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At least 487 records · Page 27Linked to original sources

PubMed1991

[Characteristics of response to isometric exercise in women with stable arterial hypertension].

In 50 females with Stage II persistent hypertension, tetrapolar thoracic rheography was employed to measure cardiac index (CI), stroke index (SI), specific peripheral resistance (SPR), blood pressure (BP), heart rate (HR) before and during isometric exercise when antihypertensive drugs were withdrawn. The patients with a family history of hypertension were found to have impaired homeostatic mechanisms preventing an excess elevation in BP during isometric exercise. The females of reproductive age showed a greater increase in BP, HR, SI, CI and a lower decrease in SPR in response to the exercise than did menopausal females. Left ventricular hypertrophy contributes to a positive inotropic action shown by sympathetic cardiac stimulation during isometric exercise, as evidenced by a lower reduction or elevation in SI. The detected responses to isometric exercise may serve as criteria for differential approach to the choice of adequate antihypertensive therapy.

Adult↗

PubMed1990

[Reconstruction of the anterior cruciate ligament. Determination of the pre- and peroperative femoral isometric point].

This study attempted to determine the femoral isometric site by a simple, reliable and easily reproducible technique for the reconstruction of a torn anterior cruciate ligament (A.C.L.). Anatomoradiological studies showed that the posterior border of the lateral condyle corresponded with the third of a circle and that the center of this circle was named the "isometric point" (F). The variations of the intra-articular length of a ligament between the point F and the center of the A.C.L. tibial attachment did not exceed 2 mm. A radiological study on 50 normal patients knees X-Rayed at 0 degree and 90 degrees of flexion showed a length dependence of 1.5 mm in 84% and 2 mm maximum in 98%. Twenty patients with acute or chronic A.C.L. rupture were operated on; the isometric point F was determined by superimposing a template of circles on the posterior border of the condyle. An original guide allowed to drill a bony tunnel with a pin emerging at the exact previous point F. A per-operative X-Ray studied the good reliability of this guide. The measurements of the variations of length of the ligament between 0 degree and 110 degrees of flexion varied less than 5% in 18 patients, which confirms the good isometry of the reconstruction. On the basis of these data, we propose to improve the implantation of autogenous or synthetic ligament in A.C.L. reconstruction by the use of a pre-operative determination of the isometric femoral point and the use of a guide able to drill easily a bony tunnel at this exact pre-determined point.

Anterior Cruciate Ligament↗

PubMedDate not supplied

[Nifedipine and isometric exercise. Evaluation of the pressure response in hypertensive patients].

Because of isometric efforts are a normal component of the usual life, we studied 35 patients suffering from mild and moderate essential hypertension, by means of an isometric exercise test, using the "handgrip method". The purpose of the experimental work was the evaluation of pressure changes at the top of an isometric stress in basal conditions and the demonstration of the protective effect against pressure increase of nifedipine, acutely administered (20 mg sublingual). The results largely confirmed the usefulness of nifedipine in the treatment of hypertension at rest and at the top of an isometric exercise. Moreover, the pressure increase during the same effort after nifedipine administration is smaller than during a therapy with others antihypertensive drugs.

Adult↗

PubMed1988

[Use of isometric load for evaluation of the anti-arrhythmia effect of drugs].

Possible use of pedal isometric stress for the assessment of antiarrhythmic effect of ethacizine was explored in 34 patients with various heart rhythm disorders. They showed similar results of pedal isometric stress test and 24-hour ECG monitoring. Heart rhythm monitoring in the presence of the acute test and a treatment course demonstrated complete agreement between positive results of the pedal isometric stress test and 24-hour ECG monitoring in 85% of the patients, exhibiting an obvious antiarrhythmic effect. The pedal isometric stress test may be useful for the assessment of antiarrhythmic medication efficacy.

Adolescent↗

PubMed1989

[The hemodynamic and neurohumoral reactions induced by submaximal dynamic and isometric loading in hypertension patients].

Changes in systemic hemodynamics and plasma catecholamine levels during and 4 min after the end of bicycle and isometric leg exercise were studied in 12 hypertensive patients. Dynamic exercise increased heart rate more and blood pressure less than isometric exercise; plasma norepinephrine (NE) level rose by 109%. Isometric exercise increased NE level only by 18%, but maximal changes (46%) occurred during recovery, probably reflecting a washout of NE from active muscles after the end of isometric contractions. It is concluded that during static exercise more pronounced pressor effect is associated with less activation of the sympathetic nervous system in comparison with dynamic exercise.

Adult↗

PubMed1989

[Effect of isometric hand-grip exercise on left ventricular diastolic filling in patients with effort angina: a pulsed Doppler echocardiographic study].

To detect myocardial ischemia and to estimate cardiac reserve in patients with effort angina pectoris without history of myocardial infarction, left ventricular diastolic filling was measured using Doppler echocardiography during isometric handgrip exercise. Nineteen patients with effort angina pectoris undergoing coronary angiography and 16 normal subjects were studied. The angina patients were categorized in two groups: 12 with single vessel disease (SVD) and seven with multiple vessel disease (MVD). Fifty percent maximum voluntary contraction isometric handgrip exercise was performed for two minutes. 1. The resting A/R in the angina group was significantly greater than that of the normal subjects (SVD: 1.20 +/- 0.24, MVD: 1.21 +/- 0.27, normal 0.85 +/- 0.10) (p less than 0.001). However, the values of many cases in these three groups overlapped. 2. In SVD, the A/R increased significantly during isometric handgrip exercise (1.20 +/- 0.24 to 1.96 +/- 0.66: p less than 0.001). The delta A/R (0.76 +/- 0.15) was significantly greater than that of patients in other groups (MVD: 0.10 +/- 0.13, normal: 0.09 +/- 0.01) (p less than 0.001). Consequently, the A/R after exercise clearly distinguished the SVD from the normal subjects. 3. In MVD, the A/R did not change significantly during exercise (1.21 +/- 0.27 to 1.31 +/- 0.41), and there were no significant differences in delta A/R as compared to the normal subjects (p less than 0.01). The A/R decreased during exercise in three of the seven patients, and this was markedly different from that of the normal subjects. These findings suggest that assessment of changes in left ventricular diastolic filling during isometric handgrip exercise is useful in detecting myocardial ischemia and in estimating cardiac reserve in patients with effort angina pectoris.

Adult↗

PubMed1989

Leg endurance training has no effect on the autonomic control of heart rate during isometric exercise.

1. Heart rate (HR) response to isometric exercise (handgrip) was investigated in 7 normal males of sedentary habits before and after endurance training involving the muscles of the lower limbs. Thirteen additional sedentary individuals and 7 middle-distance runners were also studied. Isometric exercise was performed at 100, 75 and 50% of maximum voluntary contraction (MVC) during 10, 20 and 40 s, respectively. Training produced a 15.6 +/- 1.4% (mean +/- SEM) increase in VO2max and a reduction in resting HR from 69 +/- 1.9 to 58 +/- 1.7 bpm. HR was monitored throughout each period of isometric exercise. 2. The pattern of HR response to static effort performed by untrained muscles was comparable before and after training as well as in athletes and sedentary individuals during the first 10 s of contraction, a period during which tachycardia is mainly mediated by vagal release. After the first 10 s, when the sympathetic influence on tachycardia becomes evident, athletes and trained individuals showed a slight but nonsignificant tendency toward lower HR increases. 3. These results do not demonstrate any appreciable alteration in the efferent activity of autonomic components induced by aerobic training of the leg muscles when isometric exercise is performed with untrained muscles.

Adaptation, Physiological↗

PubMed1988

Effect of isometric exercise and autonomic blockade on the haemodynamics: a noninvasive study in healthy volunteers.

Sixteen healthy young volunteers were studied with echocardiography and systolic time intervals at rest and after three minutes' isometric exercise before and during autonomic blockade with atropine and propranolol. Isometric exercise increased cardiac output by raising the heart rate from 64 +/- 3 to 72 +/- 4 bpm (SEM) (p less than 0.01). Mean blood pressure increased from 86 +/- 2 to 104 +/- 3 mmHg (p less than 0.001) without any changes in the calculated total peripheral vascular resistance. Afterload (left ventricular systolic wall stress) rose but preload (left ventricular end-diastolic diameter, LVEDD) did not change. There was no variation in fractional shortening, maximal velocity of circumfertial fibre shortening (VCFmax) or pre-ejection period (PEP) despite increased afterload. This indicates stimulated intropy during isometric exercise. Autonomic blockade enhanced cardiac output by increasing heart rate from 64 +/- 3 to 97 +/- 2 bpm (p less than 0.001). Mean blood pressure rose from 86 +/- 2 to 93 +/- 2 mmHg (p less than 0.01) while vascular resistance fell. Afterload did not change but LVEDD shortened form 45.5 +/- 0.9 to 43.5 +/- 0.9 mm (p less than 0.001). Preload-independent VCFmax did not increase despite raised heart rate. PEP rose from 99 +/- 4 to 107 +/- 3 ms (p less than 0.01) and fractional shortening fell from 29 +/- 1 to 25 +/- 1% (p less than 0.001); these changes were greater than expected from the reduced preload. Consequently autonomic blockade seems to impair myocardial contractility despite vagal dominance at rest. Heart rate and cardiac output were not influenced by isometric exercise during autonomic blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Echocardiographic vs hemodynamic monitoring during isometric exercise in patients with coronary artery disease.

BACKGROUND: Isometric exercise is able to induce myocardial asynergies in patients with coronary artery disease as demonstrated by noninvasive monitoring performed during stimulation. AIMS OF THE STUDY: In the present study, a combined echocardiographic and hemodynamic monitoring of left ventricular contractility has been conducted in order to verify, with invasive and noninvasive techniques, the ability of isometric exercise in inducing transient myocardial ischemic phenomena. METHODS: The study population was composed of 20 patients with angiographic evidence of significant coronary stenosis (> or = 50%), and 10 subjects with normal coronary angiograms. All 30 subjects admitted to the study underwent an isometric exercise stress during echocardiographic and hemodynamic monitoring of left ventricular contractility. RESULTS: Nine out of 20 patients with coronary disease showed regional asynergy during the test (Group I). The remaining 11 patients showed normal myocardial contractility (Group II). None of the 10 control subjects showed mechanical signs of ischemia during the test. Left ventricular end diastolic pressure significantly increased in both Group I (10 +/- 2 to 24 +/- 4 mmHg) and Group II (12 +/- 3 to 26 +/- 3 mmHg) (p < 0.01) while it remained unchanged in the control group (9 +/- 2 to 13 +/- 2 mmHg; p = NS); dp/dt increase (% basal) was significantly higher in the control group (45 +/- 6%) than in either Group I (25 +/- 3%) or Group II (26 +/- 3%) (p < 0.01). CONCLUSIONS: Isometric exercise was able to induce left ventricular asynergies due to regional myocardial ischemia. Hemodynamic contractility monitoring easily distinguished the control subjects from the patients with coronary disease but was not able to discriminate patients with handgrip-induced regional asynergy. Thus, the echocardiographic technique offers more detailed information about regional myocardial function than do the common hemodynamic contractility indexes.

Adult↗

PubMed1996

Effect of body position on isometric arm lifting strength.

The purpose of this study was to examine the influence of three different body positions on isometric arm lifting strength. Thirty students aged between 20 and 27 years volunteered as subjects for the study. A force Evaluation and Testing System (FET 5000) was used to measure the arm lifting strength in the supine, sitting, and standing positions. Average force of each body position was determined by the mean of two trials. At the same time, electromyographic activity of bilateral biceps brachii muscles was measured during maximal voluntary isometric arm lifting. Repeated measures analysis of variance was used to analyze the effects of body positions on the amount of average force value and integrated electromyographic (IEMG) values during isometric arm lifting. The results showed that the highest mean lifting strength was recorded in the sitting position for both males and females. Significant difference in arm lifting strength was found between each body position. Differences in force were elicited more easily between the female and male subjects. However, the average IEMG values were not significantly correlated with the force produced in arm lifting. Nevertheless, this study supports the conclusion that body position did influence the production of isometric elbow flexors strength. We conclude, therefore, that body position must be considered during rehabilitation of upper extremities.

Adult↗

PubMed1977

Isokinetic and isometric torque force relationships.

The torque forces of elbow extensor musculature of 28 men were tested with an isokinetic dynamometer to determine the relationships between maximal isokinetic torque generated at various speeds and maximal isometric forces at specified angles in the arc of elbow extension. The men were tested at constant velocities ranging from 5 to 25 rpm and at angles of elbow extension ranging from 10 degrees to 90 degrees. Product-moment correlation coefficients were calculated between the maximum isometric torque developed at each of the measured angles and the isokinetic torque generated at each of the predetermined speeds. Of the 81 correlation coefficients calculated, 13 differed significantly from zero. There were slight tendencies for the significant correlations to cluster toward the slower speeds and toward the greater angles of elbow flexion. It was suggested that the slight tendency for higher correlations to cluster toward the slower speeds may be due to slower speeds stimulating isometric effort. The slight tendency for the higher correlations to cluster toward the greater angles of elbow flexion may be due to variances in the consistency of muscular strength at different muscle lengths. Since the highest correlation attained yielded a common variability of less than 24% between the two variables tested, it was concluded that measures of isokinetic strength cannot be used to predict isometric strength capabilities.

Adult↗

PubMed2026

Acute Performance, Mechanical and Thermal Effects of Isometric Conditioning Versus Standardized Volleyball Pre-Training Activation in Highly Trained Male Players.

This study compared acute performance, neuromuscular, and thermal responses to a maximal isometric conditioning activity (ICA) versus a standardized volleyball pre-training activation (VPA) in highly trained male volleyball players, and to explore putative mechanisms underpinning post-activation performance enhancement (PAPE) considering training load. In a randomized crossover, 14 men (27 ± 3 y) completed two sessions: VPA (mobility/plyometric drills; 9 min), and ICA comprising 3×5×3-s maximal isometric back-squat contractions (knee angle 120°; 3-min inter-set rest). Countermovement jump (CMJ) height (primary), relative peak power (PP), RSImod, and contraction time (CT) were recorded pre and 3, 6, 9, and 12 min post. Rectus femoris muscle viscoelastic properties and skin surface temperature (SST) were assessed at matched time points. Analyses used repeated-measures ANOVA, responder analysis, correlations, and regression. Period×Sequence interactions favored ICA for CMJ and PP when delivered in Period 2 (lower training volume): ∆CMJ was higher under ICA versus VPA (p = 0.005, d = 1.20); PP likewise greater (p = 0.026, ηp2 = 0.35). ICA yielded more beneficial responders than VPA (9/14 vs 1/14; McNemar exact p = 0.021). In Period 2, reductions in rectus femoris muscle stiffness independently predicted CMJ gains (β_std = -0.495, p = 0.005), whereas SST changes did not (p = 0.974). RSImod and CT showed no differences. A brief, high-effort isometric squat protocol was associated with superior acute improvements in jump performance compared with a standard volleyball warm-up, but this advantage emerged specifically when the preceding training volume was reduced (Period 2), suggesting that residual fatigue from training may reduce the effects of PAPE. Gains align with neuro-mechanical rather than thermal mechanisms, supporting ICA as a practical, equipment-minimal priming strategy for elite volleyball.

Humans↗

PubMed1978

Blood pressure response to isometric and dynamic exercise in healthy black children.

One hundred seventy healthy black boys and girls (76 boys and 94 girls) had their systolic blood pressure (BP) determined at rest, during submaximum and maximum dynamic exercise, and in response to isometric exercise. Differences in BP between boys and girls were not significant. Blood pressure response to both dynamic and isometric exercise correlated with age and body surface area. Differences between resting BP and the BP during isometric exercise (BPiso), submaximum dynamic exercise (deltaBP170) and maximum dynamic exercise (deltaBPmax) for boys were: deltaBP150 18 +/- 9, deltaBP170 40 +/- 16 and deltaBPmax 55 +/- 17. Corresponding values for girls were: 16 +/- 8, 36 +/- 14 and 47 +/- 16. The higher the resting BP the less was the percentage change in BP to each stress.

Adolescent↗

PubMed1999

Superimposed single impulse and pulse train electrical stimulation: A quantitative assessment during submaximal isometric knee extension in young, healthy men.

Superimposed electrical stimulation techniques can be used to detect central activation failure (CAF), defined as incomplete central nervous system recruitment, suboptimal activation of motor units, or both. The purpose of this study was to evaluate superimposed electrical stimulation techniques to be used to detect CAF during isometric knee extension. We performed three sets of experiments and compared the torque increments from transcutaneous electrical stimulation with: (i) single impulses of different amplitudes (100 V, 150 V, and 200 V) and a pulse train of 100 Hz (100 V, 100 ms); (ii) pulse trains (100 Hz, 100 V) of different lengths (100 ms, 200 ms, and 300 ms); and (iii) pulse trains (100 Hz, 100 ms) of different amplitudes (50 V, 100 V, 150 V, and 200 V). Stimulation was evaluated at submaximal (80% of MVC) isometric knee extension in 24 healthy young men using a Biodex isokinetic dynamometer. Electrodes were placed over the rectus femoris muscle and all stimulation impulses were monophasic, rectangular waves of 0.2-ms duration. Pulse train stimulation at 100 V always elicited a torque increment, whereas single impulse stimulation, even at 200 V, only caused a torque increment in about half of the trials. For each subject, the pulse train generated a significantly larger torque increment than for any of the three single impulses. There was no significant difference in torque increment between the three pulse trains of different lengths. Pulse trains at 150 V and 200 V generated significantly larger torque increments than at 50 V and 100 V. High-frequency maximal train stimulation may thus improve the detection of CAF during isometric knee extension. Detection of CAF may be important in the clinical assessment of muscle weakness, investigating the mechanisms underlying muscle weakness, and evaluating potential therapeutic strategies.

Adult↗

PubMed2000

Activation linearity and parallelism of the superficial quadriceps across the isometric intensity spectrum.

The purpose of this study was to assess neuromuscular activation of the three superficial portions of the quadriceps femoris muscles during linearly increasing isometric contraction intensities. Thirty healthy volunteers were assessed for isometric electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles with the knee at 60 degrees of flexion. For 5 s, subjects performed isometric contractions equivalent to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of the average of three maximal voluntary contractions (MVC), in random order. Full-wave rectified and integrated EMG signals over the middle 3 s of each contraction were expressed as a percentage of the activity recorded during the three averaged MVCs. One sample t-tests and 95% confidence intervals were calculated at each relative torque level. A two-factor analysis of variance (muscle by intensity) with repeated measures was performed to evaluate parallel activation across the intensity levels. Activation linearity was assessed via regression analysis for each muscle. VM activation was shown to be significantly lower than expected at 20-70% MVC. VL and RF activations were significantly higher than expected at 10% MVC, and RF EMG was less than expected at 40-70% MVC. EMG of VM was shown to increase significantly more than VL and RF from 80% to 90% MVC. Significant linear and quadratic relations were also demonstrated for all three muscles. Parallel activation of the superficial quadriceps muscles occurred from low to moderate intensities, whereas convergence was noted at near maximal intensities.

Adult↗

PubMed1992

Facilitation of responses to motor cortex stimulation: effects of isometric voluntary contraction.

In 7 normal subjects we compared the facilitatory effect of isometric contraction of the tibialis anterior on the size of electromyographic responses evoked in this muscle by electric stimuli applied over the cervical column and by electric and magnetic percutaneous stimulation of the motor cortex. No significant difference was found between the degrees of facilitation of the responses to any of the stimuli. Using collision techniques, we also showed that the pyramidal fibers activated by spinal and cortical stimuli are the same. Facilitation induced by isometric contraction (20% maximum) was of similar or greater magnitude than that found with constant vibration of the tendon of the target muscle. In cases where vibration and contraction had equal facilitatory effects, there was no further facilitation of the responses when both conditions were applied together. These findings indicate that the facilitatory effect of isometric contraction of the target muscle essentially originates at a spinal level rather than in the motor cortex.

Adult↗

PubMed2003

Isometric muscle force measurement for clinicians treating patients with osteoarthritis of the knee.

OBJECTIVE: To evaluate the discriminant validity and, for clinicians, the test-retest reliability of isometric force in patients with knee osteoarthritis (OA). METHODS: Mean isometric muscle strength data collected for 113 patients with knee OA were compared with published normative data for 131 asymptomatic subjects. RESULTS: Patients with knee OA, ages 60-79 years, could attain only 40-53% of the knee extensor force and 35-46% of the knee flexor force generated by their age- and sex-matched peers. One-week test-retest intraclass correlations ranged from 0.79 to 0.95. Random measurement error demonstrated a favorable "signal-to-noise" ratio. CONCLUSION: The similar decrease in knee extensor and knee flexor strength demonstrated by patients with knee OA compared with their age- and sex-matched asymptomatic peers suggests that strategies should be directed at both muscle groups to optimally limit joint damage. Isometric muscle force measurement can be a useful assessment tool for clinicians.

Aged↗

PubMed1993

The effect of isometric quadriceps strength training in mid-range for osteoarthritis of the knee.

This case report describes the effect of strengthening the quadriceps of an effused osteoarthritic knee joint of a 53-year-old man isometrically in mid-range. The instruments included an isokinetic dynamometer, a knee scoring inventory, and a visual analog scale. The outcome measures of isometric quadriceps torque and work, clinical status, and pain were recorded before and after the exercise intervention. The exercises were carried out three times per week for a 6-week period with the subject seated on an exercise chair. Following training, quadriceps torque increased, clinical status improved, and pain with walking decreased. Subject to further investigation, isometric training of the quadriceps in mid-range could prove useful for improving the function of persons with painful or effused knees who might otherwise experience muscle inhibition by exercising in the more traditional inner ranges of knee extension.

Exercise Therapy↗