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Biomedical subjects

P Vink

Publications and source records attributed to P Vink.

31 records · Page 2Linked to original sources
PubMed1992

Decrease in back strength in asymmetric trunk postures.

The extension force against resistance was recorded in 23 postures for 12 subjects to find explanations for the decrease in back strength in asymmetric postures. A reduction in muscle force in asymmetric postures was found up to 40%, but was strongly dependent on the plane in which asymmetry occurred, and on the posture to which it referred. A quantitative relationship between the forces exerted in different asymmetric postures is discussed, as a basis for formulating universal ergonomic guidelines for optimal working postures. The reduction in force in different asymmetric postures can be explained by length of the muscle, the activation of the muscle, and the moment angle of the muscle.

Adult↗
PubMed1989

Elastic strain energy in the low back muscles during human walking.

A simple model of the thorax, pelvis and three columns of the intrinsic lumbar back muscles (= ILBM) was constructed. The model was used to study the length of the ILBM during the different stages of the walking cycle. The length of the right ILBM (especially the lateral column) was largest at right toe off, exactly the stage of the walking cycle in which most force was needed to prevent the torso from falling forwards and laterally.

Back↗
PubMed1988

Low back muscle activity and pelvic rotation during walking.

Gait variables, pelvic rotations in the frontal and sagittal plane and RA-EMG (rectified and averaged EMG) of the three columns of the intrinsic lumbar back muscles (= ILBM) were recorded simultaneously during 48 succeeding strides of 11 subjects on a treadmill. Bilateral activity is found in all parts of the ILBM during the double support phase. After right heel strike the right ILBM (and after left heel strike the left) show in most cases more activity than the contralateral ILBM. This is especially so in the intermediate and lateral columns, which consist mainly of the longissimus thoracis and the iliocostalis lumborum muscle and less so in the medial column, made up mainly by the multifidus and spinalis muscle. This difference is probably due to the difference in moment arm for the two directions. Pelvic rotations are described, but no evident relationships between pelvic rotations in the different planes and ILBM-activity could be seen, probably because the changes in the position of the torso are of more importance.

Adult↗
PubMed1987

Lumbar back muscle activity during walking with a leg inequality.

The influence of an artificial leg length discrepancy (= ALLD) on stride times, pelvic rotations and activity of the intrinsic lumbar back muscles (= ILBM) was investigated for 20 subjects. An ALLD was created by shoes with a raised sole. Walking with an ALLD produced an increase of the swing phase time and a decrease of the stance phase time for both feet. The influence of an ALLD on pelvic rotations in the sagittal and frontal plane and on ILBM-activity was small. Changes in pelvic rotations in the sagittal plane were too small to observe. The mean pelvic rotation angle in the frontal plane was changed 1.52 degrees when walking with an ALLD of 40 mm (6.9 degrees while standing with an ALLD of 40 mm with extended knees). Only small changes were found in activity time due to an ALLD (not in EMG-amplitude). The activity time of the ILBM around heel strike of the raised limb was increased and unilaterally shifted from toe off in the direction of heel strike with the raised limb.

Electromyography↗
PubMed1986

Residual formaldehyde in steam-formaldehyde sterilized materials.

The amounts of residual formaldehyde and paraformaldehyde present in polymeric materials after steam-formaldehyde sterilization in a commercial sterilizer were determined. Appreciable amounts of residue were detected in ethylene-vinyl alcohol copolymer (EVOH), polyamide-6 (PA-6) and natural rubber (NR). These polymers all have a relatively low contact angle with water which indicated that the wettability of a material is an important parameter in determining amount of residue. The residue present in EVOH and in PA-6,6 filter material appeared to be toxic in the HFL-test (a screening test for acute toxicity). This indicated that a more thorough investigation into the possible toxicological consequences of the use of some steam-formaldehyde sterilized materials is necessary.

Biocompatible Materials↗
PubMed1986

Aeration of ethylene oxide-sterilized polymers.

The ethylene oxide (EO) content of 17 polymers sterilized with 100% EO under conditions normally used in practice was determined as a function of aeration time, and for some polymers also as a function of sample thickness. The determination of the amount of residual EO has been carried out by gas chromatography, applying Discontinuous Gas Extraction and Head Space analysis. Generally, aeration was confirmed to be a diffusion-controlled process. Diffusion coefficients of EO for the investigated materials were determined from the rates of desorption. For a number of materials the EO content appeared to be well above the levels for EO which currently are considered to be safe, even after aeration for 15 d. For a reliable determination of aeration times required for EO-sterilized medical devices, the type and in particular also the thickness of the material from which the device is made should be considered.

Biocompatible Materials↗
PubMed1985

The stabilising function of the mm. iliocostales and the mm. multifidi during walking.

The myoelectric activity of the mm. multifidi and the mm. iliocostales lumborum of six subjects was recorded during walking. The subjects walked on a treadmill as well as on a fixed walkway. On the treadmill, recordings were made at two different speeds and with a varying loading of the spine. There was almost no difference in myoelectric activity time between the treadmill and the fixed walkway. Related to unloaded walking, both the multifidi and the iliocostales showed an increase in activity time when the subjects carried a load of 5 kg in front of the trunk and a decrease of activity time with a load of 5 kg on the back. A load on the lateral aspect of the body shortened the muscle activity time of the multifidi on the homolateral side. In three subjects the same pattern was found for the iliocostales, but in the other three subjects there was no activity registered at all. On the side contralateral to the load, the multifidi showed no increase of activity time while the iliocostales muscles demonstrated an increase. It is concluded that during walking the iliocostalis muscle has a more important function in lateral bending than the multifidus. It was remarkable that the multifidi muscles of the left side were active for longer periods than were those of the right side in all situations except during lateral loading.

Adult↗
PubMed1982

Effects of dietary carbohydrate and fat on plasma lipoproteins and apolipoproteins C-II and C-III in healthy men.

Effects of isocaloric changes in dietary fat and carbohydrate on plasma apolipoproteins (apo) C-II, C-III, and lipoproteins were assessed in nine healthy men. Carbohydrate and fat comprised 80% of total calories. After a 1-week basal diet (40% of calories from carbohydrate), the subjects received either a high (65% of calories) or low (15% of calories) carbohydrate diet for 3 weeks; subsequently the diets were switched, those initially on high carbohydrate going on to low carbohydrate, and vice versa, and the new diets were maintained for 3 weeks. ApoC-II, C-III, and triglycerides initially rose and then declined during the high carbohydrate diet period; high density lipoprotein cholesterol (HDL-C) decreased. Comparing results after 3 weeks of high carbohydrate diet to those after 3 weeks on low carbohydrate, we observed the following significant differences: 1) total plasma apoC-II and C-III were higher; the apoC-III/C-II ratio in very low density lipoproteins (VLDL) and in the lighter HDL subfraction (HDL2) was lower indicating net lipoprotein enrichment with apoC-II than with apoC-III; 2) unsialylated apoC-III0 comprised a higher percent of total VLDL apoC-III mass; 3) HDL2 and HDL2/HDL3 ratio were lower. Isocaloric changes in dietary carbohydrate and fat cause significant alterations in plasma levels of VLDL and HDL 2, the two major lipoproteins that transport apoC-III and apoC-II. Diet-induced changes in circulating apoC-III and C-II may, in part, play a role in regulation of plasma triglycerides in man.

Adult↗