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Results for “Isotonic Contraction”

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At least 865 records · Page 48Linked to original sources
PubMed1990

Axillary crutch walking: effects of three training programs.

This study compared the effects of three different training programs on physiologic and perceptual responses during axillary crutch walking (ACW) for a distance of 1 km at self-selected speeds in healthy women. Forty subjects completed 18 training sessions in six weeks according to one of the following regimens: (1) 20 minutes of aerobic arm ergometer training at 50% of peak oxygen consumption determined during arm ergometry; (2) isotonic strength and endurance training of the upper extremities with free weights; or (3) axillary crutching at self-selected speeds for 20 minutes on a rectangular indoor course. In comparison with a control group that did not do any systematic training, all three training groups significantly increased their self-selected ACW speeds after training. This also resulted in a significant increase in their heart rates during ambulation. However, no significant changes were observed in oxygen consumption at the faster ACW speeds, suggesting that the training regimens were effective in improving the metabolic efficiency of ACW. Ratings of perceived exertion were significantly lowered for the three training groups even though cardiorespiratory stress was significantly elevated. No significant differences were observed between the three training programs for any of the variables examined. Since heart rate is a reliable indicator of myocardial oxygen uptake, it was recommended that (1) individuals should be screened for cardiovascular problems before axillary crutches are prescribed as a mode of ambulation, and (2) they should be advised to reduce the speed of ambulation because of the high degree of cardiovascular stress associated with this activity.

Adult↗
PubMed1989

A novel peptide, vasoactive intestinal contractor, of a new (endothelin) peptide family. Molecular cloning, expression, and biological activity.

A new peptide family (endothelin (ET] consisting of three members in mammals appears to be present in mice according to genomic Southern blot analysis. Two ET-related genes were identified by cloning and sequence analysis of a mouse genome. One encoded a peptide identical to porcine and human vasoconstrictor peptide ET, and the other encoded a novel peptide differing from ET in 3 amino acid residues, with 4 cysteines in the same positions as in ET. This novel peptide was synthesized and confirmed to have in vivo pressor activity similar to that of ET. Northern blot analysis, however, indicated the gene of this novel peptide to be expressed only in the intestine, and not in other tissues or cell lines, or endothelial cells. Furthermore, the peptide evoked a strong contractile response in the guinea pig ileum. This peptide may thus be reasonably classified as a gastrointestinal peptide, vasoactive intestinal contractor.

Amino Acid Sequence↗
PubMed1978

[Echocardiographic measurement of left ventricular function in athletes (author's transl)].

Echocardiographic measurements were performed on fifteen football players, in moderate training and on untrained control groups. In comparison with the untrained subjects the echocardiographic tests displayed in athletes a 34% increase in the stroke volume, a 23% increase in the left cavity in diastole, a 11% increase in thickness of left wall in diastole, an increase of the area of the heart's transverse section and of the left miocardial volume. The contractility and pump indexes were the same for both groups of subjects. In conclusion, football is a compound type sport, implying mainly isotonic muscle contractions and isometric too; miocardial hypertrophy in football players' heart has a physiological character.

Adult↗
PubMed1983

Evaluation of isokinetic muscle performance.

The development and availability of isokinetic testing equipment, recording systems, and systems for computer analysis have improved the quality and quantity of information about specific skeletal muscle performance. The value of both isokinetic exercise and instrumentation designed to objectively record muscle performance characteristics is becoming more widely recognized, especially by professional members of the sports medicine community. The present demand for appropriate equipment is high and new instrumentation for this purpose is being developed. Current instrumentation continues to be modified and improved. The information gained from carefully designed testing protocols is useful and necessary for understanding the role of specific muscle groups in athletic performance and for determining the readiness of the athlete to resume training or competition following injury or deconditioning. With expanded profile data about the muscle performance characteristics of various categories of athletes, training or rehabilitation programs may be adapted to meet the strength, speed, and endurance requirements of a given sport, which may enhance the quality of participation and prevent the occurrence of injury or reinjury.

Adult↗
PubMed1983

[Relationship between isometric and isotonic contractile responses of the mammalian myocardium].

Effects of 6 and 12 mM of caffeine, 10(-5) M of verapamil, variation in stimulation frequency between 0.1 and 0.7 Hz, cooling to 15 degrees C after elevation of perfusate Ca2+ to 15 mM on isometric (IM) and isotonic (IT) contractions of guinea pig papillary muscles were studied. The first and the last interventions mentioned above were found to slow down relaxation phase and increase the IT/IM response amplitude ratio by 50-70%. Under the action of both interventions the maximum of IT response appears after the maximum of IM response with delay of 50-100 msec. A close correlation (r = 0.89) between changes of IT/IM and delay of IT peak was revealed. Different sensitivity of IM and IT responses to inotropic interventions could not be explained by the change of membrane electrical activity because the AP did not change after a transition from IM to IT mode. An analysis of experimental data suggests that the delay between IT and IM peaks and the ratio of their amplitudes depend on the rate of calcium uptake within the myocardial cell.

Action Potentials↗
PubMed1994

Resistance training increases lower body negative pressure tolerance.

This study investigated whether whole body resistance training would increase tolerance to lower body negative pressure (LBNP). Twelve males (age = 19.6 +/- 0.4 yr; mean +/- SD) underwent an acute, 12-wk program of upper and lower body resistance training (ART). Pre- and posttraining, the ART group and a control group (CON; N = 8; age = 25.4 +/- 2.4 yr) underwent LBNP tolerance tests and neck pressure-suction testing. Additionally, a group of chronically resistance-trained individuals (CRT group; N = 5; age = 22.4 +/- 0.9 yr) were tested. LBNP tolerance was increased in the ART group after training and the CRT group exhibited a significantly higher LBNP tolerance than the other groups. The ART group exhibited a decreased leg circumference change at the same absolute negative pressure at which tolerance occurred pretraining. This indicated a decreased fluid pooling after ART. The CRT group exhibited a "flattened" hypotensive portion of the carotid sinus-heart rate baroreflex curve, but this appeared to be due to the increased neck muscle mass of the subjects. We conclude that whole body ART increases LBNP tolerance possibly mediated through alterations in vascular compliance. CRT results in even greater LBNP tolerance with the responsible mediating mechanisms unclear.

Adult↗
PubMed1994

Cardiovascular responsiveness after isotonic exercise in cirrhotic patients: study on sympathoadrenergic and renin-angiotensin systems.

OBJECTIVES: The aim of this study was to evaluate cardiovascular responsiveness after isotonic exercise in cirrhotic patients. METHODS: Included were 11 cirrhotic patients and 10 age-matched normal subjects, who served as controls. Hemodynamic data were obtained on each subject before and after muscle exercise on a treadmill (7 metabolic units). Plasma noradrenaline concentration and plasma renin activity also were determined. RESULTS: In both groups, isotonic exercise increased heart rate and systolic arterial pressure, whereas diastolic arterial pressure was not modified. The increase in heart rate and systolic arterial pressure did not differ significantly between the two groups. Plasma noradrenaline concentration and plasma renin activity also were increased. The changes in plasma noradrenaline concentration and plasma renin activity was higher in cirrhotic patients than in controls (p < 0.05, p < 0.05), although the differences were not significant when calculated as a percentage. CONCLUSIONS: Cardiovascular responsiveness to isotonic exercise is almost intact in cirrhotic patients. However, supernormal activation of the sympathoadrenergic and renin-angiotensin systems is required to maintain cardiovascular homeostasis in these patients.

Adult↗
PubMed1993

Aspirin-like drugs inhibit neuronally evoked responses in isolated guinea-pig ileum.

The acute effects of non steroidal anti-inflammatory drugs (NSAIDs) were studied on guinea-pig ileum isolated preparation. Two cyclo-oxygenase inhibitors, aspirin and indomethacin, and two NSAID devoid of this effect, salicylic acid and benzydamine, were injected into the bath 1 min before PGE1 or CCK-8. All drugs tested elicited a dose-related inhibition of the neuronally evoked contractile responses to submaximal dose of PGE1 and CCK-8. These drugs depressed also the opioid system(s) activated by PGE1 or CCK-8. These results indicate that the inhibition of neuronally evoked response is a common mechanism of NSAIDs. This mechanism may have an important role on analgesic and anti-inflammatory action of these drugs.

Acetylcholine↗
PubMed1994

Neuromuscular adaptations following prepubescent strength training.

Underlying mechanisms of prepubescent strength gains following resistance training are speculative. The purpose of this investigation was to determine the effects of 8 wk of resistance training on muscular strength, integrated EMG amplitude (IEMG), and arm anthropometrics of prepubescent youth. Sixteen subjects (8 males, 8 females) were randomly assigned to trained or control groups. All subjects (mean age = 10.3 yr) were of prepubertal status according to the criteria of Tanner. The trained group performed three sets (7-11 repetitions) of bicep curls with dumbbells three times per week for 8 wk. Pre- and posttraining measurements included isotonic and isokinetic strength of the elbow flexors, arm anthropometrics, and IEMG of the biceps brachii. Planned comparisons for a 2 x 2 (group by test) ANOVA model were used for data analysis. Significant isotonic (22.6%) and isokinetic (27.8%) strength gains were observed in the trained group without corresponding changes in arm circumference or skinfolds. The IEMG amplitude increased 16.8% (P < 0.05). The control group did not demonstrate any significant changes in the parameters measured. Early gains in muscular strength resulting from resistance training prepubescent children may be attributed to increased muscle activation.

Adaptation, Physiological↗
PubMed1993

Synergistic effects of monensin in combination with permethrin or neomycin on neuronal activity.

Drug combinations have the potential to produce novel and unpredictable responses on nervous tissue. This study was designed to test the hypothesis that the effects of combinations of monensin (an ionophore antibiotic) and either neomycin (an aminoglycoside antibiotic) or permethrin (synthetic pyrethroid) are synergistic. Effects of the drug combinations upon the electrical properties and membrane activities of an in vitro sensory neuron preparation were found to be greater than expected from addition of the effects of the same drugs acting individually, indicating synergism and thus supporting the hypothesis. It was concluded that drugs acting at different neuronal membrane sites and applied in combination produce unpredictable responses. Such drug combinations behave as if they were novel drugs.

Animals↗
PubMed1993

Anterior knee pain.

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Exercise Therapy↗