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Biomedical subjects

B Schibye

Publications and source records attributed to B Schibye.

At least 19 recordsLinked to original sources
PubMed2004

Movement of the upper body and muscle activity patterns following a rapidly applied load: the influence of pre-load alterations.

Sudden loading of the spine is not only considered a risk factor for the development of low-back pain but also enables an evaluation of the stability of the spine when conducted under laboratory conditions. In the present study the upper spine was pulled in the anterior direction and the stiffness as well as activity in the erector spinae muscle was measured with different pre-tension in the erector spinae. The results showed that increased activity in the erector spinae prior to loading led to increased stiffness (stiffness coefficients from 297 Nm rad(-1) to 438 Nm rad(-1)) and a decrease in the extra neural signal input to the muscles to maintain the stability. It is therefore clear that increased tension in the erector spinae muscle will create a larger stability of the spine to anterior perturbations. However, contracting the muscles around the spine increases the load on the spinal structures. In 34% of the experiments a silent period in the electromyographic signal was present after loading in the period when the torso was moving in the anterior direction. This phenomenon is discussed.

Adaptation, Physiological↗
PubMed2004

An observation instrument for the description and evaluation of patient transfer technique.

The aim of the present study was to evaluate the reliability and validity of an observation instrument for patient transfer. The instrument, which consisted of 23 items, was evaluated on five different patient transfer tasks. A weighted score was included to evaluate the performed transfer technique. Four observers were selected for the assessment of instrument intra- and inter-observer reliability. Instrument validity was evaluated by testing whether the instrument could detect a difference between use of a self-chosen and a recommended transfer technique. Furthermore, calculated compression values at L4-L5 were compared with the weighted score for the different transfer technique situations. Eleven items were reliable. Nine items deserve further attention and three items were not reliable. The weighted score was significantly higher for the recommended transfer technique situations (p < 0.01) and an association between the weighted score and the calculated compression values was observed (r = -0.589).

Back↗
PubMed2004

Adaptation to sudden unexpected loading of the low back--the effects of repeated trials.

The purpose of this study was to investigate short-term changes in reactions to sudden unexpected loading of the low back. The study utilized a set-up where a horizontal force of 58 N pointing forward suddenly was applied to the upper part of the subject's trunk. EMG activity from the erector spinae muscles and trunk movement data were recorded during 10 trials for 19 subjects. The analysis included EMG reaction time, mean rectified EMG amplitude during the period 50-250 ms after the sudden loading, and time elapsed until stopping of the forward movement of the trunk (stopping time). Reaction time means ranged from 66 to 97 ms (79+/-9 ms), and no difference was found between the trials. Conversely, the mean stopping time for the first trial (468 ms) was significantly higher than for trials 3-10 (359- 371 ms), and the average EMG amplitude during the period 50-250 ms after the sudden loading was lower for the first trial. This study showed that some subjects adapted to sudden unexpected loadings of the low back through a reduction in stopping time and a progression in EMG response during the first few trials. This possible adaptation to repeated trials have been overlooked in previous studies.

Adaptation, Physiological↗
PubMed2003

Biomechanical analysis of the effect of changing patient-handling technique.

The objective of the study was to assess the changes in the mechanical load on the low-back when shifting from a self-chosen to a recommended patient-handling technique. Nine female health care workers without formal education in patient-handling carried out 8 different tasks involving moving, turning and lifting situations. By means of a dynamic 3D biomechanical model of the lower part of the body, peak torque, compression and shear forces at the L4/L5 joint were compared using the two different patient-handling techniques. In 5 of the 8 tasks, a significant reduction was observed in spinal loading. Application of the recommended technique decreased the compression value significantly for all tasks with a mean value above 3000 N. For the two tasks with the highest compression values when using the self-chosen technique (4223, 4446 N), the loading was reduced with 36% and 25%, respectively. If the principles behind the recommended technique are implemented and maintained, a decrease in the risk of low-back disorders during patient-handling should thus be expected.

Adult↗
PubMed2002

Intra-abdominal pressure increases during exhausting back extension in humans.

The aim of this study was to investigate in humans the effect of maintained spinal load on the intra-abdominal pressure (IAP), low back kinematics and trunk muscle activity. This study consisted of two endurance tests for the low back muscles performed 3 weeks apart. Nine healthy subjects participated in the study. In the first test (upright-test), the subject had to pull with the back muscles at a constant force in an upright position, and in the second test (incline-test), the subject had to resist a constant forward pulling force while standing with a 45 degrees inclination of the back in relation to vertical. The IAP, rate of perceived exertion and electromyogram (EMG) from the erector spinae, iliocostalis lumborum, rectus abdominus and the external and internal oblique muscles were measured using surface electrodes. There was no significant difference in endurance time between the two tests. Both tests showed a significant increase in EMG amplitude with time for all muscles except the erector spinae muscle. A decrease in the median frequency for the erector spinae muscle was found indicating fatigue, and since no increase in EMG amplitude was found a decrease in force output from the muscle must be assumed. The IAP increased significantly during both tests. There was a considerable variation between the subjects in the size of this development, but the pattern was the same for all subjects. In conclusion it was found that trunk extension until exhaustion initiates an increase in the activity of the abdominal muscles and an increase in the IAP as the low back muscles become fatigued.

Abdomen↗
PubMed2002

Increase in spinal stability obtained at levels of intra-abdominal pressure and back muscle activity realistic to work situations.

In this study, sudden load was applied to the trunk and situations with alternating low levels of intra-abdominal pressure (IAP) realistic to work situations were compared. The aim was to see if IAP and the small increases in co-contraction of back muscles that follow are capable of increasing the stiffness of the lumbar spine. Nine subjects participated in ten sudden load situations during which they were asked to hold a box and conduct a percentage of maximal IAP. The hip was fixed and the load was applied horizontally on the trunk. EMG, IAP, and movement of the trunk were measured. It was found that IAP of a size likely to appear in work situations, and the concomitant increase in muscle co-activation increased the spine stiffness. This increase in stiffness decreased the movement caused by the sudden load. These results show that both abdominal- and back muscles may have an important role in stabilising the spine, and in decreasing movements caused by sudden loads likely to appear in numerous work

Abdomen↗
PubMed2002

A dynamic 3D biomechanical evaluation of the load on the low back during different patient-handling tasks.

The objective of this study was to investigate the low-back loading during common patient-handling tasks. Ten female health care workers without formal training in patient handling performed nine patient-handling tasks including turning, lifting and repositioning a male stroke patient. The low-back loading was quantified by net moment, compression, and shear forces at the L4/L5 joint, measured muscle activity (EMG) in erector spinae muscles and rate of perceived exertion (RPE; Borg scale). The experiments were videotaped with a 50Hz video system using five cameras, and the ground and bedside reaction forces of the health care worker were recorded by means of force platforms and force transducers on the bed. The biomechanical load was calculated using a dynamic 3D seven-segment model of the lower part of the body, and the forces at the L4/L5 joint were estimated by a 14 muscles cross-sectional model of the low back (optimisation procedure). Compression force and torque showed high task dependency whereas the EMG data and the RPE values were more dependent on the subject. The peak compression during two tasks involving lifting the patient (4132/4433N) was significantly higher than all other tasks. Four tasks involving repositioning the patient in the bed (3179/3091/2932/3094N) did not differ, but showed higher peak compression than two tasks turning the patient in the bed (1618/2197N). Thus, in this study the patient-handling tasks could be classified into three groups-characterised by lifting, repositioning or turning-with different levels of peak net torque and compression at the L4/L5 joint.

Adult↗
PubMed2001

Aerobic power and muscle strength among young and elderly workers with and without physically demanding work tasks.

The aim of the study was to investigate the effect of waste collection on the physical capacity of the workers. A total of 19 young and 28 elderly male waste collectors and two age-matched control groups participated. The aerobic power was estimated. The maximal isometric muscle strength was measured for back extension and flexion, shoulder elevation and abduction, and handgrip. The aerobic power was lower among the elderly workers compared with the young workers of both groups. No differences were found between waste collectors and control groups. A general tendency to larger muscle strength was found for both young and elderly waste collectors compared with the control groups. Waste collectors generally have a higher physical capacity than the control groups which is an indication of an early selection of the young waste collectors. With respect to the elderly waste collectors, the job seems to have a training effect especially for the shoulder muscles. No training effect is found for the aerobic power, and a discrepancy between work demand and individual aerobic capacity may occur among elderly workers resulting in a negative health effect unless the work task is evaluated according to age dependent criteria.

Adult↗
PubMed2001

Mechanical load on the low back and shoulders during pushing and pulling of two-wheeled waste containers compared with lifting and carrying of bags and bins.

OBJECTIVE: Compare the mechanical load on the low back and shoulders during pushing and pulling a two-wheeled container with the load during lifting and carrying the same amount of waste. BACKGROUND: Only little is known about risk factors and mechanical loads during push/pull operations. DESIGN: A complete 2(3) factor push/pull experiment. A two-wheeled container with 25 or 50 kg was pushed in front of and pulled behind the body by seven waste collectors. Further, the same subjects lifted and carried a paper bag and a dustbin both loaded with 7 and 25 kg. METHOD: All operations were video recorded and the push/pull force was measured by means of a three-dimensional force transducer. Peak Motus and Watbak software were used for digitising and calculation of torque at L4/L5 and the shoulder joints and compression and shear forces at L4/L5. RESULTS: During pushing and pulling the compression at L4/L5 is from 605 to 1445 N. The extension torque at L4/L5 produced by the push/pull force is counteracted by the forward leaning of the upper body. The shear force is below 202 N in all situations. The torque at the shoulders is between 1 and 38 Nm. CONCLUSION: In the present experiments the torques at the low back and the shoulders are low during pushing and pulling. No relation exists between the size of the external force and the torque at the low back and the shoulder. RELEVANCE: Pushing and pulling are common in many workplaces and have often replaced lifting and carrying situations. This has emphasised the need for more knowledge of the internal mechanical load on the body during these activities.

Adult↗
PubMed1995

Musculoskeletal symptoms among sewing machine operators.

OBJECTIVES: A longitudinal study was conducted to describe the prevalences and development of musculoskeletal symptoms among sewing machine operators in relation to age and exposure and among former sewing machine operators who changed exposure by changing occupation. METHODS: Musculoskeletal symptoms were assessed among 327 sewing machine operators in 1985 with the use of the standardized Nordic questionnaire. A follow-up study in 1991 showed that approximately one-third was still working as a sewing machine operator, one-third had changed occupation, and the rest were out of employment. The exposure was assessed by a questionnaire regarding the type of machine being operated, work organization, workplace design, units produced per day, and payment system. RESULTS: High prevalences of musculoskeletal symptoms of the neck and shoulders were found, with some associations to exposure variables such as efficiency. Initially symptom-free sewing machine operators were not at a higher risk of developing symptoms when they continued sewing during the six-year follow-up when compared with those who changed to other employment. However, symptomatic sewing machine operators who quit sewing were much more likely to be relieved of their symptoms than were symptomatic operators who continued sewing, odds ratio 3.26 [95% confidence interval (95% CI) 1.38-7.72] for 12-month symptoms and odds ratio 3.90 (95% CI 1.28-11.90) for 7-day symptoms. This trend also applied to long-lasting symptoms. CONCLUSIONS: The results demonstrate that, for many sewing machine operators, neck and shoulder symptoms are reversible and may be influenced by reallocation to other worktasks.

Adolescent↗
PubMed1993

Shoulder muscle load and muscle fatigue among industrial sewing-machine operators.

Physiological responses to physical work were assessed for 29 female industrial sewing-machine operators during an 8-h working day under ordinary working conditions. During sewing-machine work, the average (left and right) static load in the trapezius muscle was 9% of the maximal electromyogram (EMG) amplitude (% EMGmax), while the average mean load was 15% EMGmax, and the average peak load was 23% EMGmax. The static load level was unrelated to the muscle strength of the sewing-machine operators, which for the group as a whole was within the normal range. The load levels remained unchanged during the working day, while changes in the EMG mean power frequency and zero crossing frequency rate occurred, both indicating the development of muscle fatigue in left and right trapezius muscle during the working day. In line with this, the rating of perceived exertion in the shoulder and neck region increased during the working day. Dividing the group of sewing-machine operators into two groups, those with the highest frequency and those with the lowest frequency of shoulder/neck troubles showed that the former group had significantly lower muscle strength, despite the fact that no differences in the surface EMG during sewing were found between the two groups. It was concluded that industrial sewing-machine work involves a pattern of shoulder muscle activity which induces fatiguing processes in the shoulder and neck regions. Furthermore, since the static shoulder muscle load was independent of muscle strength, factors other than working posture may be of significance for the static shoulder muscle load.

Adult↗
PubMed1990

Limb skeletal muscle adaptation in athletes after training at altitude.

Morphological and biochemical characteristics of biopsies obtained from gastrocnemius (GAS) and triceps brachii muscle (TRI), as well as maximal O2 uptake (VO2 max) and O2 deficit, were determined in 10 well-trained cross-country skiers before and after a 2-wk stay (2,100 m above sea level) and training (2,700 m above sea level) at altitude. On return to sea level, VO2 max was the same as the prealtitude value, whereas an increase in O2 deficit (29%) and in short-term running performance (17%) was observed (P less than 0.05). GAS showed maintained capillary supply but a 10% decrease in mitochondrial enzyme activities (P less than 0.05), whereas an increase in capillary supply (P less than 0.05) but unchanged mitochondrial enzyme activities were observed in TRI. Buffer capacity was increased by 6% in both GAS and TRI (P less than 0.05). A positive correlation was found between the relative increase in buffer capacity of GAS and short-term running time (P less than 0.05). Thus the present study indicates no effect of 2 wk of altitude training on VO2 max but provides evidence to suggest an improvement in short-term exercise performance, which may be the result of an increase in muscle buffer capacity.

Adaptation, Physiological↗
PubMed1989

Forearm oxygen uptake during maximal forearm dynamic exercise.

This study was undertaken in an attempt to determine the maximal oxygen uptake in a small muscle group by measuring directly the oxygen expenditure of the forearm. Five healthy medical students volunteered. The subjects' maximal forearm work capacity was determined on a spring-loaded hand ergometer. Exercise was continued until exhaustion by pain or fatigue. Two weeks later intra-arterial and intravenous catheters were placed in the dominant arm. Blood samples for measurement of oxygen concentration were collected via the catheters. Forearm blood flow was measured by means of the indicator dilution technique. Oxygen uptake was determined according to the Fick principle. The forearm oxygen uptake attained at maximal work loads was a mean of 201 (SD +/- 56) mumol.min-1.100 ml-1. It was impossible at maximal exercise to discern a plateau of the oxygen uptake curve in relation to work output. It is suggested that a plateau in the oxygen uptake curve is not a useful criterion for maximal oxygen uptake in a small muscle group. Skeletal muscle may have an unused capacity for oxygen consumption even at maximal exercise intensity where muscle work cannot be continued due to muscle pain and fatigue.

Adult↗
PubMed1988

Effects of acute hypoxia and CO2 inhalation on systemic and peripheral oxygen uptake and circulatory responses during moderate exercise.

The effect of acute hypoxia and CO2 inhalation on leg blood flow (LBF), on leg vascular resistance (LVR) and on oxygen supply to and oxygen consumption in the exercising leg was studied in nine healthy male subjects during moderate one-leg exercise. Each subject exercised for 20 min on a cycle ergometer in four different conditions: normoxia, normoxia + 2% CO2, hypoxia corresponding to an altitude of 4000 m above sea level, and hypoxia + 1.2% CO2. Gas exchange, heart rate (HR), arterial blood pressure, and LBF were measured, and arterial and venous blood samples were analysed for PCO2, PO2, oxygen saturation, haematocrit and haemoglobin concentration. Systemic oxygen consumption was 1.83 l.min-1 (1.48-2.59) and was not affected by hypoxia or CO2 inhalation in hypoxia. HR was unaffected by CO2, but increased from 136 beat.min-1 (111-141) in normoxia to 155 (139-169) in hypoxia. LBF was 6.5 l.min-1 (5.4-7.6) in normoxia and increased significantly in hypoxia to 8.4 (5.9-10.1). LVR decreased significantly from 2.23 kPa.l-1.min (1.89-2.99) in normoxia to 1.89 (1.53-2.52) in hypoxia. The increase in LBF from normoxia to hypoxia correlated significantly with the decrease in LVR. When CO2 was added in hypoxia a significant correlation was also found between the decrease in LBF and the increase in LVR. In normoxia, the addition of CO2 caused a significant increase in mean blood pressure. Oxygen consumption in the exercising leg (leg VO2) in normoxia was 0.97 l.min-1 (0.72-1.10), and was unaffected by hypoxia and CO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Metabolism of exercising skeletal muscle during beta 1-selective adrenoceptor blockade.

Concentrations of glycogen, glucose, glucose-6-phosphate and lactate in the lateral vastus muscle were measured in seven subjects before and after dynamic muscle exercise at a work load of 75% of each subject's maximal working capacity, and with and without intravenous administration of the beta 1-selective beta-adrenoceptor blocking agent, atenolol. Pulmonary oxygen uptake was measured during exercise. Heart rate and arterial blood pressure were measured throughout the study. Arterial concentrations of glucose, lactate and free fatty acids were measured at rest and during exercise. The muscle concentration of glycogen and the extent of glycogen depletion with exercise were not influenced by the beta 1-adrenoceptor blocker. Similarly, there was no change in the muscle concentrations of glucose, glucose-6-phosphate and lactate. Heart rate decreased at rest and during exercise. Arterial blood pressure was not influenced by beta-blockade. Pulmonary oxygen uptake decreased by 6.5%. The exercise induced rise in arterial blood concentration of free fatty acids was abolished by beta 1-selective beta-blockade. It is concluded that the decrease in lactate release from exercising muscles during beta 1-adrenoceptor blockade seen in other studies cannot be explained by an impaired breakdown of muscle glycogen. It may be inferred, however, that a reduced availability of free fatty acids in the exercising muscles during beta 1-selective (and non-selective) beta-blockade may enhance the combustion of pyruvic acid and thereby decrease the production of lactate.

Adult↗
PubMed1981

Blood pressure and heart rate response to static exercise in relation to electromyographic activity and force development.

5 healthy men performed static knee extension (90 degree knee angle) with one leg for 5 min. In one series of experiments the force was held constant at 20% of the isometric maximal voluntary contraction. In the other the initial force development was also 20%, but the smoothed, rectified electromyographic activity, (SREMG) recorded after 5 s of contraction was kept constant. Heart rate (HR), arterial mean blood pressure (MBP) (measured 20 cm proximally to the elbow in a. brachialis), EMG (surface electrodes) from the lateral portion of m. quadriceps femoris, and force were continuously recorded. HR and MBP increased approximately 40% in the force-constant experiments and approximately 20% in the SREMG-constant experiments. The greatest increase occurred during the first two minutes of contraction. In the force-constant experiments SREMG doubled, with the most marked increases occurring during the very early and late parts of the contraction. SREMG correlated with both HR (r = 0.85) and MBP (r = 0.98). In the SREMG-constant experiments force declined quickly during the first minute and remained at about 12% MVC thereafter. The observed cardiovascular responses to static contraction can best be explained as the result of the combined action of central and peripheral drives, the central drive being related to the central activity for the recruitment of motor units, and the peripheral drive being mediated through chemoreceptors in the exercising muscles.

Adult↗
PubMed1981

Response of arterial blood pressure to static exercise in relation to muscle mass, force development, and electromyographic activity.

In young men, the arterial blood pressure response during static exercise at 40% of maximal voluntary contraction (MVC) and the response after the contraction with a cuff inflated both were increased when a greater mass of skeletal muscle was involved. Also in men with a previously injured leg, the arterial systolic pressure and the smoothed, rectified electromyographic activity (EMG) were greater during static contraction of the large, strong leg than during static contraction of the small, weak leg at the same percent MVC. However, the arterial systolic pressure and the EMG were almost the same during contraction of either leg when the same force was developed. Finally, in young men, either the force developed was held constant at 20% MVC or the level of the initial EMG at 20% MVC was held constant for 5 minutes. During the force-constant experiments, the EMG doubled and correlated with the 40% increase in mean arterial pressure (r = 0.89). In the EMG-constant experiments, force declined to about 12% MVC with an increase of only 20% in mean arterial pressure. These studies of the response of arterial blood pressure to static muscular contractions can best be explained by both central and peripheral control mechanisms. The central control mechanism "central command" is probably related to the central activity for recruitment of motor units and the peripheral control mechanism is probably mediated by muscle afferents which are excited by metabolic changes in the contracting skeletal muscle.

Arteries↗