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Biomedical subjects

A Kilbom

Publications and source records attributed to A Kilbom.

At least 73 records · Page 4Linked to original sources
PubMed1983

Physiological and psychological indices of fatigue during static contractions.

The development of fatigue and the relationship between psychological and physiological indices of fatigue were studied in a group of 18 male subjects during static contractions. Exercise was performed as a static elbow flexion at 25% MVC. Heart rate (HR), intraarterial blood pressure (BP) and surface EMG [mean amplitude (MA) and central frequency (CF)] were studied during contractions sustained until exhaustion. The amount of effort expended (relative to total exhaustion) and the rating of perceived pain were recorded following contractions interrupted after 20, 30 . . . 80, and 100% of endurance time. HR, BP and EMG amplitude responses were similar to those previously recorded. The decline in CF occurred in two phases, possibly related to a change in motor unit recruitment after the initial 70% of endurance time. The subjects overestimated the amount of effort expended and thus underestimated their endurance capacity. The best correlation between perceived effort and physiological responses was obtained using blood pressure data, whereas changes in EMG data did not parallel the psychological responses. It is concluded that the perception of effort during a static contraction is produced through a complex process, in which several influences of peripheral and central origin are integrated.

Adult↗
PubMed1982

Training-induced bradycardia and intrinsic heart rate in rats.

After 10 weeks of treadmill training, female Sprague-Dawley rats had developed a bradycardia at exercise on submaximal work loads. This bradycardia was also present after autonomic denervation and in isolated perfused heart preparations. The heart weight/body weight ratio was increased in these trained animals compared to untrained littermates. Sympathectomized, trained rats developed the same degree of cardiac hypertrophy, but their heart rate after denervation and in the isolated heart was the same as in sympathectomized, untrained rats. It is concluded that the bradycardia of trained and thereafter denervated animals seen in this and a previous investigation represents an adaptation within the heart itself, since it was present in the isolated heart. These results thus provide further evidence for a non-neural component in training-induced bradycardia. Since the trained sympathectomized rats had a cardiac hypertrophy but no reduction of intrinsic heart rate, it seems likely that the myocardial mass is of minor importance for the level of intrinsic heart rate.

Adaptation, Physiological↗
PubMed1982

Leg blood flow during static exercise.

Leg blood flow was studied with the constant infusion dye technique during static exercise of the thigh muscles (quadriceps) and during hand-grips at 15 and 25-30% of MVC. Blood flow and oxygen uptake in the leg increased in quadriceps exercise and reached their highest values (around 1.21/min and 165 ml/min respectively) at 25-30% of MVC, whereas leg vascular resistance decreased. Regional circulatory adaptations and the oxygen uptake - leg blood flow relationship were in close agreement with the responses found in dynamic leg exercise. In view of the marked rise in intramuscular pressure previously observed during quadriceps contractions, a restriction of blood flow and an increased vascular resistance had been expected. Involuntary activation of leg muscles other than the quadriceps may explain the finding. Contractions of the contralateral quadriceps induced a slight increase in leg blood flow, whereas hand-grips had no influence on blood flow or vascular resistance in the leg. The distribution of the cardiac output during static contractions is discussed, and it is concluded that during hand-grips the increase in blood flow is predominantly distributed to the upper part of the body.

Humans↗
PubMed1981

Cardiovascular response to combined dynamic and static exercise.

The cardiovascular response to combined static handgrip at 20% MVC and dynamic leg exercise was studied in young male subjects. Cardiac output increased by 2.3 liters/min (30%) at isolated handgrip and by 1.0 liter/min (7%) when handgrip was added to dynamic exercise at 100 W. In spite of an increased arterial blood pressure, leg blood flow was unaffected by handgrip, both when it was performed isolated and in combination with dynamic exercise. Temperature measurements in mixed venous blood and subcutaneous tissue indicated an increased blood flow to peripheral circulatory areas. During combinations of handgrip and dynamic exercise at different levels of VO2, heart rate response to handgrip was progressively less marked as maximal oxygen uptake was approached. Therefore a vagal withdrawal seems to be the most important heart rate-increasing mechanism during combined exercise. Systolic blood pressure response to handgrip was still preserved at 25 and 45% of max VO2. At 95% of max VO2, the blood pressure response to handgrip was abolished, probably due to a competitive utilization of the same blood pressure-raising mechanism in dynamic and static exercise.

Blood Circulation↗
PubMed1980

Physical demands during folk dancing.

This investigation was undertaken to evaluate the aerobic demands during one of the most popular and demanding Swedish folk dances the "hambo". Six men and six women, ranging in age from 22 to 32, participated. Their physical work capacity was investigated on a bicycle ergometer and a treadmill, using two to three submaximal and one maximal loads. All subjects were moderately well-trained and their average maximal oxygen uptake on the treadmill were 2.5 and 3.7 l/min (42.8 and 53.2 ml/kg . min-1) for women and men, respectively. When dancing the "hambo" the heart rate was telemetered, and the Douglas bag technique was used for measurements of pulmonary ventilation and oxygen uptake. The physical demand during "hambo" dancing was high in all subjects. Oxygen uptake was 38.5 and 37.3 ml/kg . min-1 and heart rate 179 and 172 in women and men, respectively. Women used 90% and men 70% of their maximal aerobic power obtained on the treadmill. The pulmonary ventilation and respiratory quotient of the female subjects were lower when dancing as compared to running, possibly because of voluntary restriction of the movements of the thoracic cage. Some popular Scandinavian folk dances are performed at a speed and with an activity pattern resembling the "hambo", while others are performed at a slower pace. The exercise intensity used in "hambo" is more than sufficient to induce training effects in the average individual provided that the dancing is performed at the frequency and for length of time usually recommended for physical training. For older or less fit people dances with a slow pace can be used for training purposes.

Adult↗
PubMed1977

Role of the adrenergic nervous system in development of training-induced bradycardia.

Sprague-Dawley rats, normal and chemically sympathectomized with 6-hydroxy-dopamine, were trained by treadmill running. The normal rats, unlike the sympathectomized animals, showed reduction of the exercise heart rate after the training period. Compared to a sedentary control group the sympathectomized rats showed no difference in intrinsic heart rate after pithing and denervation and no increase in heart weight. The increase of the heart weight/body weight ratio after training was smaller in the sympathectomized group than in the normal one. The results show that a functioning adrenergic nervous system is necessary for an efficient adaptation to physical training. Administration of noradrenaline to pithed trained and untrained rats showed that betaadrenergic receptor sensitivity was not altered by physical training. The intrinsic heart rate of normal trained rats was lower than that of normal control rats.

Adaptation, Physiological↗
PubMed1976

Circulatory effects of isometric muscle contractions, performed separately and in combination with dynamic exercise.

Studies on central circulation and regional blood flow were performed in healthy male volunteers at rest, during sustained isometric forearm contraction at 20% of MVC, during dynamic leg exercise (100 W) and during combined isometric and dynamic exercise. In 10 subjects pulmonary oxygen uptake, arterio-venous oxygen difference, heart rate, leg blood flow and blood pressures in the pulmonary and subclavian arteries and in the right atrium were measured. In 4 of these subjects the temperature was measured in mixed venous blood and in subcutaneous tissue in an attempt to further analyse the blood flow distribution through central versus peripheral parts of the circulatory system. In 5 other subjects the splanchnic blood flow was estimated by hepatic vein catheterization and dye dilution technique at rest and during isometric forearm contraction. It was found that cardiac output, oxygen uptake, heart rate and arterial blood pressure all increased in response to isometric contraction. Quantitatively the changes in heart rate and cardiac output induced by a sustained contraction were more marked when the contraction was performed separately than when it was added to dynamic exercise. In spite of the increased arterial pressure, the leg blood flow did not increase significantly. Neither did the splanchnic blood flow increase in response to hand-grip contrmic exercise. Isometric exercise, however, caused a blood temperature fall and a rise in subcutaneous temperature indicating an increased blood flow through the skin. It is concluded that during sustained isometric muscle contraction 1. the blood flow increase is mainly distributed to peripheral circulatory areas, 2. a concomitant dynamic exercixe interferes with the circulatory adaptation only to a small extent.

Abdomen↗
PubMed1976

Endogenous prostaglandins as local regulators of blood flow in man: effect of indomethacin on reactive and functional hyperaemia.

1. The contribution of endogenously formed prostaglandins of the E series (PGE) to the development of reactive and functional hyperaemia was studied in the human forearm. 2. Forearm blood flow was recorded using venous occlusion plethysmography. The concentration of prostaglandin E-like substances (PLS) in the venous effluent from the muscle was analysed using bio-assay. For inhibition of PG biosynthesis, indomethacin (1-25 mg/kg body weight) was administered. 3. Following 5 min of arterial occlusion, a marked hyperaemia developed during the next 150 sec. Indomethacin, while not affecting the resting arterial blood flow, significantly decreased the peak level as well as the duration of the hyperaemia. The total reactive hyperaemia was 25 ml./100 ml. tissue before, and 13 ml./100 ml. tissue after administration of indomethacin. 4. During sustained isometric forearm contraction, and following isometric and dynamic forearm muscle activity, a moderate hyperaemia was observed. This was significantly diminished when indomethacin had been administered, although not to the same extent as the reactive hyperaemia. The total hyperaemia in the absence and presence of indomethacin was 113 and 77 ml./100 ml. tissue, respectively, in connexion with isometric contraction and 206 and 120 ml./100 ml. tissue, respectively, following dynamic work. 5. The venous concentration of PLS was very low at rest. A significantly increased concentration was observed after ischaemia. This increased release of PLS was entirely suppressed by indomethacin. With the present assay method, muscular activity elicited no detectable change in the venous concentration of PLS. 6. It is concluded that reactive hyperaemia depends to a considerable extent on an intact PGE synthesis. It is furthermore suggested that endogenous PGE may contribute to the functional hyperaemia that appears during and after muscle activity.

Forearm↗
PubMed1975

Exposure to white spirit. I. Concentration in alveolar air and blood during rest and exercise.

Fifteen healthy male subjects were exposed to 1,250 and 2,500 mg/m3 of white spirit in inspiratory air during rest and excercise on a bicycle ergometer. The white spirit contained approximately 83% aliphatic and 17% aromatic components. The duration of each exposure period was 30 minutes. The pulmonary ventilation, the cardiac output, and the concentration of white spirit (subdivided into aromatic and aliphatic components) in alveolar air, arterial blood, and venous blood were determined during and after exposure. The concentration of aliphatic and aromatic components in alveolar air tended to level off towards the close of each period. The resting level of the aromatic components increased approximately 2.0 times, and that of aliphatic components about 2.5 times, during exercise with increased intensities. The concentration of aliphatic components in arterial and venous blood increased at the start of each exposure period but tended to level off towards the close of the period. The resting value increased fourfold in work at the highest intensity. However, the concentration of aromatic components rose sharply during each period. The arterial blood concentration was about 15 times higher at the end of exposure during the heaviest exercise intensity than at rest. Pulmonary ventilation appeared to be more important to uptake in arterial blood than to circulation. The results are believed to be due to the differing solubilities of aliphatic and aromatic components in blood. Measurement of the concentration of white spirit in venous or arterial capillary blood is suggested as a biological check on exposure.

Adult↗