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Biomedical subjects

T Bendix

Publications and source records attributed to T Bendix.

36 records · Page 2Linked to original sources
PubMed1989

Effect of physical exercise on blood mononuclear cell subpopulations and in vitro proliferative responses.

The present study was designed to examine the effect of physical exercise on subsets and proliferative responses of blood mononuclear cells. Sixteen young, healthy volunteers underwent 60 min of bicycle exercise at 75% of maximal oxygen uptake (VO2max). After an interval of at least 1 week, six of the subjects underwent a 60-min back muscle training period at up to 30% of VO2max. Blood samples were collected before and during the last minutes of exercise, as well as 2 and 24 h later. Blood mononuclear cell (BMNC) subpopulations were determined and the proliferative responses after incubation with phytohaemagglutinin (PHA) or purified derivative of tuberculin (PPD), were quantified by [3H]thymidine incorporation. During bicycle exercise the relative blood concentration of T cells (CD3+ cells) declined, mainly due to a fall in T helper cells (CD4+ cells). The natural killer (NK) cell subset (CD16+ cells) increased during work, but reverted after; the monocytes (CD14+ cells) increased 2 h after work, whereas the B-cell subset (CD20+ cells) did not change. BMNC subsets were not significantly changed by back muscle exercise. The PHA-induced proliferative response decreased during bicycle exercise, whereas the PPD-induced response did not change. No significant changes occurred during back muscle exercise. Investigation of subgroups after incubation with [3H]thymidine showed that the proliferative response per CD4+ cell did not change in relation to exercise, but the contribution of the CD4+ subgroup to proliferation declined during bicycle exercise due to the decreased proportion of CD4+ cells. The suppression of the PHA response during bicycle exercise can be explained in part by a relative fall in CD4+ cells. The pool sizes of BMNC subfraction may be elicited by increased catecholamine and cortisol levels.

Adult↗
PubMed1988

Biomechanics of forward-reaching movements while sitting on fixed forward- or backward-inclining or tiltable seats.

Possible differences in spinal stress were evaluated during forward-reaching movements from chairs with, respectively, fixed backward-inclining, forward-inclining, and tiltable seat. Twenty-four healthy subjects, 12 female and 12 male, performed rhythmical sagittal movements with pins over a 40-cm distance. The posture in an upright and in a forward position was described by means of seven variables, measured by an inclinometer. Posture changes between these positions were then compared for the three types of chairs. No significant influence from the chairs on posture changes was observed. Thus, no variation in spinal stress can be anticipated during forward-reaching movements in any of the three types of chair. The discussion also presents a current status regarding tiltable and fixed forward-inclining seats.

Biomechanical Phenomena↗
PubMed1988

Modulation of natural killer cell activity in peripheral blood by physical exercise.

The present study was designed to examine the effect of physical exercise on human natural killer (NK) cells. Six healthy volunteers underwent two different acute physical exercise tests with an interval of at least 1 week: (1) 60 min bicycle exercise at 80% of maximal oxygen uptake (VO2max) and (2) 60 min back-muscle training at up to 29% of VO2max; blood samples were collected before and during the last few minutes of exercise, as well as 2 h and 24 h afterwards. The NK cell activity (lysis/fixed number of mononuclear cells) increased during bicycle exercise, dropped to a minimum 2 h later and returned to pre-exercise levels within 24 h. Back-muscle exercise did not significantly influence NK cell activity. Plasma levels of adrenaline, noradrenaline, and cortisol were elevated during bicycling, but not during back-muscle exercise, indicating that exercise intensity is a determinant of NK cell activity. During bicycle exercise the NK cell subset (CD16- cells) of mononuclear cells increased significantly. Furthermore an improved interleukin 2 (IL-2) boosting of the NK cell activity was found during work as compared to IFN-alpha and indomethacin-enhanced NK cell activity. These results indicate that NK cells with a high IL-2 response capacity are recruited to the peripheral blood during exercise. The decreased NK cell activity demonstrated 2 h after work was probably not due to fluctuations in size of the NK cell pool, since the proportion of CD16+ cells was normal. The finding that indomethacin fully restored the suppressed NK cell activity in vitro and the demonstration of a twofold increase in monocyte (CD20+ cells) proportions 2 h after work, strongly indicate that prostaglandins released by monocytes during the heavy physical exercise are responsible for the down-regulation of the NK cells.

Adult↗
PubMed1987

Adjustment of the seated workplace--with special reference to heights and inclinations of seat and table.

The influence of varying workplace adjustment on posture, muscular load, and subjective acceptability has been investigated in eight studies. Workplace variables were: seat height, seat inclination, backrest position, table height, and desk inclination. Moreover, some of the adjustments were investigated in relation to the tasks: desk-work, typing, large-scale drawing, and simulated assembly work. Concerning posture, the static aspect was investigated by statometry, while the dynamic aspect was estimated by analysing the movements transferred to a tiltable seat. Muscular load was assessed by means of amplitude distribution functions derived from electromyography. A five-point scale was used for subjective rating. It is recommended that the seat should be height adjusted approximately 3-5 cm above popliteal level, and the table top 3-5 cm above elbow level. A slanted desk, placed on a horizontal table, is recommended, as it had greater positive influence on the posture than varying seat adjustments. These recommendations are in accordance to subjective preferences, and to a compromise between optimizing the posture and using the backrest. In addition, the recommended seat adjustment seemed to induce more body movements than the traditionally recommended height just below popliteal level. With the high chair adjustment, the seat should be able to incline forward. A tiltable seat seemed preferable, but it is still a question whether or not such equipment facilitates movements. The backrest has been demonstrated to be a much lesser determinator for shifting the lumbar spine towards lordosis, than a slanting desk or an increased seat height. The backrest should be pushed against the back after the subject's selection of the position on the seat. This usually corresponds to an ischial-tuberosity position 6-7 cm behind the axis for seat-tilting. During touch-typing the keyboard should be at the level of the elbows, whereas the significance of a forearm/wrist support is unclear.

Back Pain↗
PubMed1986

An evaluation of a tiltable office chair with respect to seat height, backrest position and task.

The amount of spontaneous movement during seated office work was estimated by analysing the tilting movements of a tiltable office chair. Both movement frequency and amplitude range were considered. The seat inclinations and subjective acceptability were also recorded. The seat was moved more frequently and with a greater range when adjusted 6 cm above popliteal level compared to 1 cm below, or when the backrest was pushed anteriorly or posteriorly compared to a middle position. The greatest acceptability occurred with the highest seat adjustment and the backrest in the middle position. Typing or desk-work influenced movement to a similar extent.

Adult↗
PubMed1986

Muscular performance during seated work elevated by two different EMG methods.

As part of a larger ergonomic survey of seated work, the myoelectric activity of soleus and erector spinae was studied during typing and desk work while sitting on three different office chairs. Muscular performance was evaluated by two EMG methods: (1) the frequently used analysis of the amplitude probability distribution function (APDF) of the EMG signals, and (2) a recently presented method which considers muscular contraction frequencies according to the load levels. The latter indicated significant differences in contraction frequencies which did not appear from the APDF. Moreover, the APDF illustrated differences in load levels which were not evident from the frequency analyses. It is suggested that both EMG methods should be used in evaluations of muscular activity.

Adult↗
PubMed1985

Comparison of office chairs with fixed forwards or backwards inclining, or tiltable seats.

Three adjustments of an office chair seat: one inclining +10 degrees (forwards), one inclining -5 degrees (backwards), and one being freely tiltable from -8 degrees to +19.5 degrees were investigated using two groups of healthy female workers in a field (n = 12), and a laboratory study (n = 10), respectively. The seat adjustments were examined with regard to effects on foot swelling, lumbar muscular load, backrest pressure and subjective acceptability. Desk-work and typing were compared according to lumbar muscular activity, seat movements (tiltable seat), and backrest pressure. Foot swelling tended to increase with increasing seat height but was not influenced by the ability to tilt the seat or not. With the different seat adjustments lumbar muscular activity did not change systematically in spite of greater backrest pressure when the seat inclined backwards. The tiltable seat was preferred to the others. Typing was associated with a more constrained and tens posture than desk work, because movements, transferred to the tiltable seat, decreased and the muscular load increased. Backrest pressure was highest during typing. A tendency towards gradually increasing restlessness (i.e. seat movements) and increasing forward inclination of the tiltable seat with time was observed.

Adult↗
PubMed1985

Trunk posture and trapezius muscle load while working in standing, supported-standing, and sitting positions.

A study of standing, supported-standing ("riding" on a rounded seat), and sitting postures was carried out on persons simulating assembly work in places with poor leg space. These postures and the upper trapezius muscle load were examined using statometric and electromyographic methods, respectively. While supported-standing or sitting, the lumbar spine moved toward kyphosis, even where there was no backward rotation of the pelvis. In adopting the position for anteriorly placed work, the upper arms were raised 30 degrees forward or more; then, if a greater reach was necessary, the trunk was flexed as well. It is concluded that if leg space is poor, variation between supported-standing and standing should be encouraged, and an ordinary office chair avoided. Working level should be arranged so that it is lower than 5 cm above elbow level if no arm/wrist support is possible.

Adult↗
PubMed1984

A method for electromyographic analysis of muscular contraction frequencies.

A method for evaluation of muscular contraction frequencies during prolonged work is presented. It is based upon computer-aided electromyographic (EMG) analyses. Variations in muscular tension, expressed as the relative force of contraction or torque in the joint, are followed using previously described EMG techniques. The number of times muscular tension crosses an amplitude band from below is then estimated. The band represents a predetermined range of amplitude. It is moved in steps from the lowest to the highest force level which occurred during the work task, and the frequency of band-crossings is computed for each band position. The frequencies are then plotted against the force levels at which the upper limit of the band was placed. From this relationship a frequency/force index is computed. The analysis is repeated several times using different band-widths. Thus, the method considers the contraction frequencies according to the load levels. It was developed to study the function of the musculo-venous pump in the legs during prolonged sedentary work, but might also be used to analyse such factors as muscular strain during work.

Adult↗
PubMed1984

Lumbar curve, trunk muscles, and line of gravity with different heel heights.

The influence of different heel heights on the lumbar curve, pelvic inclination, trunk muscle activity, and the position of the line of gravity was examined in 18 healthy women. They were examined while standing on heel-supports, being 4.5 cm elevated, at the level of and 2.5 cm lower than the support of the forefoot, respectively (Figure 1). Each examination was preceeded by one-hour adaptation to a corresponding shoe type. With increasing heel height, the lumbar lordosis and the pelvis inclination were decreased. The back and abdominal muscles did not alter their activities. The position of the line of gravity kept the distance from the forefoot almost constant, but the ankle joint was shifted towards the line of gravity with increasing heel height.

Adult↗
PubMed1983

Posture of the trunk when sitting on forward inclining seats.

Changes in posture during one hour of sitting were measured by a statometric method on ten subjects. Four seats were used, one horizontal and three with forward inclinations respectively of 5 degrees, 10 degrees and 15 degrees. With increasing forward inclination of the seat, the spine moved toward lumber lordosis. A supplementary sample showed that 1/3 of the body's adaptation to the seat inclination took place in the spine and 2/3 in the hip joints. A tendency to a more vertical position of the trunk as a whole was observed on the 5 degrees chair, but the posture of the cervical spine was not influenced by the seat inclination. During the hour of sitting a slight tendency was observed for the subjects to sit with the trunk in the most vertical position at the first measurements. The back curves did not change in any systematic way during the hour. A comfort evaluation showed the 5 degrees forward inclination and the horizontal seats to be preferred.

Adult↗
PubMed1982

Fatigue and cardiorespiratory function following abdominal surgery.

Subjective feelings of fatigue were assessed before operation and 10, 20 and 30 days after uncomplicated elective abdominal surgery in 16 otherwise healthy patients, using a constructed fatigue scale model. In addition, all patients had an orthostatic stress test performed at the same times. Six of the patients also underwent a bicycle ergometer test measuring heart rate and oxygen consumption. Subjective feelings of fatigue were increased (P less than 0.01) at all three postoperative observations, and only 5 of 16 patients returned to their preoperative level. The increased subjective feeling of fatigue correlated positively (RS = 0.53, P less than 0.001) with the increased pulse rate seen during orthostatic stress after operation. Heart rate was about 5 per cent higher (n.s.) after operation when bicycling at the same work loads, while oxygen consumption decreased by about 2 per cent (P less than 0.01) at all three postoperative bicycle tests. It is concluded that even electric uncomplicated abdominal surgery is followed by a pronounced feeling of fatigue, which may persist 1 month after surgery in about one-third of patients. The fatigue scale model seems applicable for future studies on the pathogenesis and treatment of the postoperative fatigue syndrome.

Abdomen↗
PubMedDate not supplied

Multidisciplinary intensive treatment for chronic low back pain: a randomized, prospective study.

BACKGROUND: Americans with low back pain have been helped to return to work by multidisciplinary intensive treatment programs. Whether this treatment method will succeed in countries with a more generous social welfare system, where the incentive to return to work might be less, is not proven. OBJECTIVES: To evaluate a Danish program of functional restoration combined with behavioral support. METHODS: Patients who had experienced at least 6 months of disabling low back pain were randomly assigned to either a 3-week intensive treatment program (n = 55) or an untreated control group (n = 51). RESULTS: Of the 106 patients randomized, 94 (89%) returned for a 4-month follow-up visit. At that time, 29 (64%) of the 45 treated patients were able to work, compared with 14 of 49 (29%) in the control group. The treated patients had used fewer days of sick leave (P < .02), had contacted health care. professionals fewer times (P < .001), and had lower pain and disability scores. CONCLUSIONS: Although such programs are expensive, they can reduce pension expenditures, sick leave days, health care contacts, and pain.

Activities of Daily Living↗