SEARCH · PubMed Health

Results for “Isometric”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,189 records · Page 66Linked to original sources

PubMed1991

Left ventricular dynamics and plasma catecholamines during isometric exercise in patients following cardiac transplantation.

Haemodynamics and plasma catecholamine responses to isometric exercise were evaluated invasively in 11 orthotopic heart transplant recipients and seven control subjects. Differences in haemodynamic responses between the two groups were already apparent after one min of handgrip at 30% of maximal voluntary contraction, and very pronounced at the end of the fourth minute. At this point transplanted patients showed smaller increments in heart rate (4.8 +/- 3.2 vs 20.4 +/- 14.1 beats.min-1, P less than 0.001), mean arterial pressure (13.7 +/- 7.2 vs 31.5 +/- 12.2 mmHg, P less than 0.001) and cardiac index (0.51 +/- 0.22 vs 1.02 +/- 0.53 L.min-1.m-2, P less than 0.01), whereas left ventricular end-diastolic pressure increased to a greater extent (8.8 +/- 4.9 vs 2.2 +/- 1.8 mmHg, P less than 0.01). Stroke volume index increased similarly (3.8 +/- 1.8 vs 2.0 +/- 3.5 ml beat-1.m-2, NS) and systemic vascular resistance remained unchanged in both groups. The slopes of the left ventricular function curves (ratio of change in left ventricular work to change in left ventricular end-diastolic pressure) indicated depressed left ventricular function in the transplanted patients. The two groups showed similar increments in mixed venous plasma norepinephrine and epinephrine indicating normal sympathoadrenal activation in the transplanted patients. In conclusion, transplanted hearts respond to handgrip with attenuated increases in heart rate, cardiac output and arterial pressure and by increasing left ventricular filling pressure, suggesting a poor contractile reserve probably due to denervation. Circulating catecholamines, especially epinephrine, probably contribute to the cardiac responses to isometric exercise.

Adult↗

PubMedDate not supplied

[Cardiovascular effects of isometric contraction of the masticatory muscles in humans].

The cardiovascular responses to static exercise do not include, until now, studies about masticatory muscles. In this work the cardiocirculatory effects of the isometric contraction of masticatory muscles were compared with those evoked by the handgrip exercise. Non invasive and, in one case, invasive (aortic catheterism) monitoring of arterial blood pressure was performed. The findings show that mean blood pressure and especially heart rate do not increase during static exercise of masticatory muscles as reported in the literature for other muscular groups: it is suggested that the peculiar architecture of masticatory muscles may explain the absence of significant cardiovascular response to their isometric contraction.

Blood Pressure↗

PubMed1987

Cardiovascular effects of ketanserin during cold pressure and during isometric and dynamic exercise in hypertensive patients.

Ketanserin is an arteriolar vasodilator, acting on serotoninergic (5-HT2) and adrenergic (alpha 1) receptors. In animals, ketanserin exerts a centrally mediated inhibition of sympathetic nerve activity. In humans it is not established whether ketanserin reduces basal or reflex increases in sympathetic outflow. In different groups of patients, we have investigated the cardiovascular response as well as plasma noradrenaline (pNA) during rest, during the cold pressure test (0 degree C for 3 min), and during isometric (handgrip), and/or dynamic exercise in order to see whether ketanserin reduces the normal increase in sympathetic tone during these maneuvers. Twenty-one patients with essential hypertension were given oral ketanserin (40 mg) once or twice daily for 4 weeks after a 2-4-week single-blind control period. Ketanserin significantly lowered systolic and diastolic blood pressure as well as heart rate during rest. Resting pNA was not significantly reduced, but the change in pNA was significantly correlated to the reduction in blood pressure and heart rate. During exercise, blood pressure and heart rate remained reduced. Moreover, the relative increase in systolic blood pressure during handgrip and the relative increase in heart rate during bicycle ergometry were significantly reduced during ketanserin therapy. During isometric exercise the relative reduction in blood pressure was significantly correlated to the relative reduction in pNA.

Aged↗

PubMed1988

Effect of intravenous digoxin on the heart at rest and during isometric exercise: a noninvasive study in normal and autonomically blocked volunteers.

Nine healthy volunteers were studied with echocardiography and systolic time intervals before and after administration of 1 mg digoxin intravenously at supine rest and during 3-min isometric handgrip exercise. Eight of them were also studied following autonomic blockade, atropine (0.04 mg/kg), and propranolol (0.2 mg/kg) administered intravenously, otherwise the study program was the same. At rest, intravenous digoxin decreased the heart rate from 61 +/- 3 to 50 +/- 2 beats/min (p less than 0.001). Blood pressure, preload [defined as left ventricular end-diastolic diameter (LVEDD)] or afterload [estimated as left ventricular midsystolic circumferential wall stress (WS)], did not change. Fractional shortening increased from 29 +/- 2 to 33 +/- 2% (p less than 0.05), and the electromechanic systole time index (QS2i) decreased from 522 +/- 7 to 500 +/- 5 ms (p less than 0.01). The results indicate improved contractility due to digoxin. During handgrip, the heart rate decreased from 73 +/- 5 to 65 +/- 5 beats/min (p less than 0.01) as a result of digoxin. The LVEDD, WS or ejection phase indices, and systolic time intervals, did not change, suggesting that digoxin does not affect inotropy during isometric exercise. There was no changes in heart rate, preload or afterload, as a result of intravenous digoxin during autonomic blockade. Fractional shortening rose from 25 +/- 1 to 29 +/- 2 (p less than 0.05) and QS2i fell from 561 +/- 3 to 533 +/- 4 ms (p less than 0.001). The results indicate increased inotropy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

[Rheocardiographic evaluation of left-ventricular contractility in the measured isometric pedal test].

Central hemodynamic parameters were assessed by tetrapolar chest rheography during rationed isometric pedal stress exposure in 54 normal subjects and 24 angina patients. The relationship between left-ventricular contractility and the magnitude of increasing static effort at different steps of stress exposure was examined. In normal subjects, the increase in static effort was shown to affect significantly left-ventricular contractile capacity, left-ventricular performance index and left-ventricular contractile index, and has no effect on the myocardial contractility index. In anginal patients, developing myocardial ischemia in response to stress, there was a significant drop in left-ventricular contraction intensity, myocardial contractility index and left-ventricular contractile index, as compared to the pre-ischemic values. The rheographic left-ventricular contractile index is believed to be the best instrument for the assessment of left-ventricular inotropic activity in isometric stress.

Adult↗

PubMed1989

Isometric muscle force and anthropometric values in normal children aged between 3.5 and 15 years.

Isometric muscle force was measured in 217 normal children aged 3.5-15 years. The standard error of a single determination made by the same observer was ca. 9% of the muscle force. When two measurements were made by different observers the standard error of the difference was estimated at ca. 17%. Reference values for isometric force are given for boys and girls separately. With regard to 7 of the 10 muscle groups tested the force was significantly greater in boys than in girls as early as at ca. 10 years of age. Age and weight were the most important predictors of muscle force.

Adolescent↗

PubMedDate not supplied

Electromyographic analysis of movement following a maximal isometric contraction.

A post-contraction sensory discharge effect following an isometric contraction is commonly cited as the explanation for perception of movement or distortion of limb proprioception during post-contraction movements. The purpose of this study was to compare motor output of agonist neuromuscular activity between a control positioning movement and a post-contraction movement. Terminal positioning accuracy and electromyographic (EMG) data of the triceps brachii during rapid elbow extension were recorded during normal movements and during movements following a maximal isometric contraction. Separate t-tests revealed the post-contraction positioning resulted in significant undershooting of the target position, and also the integrated EMG (IEMG) for the post-contraction conditions was significantly less than the control condition. No difference was observed in mean peak frequencies between the control and post-contraction conditions. Apparently, the post-contraction target undershooting is a result of less total motor output rather than a change in neuromuscular frequency firing rates.

Adolescent↗

PubMed1989

Interindividual variability of isometric endurance with regard to the endurance performance limit for static work.

In literature there are doubts concerning the 15% MVC (maximal voluntary contraction) level and invariability of isometric endurance, as described by ROHMERT (1962) as a "biologische Konstante". Therefore, 3 experimental sets using different levels of relative loads from approximately 2.9% (individual weight of forearm) to 50% MVC and different holding times (up to 1 hr) were performed concerning elbow flexion and knee extension. Measurements of the times until exhaustion and muscular fatigue (EMG) underlined the great variability of the holding times and showed that the mean endurance performance limit for isometric exercise lies neither at the 15% MVC level nor can it be used as a "biologische Konstante". The muscle fibre composition is discussed as the main reason for the observed variability.

Adult↗

PubMed1985

Cardiovascular response to hand-grip isometric exercise in healthy men. Noninvasive study.

Noninvasive polygraphic tracings obtained at rest and during isometric hand-grip exercise were analysed in 67 healthy subjects. The purpose of the study was to determine the response of noninvasive polygraphic parameters to isometric exercise. During the third minute of sustained squeezing of a balloon dynamometer (30% of maximal voluntary contraction) a significant increase occurred in heart rate (+16.8 +/- 10.7 beats/min) an increase in both systolic and diastolic blood pressure (+3.4 +/- 1.6 kPa and 2.6 +/- 1.7 kPa respectively), increase in apexcardiographic index 100.a/D (+14.5 +/- 15.0% "D" amplitude), decrease of diastolic amplitude time index square root 2-c/(2-0) X (a/D) (-20.1 +/- 26.5), shortening of pulse transmission time (-0.006 +/- 0.005 s) and prolongation of cardiac cycle length corrected for left ventricular ejection time (+0.011 +/- 0.010 s) discussed. All these changes were statistically significant.

Adult↗

PubMed1985

Influence of the metabolic environment on oxygen uptake and isometric developed tension of isolated rat portal vein.

Oxygen uptake and isometric developed tension (IDT) of isolated rat portal vein were simultaneously measured after glucose removal, following the readmission of metabolic substrates and addition of 2-deoxy-D-glucose (2-DG) or insulin. In control conditions, basal O2 uptake was 0.128 +/- 0.004 microliter O2/mg dry weight/min (n = 50). After 40 min of incubation in a glucose-free medium, IDT and O2 uptake decayed to a similar degree. Addition of 11 mM glucose, 5 mM pyruvate, acetate, lactate or butyrate to hypodynamic veins, elicited differential recoveries in the mechanical and metabolic parameters, pyruvate and acetate being the most effective. Insulin (0.1 U/ml) added 5 min prior to readmission of 11 mM glucose, increased the restoration of IDT without any effect on oxygen uptake. 2-DG 5.5 mM, when added in glucose-free medium, abolished IDT but only depressed the cellular respiration by 38% at 20 min; these effects were decreased in presence of glucose (11 mM). These results suggest that the oxygen uptake of this vessel depends, among other factors, on the exogenous substrate offered. They show also the relationship between peak of developed isometric force and metabolic activity as well as the relevance of glycolytic and oxidative pathways in this tissue.

Adenosine Triphosphatases↗

PubMed1988

Force variability in isometric responses.

In the present study we examined the contribution of different impulse parameters to peak force variability in an isometric task. Five experiments are reported that each held constant a different impulse parameter while allowing the other impulse parameters to vary. The results indicate that change in force level is the parameter that has the greatest effect on peak force variability, although time to peak force and preload also systematically influence response variability. A formula that accommodates the relation between impulse parameters and force variability is proposed. The data suggest that even in isometric tasks, it is the force-time properties of the impulse, rather than discrete parameters such as peak force, that determine the outcome variability.

Adult↗

PubMed1988

Activity levels during isometric test contractions of neck and shoulder muscles.

In order to analyse isometric muscle test contractions in the neck and shoulder region, an electromyographic (EMG) study of ten healthy females was undertaken. A series of 13 standardized isometric contractions with manual resistance was performed in the sitting position. Rectified time-averaged EMG was recorded, using surface electrodes. All tests activated all muscles studied to some extent and at various levels, but four different patterns of activation could be identified. Maximum level of activity was obtained: 1) in the cervical erector spinae muscles during neck extension, 2) in the splenius and levator scapulae muscles during lateral flexion of the cervical spine, 3) in the trapezius, pars descendens muscle during abduction of the arm in the plane of the scapula, 4) in the thoracic erector spinae/rhomboids muscles during shoulder elevation or scapular retraction/elevation.

Adult↗

PubMed1987

[Value of the treadmill test, bicycle ergometry test and the isometric test in evaluating the severity of coronary insufficiency].

Possibilities of the treadmill test, bicycle ergometry and the isometric test are reviewed with respect to the diagnosis and assessment of the severity of coronary heart disease (CHD). A study of 40 normal males and 95 coronary patients (including 57 aneurysm-free ones and 38 with left ventricular postinfarction aneurysm) demonstrated low diagnostic value of standard dynamic load programs for the assessment of coronary insufficiency. An original treadmill test program has been developed where each new step carries a 1 MET increment of the load, allowing to assess the severity of CHD within a wide range of clinical manifestations, and group patients according to the involvement of 1 or 2 coronary arteries. The isometric test is of little value for the diagnosis of CHD, yet it can be useful in the assessment of the severity of coronary insufficiency and identification of patients with the involvement of 2 and 3 coronary arteries.

Adult↗

PubMed1987

Cardiovascular responses to isometric handgrip exercise: an invasive study in pregnancy-induced hypertension.

Nine patients with pregnancy-induced hypertension and nine healthy pregnant controls were compared in the last trimester with regard to cardiovascular and sympathoadrenal reactivity during a standardized isometric handgrip exercise test. At rest, the blood pressure elevation with pregnancy-induced hypertension resulted from increased systemic vascular resistance. The test increased the blood pressure, heart rate, cardiac output, stroke volume, and epinephrine and norepinephrine concentrations in arterial plasma, but did not change the calf or systemic vascular resistance. The responses of the two groups did not differ significantly with regard to any of the above variables. Thus, pregnancy-induced hypertension does not seem to be associated with exaggerated cardiovascular or sympathoadrenal reactivity to isometric exercise when compared with normal pregnancy. The mechanism underlying the blood pressure response appears to be similar in the two groups, ie, an increase in cardiac output.

Adult↗

PubMed1987

Comparison of echocardiographic and radionuclide methods with contrast angiography assessment of left ventricular function--response to isometric exercise in subjects without definite heart disease.

In order to study the validity of non-invasive assessment of left ventricular response to isometric exercise, 21 subjects with chest pain, but without any cardiac abnormalities performed an isometric handgrip test during cardiac catheterization, M-mode echocardiography and radionuclide angiography. Fourteen of the subjects were suitable for comparison of all the three methods. In response to handgrip exercise the ejection fraction (EF) remained unchanged in contrast angiography (68 +/- 9% at rest; 68 +/- 9% during exercise) and echocardiography (74 +/- 4% at rest; 74 +/- 5% during exercise), but showed a small increase on radionuclide angiography (from 57 +/- 5% to 60 +/- 7% (p less than 0.01). Individual changes in ejection fraction during the handgrip exercise had a reasonable correlation between contrast angiography and radionuclide angiography (r = 0.63, p less than 0.01). In order to validate the reproducibility of M-mode echocardiography and radionuclide angiography, the haemodynamic and left ventricular responses during two consecutive handgrip tests were compared in eight subjects. No significant differences were seen in the haemodynamic responses or between the changes in ejection fraction or fractional shortening in the two tests. Thus, in subjects without heart disease the non-invasively determined results of the left ventricular response to the handgrip exercise were similar to those obtained invasively and could be reliably reproduced.

Cardiac Catheterization↗

PubMed1987

[Functional status of the left side of the heart in patients with ischemic heart disease during isometric exercise].

Hemodynamic parameters of left-ventricular and left-atrial contractility and pumping function were examined in 47 males with postinfarction cardiosclerosis and no clinical signs of circulatory insufficiency and in 30 normal male subjects, exposed to isometric leg exercise with the highest possible compression force. At the height of exercise, normal subjects showed increased left-ventricular myocardial contractility along with the initiation of the Frank-Starling mechanism, spreading to the left atrium as well, while coronary patients responded to increased stress by growing left-atrial reservoir function during the first minutes of exercise, and activated left-atrial transport and pumping functions afterwards. Isometric leg exercise is capable of detecting left-atrial and left-ventricular pumping and contractility disorders in coronary patients.

Adult↗

PubMed1985

Haemodynamic effects of prazosin combinations during dynamic and isometric exercise.

Haemodynamic effects of atenolol 50 mg, clonidine 0.15 mg, and prazosin 5 mg, given twice daily, and of the combinations atenolol + prazosin and clonidine + prazosin were studied in 8 hypertensive outpatients. Measurements were made at rest, during isometric sustained handgrip and submaximal ergometer work in mostly double-blind and cross-over fashion. Given individually atenolol and prazosin lowered resting supine blood pressure. The addition of prazosin increased the antihypertensive effects of atenolol but not of clonidine. At the end of the isometric exercise atenolol and prazosin given alone both lowered diastolic blood pressure as compared to respective pretreatment values. During handgrip prazosin contributed a little, but not much, to the antihypertensive effects of atenolol and clonidine. During dynamic exercise atenolol, clonidine, and prazosin given alone each lowered blood pressure, prazosin decreasing diastolic blood pressure in particular. Prazosin added to the antihypertensive effect of atenolol more than that of clonidine. Echocardiographic measurements revealed no significant differences between treatments at rest. During handgrip the mean velocity of left ventricular circumferential muscle fibre shortening was reduced by atenolol as compared to pretreatment values. We conclude that atenolol + prazosin may help the patients to maintain adequate haemodynamics during daily physical stresses whilst the combination prazosin + clonidine may not offer any particular advantages.

Adult↗

PubMed1986

Effect of ankle position on isometric quadriceps strengthening.

A prospective study of 20 normal subjects was undertaken to determine the effect of three ankle positions (active dorsiflexion, active plantar flexion, natural or rest position) on comfort and facilitation of quadriceps contraction in isometric strengthening in a supine position with the hip and knee fully extended. Surface EMG activity was found to be greatest for the vastus lateralis followed by the vastus medialis and least for the rectus femoris. Equal facilitation was apparent with either active ankle dorsiflexion or plantar flexion. Both were superior to the natural (rest) position. In situations where isometric quadriceps exercises are required, the authors recommend either active ankle dorsiflexion or plantar flexion to facilitate quadriceps strengthening. The choice between the two positions should be based on patient comfort.

Adult↗