fibre direction. The accuracy of the DTI method was therefore studied by comparison of DTI fibre directions in the rat tibialis anterior muscle with fascicle striation patterns visible on high-resolution magnetic resonance imaging (MRI) and with fibre directions in an actual longitudinal section (ALS) through the same muscle. The results showed an excellent qualitative agreement between high-resolution MRI and DTI. Despite less accurate quantitative comparison with ALS, it was concluded that DTI does indeed measure skeletal muscle fibre direction. After the experiment, it was possible to determine an appropriate voxel size (0.9 mm3) that provided enough resolution and acceptable accuracy (5 degrees) to use DTI fibre directions in biomechanical analyses. Muscle deformation during contraction, resulting from a finite element simulation with a mesh that was directly generated from the experimental data, has been presented.

Animals↗

PubMed1999

Three dimensional registration of mechanical bladder activity using polystyrene fluorescent spheres: A technical note.

Optical marker tracing methods have been applied successfully in recent years to quantify local material deformation of heart tissue, skin and striated muscles. In this study, polystyrene fluorescent spheres (d = 0.6 mm) are glued to the ventral serosal bladder wall in the rabbit. Three dimensional video registration of the polystyrene spheres is used to calculate two directions of principal strain (epsilon (1), epsilon (2) ) on the bladder surface in vivo. The aim is to investigate the feasibility of the technique for this new application in two experimental circumstances: during spontaneous bladder wall activity and after electrical stimulation of bladder innervating nerve fibers. During spontaneous activity, random contraction and relaxation occurred simultaneously and separately across the bladder wall for the two principal strains epsilon (1) and epsilon (2). After extradural electrical stimulation of sacral nerve root S2, the principal strains epsilon ( 1) and epsilon (2) synchronized in time in such a way that epsilon ( 1) and epsilon (2) both represented contraction or both represented relaxation. One and the same bladder wall area passed through phases of contraction followed by relaxation and vice versa. After multiple stimulation periods, the coordination between the two principal strains during stimulation was reduced. This technique allows to identify local areas of contraction and relaxation in the intact bladder wall in vivo. Three dimensional video registration of polystyrene fluorescent spheres to study bladder wall contraction and its relaxation proved to be a feasible technique, with which electrical stimulation effects and spontaneous activity could be measured.

Animals↗

PubMed1999

Postural muscle responses in the spinal cord injured persons during forward reaching.

To compensate for postural muscle function loss spinal cord injured (SCI) people have to use parts of the sensorimotor system which are still intact. In this study, postural control was investigated in high and low thoracic SCI people and in able-bodied controls, using a bimanual forward-reaching task. Muscle activity was recorded bilaterally from the erector spinae (ES) at level L3, T9 and T3, latissimus dorsi (LD), ascending part of the trapezius muscle (TPA), serratus anterior (SA), sternocostal head of the pectoralis major (PM) and the oblique abdominal muscles (OA) by means of surface electromyography. Sitting balance was monitored by measuring the changes in the location of the centre of pressure (CP) using a force platform. Muscle activity analyzed in different phases of the movement showed that SCI people adopt different postural adjustments to face the balance changes due to the reaching movement. SCI people make alternative use of non-postural muscles like the LD and TPA to maintain their sitting balance.

Adaptation, Physiological↗

PubMed1998

Mechanical blood-tissue interaction in contracting muscles: a model study.

A finite element (FE) model of blood perfused biological tissue has been developed. Blood perfusion is described by fluid flow through a series of 5 intercommunicating vascular compartments that are embedded in the tissue. Each compartment is characterized by a blood flow permeability tensor, blood volume fraction and vessel compliance. Local non-linear relationships between intra-extra vascular pressure difference and blood volume fraction, and between blood volume fraction and the permeability tensor, are included in the FE model. To test the implementation of these non-linear relations, FE results of blood perfusion in a piece of tissue that is subject to increased intramuscular pressure, are compared to results that are calculated with a lumped parameter (LP) model of blood perfusion. FE simulation of blood flow through a contracting rat calf muscle is performed. The FE model used in this simulation contains a transversely isotropic, non-linearly elastic description of deforming muscle tissue, in which local contraction stress is prescribed as a function of time. FE results of muscle tension, total arterial inflow and total venous outflow of the muscle during contraction, correspond to experimental results of an isometrically and tetanically contracting rat calf muscle.

Animals↗

PubMed1998

Acute and sustained effects of isometric and lengthening muscle contractions on high-energy phosphates and glycogen metabolism in rat tibialis anterior muscle.

Previous studies have shown that lengthening contractions, in contrast to isometric contractions, readily result in sustained malfunctioning of the exercised muscles. The present study was performed to investigate whether an exercise period with many (240) lengthening contractions (LC) results in alterations in muscle high-energy phosphates and inosine monophosphate (IMP) content, different from muscles performing a few (60) lengthening or a few (60) or many (240) isometric contractions (IC). Moreover, we sought for a possible cause(s) of the inability to replenish muscle glycogen stores following LC. Rat tibialis anterior muscles were subjected in vivo to either 60 or 240 LC or IC. Structural muscle damage occurred only after 240 LC. The fact that tissue glycogen levels declined to a similar extent during LC and IC suggests that the energy demand was comparable during both types of exercise. Nevertheless, the observation that on the one hand tissue stores of adenine nucleotides showed a greater decline, and on the other hand the tissue content of IMP increased to a significantly higher level after LC than after IC, clearly indicates that muscle energy metabolism is more disturbed during LC than during IC. The high tissue levels of IMP may contribute to impaired mechanical function as previously observed in muscles subjected to LC. In contrast to 240 IC, 24 hours after 240 LC, tissue glycogen stores and high-energy phosphate levels were not restored to control values. The present findings indicate that depressed glycogen synthase activity and impaired activity of the mitochondrial marker enzyme cytochrome C oxidase probably contribute to a continuous disturbance of energy metabolism in the exercised muscles during the 24 hours following 240 LC.

Adenosine Diphosphate↗

PubMed1998

Isokinetic aerobic power output testing of the quadriceps muscle.

A stepwise increasing exercise protocol to measure the maximal aerobic power output of the quadriceps muscle is proposed for use in rehabilitation medicine. Sixteen healthy volunteers performed isokinetic knee extension/flexion exercises at an angular velocity of 180 degrees x s(-1). The protocol consisted of stages of 200 knee movements from 100 flexion to full extension, starting at 10% peak torque (PT) and increasing by 10% PT each following stage until exhaustion. Quadriceps work, oxygen uptake, heart rate, plasma lactate concentration and surface electromyography were monitored. Quadriceps power output (Pext) was highly related (r = 0.95) to the extension torque at which the subjects were instructed to exercise. The test-retest (r = 0.82) and left to right (r = 0.94) correlations of maximum quadriceps power output (Pmax) were high. Both sexes (males 43+/-9W, females 36+/-8W) achieved their Pmax at 47% PT. At submaximal power output stages oxygen uptake (r = 0.85) and EMG-amplitude (r = 0.88) were linearly related to Pext. Mechanical efficiency (optimum at 60% Pmax) showed a large variation between power output stages and between subjects. The relationship between relative oxygen uptake and heart rate or plasma lactate concentration was similar to that of whole body exercise, e.g. running. We conclude that the proposed test is reliable for assessing the maximal aerobic power output of the quadriceps muscle. This parameter of the muscle function may add useful information for assessing the rehabilitation process after knee immobilization.

Adult↗

PubMed1997

Nonhomogeneous permeability of canine anulus fibrosus.

STUDY DESIGN: This report examines the permeability coefficient and aggregate modulus of slices of anulus cut from canine lumbar intervertebral discs. OBJECTIVES: To examine the influence of radial position on the properties of these materials, including outer samples with intact anulus edge. SUMMARY OF BACKGROUND DATA: The outer edge of anulus fibrosus shows radial bulge during axial compression of motion segments. The radial bulge increases monotonically when the axial compression is sustained for several hours, until a plateau is reached. Triphasic modeling of axial compression shows that this time course of radial bulge can not be obtained using a uniform permeability coefficient according to values in the literature. METHODS: Confined consolidation experiments (controlled load) were designed to measure the time course of uniaxial deformation of samples of anulus that were 4 mm in diameter and 1 mm tall. The rotation symmetry axis of the samples was defined in the radial direction of the disc. The radial permeability coefficient and the aggregate modulus were determined using the consolidation data and the linear biphasic theory. RESULTS: The permeability coefficient was lower at the periphery than in deeper layers of the anulus. Outer samples with outer surfaces that were 0.0-0.5 mm from the anulus edge had an average permeability coefficient of (1.02 +/- 0.57) x 10(-16) m4/Ns (n = 24). Inner samples that were 2.0-2.5 mm from the anulus edge had an average permeability coefficient of (2.81 +/- 0.98) x 10(-16) m4/Ns (n = 13). The aggregate modulus HA of outer samples was significantly higher (HA = 1.56 +/- 0.34 MPa) than that of inner samples (HA = 1.31 +/- 0.47 MPa). CONCLUSIONS: The fact that the outer anulus is less permeable than the inner anulus may explain why radial bulge of anulus fibrosus increases monotonically in time to an equilibrium value during sustained axial compression of a motion segment.

Animals↗

PubMed1997

Finite-element simulation of blood perfusion in muscle tissue during compression and sustained contraction.

Mechanical interaction between tissue stress and blood perfusion in skeletal muscles plays an important role in blood flow impediment during sustained contraction. The exact mechanism of this interaction is not clear, and experimental investigation of this mechanism is difficult. We developed a finite-element model of the mechanical behavior of blood-perfused muscle tissue, which accounts for mechanical blood-tissue interaction in maximally vasodilated vasculature. Verification of the model was performed by comparing finite-element results of blood pressure and flow with experimental measurements in a muscle that is subject to well-controlled mechanical loading conditions. In addition, we performed simulations of blood perfusion during tetanic, isometric contraction and maximal vasodilation in a simplified, two-dimensional finite-element model of a rat calf muscle. A vascular waterfall in the venous compartment was identified as the main cause for blood flow impediment both in the experiment and in the finite-element simulations. The validated finite-element model offers possibilities for detailed analysis of blood perfusion in three-dimensional muscle models under complicated loading conditions.

Animals↗

PubMed1996

Strain distribution on rat medial gastrocnemius (MG) during passive stretch.

Deformation of the surface of passive medial gastrocnemius muscle (MG) was measured in vivo while performing a hysteresis test. The gastrocnemius muscle of male rats were dissected free and the distal tendon was cut. The lateral head was separated from the medial head. The muscle origins were left intact. 60-70 fluorescent, polystyrene spheres (diameter 0.7 mm) were attached to the surface of the MG. During the experiment, two-dimensional video recordings of the movements of the MG were made. The coordinates of the marker centroids were obtained by computer processing of digitized images and marker displacements as a function of time were calculated. Green-Lagrange strains in two principal directions were calculated (epsilon 1, epsilon 2) for three specimens. epsilon 1 had approximately the same direction as the muscle fibers. The longitudinal strain of the fibers (20-30%) was larger than the strain of the aponeurosis (1-5%); p < 0.001. No significant difference was found between the values of the transverse strains of muscle fibers and aponeurosis; the value of epsilon 2 was -6 to -9% for both tissue structures.

Analysis of Variance↗

PubMed1996

Three-dimensional reconstruction of the rat triceps surae muscle and finite element mesh generation of the gastrocnemius medialis muscle.

In order to simulate blood flow in skeletal muscle, our group has developed a finite element description of perfused skeletal muscle. This model requires input parameters concerning the vascular system, muscle contraction and the geometry of a muscle, including its aponeuroses. The objective of the present paper is to create a geometrical reconstruction of the rat gastrocnemius medialis muscle that can be incorporated in the finite element model. Since this muscle is connected to the plantaris and the gastrocnemius lateralis muscle, a detailed computer graphical reconstruction of the triceps surae muscle, based on histological cross-sections, has been accomplished first. Using this reconstruction, relevant sections were selected to create the finite element mesh of the gastrocnemius medialis muscle. Special attention was payed to the location of the aponeuroses. The mesh can be used in finite element simulations of perfused skeletal muscle.

Animals↗

PubMed1996

Determination of muscle fibre orientation using Diffusion-Weighted MRI.

Biomechanical studies have shown that the distribution of stress and strain in biological tissue is strongly dependent on fibre orientation. Therefore, to analyze the local mechanical load, accurate data on muscle fibre orientation are needed. Traditional techniques to determine fibre orientation are inherently invasive. Here we used Diffusion Weighted MRI to non-invasively determine, in each image voxel of 0.23 x 0.23 mm, the diffusion tensor of water in the cat semimembranosus muscle. The direction corresponding to the largest eigenvector of this tensor was calculated. This direction was found to correspond qualitatively to the muscular fibre direction, as determined by visual inspection.

Animals↗

PubMed1995

Physical workload of ambulance assistants.

The physical workload of ambulance assistants was assessed by means of the Ovako Working posture Analysis System (OWAS) observation method and a Work and Health Questionnaire (WHQ) for measuring perceived workload. In addition, a biomechanical model was applied to several specifically strenuous conditions that were simulated in a laboratory situation. Bad postures were identified for a number of activities: 16% to 29% of a work shift was spent in harmful positions. Strenuous situations occur particularly during rides in emergency situations. The results of observed and perceived workload are generally in agreement. A number of practical recommendations are made. They concern, for example, the equipment in ambulance cars, training of ambulance assistants and adaptations in working procedures.

Ambulances↗

PubMed1995

Confined compression of canine annulus fibrosus under chemical and mechanical loading.

Uniaxial confined compression and swelling experiments on cylindrical specimens taken either in an axial or in a radial direction from a canine lumbar annulus fibrosus are presented. The loading protocol consisted of a combination of stepwise mechanical and chemical loading. Swelling and consolidation curves of normalized displacement versus square root of normalized time did not show a dependence on site or orientation of the specimen. All stages in which height increases, namely, conditioning, swelling, and desolidation show only slight differences in these normalized curves. Consolidation is initially faster, and later slower. The transport coefficient for axial specimens is higher than for radial specimens, for consolidation e.g., 3.14 +/- 1.56 10(-10) m2s(-1) and 1.11 +/- 0.33 10(-10) m2s(-1) respectively, the biphasic aggregate moduli are 1.01 +/- 0.31 MPa and 0.66 +/- 0.30 MPa, respectively.

Animals↗

PubMed1994

EMG profiles of ACL-deficient patients during walking: the influence of mild fatigue.

The purpose of this study was to determine muscle activities after ACL rupture during walking and running and to investigate the influence of mild fatigue (10 min walking) on these activities. A group of 12 patients with ACL-ruptures was compared with a control group (healthy volunteers) of 15 persons. Linear envelopes of EMG-activity from vastus medialis, vastus lateralis, biceps femoris and medial hamstrings were measured. Patients and control persons walked on a treadmill at speeds of 1.2 m/s (samples at t = 2 min and t = 12 min) and 2.8 m/s i.e. running (sample at t = 15 min). The patient group showed significantly lower muscle activities of vastus lateralis (p < 0.001) and medial hamstrings (p < 0.05) for both the injured and uninjured leg during running compared to the control group. After 10 minutes walking, the mean-EMG of biceps femoris (p < 0.05) and medial hamstrings (p < 0.01) decreased as did the activity time of biceps femoris (p < 0.05), medial hamstrings (p < 0.01) and vastus medialis (p < 0.001) for the injured leg of the patient group. Control persons showed no significant changes. Thus, mild fatigue did effect only the EMG-pattern of the patients. Patients with ACL-ruptures should be trained not only on strength and stabilisation, but also on endurance. A decrease in hamstrings activity during walking might be a sensitive measure for evaluation of the rehabilitation process, as those muscles may be able to substitute ACL-deficiency.

Anterior Cruciate Ligament Injuries↗

PubMed1994

An evaluation of patient lifting techniques.

In the present laboratory study five two-person manual lifting techniques were evaluated as to the amount of physical exertion required of the nurses. Ten female volunteers served as nurses; two healthy volunteers (weight: 55 kg and 75 kg) served as passive patients. The working postures and motions were recorded on videotape. The data thus obtained were used in a anatomical-biomechanical analysis. The perceived exertion by the nurses was measured as well. In almost all situations the compressive forces on the nurse's spine exceeded their acceptable limit of 3425 N. Differences between the lifting techniques were most obvious when the 55 kg patient was lifted. Ratings of the perceived exertion (RPE scores) were higher in symmetrical handling than in asymmetrical handling. The three techniques using asymmetrical hand positions produced less subjective stress. RPE scores and rotation of the back were negatively correlated. Rotating the back when moving a patient from one side to the other seems to ease the task. On the whole, the results of the biomechanical evaluation are in line with the subjective perception of the nurses. In both instances the barrow lift appeared to be the most strenuous one; the Australian lift resulted in low compressive forces and a moderate level of perceived exertion.

Adult↗