oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
THE INFLUENCE OF VIBRATION ON MUSCLE ACTIVATION AND RATE OF FORCE DEVELOPMENT DURING MAXIMAL ISOMETRIC CONTRACTIONS  [cached]
Brendan Humphries,Geoff Warman,Jason Purton,Tim L. A. Doyle
Journal of Sports Science and Medicine , 2004,
Abstract: At present there appears to be a need for research conducted on the effects of vibration on the contractile ability of skeletal muscle tissue. The aim of this study was to address this issue by examining the effects of a superimposed muscle/tendon vibration at 50.42±1.16 Hz (acceleration 13.24 ± 0.18ms-2: displacement 5mm) on muscular activation and maximal isometric contraction. Sixteen participants with a mean age, body mass, and height of 22 ± 4.4 years, 73.2 ± 11.7 kg and 173.1 ± 9.7 cms, respectively, were recruited for this study. Electromyography and accelerometry from the rectus femoris, and maximal isometric force data characteristics were collected from the dominant limb under conditions of vibration, and no-vibration. A superimposed 50 Hz vibration was used during the contraction phase for the maximal isometric leg extension for the condition of vibration. A one-way ANOVA revealed no significant (p > 0.05) differences between the vibration and no-vibration conditions for peak normalized EMGRMS (84.74% Vs 88.1%) values. An ANOVA revealed significant (p > 0.05) differences between the peak fundamental frequencies of the FFT between the conditions vibration (27.1 ± 12.2 Hz) and no-vibration (9.8 ± 3.5 Hz). Peak isometric force, peak rate of force development, rate of force development at times 0.05, 0.01, 0.1, 0.5 seconds, and rate of force development at 50, 75, and 90% of peak force were not significantly different. The results of this study suggest that the application of vibration stimulation at 50 Hz during the contraction does not contribute to muscle activation, or enhance force production for maximal isometric contractions.
Evaluation of electromyographic activity and heart rate responses to isometric exercise. The role played by muscular mass and type
Silva, E.;Oliveira, L.;Catai, A.M.;Ferreira-Filho, P.;Bérzin, F.;Gallo Jr., L.;
Brazilian Journal of Medical and Biological Research , 1999, DOI: 10.1590/S0100-879X1999000100017
Abstract: the purpose of the present study was to examine the relationship between the electromyographic (emg) activity and heart rate (hr) responses induced by isometric exercise performed by knee extension (ke) and flexion (kf) in men. fifteen healthy male subjects, 21 ± 1.3 years (mean ± sd), were submitted to ke and kf isometric exercise tests at 100% of maximal voluntary contraction (mvc). the exercises were performed with one leg (right or left) and with two legs simultaneously, for 10 s in the sitting position with the hip and knee flexed at 90o. emg activity (root mean square values) and hr (beats/min) were recorded simultaneously both at rest and throughout the sustained contraction. the hr responses to isometric exercise in ke and kf were similar when performed with one and two legs. however, the hr increase was always significantly higher in ke than kf (p<0.05), whereas the emg activity was higher in ke than in kf (p<0.05), regardless of the muscle mass (one or two legs) involved in the effort. the correlation coefficients between hr response and the emg activity during ke (r = 0.33, p>0.05) and kf (r = 0.15, p>0.05) contractions were not significant. these results suggest that the predominant mechanism responsible for the larger increase in hr response to ke as compared to kf in our study could be dependent on qualitative and quantitative differences in the fiber type composition found in each muscle group. this mechanism seems to demand a higher activation of motor units with a corresponding increase in central command to the cardiovascular centers that modulate hr control.
Evaluation of electromyographic activity and heart rate responses to isometric exercise. The role played by muscular mass and type  [cached]
Silva E.,Oliveira L.,Catai A.M.,Ferreira-Filho P.
Brazilian Journal of Medical and Biological Research , 1999,
Abstract: The purpose of the present study was to examine the relationship between the electromyographic (EMG) activity and heart rate (HR) responses induced by isometric exercise performed by knee extension (KE) and flexion (KF) in men. Fifteen healthy male subjects, 21 ± 1.3 years (mean ± SD), were submitted to KE and KF isometric exercise tests at 100% of maximal voluntary contraction (MVC). The exercises were performed with one leg (right or left) and with two legs simultaneously, for 10 s in the sitting position with the hip and knee flexed at 90o. EMG activity (root mean square values) and HR (beats/min) were recorded simultaneously both at rest and throughout the sustained contraction. The HR responses to isometric exercise in KE and KF were similar when performed with one and two legs. However, the HR increase was always significantly higher in KE than KF (P<0.05), whereas the EMG activity was higher in KE than in KF (P<0.05), regardless of the muscle mass (one or two legs) involved in the effort. The correlation coefficients between HR response and the EMG activity during KE (r = 0.33, P>0.05) and KF (r = 0.15, P>0.05) contractions were not significant. These results suggest that the predominant mechanism responsible for the larger increase in HR response to KE as compared to KF in our study could be dependent on qualitative and quantitative differences in the fiber type composition found in each muscle group. This mechanism seems to demand a higher activation of motor units with a corresponding increase in central command to the cardiovascular centers that modulate HR control.
Reliability of Power Spectral Analysis of Surface Electromyogram Recorded during Sustained Vastus Medialis Isometric Contraction in Assessment of Muscle Fatigability  [PDF]
Yuta Minoshima, Yukihide Nishimura, Hiroyuki Tsuboi, Hideyuki Satou, Yoshi-ichiro Kamijo, Hideki Arakawa, Yuichi Umezu, Fumihiro Tajima
Open Journal of Therapy and Rehabilitation (OJTR) , 2017, DOI: 10.4236/ojtr.2017.52005
Abstract: The aim of this study was to determine the within-day and between-days reliability of surface electromyographic (EMG) power spectral analysis in assessing fatigability of the vastus medialis (VM) muscle during knee and hip flexion under constant load application. The subjects were 13 healthy adult men free of knee abnormalities. Surface EMG was recorded from vastus medialis obliquus (VMO) and vastus medialis longus (VML) during sustained isometric contractions at 60% of maximal voluntary contraction until exhaustion on the leg press machine (static leg press test). Linear regression analysis was applied to median frequency (MF) time series to calculate initial MF and MF slope. For VMO and VML, the initial MF showed moderate to high reliability, while the MF slope showed high reliability (Intraclass correlation coefficient (ICC) = initial MF: 0.63 - 0.92, MF slope: 0.70 - 0.86). The results demonstrated that spectral analysis of surface EMG recording during isometric VM muscle contraction has high within-day and between-days reliability in the assessment of fatigability of the VMO and VML.
Correlation between the clinical phonoaudiological assessment and electromyographic activity of the masseter muscle
Biasotto, Daiana Cristina;Biasotto-Gonzalez, Daniela Ap.;Panhoca, Ivone;
Journal of Applied Oral Science , 2005, DOI: 10.1590/S1678-77572005000400020
Abstract: objective: the objective of this paper was to evaluate the specificity of masseter muscle palpation when compared to its electromyographic activity. materials and methods: twenty-one young female adults, aged between 17 and 25, participated in this research. the speech therapy evaluation data were obtained by two speech therapists through masseter muscle palpation during isometric contraction, and the electromyographic exam was achieved by using bipolar superficial electrodes, positioned on the masseter muscle. the volunteers were instructed to chew the parafilm m? material bilaterally and simultaneously. the capture of the electromiographic signals occurred during masseter muscle isometric contractions. the electrical activity study of the masticatory muscle was analyzed through the root mean square value during its isotonic contraction. statistical analysis: all data were then submitted to kappa statistical analysis. results: the results of this study have shown a low correlation between palpation and electromyography (25%), as well as between evaluators (40%). conclusion: according to the findings of the present study, it could be observed that the correlation between masseter muscle palpation and its electromyographic activity was very low, which allows to conclude that muscular palpation cannot effectively replace the eletromyographical exam, but complement it instead.
EFFECTS OF MAXIMUM ISOMETRIC CONTRACTION ON EXPLOSIVE POWER OF LOWER LIMBS (JUMP PERFORMANCE)  [PDF]
Erol Kova?evi?,Armen Klino,Fuad Babaji?,Asim Bradi?
Sport Scientific And Practical Aspects , 2010,
Abstract: The aim of the research was to determine acute effects of maximal isometric contraction on explosive power of lower limbs (jump performance). Nine elite senior tennis players were taken as sample examinees for this research. Tennis players from this group had not had any severe injuries of trunk and lower limbs in the last six months. To assess explosive power, this research used variables for assessment of vertical and horizontal component of explosive power (high jump and long jump). Maximum isometric concentric contraction was used in a semi-squat exercise as an operator for stimulation of post-activation potentiation. There is a statistically significant difference with control variable of a vertical jump between a pre-activation and a post-activation attempt after time period of 60 and 90 seconds. With other control variable - horizontal jump - there is no statistically significant difference between a pre-activation and a post-activation jump.
Survey of Charactristic of Frequency Spectrum in Electromyographic Signal in Different Lengths of Abd. Policis Brevis Muscle in Isometric and Dynamic Contractions.
GR Olyaei,MR Hadian,S Talebian,H Bagheri
Modern Rehabilitation , 2007,
Abstract: Background and Aim: In this study, we investigated : 1) The effect of diferent lengths of Abd. policis brevis muscle on variations EMG frequency spectrum. 2) The effect of muscle contractions on frequency spectrum and 3) The effect of different lengths of muscle on local muscle fatigue.Material and Method: 20 normal subjects participated in this study. (with range of 20 - 34 years old). Each test carried out in four steps. Every person performed 3 minutes of isometric contraction in Abd. policis brevis muscle and EMG signals were saved for 5 seconds before and after the test. Then the same procedure was performed while individual did 6 minutes free dynamic contraction and 6 minutes high speed dynamic contraction and 6 minutes forceful dynamic contraction respectively.Results:This study showed that when the individual performed muscle contraction in short length, median and mean frequency increased (P = % 0) and fatigue test caused a decrease in frequency charactristics that was more in dynamic contractions in compare with isometric contraction (it was more obvious in forceful dynamic contraction). These parameters didnt change in different lengths (P = %9, P = %4, P= %3 for 0 - 45, 0 -90 and 45 - 90 degrees respectively). Conclusion and discussion:This study showed that different muscle lengths and muscle contractions affect on frequency spectrum and it also showed the effect of different muscle lengths and muscle contractions on local muscle fatigue.
Fatigue Effect on Low-Frequency Force Fluctuations and Muscular Oscillations during Rhythmic Isometric Contraction  [PDF]
Yen-Ting Lin, Chia-Hua Kuo, Ing-Shiou Hwang
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0085578
Abstract: Continuous force output containing numerous intermittent force pulses is not completely smooth. By characterizing force fluctuation properties and force pulse metrics, this study investigated adaptive changes in trajectory control, both force-generating capacity and force fluctuations, as fatigue progresses. Sixteen healthy subjects (20–24 years old) completed rhythmic isometric gripping with the non-dominant hand to volitional failure. Before and immediately following the fatigue intervention, we measured the gripping force to couple a 0.5 Hz sinusoidal target in the range of 50–100% maximal voluntary contraction. Dynamic force output was off-line decomposed into 1) an ideal force trajectory spectrally identical to the target rate; and 2) a force pulse trace pertaining to force fluctuations and error-correction attempts. The amplitude of ideal force trajectory regarding to force-generating capacity was more suppressed than that of the force pulse trace with increasing fatigue, which also shifted the force pulse trace to lower frequency bands. Multi-scale entropy analysis revealed that the complexity of the force pulse trace at high time scales increased with fatigue, contrary to the decrease in complexity of the force pulse trace at low time scales. Statistical properties of individual force pulses in the spatial and temporal domains varied with muscular fatigue, concurrent with marked suppression of gamma muscular oscillations (40–60 Hz) in the post-fatigue test. In conclusion, this study first reveals that muscular fatigue impairs the amplitude modulation of force pattern generation more than it affects the amplitude responsiveness of fine-tuning a force trajectory. Besides, motor fatigue results disadvantageously in enhancement of motor noises, simplification of short-term force-tuning strategy, and slow responsiveness to force errors, pertaining to dimensional changes in force fluctuations, scaling properties of force pulse, and muscular oscillation.
Maximum Voluntary Isometric Contraction produced in three static lifting styles
Sarrafzadeh J,Ebrahimi Takamjani A,Khosravi A,Haery F
Tehran University Medical Journal , 2007,
Abstract: Background: There is considerable professional debate over which technique is the best for lifting. The aim of this study is to compare three static lifting styles, the stoop, semi-squat and arm lift, using maximum isometric voluntary contraction (MIVC) as one indicator for recommending a lifting style. Methods: Thirty healthy women (mean age: 22.37 years) participated in this quasi-experimental study. They performed the tests in static postures by standing on the platform of the Lift TrackTM and pulling the dynamometer of the instrument with maximum effort in three lifting styles: the stoop, semi-squat and arm lift. The subjects warmed-up by practicing the lifts first. The mean MIVC from the two other sets of lifts were used for statistical analysis by repeated measurements and SPSS (ver.10) software. Results: There were significant differences between the MIVC of the three lifting styles in this study. The largest MIVC was for the semi-squat lift and was the least was for the arm lift (p<0.001). The MIVC of the stoop lift was larger than that of the arm lift (p<0.001). Conclusion: The largest MIVC for the semi-squat lift suggests that this style is useful for lifting objects from the floor. The differences in biomechanical and muscle pattern activity changes could explain these results. It seems that activation of the quadriceps muscles in the semi-squat lift was a main factor for producing more MIVC, so when this style is recommended for lifting, attention to the power of the quadriceps is important.
Electromyographic activity assessment of individuals with and without temporomandibular disorder symptoms
Tosato, Juliana de Paiva;Caria, Paulo Henrique Ferreira;
Journal of Applied Oral Science , 2007, DOI: 10.1590/S1678-77572007000200016
Abstract: introduction: temporomandibular disorders (tmd) present several signs and symptoms that hinder their correct diagnosis, which is imperative on the elaboration of a treatment plan. over the past years, several studies have been conducted to characterize and classify tmd to better understand these disorders. therefore, the purpose of this study was to assess the electromyographic behavior of the masseter and temporal muscles in individuals with and without myogenic, arthrogenic and mixed tmd. method: forty volunteers of both genders responded to the research diagnostic criteria for temporomandibular disorders (rdc-tmd) questionnaire, were submitted to clinical exam and underwent bilateral electromyographic exam of the masseter and temporal muscles. results: no statistically significant difference (p>0.05) was observed during the assessment of isotonic contraction. regarding isometric contraction, pairing between the mixed tmd group and the asymptomatic subjects did not present significant difference (p>0.05). comparison between the myogenic and arthrogenic tmd groups and the asymptomatic group showed statistically significant difference (p<0.05). the findings of the present study demonstrated alteration on the muscle contraction pattern of tmd individuals compared to that of asymptomatic patients.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.