Concentric Muscle Actions Research Articles

Intersession reliability of the interpolated twitch technique applied during isometric, concentric, and eccentric actions of the human knee extensor muscles.

Although it has been shown that voluntary activation (%VA) of the knee extensors during isometric contractions can be reliably assessed with the interpolated twitch technique, little is known about the reliability of %VA during concentric and eccentric muscle actions. Therefore, relative and absolute intersession reliability of quadriceps muscle's %VA during different contraction modes was determined. After a familiarization session, 21 participants (17 males, 25 ± 2 yrs) completed two testing sessions. Paired supramaximal electrical stimuli were administered to the femoral nerve during isometric, concentric, eccentric MVCs, and at rest to assess %VA (stimuli were applied at 70° knee flexion). Data indicate that %VA of the knee extensors can be reliably measured during isometric [intraclass correlation coefficient (ICC) = 0.89, coefficient of variation (CV) = 4.1%], concentric (ICC = 0.87, CV = 6.6%), and eccentric muscle actions (ICC = 0.86, CV = 7.0%). Muscle Nerve 56: 324-327, 2017.

Pisa syndrome in Parkinson's disease: electromyographic quantification of paraspinal and non-paraspinal muscle activity.

Patients with Parkinson's disease (PD) and Pisa syndrome (PS) may present tonic dystonic or compensatory (i.e. acting against gravity) hyperactivity in the paraspinal and non-paraspinal muscles. Electromyographic (EMG) activity was measured in nine patients with PD and PS, three with PD without PS, and five healthy controls. Fine-wire intramuscular electrodes were inserted bilaterally into the iliocostalis lumborum (ICL), iliocostalis thoracis (ICT), gluteus medius (GM), and external oblique (EO) muscles. The root mean square (RMS) of the EMG signal was calculated and normalized for each muscle. In stance condition, side-to-side muscle activity comparisons showed a higher RMS only for the contralateral ICL in PD patients with PS (p=0.028). Moreover, with increasing degrees of lateral flexion, the activity of the EO and the ICL muscles progressively increased and decreased, respectively. The present data suggest that contralateral paraspinal muscle activity plays a crucial compensatory role and can be dysfunctional in PD patients with PS.

Muscle- and Mode-Specific Responses of the Forearm Flexors to Fatiguing, Concentric Muscle Actions.

Background: Electromyographic (EMG) and mechanomyographic (MMG) studies of fatigue have generally utilized maximal isometric or dynamic muscle actions, but sport- and work-related activities involve predominately submaximal movements. Therefore, the purpose of the present investigation was to examine the torque, EMG, and MMG responses as a result of submaximal, concentric, isokinetic, forearm flexion muscle actions. Methods: Twelve men performed concentric peak torque (PT) and isometric PT trials before (pretest) and after (posttest) performing 50 submaximal (65% of concentric PT), concentric, isokinetic (60°·s−1), forearm flexion muscle actions. Surface EMG and MMG signals were simultaneously recorded from the biceps brachii and brachioradialis muscles. Results: The results of the present study indicated similar decreases during both the concentric PT and isometric PT measurements for torque, EMG mean power frequency (MPF), and MMG MPF following the fatiguing workbout, but no changes in EMG amplitude (AMP) or MMG AMP. Conclusions: These findings suggest that decreases in torque as a result of fatiguing, dynamic muscle actions may have been due to the effects of metabolic byproducts on excitation–contraction coupling as indicated by the decreases in EMG MPF and MMG MPF, but lack of changes in EMG AMP and MMG AMP from both the biceps brachii and brachioradialis muscles.

High-Speed Resistance Training in Older Women: The Role of Supervision

Older women participated in a 12-week high-speed resistance training program under two supervisor-to-subject ratio methods (i.e., high versus low supervision) to assess its effects on muscle strength, power, functional performance, and quality of life assessed before (T1) and after (T2) intervention. Women were divided into either the control group (CG, n = 15), high supervision group (HSG, n = 30), or low supervision group (LSG, n = 28). The training program included exercises requiring high-speed concentric muscle actions. No differences were observed among groups at T1. Between T1 and T2, the HSG showed a higher (p < .05) improvement in muscle strength (ES = 0.36-1.26), power (ES = 0.5-0.88), functional performance (ES = 0.52-0.78), and quality of life (ES = 0.44-0.82) compared with LSG and CG. High-speed resistance training under closer supervision is more effective for improving muscle strength, power, functional performance, and quality of life in older women.

Brain activation differences between muscle actions for strength and fatigue: A brief review.

BACKGROUND: Brain activation differences for strength and fatigue have recently been investigated due to advancements in brain-imaging methods.AIM: To review brain activation differences between concentric, eccentric and isometric muscle actions for strength and fatigue.METHODS: 12 studies were selected by accessing PubMed and Web of Knowledge databases.RESULTS: Collectively, the literature demonstrates that for strength the parietal and frontal lobes of the cortex that control movement preparation, planning and execution, and process feedback information are more activated during eccentric than concentric actions. In the supplementary motor area, event-related desynchronization is continued for both concentric and eccentric actions, but only present at the beginning and end of isometric actions. This indicates the CNS specifically controls each of these muscle actions. For fatigue, cortical activation is greater in the supplementary and premotor areas during isometric actions, but may be greater primarily in the central, occipital and parietal cortical areas for concentric and eccentric actions.INTERPRETATION:Muscular strength can be elicited with eccentric actions to more effectively activate control and memory of movement in the parietal and frontal lobes. Muscular fatigue can be elicited with isometric actions to selectively activate supplementary and premotor areas, or with concentric and eccentric actions for central, occipital and parietal cortical areas.

Reduced muscle activity during isokinetic contractions associated with external leg compression.

The potential mechanism of compression apparel remains unclear to date because of insufficient knowledge on the influence of compressive level on muscular responses. To explore the influence of external leg compression on (a) the muscle force and endurance of the quadriceps femoris and (b) the muscle activation patterns during prolonged muscle actions. Twelve male participants performed consecutive maximal concentric muscle actions of the quadriceps in compression garment (CG) and control condition (CON) at two angular velocities on the Contrex. The EMG amplitude and frequency of the rectus femoris (RF), vastus lateralis (VL), and vastus medialis were quantified during the concentric phase of the knee extension movement. There was no significant compression effect on muscle force and total work during knee extensions. Contrarily, the overall EMG amplitude was significantly lower in CG than in CON at 60 and 300°/s. Additionally, the EMG frequency of the RF and VL was significantly higher in CG than in CON at 60°/s. Increased external pressure is associated with changes in EMG time and frequency domain behavior. These effects can potentially relieve muscle fatigue and improve muscle endurance during long-term exercise.

Increased Extracellular Matrix Degradation Following Eccentric Versus Concentric Muscle Actions in Humans

Increased Extracellular Matrix Degradation Following Eccentric Versus Concentric Muscle Actions in Humans

Evaluación isocinética de músculos flexores y extensores en jugadores de fútbol profesional antes de iniciar la fase de pretemporada

ObjectiveAssessment the concentric isokinetic performance of the flexor and extensor muscles of the joints of the knees legs dominant and not dominant prior to the commencement of a new soccer season. Material and methodsA total of 30 high-performance professional soccer players aged between 18 and 33 years, and 86% had the right leg as dominant (kick) and the remaining 14% left leg. All underwent isokinetic testing in angular velocity of 60°/s in the dynamometer using concentric muscle action. ResultsThe following results were obtained: peak torque in angular velocity of 60°/s of the flexors of the dominant leg (DL) was higher than 3% to the non-dominant leg (NDL), but this difference was not significant. Unlike the torque pique the extensor muscles of the NDL was 9% higher (P = 0.06) than DL. The percentage of flexors/extensors ratio for peak torque NDL was abnormal and below 7% (P = 0.09) than DL. ConclusionThese results indicate the need for prior assessment of the flexor and extensor muscles of the knee as a preventive conduct before starting the training program of high performance soccer players.

Differential Effects of Unilateral Concentric Vs. Eccentric Exercise on the Dominant and Nondominant Forearm Flexors.

The purpose of this study was to compare the electromyographic (EMG) intensity patterns after unilateral concentric vs. eccentric exercise in the dominant (DOM) and nondominant (NONDOM) forearm flexors. Twenty-six men (mean ± SD: age, 24.0 ± 3.7 years) volunteered to perform a maximal isometric muscle action of the DOM and NONDOM forearm flexors before (PRE) and immediately after (POST) a series of maximal concentric isokinetic or maximal eccentric isokinetic muscle actions of the DOM forearm flexors. The concentric isokinetic and eccentric isokinetic muscle actions were performed on separate days that were randomly ordered. However, in both cases, the subjects performed 6 sets of 10 maximal muscle actions. A bipolar surface EMG signal was detected from the biceps brachii of the DOM and NONDOM limbs during the PRE and POST isometric muscle actions. The signals were then analyzed with a wavelet analysis, and the resulting intensity patterns were classified with a paired pattern classification procedure. The results indicated that the EMG intensity patterns could be correctly classified into their respective PRE vs. POST categories with an accuracy rate that was significantly better than random (20 of 26 patterns = 76.9% accuracy) but only for the DOM limb following the eccentric muscle actions. All other classifications were not significantly better than random. These findings indicated that eccentric exercise had a significant influence on the muscle activation pattern for the forearm flexors. It is possible that the muscle damage resulting from eccentric exercise affects muscle spindle or golgi tendon organ or both activity, thereby altering the muscle activation pattern.

The effects of velocity on peak torque and neuromuscular responses during eccentric muscle actions

BACKGROUND: Previous investigations have examined the torque and neuromuscular responses to maximal concentric and isometric muscle actions. The literature, however, has paid less attention to the effects of performing maximal eccentric muscle actions. Furthermore, the available information in this regard is contradictory. OBJECTIVE: The purpose of the present investigation was to examine eccentric, isokinetic peak moment (PMe), electromyographic (EMG) amplitude (AMP), EMG mean power frequency (MPF), mechanomyographic (MMG) AMP, and MMG MPF patterns of responses to repeated, maximal, eccentric muscle actions at 60, 120, and 180°/s. METHODS: Twelve resistance-trained men visited the laboratory on three occasions (separated by ≥ 72 h) and performed 30 repeated, maximal, eccentric muscle actions of the dominant leg extensors on an isokinetic dynamometer at randomly ordered velocities of 60, 120, and 180°/s. RESULTS: There were no changes (p > 0.05) across the 30 repeated, eccentric muscle actions for PMe, MMG AMP, and EMG MPF for any of the velocities. There were, however, increases in EMG AMP and decreases in MMG MPF for each velocity. CONCLUSIONS: The decrease in MMG MPF, which reflects the global firing rate of the activated motor units, in conjunction with the lack of change in MMG AMP, which reflects motor unit recruitment, suggested that the increase in EMG AMP was due to motor unit synchronization.

Changes in the activity of trunk and hip extensor muscles during bridge exercises with variations in unilateral knee joint angle.

[Purpose] This study compared abdominal and hip extensor muscle activity during a bridge exercise with various knee joint angles. [Subjects and Methods] Twenty-two healthy male subjects performed a bridge exercise in which the knee joint angle was altered. While subjects performed the bridge exercise, external oblique, internal oblique, gluteus maximus, and semitendinosus muscle activity was measured using electromyography. [Results] The bilateral external and internal oblique muscle activity was significantly higher at 0° knee flexion compared to 120°, 90°, and 60°. The bilateral gluteus maximus muscle activity was significantly different at 0° of knee flexion compared to 120°, 90°, and 60°. The ipsilateral semitendinosus muscle activity was significantly increased at 90° and 60° of knee flexion compared to 120°, and significantly decreased at 0° knee flexion compared with 120°, 90°, and 60°. The contralateral semitendinosus muscle activity was significantly higher at 60° of knee flexion than at 120°, and significantly higher at 0° of knee flexion than at 120°, 90°, and 60°. [Conclusion] Bridge exercises performed with knee flexion less than 90° may be used to train the ipsilateral semitendinosus. Furthermore, bridge exercise performed with one leg may be used to train abdominal and hip extensor muscles.

Characteristics of lower limb muscle activity during upper limb elevation in badminton players.

[Purpose] To clarify the characteristics of postural control in badminton players by examining their lower-limb muscle activity during upper-limb elevation. [Subjects and Methods] Fourteen badminton players and 14 non-players were studied. The subjects were instructed to perform an upper-limb elevation task in order to measure the activities of the biceps femoris and biceps brachii. [Results] When elevating the dominant hand, the mean biceps femoris integrated electromyogram showed markedly higher values in the player group, for the contralateral compared with the ipsilateral leg. Similarly, when elevating the dominant hand, the difference in the maximum integrated electromyogram response time between the ipsilateral and contralateral legs was significantly smaller in the players compared with non-players. [Conclusion] It may be possible to reduce the time needed to elevate the dominant hand by shifting lower-limb activity from the ipsilateral to the contralateral leg more quickly, while increasing the rate of rise in contralateral leg muscle activity.

Influence of Hamstring Fatigue on the Estimated Percentage of Fast-Twitch Muscle Fibers for the Vastus Lateralis.

A previous study has demonstrated the ability to roughly estimate the percentage of fast-twitch muscle fibers for the vastus lateralis through the analysis of peak torque values during fatiguing isokinetic testing. We examined whether use of the hamstrings influenced peak torque and electromyographic (EMG) responses for the quadriceps during fatiguing isokinetic muscle actions. On 2 separate occasions, 21 men (mean age = 23 years) performed 50 repeated, maximal concentric isokinetic muscle actions of the left leg extensors at a velocity of 180°·s. For 1 trial, the subjects maximally flexed the knee joint after each full extension to bring the dynamometer's lever arm back to the starting position. For the other trial, the subjects relaxed after each maximal extension and an investigator assisted in returning the lever arm. Surface EMG signals were detected from the vastus lateralis and biceps femoris throughout testing. Dependent variables that assessed the decline in peak torque and EMG mean frequency for the vastus lateralis were examined using dependent samples t-tests, effect size statistics, and the number of subjects who exceeded the minimal difference needed to be considered real. Our results showed small mean differences between the trials (Cohen's d ≤0.136). For the estimated percentage of fast-twitch fibers, none of the subjects showed a difference between trials that we considered meaningful. The mean estimated percentages of fast-twitch fibers were 61.6 and 60.1. Collectively, use of the hamstrings during fatiguing isokinetic testing of the quadriceps had little influence on peak torque and EMG.

Effects of age and muscle action type on acute strength and power recovery following fatigue of the leg flexors.

Short-term strength and power recovery patterns following fatigue have received little research attention, particularly as they pertain to age-specific responses, and the leg flexors (i.e., hamstrings) muscle group. Thus, research is warranted addressing these issues because both age-related alterations in the neuromuscular system and mode of muscle action (e.g., eccentric, concentric, isometric) may differentially influence recovery responses from fatigue. The aim of this study was to investigate the strength and power recovery responses for eccentric, concentric, and isometric muscle actions of the leg flexors in young and older men following an isometric, intermittent fatigue-inducing protocol. Nineteen young (age = 25 ± 3 years) and nineteen older (71 ± 4) men performed maximal voluntary contractions (MVCs) for eccentric, concentric, and isometric muscle actions followed by a fatigue protocol of intermittent (0.6 duty cycle) isometric contractions of the leg flexors at 60% of isometric MVC. MVCs of each muscle action were performed at 0, 7, 15, and 30 min following fatigue. Peak torque (PT) and mean power values were calculated from the MVCs and the eccentric/concentric ratio (ECR) was derived. For PT and mean power, young men showed incomplete recovery at all time phases, whereas the older men had recovered by 7 min. Eccentric and isometric muscle actions showed incomplete recovery at all time phases, but concentric recovered by 7 min, independent of age. The ECR was depressed for up to 30 min following fatigue. More rapid and pronounced recovery in older men and concentric contractions may be related to physiological differences specific to aging and muscle action motor unit patterns. Individuals and clinicians may use these time course responses as a guide for recovery following activity-induced fatigue.

An Examination of Fatigue Index and Velocity-Related Force Loss for the Forearm Flexors.

The purpose of this study was to examine the relationship between the fatigue index from an isokinetic fatigue test and the velocity-related decrease in peak torque for the forearm flexors. After a familiarization session, 13 habitually active males (mean ± SD, age = 23.8 ± 3.1 years) reported to the laboratory to perform either 50 repeated, maximal, concentric isokinetic muscle actions of the dominant forearm flexors at a velocity of 180°·s(-1) or 6 separate sets of 3 maximal concentric isokinetic muscle actions at randomly ordered velocities of 30, 90, 150, 270, and 330°·s(-1). The correlation between the relative percent declines in peak torque during the 2 isokinetic tests was then examined. The results indicated an inverse relationship (r = -0.75, p < 0.01) between these 2 variables. That is, the subjects who demonstrated the greatest fatigue indexes (i.e., those who were most susceptible to fatigue) were generally the most resistant to a velocity-related torque loss. These findings support the possibility of using a multiple-velocity isokinetic test to estimate fiber type composition, just as fatigue-based tests have been used.

Acute effects of two different stretching techniques on isokinetic strength and power

ObjectivesTo examine and compare the acute effects of short duration static and dynamic lower-limb stretching routines on the knee flexor and extensor peak torque and mean power during maximal concentric and eccentric muscle actions. MethodForty-nine active adults completed the following intervention protocols on separate days: non-stretching, static stretching and dynamic stretching. After the stretching or control intervention, concentric and eccentric isokinetic peak torque and mean power of the leg extensors and flexors were measured in prone position. Measures were compared via a fully-within-groups factorial ANOVA. ResultsNeither static nor dynamic stretching has influence on isokinetic peak torque and mean power when they were compared with the control condition. Paired comparison also showed that the isokinetic strength and power results reported by dynamic stretching session were slightly higher than those found during the static stretching session. ConclusionsShort pre-exercise static and dynamic lower-limb stretching routines did not elicit stretching-induce reductions or improvements in knee flexor and knee extensor isokinetic concentric and eccentric strength. In addition, the findings of the current study support the claim that dynamic stretching may be preferable to static stretching as part of a warm-up designed to prepare for physical activity.

Acute effects of Kinesio taping on muscle strength and fatigue in the forearm of tennis players.

To explore the immediate effects of Kinesio taping applied over the wrist extensors and flexors on muscle strength and endurance during isometric and isokinetic muscle actions. The study had a single-blinded, placebo control, and randomized design. Fourteen trained male volunteers were required to complete 5s isometric maximal voluntary contractions and 50 consecutive maximal concentric wrist extension and flexion repetitions at each of two angular speeds (60°/s and 210°/s) in three taping conditions: Kinesio taping (KT), placebo taping (PT), and no taping (NT). KT did not improve peak moment, peak power, average power, and total work for wrist extensors and flexors in the isometric and isokinetic contractions. However, KT showed a 13% decrease in work fatigue of the wrist flexors compare to NT (p=0.014) at 60°/s. Furthermore, a 20% decrease was also observed in the rate of decline of moment (k) of the wrist flexors in KT compared to NT (p=0.007), and the k in PT was also significantly lower in magnitude compared to NT (p=0.035). Moreover, there was also a trend in terms of magnitudes for kKT<kPT<kNT in the wrist flexors at 210°/s. Kinesio taping may not be able to modulate strength production in healthy athletes immediately, but does have a significant positive effect on reducing muscle fatigue during repeated concentric muscle actions. Additionally, the potential beneficial effects of placebo taping on muscle endurance should not be ignored either.

Relative differences in strength and power from slow to fast isokinetic velocities may reflect dynapenia.

We compared absolute and normalized values for peak torque (PT), mean power (MP), rate of velocity development, and electromyography (EMG) amplitude during maximal isometric and concentric isokinetic leg extension muscle actions, as well as the %decrease in PT and %increase in MP from 1.05 to 3.14 rad·s(-1) in younger versus older men. Measurements were performed twice for reliability. Isokinetic measurements were normalized to the isometric muscle actions. Absolute isometric PT, isokinetic PT and MP, and EMG amplitudes at 1.05 and 3.14 rad·s(-1) were greater in the younger men, although normalizing to isometric PT eliminated the age differences. The older men exhibited greater %decrease in PT (37.2% vs. 31.3%) and lower %increase in MP (87.6% vs. 126.4%) regardless of normalization. Normalization eliminated absolute differences in isokinetic strength and power, but the relative differences from slow to fast velocities may reflect dynapenia characterized by age-related decreases in fast-twitch fiber function.

Motor cortex tDCS does not improve strength performance in healthy subjects

The influence of transcranial direct current stimulation (tDCS) upon maximal strength performance in exercises recruiting large muscle mass has not been established in healthy populations. The purpose of this study was to investigate whether anodal tDCS was able to increase the performance during maximal strength exercise (MSEX) in healthy subjects. Fourteen volunteers (age: 26 ± 4 yrs) performed two MSEX after anodal or sham tDCS (2mA; 20min prior MSEX), involving knee extensors and flexors in concentric isokinetic muscle actions of the dominant limb (3 sets of 10 repetitions). The electrical muscle activity (sEMG) of four recruited muscles was recorded during MSEX. Anodal tDCS was not able to improve force production (i.e., total work and peak torque), fatigue resistance, or electromyographic activity during MSEX when compared to sham condition. In conclusion, anodal tDCS applied upon the contralateral motor cortex was not capable of increasing the strength performance of knee extensors and flexors in young healthy subjects.

The Effects of Heat and Active Stretch on Subjects Performing the Wingate Power Test

Pre-participation static stretching (SS) along with heat application to increase the temperature of the tissues is performed to improve joint range of motion (ROM); presumably by increasing the elasticity of connective tissue during eccentric and concentric muscle actions that are components of dynamic exercise. PURPOSE: To compare the effect of the following conditions ): no static stretching (nSS), heat no static stretch (HnSS), Heat and static stretch (HSS), and static stretch (SS) on indices of the Wingate Power Test (WPT); peak power (PP), mean power (MP), total work (TW), total time to peak power (TTPP). METHODS: 12 male (age 20.2 ± 1.2 yr, ht 181 ± 5.3 cm, wt 73.1 ± 7.9 kg) intercollegiate soccer players were randomly assigned to 4 treatment conditions using a counterbalanced order for nSS, HnSS, HSS, and SS. 7 ROM exercises (plantar/dorsi flexion, Achilles tendon stretch, hamstring/quadriceps stretch, hip abductor, and gluteal stretch) were performed by subjects for a duration of 7 min on dry land or immersed up to the level of the umbilicus in a temperature control (T 43.3 ± 1.6 °C) water bath. WPT was performed within 4 min of condition. A 1-way ANOVA for repeated measures set at the p< .05 level and a post hoc analysis was used to determine contrasting conditions. RESULTS: MP, passive heat (HnSS) or combined with exercise (HSS) were significantly different than the no stretch (nSS) condition (p<.05). TW was significantly lower in the HSS and SS trial compared to the nSS trial. (P< .05) While not statistically significant, the nSS condition compared to all others achieved the lowest TTPP. CONCLUSION: Prior to performance, indices of muscular power and work output are adversely affected by increasing the distensibility of muscle tissue by active ROM exercise and/or passive heat.Table: No title available.