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Dae-Hyun Kim, Jin-Hee Lee, Seul-Min Yu and Chang-Man An

extension, and leg press, are used in the rehabilitation and sports fields. 5 However, performing these exercises is difficult for elderly people who do not have enough capacity to perform them and for acute immobilized patients who experience pain after injury. In this case, isometric contraction exercise

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Eiji Yamada, Takashi Kusaka, Satoshi Tanaka, Satoshi Mori, Hiromichi Norimatsu and Susumu Itoh

Objective:

To investigate changes in motor-unit activity and muscle oxygenation (MO) during isometric contraction with and without vascular occlusion using surface electromyography (EMG) and near-infrared spectroscopy.

Design and Setting:

MO and EMG of the right vastus medialis muscle were measured during isometric contraction at 30%, 50%, and 70% maximal voluntary contraction (MVC), with and without vascular occlusion.

Participants:

6 healthy men.

Results:

Integrated EMG (IEMG) and mean power frequency were significantly higher with vascular occlusion at 30% and 50% MVC. MO reduction at each load was significantly lower with vascular occlusion. A significant positive correlation was found between IEMG and changes in MO level under both conditions.

Conclusions:

These results suggest that oxygen supply to active muscles was impaired by occlusion and that type II fibers were then preferentially recruited, which suggests that hypertrophy occurs in low-intensity exercise in patients with limitations resulting from advanced age, pain, or postsurgery limitation.

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Ryota Akagi, Soichiro Iwanuma, Satoru Hashizume, Hiroaki Kanehisa, Toshimasa Yanai and Yasuo Kawakami

The purpose of this study was to determine in vivo moment arm lengths (MAs) of three elbow flexors at rest and during low- and relatively high-intensity contractions, and to examine the contraction intensity dependence of MAs at different joint positions. At 50°, 80° and 110° of elbow flexion, MAs of the biceps brachii, brachialis and brachioradialis were measured in 10 young men using sagittal images of the right arm obtained by magnetic resonance imaging, at rest and during 20% and 60% of isometric maximal voluntary elbow flexion. In most conditions, MAs increased with isometric contractions, which is presumably due to the contraction-induced thickening of the muscles. This phenomenon was especially evident in the flexed elbow positions. The influence of the contraction intensities on the increases in MAs varied across the muscles. These results suggest that in vivo measurements of each elbow flexor MA during contractions are essential to properly examine the effects on the interrelationships between elbow flexion torque and individual muscle forces.

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Lílian Ramiro Felicio, Marcelo Camargo Saad, Rogério Ferreira Liporaci, Augusto do Prado Baffa, Antônio Carlos dos Santos and Débora Bevilaqua-Grossi

Purpose:

To evaluate patellar kinematics of volunteers without knee pain at rest and during isometric contraction in open- and closed-kinetic-chain exercises.

Methods:

Twenty individuals took part in this study. All were submitted to magnetic resonance imaging (MRI) during rest and voluntary isometric contraction (VIC) in the open and closed kinetic chain at 15°, 30°, and 45° of knee flexion. Through MRI and using medical e-film software, the following measurements were evaluated: sulcus angle, patellar-tilt angle, and bisect offset. The mixed-effects linear model was used for comparison between knee positions, between rest and isometric contractions, and between the exercises.

Results:

Data analysis revealed that the sulcus angle decreased as knee flexion increased and revealed increases with isometric contractions in both the open and closed kinetic chain for all knee-flexion angles. The patellar-tilt angle decreased with isometric contractions in both the open and closed kinetic chain for every knee position. However, in the closed kinetic chain, patellar tilt increased significantly with the knee flexed at 15°. The bisect offset increased with the knee flexed at 15° during isometric contractions and decreased as knee flexion increased during both exercises.

Conclusion:

VIC in the last degrees of knee extension may compromise patellar dynamics. On the other hand, it is possible to favor patellar stability by performing muscle contractions with the knee flexed at 30° and 45° in either the open or closed kinetic chain.

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Kevin McQuade, Michelle L. Harris-Love and Jill Whitall

The purpose of this study was to determine whether the phenomenon of bilateral deficit in muscular force production observed in healthy subjects and mildly impaired stroke patients also exists in patients with more chronic and greater levels of stroke impairment. Ten patients with chronic hemiparesis resulting from stroke performed unilateral and bilateral maximal voluntary isometric contractions of the elbow flexors. When the total force produced by both arms was compared, 12% less force was produced in the bilateral compared with unilateral condition (p = 0.01). However, studying the effect of task conditions on each arm separately revealed a significant decline in nonparetic (p = 0.01) but not paretic elbow flexor force in the bilateral compared with unilateral condition. Results suggest that a significant bilateral force deficit exists in the nonparetic but not the paretic arm in individuals with chronic stroke. Bilateral task conditions do not seem to benefit or impair paretic arm maximal isometric force production in individuals with moderate-severity chronic stroke.

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Theodoros Kannas, Eleftherios Kellis, Fotini Arampatzi and Eduardo Saez Saez de Villarreal

The aim of this study was to examine the differences in muscle architecture during isometric tests between children and adults. Eight boys (age= 11.2 ± 0.26 years) and eight men (age= 22.3 ± 2.01 years) performed plantar flexion isometric efforts at angles of -15°, 0°, 15° at 0%, 40%, 60%, 80% of MVC. Analysis of variance tests indicated that adults showed greater fascicle length from rest to 80% of MVC (p < .05), greater pennation angle at 80% and 100% of MVC (p < .05) and greater aponeuroses displacement at levels of effort greater than 60% of MVC (p < .05). These differences observed in MG would appear to favor better utilization of the force-length and the force-velocity relationships, of the muscle in adults compared with children.

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Igor E.J. Magalhães, Rinaldo A. Mezzarane and Rodrigo L. Carregaro

motor unit recruitment. We hypothesized that different elastic taping techniques like FAC and INHI applications 7 would, respectively, increase and decrease the reflex excitability of the soleus muscle during isometric contractions. Method Study Design This is a longitudinal study with repeated

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Matheus Lima Oliveira, Isabela Christina Ferreira, Kariny Realino Ferreira, Gabriela Silveira-Nunes, Michelle Almeida Barbosa and Alexandre Carvalho Barbosa

coaches to objectively monitor strength without technical (as rater experience, previous training to use equipment/software) or financial issues (expensive equipment). The maximal isometric contraction improvements reflect combination of central and peripheral adaptations in muscle strength. 10 Thus

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Yi-Ching Chen, I-Chen Lin, Yen-Ting Lin, Wei-Min Huang, Chien-Chun Huang and Ing-Shiou Hwang

self-organization of brain and behavior . Cambridge, MA : MIT Press . Kennedy , D.M. , & Christou , E.A. ( 2011 ). Greater amount of visual information exacerbates force control in older adults during constant isometric contractions . Experimental Brain Research, 213 ( 4 ), 351 – 361

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Maria W.G. Nijhuis-Van der Sanden, Edwin H.F. Van Asseldonk, Paul A.T.M. Eling and Gerard P. Van Galen

This study examined the relationship between decreased speed-accuracy tradeoff and increased neuromotor noise in girls with Turner Syndrome (TS). Fifteen girls with TS and 15 age-matched controls performed isometric force contractions with both index fingers separately at 5 force levels, based on their maximum voluntary contraction. The results revealed that (a) groups did not differ in speed-accuracy tradeoff or neuromotor noise, (b) output-variability increased linearly with force level, (c) signal-to-noise ratio changed according to an inverted U-shaped function, (d) broadening in the frequency profile is highest at the lower force levels, (e) with increasing force level, the power peak in the 0–4 Hz domain dominates, (f) frequency profile broadens more in the dominant hand. These findings suggest that, in girls with TS, motor performance is not diminished in an isometric force task, that motor recruitment is intact, and that neuromotor noise is not increased. The findings are discussed with respect to motor control and neuromotor noise.