Article

The effects of eccentric velocity on activation of elbow flexors: Evaluation by magnetic resonance imaging

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

To compare magnetic resonance imaging (MRI) signal intensity changes in the primary elbow flexors during two isotonic exercise protocols varying in eccentric velocity and the ratio of eccentric to concentric activity. Twelve men performed two exercise protocols. The right and left arms were randomly assigned to one of two protocols that had the same workload (60% 1RM) and same total time of exercise (144 s) but differed in the velocity and ratio of eccentric to concentric activity (1:1 and 5:1 for the fast and slow protocols, respectively). MRI signal intensity changes were quantified pre- and post-exercises using an inversion recovery sequence with a 1.5T MRI system (TR = 2500 ms, TE = 90 ms, TI = 140 ms). Percent change in MRI signal intensity, rate of perceived exertion (RPE), and delayed onset muscle soreness (DOMS) were recorded and analyzed. The biceps brachii was found to be preferentially recruited during the fast protocol compared with the brachialis, whereas the brachialis was found to be preferentially recruited during the slow protocol (P < 0.05). The fast exercise protocol was perceived as being more strenuous (RPE = 8.3 +/- 2.1) than the slow (RPE = 5.4 +/- 1.5, P < 0.05) and produced DOMS in 58% of the tested subjects. These results suggest that agonists respond to various loading conditions nonhomogeneously. These findings may have implications with respect to exercise prescriptions for specific muscles.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Já quando as contrações excêntricas são priorizadas (com maior tempo de execução), menor IEP é verificado neste tipo de contração comparado à contração concêntrica (43) . Neste estudo (43) foi realizado um protocolo em que as fases concêntricas e excêntricas apresentaram a mesma duração (dois segundos para cada fase) e outro protocolo em que a duração da fase excêntrica era 5 vezes maior (2 segundos na fase concêntrica e 10 segundos na fase excêntrica). ...
... Já quando as contrações excêntricas são priorizadas (com maior tempo de execução), menor IEP é verificado neste tipo de contração comparado à contração concêntrica (43) . Neste estudo (43) foi realizado um protocolo em que as fases concêntricas e excêntricas apresentaram a mesma duração (dois segundos para cada fase) e outro protocolo em que a duração da fase excêntrica era 5 vezes maior (2 segundos na fase concêntrica e 10 segundos na fase excêntrica). Foram utilizadas mesmas cargas (60% de 1RM), número de série (3) e tempo total de duração (144 segundos), variando apenas na quantidade de repetições (12 vs. 4). ...
... Desta forma, podemos verificar que nas contrações excêntricas, a diferenciação das cargas utilizadas também é verificada através da PE, porém com maior dificuldade, o que poderia ser justificado possivelmente, pelo diferente padrão de recrutamento muscular neste tipo de contração (41) . Ainda, maior PE é apresentada nas contrações concêntricas, possivelmente por maior ativação muscular e maior produção de lactato neste tipo de contração (43) . ...
Article
Full-text available
A percepção de esforço (PE) é definida por Robertson e Noble(1) como sendo a intensidade subjetiva de esforço, tensão, desconforto e/ou fadiga que são experimentados durante os exercícios físicos aeróbicos e de força. Sua aplicabilidade é bastante grande, tendo como ponto principal a mensuração do esforço físico. Um mesmo padrão neurofisiológico, através da integração dos comandos feedforward-feedback poderia explicar a PE(2). Diferentes escalas (RPE, CR10, VAS, Omni) foram elaboradas e têm sido aplicadas em estudos que investigaram diferentes exercícios e populações, apresentando fortes correlações com importantes variáveis fisiológicas. Inúmeros estudos têm sido desenvolvidos, principalmente na última década, buscando verificar o comportamento da PE em relação às diferentes variáveis do treinamento de força (TF). Em relação à variável carga, maiores cargas produzem maiores PE, mesmo quando volumes ou o número de repetições diferenciados é utilizado, apresentando altas e significativas correlações entre a PE e diferentes cargas. Esforços máximos (repetições máximas) causam uma similar PE, independente do número de repetições. Ainda, quanto maior a carga utilizada, menor a variabilidade das respostas da PE entre os sujeitos. A PE aumenta conforme o crescimento do número de repetições realizadas na série, para uma mesma carga, parecendo não existir diferenças na PE entre homens e mulheres. Outras variáveis do TF ainda merecem ser investigadas, não sendo possível apresentar dados conclusivos sobre o comportamento da PE quando estas variáveis são avaliadas. Contudo, os estudos apresentados até então têm indicado que as contrações excêntricas e maiores velocidades de execução indicam uma menor PE, enquanto que a ordem, a quantidade e o tipo de exercícios indicam ter pouca ou nenhuma influência. Quanto ao nível de treinamento dos sujeitos, mais estudos são necessários, sendo contraditórios os dados apresentados até então pela literatura. Possivelmente, a grande dificuldade destes estudos não está na aplicação da PE em si, mas sim, no isolamento de cada uma das variáveis do TF. Seguindo-se os protocolos similares aos utilizados nos estudos, respeitando o controle das variáveis do TF, parece ser possível a utilização da PE na modulação da intensidade no TF.
... However, in a study by Nogueira et al. [15], training (40-60% RM; 3 sets x 8 reps; twice per week; 10 weeks) with medium slow eccentric and fast concentric movement (3/0/1/0) produced greater increases in muscle thickness, compared to tempo with equal durations of eccentric and concentric phases (3/0/3/0). Longer eccentric duration combined with fast concentric (4/0/1/0) resulted in significantly higher hypertrophy and strength gains, compared to faster (1/0/1/0), when repetitions were performed until muscle failure (3 sets x 8 RM; twice per week; 12 weeks) [16]. However, when faster (2/0/2/0) and slower (4/0/2/0) contractions were identical by total work [17,18] or TUT [19] the effects were equal. ...
... Recent studies detected muscle failure as the most potent stimulus for hypertrophy, regardless of the load size [1,20,21]. From such a perspective, Pereira et al. [16] showed that longer durations of the eccentric phase appear to be superior for gaining muscle mass and developing strength in biceps brachii muscle (BB) in well-trained men. ...
... In the present study, both groups showed a significant increase in BB thickness from pre-test, whereas ANCOVA revealed no differences between groups. In contrast, Pereira et al. [16] reported that a slower tempo (4/0/1/0) caused greater hypertrophy than faster al. [34] reported that rapid eccentric contractions led to more efficient ...
Article
Full-text available
The aim of the study was to compare the effects of two different training protocols, which differ in the duration of the eccentric phase, on the one-repetition maximum (1RM), thickness and contractile properties of elbow flexors. Twenty untrained college students were randomly divided into two experimental groups, based on the training tempo: FEG (Faster Eccentric Group: 1/0/1/0) and SEG (Slower Eccentric Group: 4/0/1/0). Training intervention was a biceps bending exercise, conducted twice a week for 7 weeks. The intensity (60–70% RM), sets (3–4) and rest intervals (120 s) were held constant, while repetitions were performed until it was not possible to maintain a set duration. In the initial and final measurements, 1RM, muscle thickness and tensiomyography parameters – contraction time (Tc) and radial deformation (Dm) – were evaluated. An ANCOVA model (using baseline outcomes as covariates) was applied to determine between-group differences at post-test, while Pearson’s product-moment correlation coefficient was used to investigate the relationship between absolute changes in muscle thickness and Dm. Muscle strength increase was greater for SEG than for FEG (6.0 ± 1.76 vs. 3.30 ± 2.26 kg, p < 0.01). In both groups muscle thickness increased equally (FEG: 3.24 ± 2.01 vs. SEG: 3.57 ± 1.17 mm, p < 0.01), while an overall reduction in Dm was observed (FEG: 1.99 ± 1.20 vs. SEG: 2.26 ± 1.03 mm, p < 0.01). Values of Tc remained unchanged. A significant negative relationship was observed between changes in muscle thickness and Dm (r = -0.763, Adj.R² = 0.560, p < 0.01). These results indicate that the duration of the eccentric phase has no effect on muscle hypertrophy in untrained subjects, but that slower eccentric movement significantly increases 1RM.
... Já quando as contrações excêntricas são priorizadas (com maior tempo de execução), menor IEP é verificado neste tipo de contração comparado à contração concêntrica (43) . Neste estudo (43) foi realizado um protocolo em que as fases concêntricas e excêntricas apresentaram a mesma duração (dois segundos para cada fase) e outro protocolo em que a duração da fase excêntrica era 5 vezes maior (2 segundos na fase concêntrica e 10 segundos na fase excêntrica). ...
... Já quando as contrações excêntricas são priorizadas (com maior tempo de execução), menor IEP é verificado neste tipo de contração comparado à contração concêntrica (43) . Neste estudo (43) foi realizado um protocolo em que as fases concêntricas e excêntricas apresentaram a mesma duração (dois segundos para cada fase) e outro protocolo em que a duração da fase excêntrica era 5 vezes maior (2 segundos na fase concêntrica e 10 segundos na fase excêntrica). Foram utilizadas mesmas cargas (60% de 1RM), número de série (3) e tempo total de duração (144 segundos), variando apenas na quantidade de repetições (12 vs. 4). ...
... Desta forma, podemos verificar que nas contrações excêntricas, a diferenciação das cargas utilizadas também é verificada através da PE, porém com maior dificuldade, o que poderia ser justificado possivelmente, pelo diferente padrão de recrutamento muscular neste tipo de contração (41) . Ainda, maior PE é apresentada nas contrações concêntricas, possivelmente por maior ativação muscular e maior produção de lactato neste tipo de contração (43) . ...
Article
Perceived exertion (PE) is defined by Robertson and Noble(1) as the subjective intensity of effort, strain, discomfort and/or fatigue experienced during both aerobic and resistance exercise. Its application is fairly wide and has as main focus the measurement of physical exertion. The same neuro-physiological pattern, through the integration of feedforward-feedback commands could explain PE(2). Different scales (RPE, CR10, VAS, OMNI) were developed and have been applied in studies that investigated different exercises and populations, showing high correlations with important physiological variables. Several studies have been developed, especially in the last decade, in order to verify the PE behavior concerning different variables of the strength training (ST). Regarding the load variable, the results showed that higher loads produce greater PE, even when different volumes or number of repetitions are used, with high and significant correlations between PE and different loads. Maximum efforts (repetition maximum) cause a similar PE, regardless of the number of repetitions. Moreover, the higher the load used, the lower the responses variability of the PE among subjects. PE increases according to the number of repetitions performed in the sets for the same load, with no differences in PE being shown between men and women. Further ST variables must be investigated and it is not possible to provide conclusive data on the PE performance when these variables are evaluated. However, the studies presented until the present moment, have indicated that eccentric contractions and higher performance speeds indicate lower PE, while order, amount and type of exercises show little or no influence. Further studies should be conducted about the trainability status of the subjects, and contradictory data were found so far by the literature. Possibly, the major difficulty of these studies is not the PE application per se, but the isolation of each ST variable. As long as protocols similar to those used in the studies, respecting the control of the ST variables are used, the use of PE in modulating the intensity in ST seems possible.
... This finding is in accordance with the larger edema (assessed using T 2 -MRI measurements) observed in rectus femoris than vastus lateralis and vastus medialis after repeated eccentric contractions (Prior et al. 2001;Paulsen et al. 2010). Similar results were reported for the biceps brachii that exhibited a higher T 2 signal intensity change after a fast eccentric exercise than the brachialis (Kulig et al. 2001). This finding is likely explained by the predominance of fast twitch fibers in these muscles (rectus femoris and biceps brachii) (Johnson et al. 1973). ...
... This finding is likely explained by the predominance of fast twitch fibers in these muscles (rectus femoris and biceps brachii) (Johnson et al. 1973). Indeed, several studies in human (e.g., Chapman et al. 2013;Kulig et al. 2001;Paddon-Jones et al. 2005) suggest that type II fibers are more prone to damage, although none of them has demonstrated this relationship directly. In addition, other works showed that the rectus femoris experienced greater damage due to the longer muscle lengthening distance during seated eccentric knee extension compared to daily life multi-joints tasks (Takahashi et al. 1994;Prior et al. 2001). ...
Article
Full-text available
PurposeThis study aimed to determine whether an increase in muscle shear modulus measured 30 min after eccentric exercise (30 min) reflects the magnitude of force deficit measured 48-h post-exercise (48 H). MethodsA total of 53 healthy participants were distributed in five groups. Four groups performed either repeated eccentric elbow flexions or knee extensions at either a low or high load. A fifth group performed repeated concentric elbow flexions (control load). ResultsA significant decreased peak torque was found for elbow flexors and knee extensors 48 h after the eccentric exercises (all P values < 0.001). A significant increase in shear modulus was found at 30 min for the elbow flexors for low (+70.5 ± 44.3%, P < 0.001) and high load (+153.9 ± 192.4%, P < 0.001). Similarly, the shear modulus of knee extensors increased for low (+26.7 ± 19.1%, P < 0.001) and high load (+79.4 ± 67.1%, P < 0.001). The relative increase in shear modulus measured at 30 min was significantly correlated to the relative decrease in peak torque measured at 48 H for both elbow flexors (r = −0.80) and knee extensors (r = −0.82). A further analysis suggested that biceps brachii and rectus femoris were more affected by muscle damage than their synergists. Conclusion This study shows that an increase in muscle shear modulus measured 30 min after a damaging exercise reflects the decrease in peak torque measured at 48 H. Shear modulus may therefore, provide a useful tool for coaches and clinicians to non-invasively estimate the amount of muscle damage induced by a damaging exercise.
... However, investigating the effect of contraction velocity on muscle damage is not simple, because the time under tension is in reverse proportion to contraction velocity. It is commonly accepted that the initial muscle injury results from a mechanical event [21] and is strongly associated with the level of strain placed on contracting fibres [14,15] . Two factors affecting the total strain placed on a muscle during maximal voluntary contraction are total time in which the muscle is under strain (tension time) and total number of muscle contractions. ...
... It has been shown recently that increased phosphorylation of myosin regulatory light chain makes muscle fibres more susceptible to eccentric exercise-induced muscle damage by increasing the number of force-generating cross- bridges [5] . It would appear that the faster velocity protocol produced greater mechanical stress to active fibres, since the amount of individual fibre strain is posited to be a major determinant of the magnitude of fibre injury [14]. Furthermore, using single fibre segments of extensor digitorum longus and soleus muscles of rats, MacPherson et al. [18] demonstrated that the magnitude of the force deficit was greater in Type II (i. ...
Article
Full-text available
Debate exists concerning the effect of contraction velocity on muscle damage, and few human studies have yet to address this issue. This study examined whether the velocity of eccentric exercise affected the magnitude of muscle damage. Twelve untrained subjects performed a series of slow velocity isokinetic eccentric elbow flexions (SV: 30 degrees . s (-1)) of one arm and a fast velocity exercise (FV: 210 degrees . s (-1)) of the other arm, separated by 14 days. In order to standardise the time under tension (120 s) for the two conditions, the number of muscle actions for SV was 30 and 210 for FV. Criterion measures consisted of maximal voluntary torque for isometric, concentric (4 velocities) and eccentric contractions (2 velocities), range of motion (ROM) and relaxed elbow joint angle (RANG), upper arm circumference, muscle soreness and plasma creatine kinase (CK) activity. Measures were taken before, immediately after, 0.5 hour and 24 - 168 hours (240 hours for CK) after each eccentric exercise protocol, and changes in the measures over time were compared between FV and SV by two-way repeated measures ANOVA. Both protocols resulted in significant decrements in isometric and dynamic torque (p < 0.01), but FV showed significantly (p < 0.05) greater reductions over time ( approximately 55 %) and a slower recovery compared to SV ( approximately 30 %). Significantly (p < 0.05) larger decreases in, and delayed recovery of, ROM and RANG were evident after FV compared to SV. FV had significantly (p < 0.05) larger increases in upper arm circumference and soreness compared to SV, and peak plasma CK activity was 4.5-fold greater (p < 0.05) following FV than SV. These results suggest that, for the same time under tension, fast velocity eccentric exercise causes greater muscle damage than slow velocity exercise in untrained subjects.
... Since pain sources are quite variable (i.e., chemical, temperature, mechanical) and one's awareness of pain can be affected by both physiological and psychological perceptions, we would expect that pain-induced inhibition would have very individual responses. Golgi tendon organ Ib afferents are commonly thought to inhibit homonymous and synergistic motoneuron activity, but with fatigue, spindle afferent convergence on Ib inhibitory interneurons can result in excitation (Gandevia, 1998; Kulig et al., 2000 ). The specific action of Ib afferents on the motoneuron is complex , since they can be presynaptically inhibited and can also receive input from Ia, III, and IV afferents (Kulig et al., 2000 ). ...
... Golgi tendon organ Ib afferents are commonly thought to inhibit homonymous and synergistic motoneuron activity, but with fatigue, spindle afferent convergence on Ib inhibitory interneurons can result in excitation (Gandevia, 1998; Kulig et al., 2000 ). The specific action of Ib afferents on the motoneuron is complex , since they can be presynaptically inhibited and can also receive input from Ia, III, and IV afferents (Kulig et al., 2000 ). Furthermore, with sustained contractions , the gain in force feedback is reduced due to Ib inhibitory postsynaptic potentials (Gandevia, 1998 ). ...
Article
Full-text available
Whereas many definitions of fatigue include externally measurable decrements in force or performance, fatigue can be present with no change in the external output of the muscle. The maintenance of submaximal forces can be considered a compromise between neuromuscular force enhancement and competing inhibitory influences. An example of a muscle facilitatory process includes postactivation potentiation that results in an increased sensitivity to Ca++. The neuromuscular system copes with metabolic disruption and subsequent loss of force by recruiting additional motor units and increasing the firing frequency. If the contraction persists, firing frequency may decrease so as to optimize the stimulus rate with the prolonged duration of the muscle fibre action potential (muscle wisdom). The insertion of additional neural impulses into the train of stimuli can result in force potentiation (catch-like properties). Furthermore, there is evidence of neural potentiation and a dissociation of muscle activity with submaximal fatigue. Conversely, inhibition may be derived supraspinally or at the spinal level. While there may be some evidence of intrinsic motoneuronal fatigue, inhibitory afferent influences from chemical, tensile, pressure, and other factors play an important role in the competing influences on force output.
... R atings of perceived exertion (RPE) have been assessed for female and male subjects performing concentric and eccentric resistance exercise paradigms that varied the total volume of weight lifted (i.e., volume loading), percent of one repetition maximum muscular action (% 1-RM; i.e., intensity loading), and rest periods between separate sets and exercises (1,6 -8,14,17-19,26,27). These resistance exercise paradigms: (a) established force-effort psychophysical functions using torque, electromyography (EMG), and magnetic resonance imaging (MRI) as criterion measures (5,10,19,21); (b) examined blood lactic acid concentration ([Hla]), HR, EMG, epinephrine, norepinephrine, cortisol, betaendorphins, and pain as possible physiological mediators of the effort sense (1,4,7,8,11,13,(17)(18)(19)27,28); and (c) used RPE to prescribe muscular strength, endurance and hypertrophic training programs, and to track conditioning progress (1)(2)(3)9). In these foregoing investigations, RPE was assessed using the original and modified versions of Borg's 15-category scale and Borg's Category-Ratio (CR-10) scale. ...
... For modes such as cycling and walking, the intensity of the various differenti-ated perceptual signals usually differs from that of the undifferentiated signal at a given time point during submaximal exercise (23). Some investigations involving resistance exercise have measured only the overall RPE (1,7,8,10,17,27,29) with perceptual estimates primarily recorded during the postexercise recovery period (2,29). However, a number of other investigations have differentiated RPE to active muscles during resistance exercise (2-5,11,12,18,20 -22), providing anatomic specificity to the perceptual response. ...
Article
Full-text available
Unlabelled: The criterion variables were total weight lifted (Wttot ) determined separately for women and men during BC and KE, and blood lactic acid concentration ([Hla]) determined for a combined female ( N = 10) and male ( N = 10) subset during BC. Subjects performed three separate sets of 4, 8, and 12 repetitions for BC and KE at 65% one-repetition maximum. Rating of perceived exertion for the active muscles (RPE-AM) was measured during the mid and final repetition and RPE for the overall body (RPE-O) during the final repetition. : For both female and male groups across the three sets: (a) RPE-AM ranged from 3.6 to 8.2 for BC and 5.1 to 9.6 for KE and (b) RPE-O ranged from 2.4 to 6.7 for BC and 4.2 to 7.6 for KE. Positive linear regressions ranged from r = 0.79 to 0.91 ( P < 0.01) between Wttot and RPE-AM (mid), RPE-AM (final), and RPE-O for both BC and KE in both sex groupings. A positive ( P < 0.01) linear regression was found between [Hla] and RPE-AM (final) (r = 0.87) during BC. RPE did not differ between women and men at any measurement point within each set for BC and KE. RPE-AM (final) was greater ( P < 0.01) than RPE-O in the three sets of BC and KE. Conclusion: Findings provided concurrent validation of the OMNI-RES to measure RPE for the active muscle and overall body in young recreationally trained female and male weight lifters performing upper- and lower-body resistance exercise.
... The tendon of the superficial head of the brachialis muscle inserts distal to the deep head, along the coronoid process, providing its greatest mechanical advantage when the arm is at 90 degrees flexion and thus stabilizing an already flexed arm [8]. The brachialis muscle is also responsible for maintaining the stability of the elbow throughout concentric and eccentric contraction [9]. ...
... Kulig et al showed that the brachialis muscle is preferentially recruited over the biceps brachii when undergoing eccentric contraction [9]. In the cases reported by Nishida et al, it was precisely this motion that these particular athletes underwent. ...
Article
Full-text available
We present the case of a rupture of the brachialis muscle in a 17-year-old male. We provide an overview of the current literature discussing previously reported cases, the clinical features, and recommended treatment. The anatomy and function of the brachialis muscle and possible mechanism of injury are also discussed.
... A T2-weighted spinecho sequence (repetition time 2500 ms, echo time 30 and 90 ms, 256 × 256 matrix, and scan time 286 s) was applied to each arm using an extremity body coil, while each participant laid supine on the bed of the system. The images of biceps brachii and brachialis were obtained at two-thirds of the distance from the acromion to the lateral epicondyle of the humerus (Kulig et al. 2001). The image of brachioradialis was obtained at 6 cm below the lateral epicondyle of the humerus. ...
... These values were greater than those reported in the study by Qi et al. (2011), in which submaximal contractions were performed, and also those reported in the study by Komi et al. (2000), in which maximal contractions were performed. It was stated that MRI T2 relaxation time change immediately after exercise showed cumulative muscle activity during exercise, whereas EMG was representative of muscle activity of the time of muscle contraction (Kulig et al. 2001). Thus, the smaller T2 increase immediately after ECC than CON suggests that fewer muscle fibres were recruited during ECC, in spite of the greater peak torque during first two sets in ECC than CON. ...
Article
Full-text available
PurposeThis study compared maximal eccentric (ECC) and concentric (CON) contractions of the elbow flexors for changes in transverse relaxation time (T2) and indirect markers of muscle damage. Methods Twelve young men performed five sets of six maximal isokinetic (30°/s) ECC with one arm followed by CON with the other arm. Magnetic resonance images to assess T2 and cross-sectional area (CSA) of biceps brachii, brachialis, and brachioradialis, and measurements of maximal voluntary isometric contraction (MVC) torque, range of motion (ROM), and muscle soreness were taken before, immediately after, and 1, 3, and 5 days after each exercise. ResultsMVC torque and ROM decreased greater after ECC than CON (p < 0.05), and muscle soreness developed only after ECC. Biceps brachii and brachialis CSA increased immediately after CON, but delayed increases in brachialis CSA were found only after ECC (p < 0.05). T2 of the muscles increased greater after CON (27–34 %) than ECC (16–18 %) immediately post-exercise (p < 0.05), but returned to baseline by 1 day after CON. The biceps brachii and brachialis T2 increased by 9–29 % at 1–5 days after ECC (p < 0.05). The post-ECC T2 changes showed no significant correlations with the changes in MVC torque, muscle soreness, and CSA, but the T2 increase immediately post-ECC was correlated with the peak T2 in 1–5-day post-ECC (r = 0.63, p < 0.05). Conclusion These results suggest that muscle activity during exercise was lower in ECC than CON, and the T2 changes after ECC do not necessarily relate to the changes in other indirect markers of muscle damage.
... It has been demonstrated that high-threshold motor units can be selectively recruited during eccentric contractions, particularly at fast eccentric velocities [40]. It has further been shown that preferential recruitment of predominantly fast-twitch synergists can occur with increasing eccentric contraction velocities [41,42]. However, most studies have found little difference in motor unit recruitment between contraction types [43][44][45][46]. ...
... EMG activity does not appear to vary with eccentric contraction velocity, indicating that factors other than motor unit recruitment (e.g. viscoelastic properties and non-contractile elements) contribute to an increased force production capacity that can be observed with increased velocity [41]. The differences in force-velocity relationships between concentric and eccentric contractions mean that the discrepancy between moments becomes even greater with increasing angular velocities [54]. ...
Article
Full-text available
An eccentric contraction involves the active lengthening of muscle under an external load. The molecular and neural mechanisms underpinning eccentric contractions differ from those of concentric and isometric contractions and remain less understood. A number of molecular theories have been put forth to explain the unexplained observations during eccentric contractions that deviate from the predictions of the established theories of muscle contraction. Postulated mechanisms include a strain-induced modulation of actin-myosin interactions at the level of the cross-bridge, the activation of the structural protein titin, and the winding of titin on actin. Accordingly, neural strategies controlling eccentric contractions also differ with a greater, and possibly distinct, cortical activation observed despite an apparently lower activation at the level of the motor unit. The characteristics of eccentric contractions are associated with several acute physiological responses to eccentrically-emphasised exercise. Differences in neuromuscular, metabolic, hormonal and anabolic signalling responses during, and following, an eccentric exercise bout have frequently been observed in comparison to concentric exercise. Subsequently, the high levels of muscular strain with such exercise can induce muscle damage which is rarely observed with other contraction types. The net result of these eccentric contraction characteristics and responses appears to be a novel adaptive signal within the neuromuscular system.
... Several mechanical factors involving exercise prescription have been investigated, such as velocity, 48 intensity, 49-51 duration of exercise, 49 resting period, 52 starting position, 53,54 and muscle attachment. 45 Kulig et al 48 compared fast and slow eccentric movement of elbow flexors at the same work load (60% 1-RM) and duration (144 s). ...
... The brachialis was more active during the slow movement protocol, whereas the biceps brachii were more active during the fast protocol. 48 Kulig et al 48 did not compare the same muscle when comparing the two velocities. The number of repetitions might be a more important factor in the severity of muscle damage than the velocity of exercise. ...
Article
Full-text available
Eccentric exercise is part of regular rehabilitation and sports training. Unaccustomed eccentric exercise causes muscle damage that presents as delayed soreness, strength and range of motion loss, swelling, and increased passive stiffness. These symptoms reduce the ability to exercise and might be harmful if further exercise is continued. Several interventions such as warm-up, stretching, massage, acupuncture, anti-inflammatory drugs, and estrogen supplements have been researched in order to find interventions that successfully alleviate the severity of muscle damage. The results are controversial due mainly to the variety of exercise-induced muscle damage protocols, the types of intervention protocols, and the doses of application. From a practical point of view prevention strategies are preferred by practitioners because they reduce time lost from training, reduce the cost of treatment, and reduce the risk of further injury. For that reason, this article emphasizes the mechanism of initial events and the factors involving the severity of muscle damage. Research on the prevention of eccentric exercise-induced muscle damage is reviewed and discussed. Appropriate preventative strategies for muscle damage from eccentric exercise are suggested.
... The lower neuromuscular conditioning in untrained individuals may inhibit the improved gaps in muscle activity between muscle actions due to the difficulty of reaching maximal force production during eccentric actions [34]. Since faster velocities of muscle lengthening may further promote the preferential recruitment of whole muscle with more fast twitch motor units and muscle fibers [42,43], untrained individuals may also struggle to benefit from AEL if they require slower pacing strategies to control the heavier eccentric loading. Moreover, during overloaded eccentric actions there may be protective inhibitory mechanisms of reduced motor neuron responsiveness as a result of Golgi tendon organs being triggered to protect against potential damage to the muscle-tendon unit [41,44]. ...
Article
Full-text available
Accentuated eccentric loading (AEL) employs heavier load magnitudes in eccentric actions than concentric actions of complete stretch-shortening cycles. In doing so, unique neuromuscular and molecular responses are expected to result in acute post-activation performance enhancements, as evidenced by increased movement velocity or power. Improvements are dependent upon load selection, which varies across exercises, such as jumps and bench press throws (eccentric: 20-40 kg or 20-30% of body mass; concentric: body mass only), and squats and bench press (eccentric: 77.3-120% One-Repetition Maximum (1-RM); concentric: 30-90% 1-RM). The efficacy of AEL is dependent upon the concentric load used, which in turn is influenced by the magnitude of the eccentric load. Greater strength relative to body mass may enable the maintenance of technique and pacing during AEL, necessary for resultant performance enhancements, particularly when using eccentric loads exceeding the individual’s concentric 1-RM. Before prescribing AEL practitioners should consider: training experience, strength relative to body mass, the particular exercise, AEL application method, and the magnitude of both eccentric and concentric loads. Thus, the aims of this brief review are to describe: 1) neuromuscular and molecular constructs of AEL; 2) acute effects of AEL; 3) chronic effects of AEL; 4) loading considerations; 5) practical applications.
... If relative intensity is defined as a percentage of the 1 repetition maximum (1RM), it is clearly a low-intensity workout, as the average load is greatly lessened in comparison with traditional resistance training (25,27). When comparing fast (2 seconds) and slow (10 seconds) eccentric protocols, the rates of perceived exertion (RPE) were 8.3 ± 2.1 and 5.4 ± 1.5 respectively (30). Therefore even if intensity is estimated by "perceived difficulty," which is relatively uncommon in resistance training research but has been recently validated (31), Superslow training should not be considered a high-intensity workout. ...
Article
summary: Superslow training, a form of low-velocity resistance training, is continuing to gain popularity in the U.S. This brief review examines the validity of the Superslow philosophy and its supposed benefits. (C) 2005 National Strength and Conditioning Association
... Não houve controle na velocidade de execução das repetições com objetivo de aproximar ao máximo do modo como esses exercícios são executados em sessões típicas. Entretanto, com intuitos de evitar influências da velocidade de execução na PSE por causa da maior ativação muscular e resposta metabólica (KULIG et al., 2011) os participantes foram orientados a executar cada repetição com velocidade moderada (ACSM., 2009) de ± 2s na fase concêntrica e ± 2s na fase excêntrica. Além disso, estímulos verbais foram realizados a fim de manter alto o nível de rendimento (MCNAIR et al., 1996). ...
Article
Full-text available
The aim of this study was to observe the effect of different orders of resistance exercises for upper limbs in lactatemia [LAC], total volume (VT) and ratings of perceived exertion (RPE). The sample consisted of nine men untrained in Strength Training (ST) (age: 24.22 ± 2.44 years, body mass: 70.94 ± 7.99 kg; height: 1.73 ± 0.05 m). The protocol consisted of five sessions separated by at least 48 hours. Day 1 - presentation of research. Days 2 and 3 - test and re-test load corresponding of 10 repetitions maximum (10RM). Days 4 and 5 - implementation of randomized training protocols characterized by two inverted order with respect to the size of the muscle group. Consisting of three sets and the maximum repetitions to the load of 10RM and two minutes recovery between sets and exercises. GP - rowing machine (RM), bench press with long bar (BP), biceps against the wall with straight bar (RB) and triceps pushdowns (TP), PG - TP, RB, SH and RMQ. The one-way ANOVA showed significant difference between sets and exercises for the two orders, the first exercises could perform a greater number of repetitions, corroborating previous studies. The results showed that the RPE and [LAC] suffered no differences between the orders. Regarding the performance of the orders there were no significant differences. We conclude that the results provide important tools for the preparation of resistance training in relation to the positioning of the exercises.
... This may have arisen from changes in distribution of loading among agonist muscles. 45 Movement strategy, although well described in motor control fields 20,21 is not well defined in the exercise literature. In current exercise prescription guidelines adopted by the ACSM, 19 cadence control is discussed while movement strategy is not described. ...
Article
Full-text available
Despite the common use of elastic resistance in training, only the static loading characteristics have been studied while the dynamic components remain undetermined. The purpose was to determine the effect of two movement strategies on the shoulder resultant joint moment (RJM) during internal/external rotation exercise with elastic load. Ten healthy subjects performed sweep and step movement strategies over a constant range of motion and cadence (1:1). Shoulder RJM was determined using a Newtonian model with elastic force measured by force transducer, joint angle by electrogoniometer, and limb acceleration by accelerometer. Relative to the sweep strategy, the step strategy revealed a 49% increase in angle specific RJM during the initial phase, RJM was reduced to 67-69% during mid-range, and increased to over 110% at the end of the repetition. These RJM differences were wholly attributable to strategy dependent changes in limb acceleration. Shoulder RJM in the sweep strategy was almost entirely explained by moment of elastic force. Movement strategy can substantially alter shoulder loading despite constant range of motion and cadence, impacting the magnitude and nature of the stimulus for neuromuscular adaptation. These acceleration dependent changes in shoulder RJM may be important to consider for exercise efficacy and safety.
... Moreover, elbow flexor muscles do not respond homogeneously to different contraction speeds. KULIG et al. [44] showed that during fast elbow flexion, the biceps brachii was more active compared with the brachialis, while the brachialis was recruited more during slow flexion. Since different force-time gradients can cause altered agonist coactivation, the biceps brachii may have been activated to various levels among the subjects during the initial two-second interval. ...
Article
Full-text available
The purpose of this study was to develop a statistical model to describe the electromyography (EMG) signal frequency changes during a submaximal isometric contraction. Thirty subjects performed a 30-second isometric contraction of the biceps brachii muscle at 80% of the maximal voluntary isometric force. Surface EMG electrodes recorded electrical activity of the biceps brachii. Zero-Crossing-Rate was calculated to identify EMG frequency shifts. The mean frequencies for every one-second period were used to calculate a linear relationship between frequency and time. A significant relationship (p<0.05) between slope and initial frequency value was identified. The model described EMG frequency changes during submaximal effort of biceps brachii up to 15 seconds. The prediction error was 9.8%. Modifying this equation to initial values of frequency of each participant decreased prediction error to 7.2%. These results demonstrate that despite individual differences between subjects it is possible to derive single equation that describes EMG alterations during submaximal, isometric contractions across a homogeneous group of people.
... Noble and Robertson define PE as ''the subjective intensity of exertion, tension, discomfort and fatigue that is felt or experienced during aerobic and strength exercises'' (26). Studies have investigated the behavior of PE in relation to the different variables of ST, such as velocity of execution (17), order of the exercises (37), number of repetitions (30), among others. Regarding the load used, studies have indicated that the greater the load used the greater the ratings of PE (RPE) (7,20,30,43), even when different volumes are compared (7,41). ...
Article
The aim was to analyze the relationship between the perceived exertion (PE) and different loads in strength exercises (SEs), in sedentary, active, and trained adult subjects. Thirty young men (18-34 years) were divided into 3 groups (experimental group [EG]): sedentary EG (SEG), physically active group (PAG), and the strength trained group (STG). Maximum strength was established using the 1 repetition maximum test (1RM). Using series of 12 repetitions, different loads were applied until the 4 ratings of PE (RPEs) (11, 13, 15, and 17) from 15 category Borg Perceived Exertion Scale (RPE 6-20). The pace of the repetitions and the intervals between the sets were controlled, the loads were blind, the order of the RPE randomized, whereas the PE was localized and determined after completion of the series. Strength correlations between the RPE and the %1RM, according to the EGs and SEs (0.826-0.922, p < 0.001), were observed. Similar behavior was seen in the SEs. Higher loads are related to higher RPEs and are differentiated between the EGs. The STG used higher %1RM when compared to the SEG, whereas the PAG, displayed an intermediary behavior in relation to the other groups. The use of PE represents a reliable instrument for the measurement of intensity in strength training.
... 2 In particular, altering the variables involved in the ECC isotonic and CON-ECC isokinetic exercise protocols may result in outcomes that are different from those we found, as authors 19 of at least one study have reported greater muscle damage after fastvelocity versus slow-velocity isokinetic muscle actions; however, isotonic exercise does not appear to be affected by the speed of the eccentric contraction. 34 Additionally, the inclusion of concentric muscle actions in the CON-ECC isokinetic group directly limits our findings, as the concentric action represented 46% of the total CON-ECC training volume. As previously discussed, we matched total workload between groups but were not able to match eccentric-specific workloads between the 2 protocols because of the voluntary nature of eccentric isokinetic exercise. ...
Article
Full-text available
Rehabilitation protocols involving eccentric resistance exercise performed with loading more than 100% concentric 1-repetition maximum are effective in increasing muscle function in both healthy and injured populations. The mode of eccentric exercise (isokinetic versus isotonic) may be an important factor in limiting symptoms of delayed-onset muscle soreness and in improving muscle function after training. To compare functional and symptomatic responses after an eccentric-only (ECC) isotonic exercise protocol and after a combined concentric-eccentric (CON-ECC) isokinetic exercise protocol matched for total exercise volume. Observational study. Controlled research laboratory. Twenty-four healthy, untrained, college-aged men (n = 12) and women (n = 12). Participants were randomly assigned to the ECC isotonic or CON-ECC isokinetic exercise group and performed a single bout of resistance exercise involving the elbow flexors. Measurements of elbow flexion and extension, isometric strength, and muscle point tenderness were obtained before exercise (baseline) and during follow-up sessions (days 2, 4, 7, and 14). Separate 1-way analyses of variance and repeated-measures analyses of variance were used to determine outcome differences. Tukey post hoc testing was performed when indicated. At baseline, no differences were present between groups for any measure. The ECC isotonic exercise protocol resulted in a 30% to 36% deficit in muscle strength, a 5% to 7% reduction in elbow flexion, and a 6% to 8% reduction in elbow extension at follow-up days 2 and 4 (P < .01). The CON-ECC isokinetic exercise protocol did not alter muscle strength or range of motion at any time when compared with baseline. Muscle point tenderness increased from baseline on days 2 and 4 in both groups (P < .05) but was not different between groups throughout the recovery period. Our results indicated more pronounced functional deficits occurred after a single bout of ECC isotonic exercise than with a CON-ECC isokinetic exercise protocol matched for training volume.
... The endurance times of submaximal contractions that involve multiple muscles, however, could also be influenced by variation in the pattern of muscle activation (10,24,44,45), perhaps including differences between men and women (42,43). These observations raised the question of the relative contributions of the target force, circulatory limitations, and pattern of muscle activation to the observed sex difference in endurance time of the elbow flexor muscles. ...
Article
Full-text available
Women are capable of longer endurance times compared with men for contractions performed at low to moderate intensities. The purpose of the study was 1) to determine the relation between the absolute target force and endurance time for a submaximal isometric contraction and 2) to compare the pressor response and muscle activation patterns of men [26.3 +/- 1.1 (SE) yr] and women (27.5 +/- 2.3 yr) during a fatiguing contraction performed with the elbow flexor muscles. Maximal voluntary contraction (MVC) force was greater for men (393 +/- 23 vs. 177 +/- 7 N), which meant that the average target force (20% of MVC) was greater for men (79.7 +/- 6.5 vs. 36.7 +/- 2.0 N). The endurance time for the fatiguing contractions was 118% longer for women (1,806 +/- 239 vs. 829 +/- 94 s). The average of the rectified electromyogram (%MVC) for the elbow flexor muscles at exhaustion was similar for men (31 +/- 2%) and women (30 +/- 2%). In contrast, the heart rate and mean arterial pressure (MAP) were less at exhaustion for women (94 +/- 6 vs. 111 +/- 7 beats/min and 121 +/- 5 vs. 150 +/- 6 mmHg, respectively). The target force and change in MAP during the fatiguing contraction were exponentially related to endurance time (r(2) = 0.68 and r(2) = 0.64, respectively), whereas the change in MAP was linearly related to target force (r(2) = 0.51). The difference in fatigability of men and women when performing a submaximal contraction was related to the absolute contraction intensity and was limited by mechanisms that were distal to the activation of muscle.
... Second, despite similar recruitment during the eccentric exercise, the activated muscles can be affected differently by lengthening contractions due to their specific architecture (i.e. fascicle length and pennation angle) and fibre typology (Kulig et al. 2001). Indeed, compared with soleus, gastrocnemius is composed by a higher percentage of type II muscle fibres which are more susceptible to damage (Friden & Lieber 1998, Takekura et al. 2001. ...
Article
Full-text available
Changes in muscle stiffness after exercise-induced muscle damage have been classically inferred from passive torque-angle curves. Elastographic techniques can be used to estimate the shear modulus of a localized muscular area. This study aimed to quantify the changes in shear elastic modulus in different regions of the elbow flexors after eccentric exercise and their relation to muscle length. Shear elastic modulus and transverse relaxation time (T2 ) were measured in the biceps brachii and brachialis muscles of sixteen participants, before, 1h, 48h and 21 days after 3 sets of 10 maximal isokinetic eccentric contractions performed at 120°.s(-1) . The shear elastic modulus of the elbow flexors significantly increased 1h (+46%; P=0.005), with no significant change at 48h and 21D, post-exercise. In contrast, T2 was not modified at 1h but significantly increased at 48h (+15%; P<0.05). The increase in shear elastic modulus was more pronounced at long muscle lengths, and reached a similar extent in the different regions of the elbow flexors. The normalized hysteresis area of shear elastic modulus-length relationship for the biceps brachii increased 1h post-exercise (31%) in comparison to the pre-exercise value (18%), but was not significantly altered after five stretching cycles (P=0.63). Our results show homogeneous changes in muscle shear elastic modulus within and between elbow flexors. The greater increase in shear elastic modulus observed at long muscle lengths suggest the putative involvement of both cross-bridges number and titin in the modifications of muscle shear elastic modulus after damaging exercise. This article is protected by copyright. All rights reserved.
... Eccentric exercise protocols have been used successfully in previous studies to induce muscle injury. 29,30,[35][36][37][38] ...
... Second, despite similar recruitment during the eccentric exercise, the activated muscles can be affected differently by lengthening contractions due to their specific architecture (i.e. fascicle length and pennation angle) and fibre typology (Kulig et al. 2001). Indeed, compared with soleus, gastrocnemius is composed by a higher percentage of type II muscle fibres which are more susceptible to damage (Friden & Lieber 1998, Takekura et al. 2001). ...
... Dynamic contractility of elbow in concentric or eccentric contraction is also controlled by brachialis muscle along with biceps brachii. While pronating forearm from supination, eccentric contraction of muscle may be responsible for rupture of brachialis muscle in athletes [11]. The rarity of brachialis muscle tear may promote misdiagnosis or mistreatment of this injury. ...
Article
Full-text available
Isolated traumatic brachialis muscle tears are uncommonly reported - leading to occasional misdiagnosis and misdirected treatment. The rarity of brachialis muscle tear may promote misdiagnosis or mistreatment of this injury. We report an isolated brachialis muscle tear in a young female, possibly caused by strenuous exercise in the gymnasium. The diagnosis was made clinically and confirmed by magnetic resonance imaging. The patient was subsequently managed adequately with conservative treatment. We herein present a 35-year-old woman who was diagnosed with an acute brachialis muscle tear being diagnosed with a combination of clinical signs and imaging and successfully managed non-operatively. A chronologically arranged review of literature is also presented.
... It has been shown, however, that resistance exercise using high-intensity or loads causes delayed strength recovery due to muscle damage (Ahtiainen et al., 2003). Moreover, studies demonstrated that faster speed of movement induced greater delayed onset muscle soreness (DOMS) (Kulig et al., 2001) as well as Z-band disruption (Shepstone et al., 2005). These factors lead to long-lasting impairments in motor performance, thereby restricting the use of high-intensity resistance training within the weekly routine of team sports athletes. ...
Article
Full-text available
The purpose of this study was to explore the effects of slow-speed resistance training with low intensity (SRT) on muscle power output in elite futsal players with respect to traditional resistance training. The authors hypothesized that the muscle deoxygenation during SRT causes early recruitment of fast twitch fibers that would positively affect strength and power performance. Thirty male elite futsal players were recruited and randomly assigned either to SRT group or to traditional resistance training (TRT) group. All players underwent an 8-weeks experimental protocol consisting of 2 training sessions per week at both leg curl and leg extension machines. In the SRT, players lifted 50% of one maximum repetition (1RM) involving 3 s for eccentric and concentric actions. In the TRT, players lifted 80% of 1RM involving 1 s for eccentric and concentric actions. All players were tested twice (pre and post) for sprint and jump performances, maximal isometric voluntary contraction (MVC) and maximal isokinetic peak torque (Peak TQ) and total work (TW) at 60 and 120 • /s (on knee extensors and flexors). The two groups presented remarkable differences in the within-group changes for all the variables. SRT exhibited greater improvements in both Peak TQ and TW for knee extensors and flexors at 120 • /s. Conversely, TRT showed greater improvements in MVC, and in both Peak TQ and TW for knee extensors and flexors at 60 • /s, except for Peak TQ of the knee extensors, where no significant difference was found between TRT and SRT. Countermovement jump showed a decrease in eccentric time and an increase in concentric force in SRT group. SRT and TRT resulted effective to enhance the strength performance indices during the 8-weeks experimental protocol. Peak torque at 120 • /s explained more of the contractile characteristic effects of SRT training than MVC, suggesting that slow-speed training can cause fast twitch fibers hypertrophy in elite athletes. Since slow-speed training is supposed to produce a decreased exercise-induced muscle damage, SRT method is a suitable option in strength training for futsal and team sports.
... The brachialis muscle travels over the biceps brachii when the arm is eccentrically contracted. 13 As such, it is particularly susceptible to injury when an individual eccentrically contracts the arm with both the forearm and the elbow pronated and extended, respectively. In case reports describing isolated brachialis tears, patients report a range of injury mechanisms but most commonly describe a traumatic hyperextension injury typically related to weighted resistance. ...
Article
Full-text available
Isolated tears of the brachialis muscle are rare and often take on the clinical appearance of other pathology, such as a distal biceps brachii tendon tear or an intramuscular tumor, thus making diagnosis especially difficult. The authors describe the case of a 31-year-old competitive male weight lifter who was found to have a full-thickness tear of the brachialis tendon at its distal ulnar attachment after performing a 40.8-kg biceps curl. The authors describe the differential diagnosis, radiographic findings, and methods used that led to the diagnosis and also provide a comprehensive review of the literature on brachialis muscle injuries. The patient decided to proceed with conservative management consisting of a period of rest and physical therapy. At 10 months after the injury, the patient went back to weightlifting and biceps curls. He had progressed to full strength and had returned to all weightlifting activities at final follow-up. Isolated full-thickness brachialis muscle ruptures can be treated successfully with conservative management, including rest and physical therapy. [Orthopedics. 201x; xx(x):xx-xx.].
... The circumference, or girth, of the upper arm (60% the distance between the acromion process and the lateral epicondyle of the humerus) was measured with an inextensible tape measure with the participant standing with the arm hanging freely (Kulig et al. 2001). The measurement point was marked with a permanent marker for repeated testing. ...
Article
Full-text available
Purpose To determine how muscle stiffness and pain which develop after eccentric exercise are affected by gentle stretching and repeated exercise. Methods Twenty-one healthy female participants undertook eccentric exercise of the elbow flexors and changes in resting elbow flexion angle (REFA; a measure of muscle stiffness), pain on stretch scale, pain elicited by pressure (PPT pain, a measure of mechanoreceptor hypersensitivity), and upper arm girth were followed for 7 days after exercise. The effects of gentle passive stretching on pain and muscle stiffness were investigated 2 and 4 days after exercise. Eleven participants also repeated the exercise with the same arm 6 weeks after the first bout. Results There was a significant relationship between the pain on stretch scale and increased REFA (day 4; R² = 0.65, p < 0.001), whereas there was no relationship between REFA and PPT pain. REFA was reduced by passive stretching and pain on stretch scale was also reduced from 3.0 (1.4, 5.1) to 0.75 (0.0, 2.0) [median (IQR), p = 0.01]. PPT pain was unaffected by the passive stretching, as was muscle swelling. Following the repeated bout, increases in REFA were much reduced, as was pain on stretch scale (p = 0.02). However, PPT pain was not significantly different between the two bouts of exercise. Conclusions The results indicate that reductions in pain on stretch scale, either by gentle passive stretching or as the result of repeated exercise, are primarily due to reductions in muscle stiffness which develops after eccentric exercise, whereas mechanoreceptor hypersensitivity is relatively unaffected.
... This muscle is only one part of the four major components of the elbow flexors (short and long heads of BB, BR and brachialis), with the brachialis contributing for almost the same force as the entire BB (Edgerton et al. 1986;Kawakami et al. 1994). In that context, it has been reported that the magnitude of the activation of each elbow flexor muscles can differ in function of the characteristics of the movement (i.e., load, speed, contraction type, muscle length, etc.; see Brown et al. 1993;Kulig et al. 2001). However, despite potential specific training-related adaptations, a similar hypertrophy has been reported for BB, BR and brachialis following 12 weeks of strength training against a load of ~ 70% of 1RM (Erskine et al. 2014). ...
Article
Full-text available
Aim This study investigated the efficacy of a new strength training method on strength gain, hypertrophy, and neuromuscular fatigability. Methods The training exercise consisted of elbow flexion against a load of ~ 70% of one repetition maximal (1RM). A new method (3/7 method) consisting of five sets of an increasing number of repetitions (3 to 7) during successive sets and brief inter-set intervals (15 s) was repeated two times after 150 s of recovery and compared to a method consisting of eight sets of six repetitions with an inter-set interval of 150 s (8 × 6 method). Subjects trained two times per week during 12 weeks. Strength gain [1RM load and maximal isometric voluntary contraction (MVC)], EMG activity of biceps brachii and brachioradialis, as well as biceps’ brachii thickness were measured. Change in neuromuscular fatigability was assessed as the maximal number of repetitions performed at 70% of 1RM before and after training. Results Both 3/7 and 8 × 6 methods increased 1RM load (22.2 ± 7.4 and 12.1 ± 6.6%, respectively; p < 0.05) and MVC force (15.7 ± 8.2 and 9.5 ± 9.5%; p < 0.05) with a greater 1RM gain (p < 0.05) for the 3/7 method. Normalized (%Mmax) EMG activity of elbow flexors increased (p < 0.05) similarly (14.5 ± 23.2 vs. 8.1 ± 20.5%; p > 0.05) after both methods but biceps’ brachii thickness increased to a greater extent (9.6 ± 3.6 vs. 5.5 ± 3.7%; p < 0.05) for the 3/7 method. Despite subjects performing more repetitions with the same absolute load after training, neuromuscular fatigability increased (p < 0.05) after the two training methods. Conclusion The 3/7 method provides a better stimulus for strength gain and muscle hypertrophy than the 8 × 6 method.
... In addition, the mechanism of differential recruitment in the case of the elbow flexors: biceps brachii which is preferentially recruited during high velocity contractions vs. the brachialis which is preferentially recruited during slow velocity contractions [39] may explain the results. These authors demonstrated that CK plasma activity was similar between fast and slow groups, suggesting that both groups have the same structural damage [26]. ...
Article
Full-text available
The velocity at which eccentric exercise is performed may be a factor in the extent of muscular damage. However, studies differ regarding the exercise velocity that promotes greater muscle damage. The purpose of this review was to analyze studies that looked into at least two different eccentric exercise velocities and verified markers of muscle damage. Relevant studies for this review were identified and the methodological quality of each study was calculated based on the Physiotherapy Evidence Database (PEDro) scale. Twelve studies were included herein. The mean PEDro rating was 6.67, ranging from 5 to 7. Seven studies reported that the faster eccentric exercise velocity induced greater muscle damage. Four studies showed no differences between velocities and a single study has indicated a greater magnitude of muscle damage after slow eccentric exercise. Therefore, it seems that fast eccentric exercise may indeed be associated with greater muscle damage even though exercise velocity per se is not the main factor involved in eccentric exercise-induced muscle damage in both animal and human models.
... A padronização de execução dos movimentos pospostos seguiu a normatização delineada por Evans (2007). Não houve controle da velocidade com fins de se aproximar a sessões típicas em academia (KULIG et al., 2001), porém, os voluntários foram instruídos a manter uma velocidade constante e moderada a fim de minimizar a influência da velocidade. ...
Article
Full-text available
Lactate plays an important role in anaerobic and aerobic exercises, and an analysis of blood lactate concentration throughout the activity may reflect magnitude and intensity with which it was performed. Therefore, the aim of this study was to analyze the blood lactate concentration in moments before, during and post-test in running exercise on treadmill and in resistant exercise in circuits. For this, 30 subjects were allocated in two groups, one to perform aerobic exercise and another resistance exercise. There were five moments for blood lactate harvest: pre-exercise, 5 minutes during protocol (Mom 1), 10 minutes during exercise (Mom 2), at the end of the protocol (Final) and 15 min after the end of the protocol (Rec 15). As a result, lactate concentration was higher at the end of the activity (12.53 ± 3.03 mmol/L in the aerobic and in the resistant 15.36 ± 3.45 mmol/L) than in other moments. There was a significant difference between the two intervention protocols, specifically in Mom 1 (p = 0.013), end of exercise (p = 0.024) and Rec 15 (p = 0.001), with higher values in lactate concentration in the resistant exercise protocol. Despite this, there was a gradual increase in lactate concentration throughout both exercise protocols, which corroborates results found in other studies regarding this subject. It was concluded that both aerobic activity and resistant exercise tested caused increase in blood lactate concentration during the moments of exertion, with later decline during the recovery phase at rest, which can be justified by the high metabolic demand for ATP and extra demand for energy in intense exercise. Keywords: Lactate. Aerobic. Resistant.
... Existem evidências que a velocidade, durante a realização dos exercícios concêntricos e excêntricos, quando realizados de forma isocinética, infl uenciaram no ganho de força e na hipertrofi a muscular [15,16,22,23,25,26]. O exercício excêntrico, realizado de forma rápida, gera um maior ganho de força muscular, quando comparado aos exercícios concêntricos realizados de forma lenta e/ou rápida [12,22]. ...
Article
Os exercícios concêntricos e excêntricos são utilizados com o propósito de ganho de força, prevenção de lesões e para melhorar o desempenho funcional dos indivíduos. A escolha desses exercícios dentro de um programa de treinamento depende de vários fatores. O objetivo deste estudo foi verificar, através de uma revisão bibliográfica, os benefícios das contrações concêntrica e excêntrica no trabalho de fortalecimento muscular. Utilizou-se as bases de dados Medline e Cochrane, com as palavras-chaves: strength, concentric, eccentric, training, maximal force, exercise. Os critérios de inclusão foram artigos publicados no período de 1995 a 2005; nas línguas inglesa, espanhola e portuguesa; estudos em modelo humano, na faixa etária de 18 a 45 anos e sem restrição de gênero. Existem evidências que os exercícios excêntricos causam maior dor muscular tardia e um processo inflamatório reacional após a sua execução, mas com uma adaptação rápida do tecido que possibilitará a sua utilização com cargas altas e com ganhos musculares satisfatórios e rápidos. As contrações concêntricas promovem também um aumento da força e da hipertrofia muscular, mas demonstram um maior consumo de oxigênio e um maior tempo no ganho de força muscular, quando comparadas ao exercício excêntrico.Palavras-chave: exercícios fisioterapêuticos, métodos de fortalecimento, revisão da literatura.
... This aim of this study was identify differences in patterns of muscular contraction onset and of relative muscular and Costill, 2001). In this study, we controlled the speed of hip joint abduction as a common condition based on the research reporting that movement speed affects forms of motility control (Hodges and Richardson, 1999) and that reactions of the agonistic muscles vary in exercises with different eccentric speeds (Kulig et al., 2001). The However, the muscles in the lower limbs are not wide in terms of working range, and it is difficult to perform uniform motion. ...
... Data from the study of Adams et al. (1992). Akima, et al., 2000b, Akima, et al., 1999, Hayashi, et al., 1998, Ploutz, et al., 1994, Ray & Dudley 1998, Richardson, et al., 1998, Weidman, et al., 1991, elbow flexion (Adams, et al., 1992, Kulig, et al., 2001, Meyer & Prior 2000, Shellock, et al., 1991, Yue, et al., 1994, neck extension and flexion (Conley, et al., 1995, Conley, et al., 1997, ankle extension and flexion (Akima, et al., 2000a, Akima, et al., 2003, Fisher, et al., 1990, Jenner, et al., 1994, Kennan, et al., 1995, Kinugasa & Akima 2005, Price, et al., 2003, Price, et al., 1998, Segal & Song 2005, Vandenborne, et al., 2000, Yanagisawa, et al., 2003, running (Sloniger, et al., 1997), and pedaling (Akima, et al., 2005b, Fleckenstein, et al., 1991, Hug, et al., 2004, Kinugasa, et al., 2004, Reid, et al., 2001, Richardson, et al., 1998, Saunders, et al., 2000. ...
Article
Imaging is a powerful strategy for the visualization of anatomical and functional information (levels and patterns of activation, perfusion, circulation, and metabolism etc.) in human skeletal muscle. Recent innovations in scientific technology, several new techniques and methods have been developing that visualize the function of muscle regarding recruitment, perfusion, and/or metabolism in exercise. This review is focused on three novel imaging techniques; magnetic resonance imaging, positron emission tomography, and near infrared spectroscopic imaging. These noninvasive imaging techniques provide us crucial information about human muscle function in exercise. The information includes following the assignments; 1) training effects on muscle function, 2) differences in muscle function and metabolism between trained and untrained individuals, and 3) heterogeneity of activation perfusion and metabolism within a single muscle or muscle group. Recent research studies applying these imaging techniques to human muscles are discussed in detail in this review.
... Dynamic contractility of elbow in concentric or eccentric contraction is also controlled by brachialis muscle along with biceps brachii. While pronating forearm from supination, eccentric contraction of muscle may be responsible for rupture of brachialis muscle in athletes [11]. The rarity of brachialis muscle tear may promote misdiagnosis or mistreatment of this injury. ...
Article
Background The brachialis muscle lies in close anatomic relation to the anterior capsule of the elbow joint. The contribution of the brachialis muscle to elbow stability has not yet been fully investigated. Therefore, the aim of this biomechanical in-vitro study was to analyze its influence on joint stability. Methods Nine fresh frozen cadaveric elbows were evaluated for stability against valgus and varus/posterolateral rotatory forces. Brachialis loading was measured indirectly using strain gauges. Three distinct scenarios were analyzed: A) with intact lateral ulnar and ulnar collateral ligaments B) with a ruptured lateral ulnar collateral ligament C) with ruptured lateral ulnar and ulnar collateral ligaments. Findings In all scenarios, an increased strain was observed under posterolateral rotatory/varus forces. The maximum measured strain occurred with elbow flexion of 30° and pronation of the forearm. The strain was significantly higher with dual-ligament rupture (mean - 210.5 μm/m; min. 97.8 μm/m; max. -310 μm/m; SD 107.8 μm/m; p = .034) compared to intact ligaments (mean − 106.9 μm/m; min. -32.51 μm/m, max. -287 μm/m; SD 100.2 μm/m) and single-ligament rupture (mean – 109.5 μm/m; min. - 96.7 μm/m; max - 130.4 μm/m; SD 18.2). Interpretation A strain of the brachialis muscle was observed under varus/posterolateral rotatory forces with a pronated forearm and the strain increased significantly in the event of a dual-ligament rupture. This suggests that the brachialis muscle may influence varus/posterolateral rotatory stability of the elbow. Hence, a concomitant tear of the brachialis muscle might result in pronounced instability following simple elbow dislocation. Level of evidence Basic Science Study, Biomechanics.
Article
A 22-year-old male varsity collegiate wrestler presented for general chiropractic care for an unrelated condition and noted right elbow pain that had progressively increased over the past few weeks. The athlete was diagnosed with a right brachialis strain and advised to follow up with his athletic trainer for co-management of his injury. The patient responded positively to prescribed treatments and rehabilitation to decrease pain and restore functionality (<14 days) while only missing one competitive match. The location of the brachialis muscle and scarcity of literature makes diagnosis and treatment complex. The physical examination and conservative treatment presented in this report demonstrate the need for comprehensive and exploratory examination and co-management of wrestling athletes with a brachialis strain.
Article
We sought to determine if the velocity of an acute bout of eccentric contractions influenced the duration and severity of several common indirect markers of muscle damage. Subjects performed 36 maximal fast (FST, n = 8: 3.14 rad x s(-1)) or slow (SLW, n = 7: 0.52 rad x s(-1)) velocity isokinetic eccentric contractions with the elbow flexors of the non-dominant arm. Muscle soreness, limb girth, plasma creatine kinase (CK) activity, isometric torque and concentric and eccentric torque at 0.52 and 3.14 rad x s(-1) were assessed prior to and for several days following the eccentric bout. Peak plasma CK activity was similar in SLW (4030 +/- 1029 U x 1(-1)) and FST (5864 +/- 2664 U x 1(-1)) groups, (p > 0.05). Both groups experienced similar decrement in all strength variables during the 48 hr following the eccentric bout. However, recovery occurred more rapidly in the FST group during eccentric (0.52 and 3.14 rad x s(-1)) and concentric (3.14 rad x s(-1)) post-testing. The severity of muscle soreness was similar in both groups. However, the FST group experienced peak muscle soreness 48 hr later than the SLW group (24 hr vs. 72 hr). The SLW group experienced a greater increase in upper arm girth than the FST group 20 min, 24 hr and 96 hr following the eccentric exercise bout. The contraction velocity of an acute bout of eccentric exercise differentially influences the magnitude and time course of several indirect markers of muscle damage.
Article
Muscle activation produces increases in magnetic resonance ( T(2)) signal intensity leading to recruitment images that demonstrate spatial patterns and intensity of muscle activation. These T(2) activation maps are useful for visualizing and quantifying various aspects of muscle function. Activity-dependent changes in T(2) result from an increase in the T(2) relaxation time of muscle water. The current state of investigation indicates that the mechanism of increased T(2) results from osmotically driven shifts of muscle water that increase the volume of the intracellular space and from intracellular acidification resulting from the end products of metabolism. Although the spatial resolution of magnetic resonance imaging is still insufficient to map territories of individual motor units, it is possible to demonstrate nonuniform activation between subregions or compartments of muscle. Taken together, the attributes of the T(2) mapping technique hold great potential for demonstrating aberrant muscle activation patterns in pathology and positive adaptation to exercise or rehabilitative intervention.
Article
Full-text available
Lacerda, LT, Costa, CG, Lima, FV, Martins-Costa, HC, Diniz, RCR, Andrade, AGP, Peixoto, GHC, Bemben, MG, and Chagas, MH. Longer concentric action increases muscle activation and neuromuscular fatigue responses in protocols equalized by repetition duration. J Strength Cond Res 33(6): 1629-1639, 2019-The aim of this study was to investigate the impact of protocols equalized by the repetition duration but composed of different concentric (CON) and eccentric (ECC) durations on muscle activation and neuromuscular fatigue. Seventeen males with previous experience in resistance training performed 3 training protocols (A-2 second CON: 4 second ECC; B-3 second CON: 3 second ECC; and C-4 second CON: 2 second ECC) with the Smith machine bench press exercise, all with 3 sets, 6 repetitions, 3 minutes' rest, and 60% of 1RM. The normalized root mean square of the electromyographic signal (EMG RMS) and mean frequency elec-tromyography (EMG MF) for pectoralis major and triceps brachii muscles were calculated for second and fifth repetitions in each set. The results showed an EMG MF decrease across the repetitions accompanied by a progressive increase of the EMG RMS across the repetitions for all protocols and muscles. The EMG RMS was higher in protocol C when compared with protocol A and B for pectoralis major. The EMG MF was lower in protocols B and C than in protocol A for pectoralis major throughout the sets and repetitions. A higher EMG RMS and a lower EMG MF were observed in protocols B and C compared with protocol A for triceps brachii, solely in the fifth repetition. In conclusion, training protocols conducted with the same repetition duration, but with different concentric and eccentric durations , produce distinct muscle activation and neuromuscular fatigue responses, in which performing longer concentric durations could be the more appropriate strategy to increase muscle activation and neuromuscular fatigue.
Article
The primary aim was to describe perceived exertion responses to different intensities of eccentric exercise in women and men. 42 adults (21 men and 21 women, 7 per condition) completed elbow extension exercises with a weight corresponding to 80%, 100%, or 120% of maximal voluntary concentric strength. Total work was equated by manipulating the number of repetitions in the 80% (N = 45), 100% (N = 36), and 120% (N = 30) conditions. A two-way ANOVA showed significant main effects for the intensity and sex factors. Perceived exertion ratings were strongly dependent on exercise intensity, and women reported lower RPEs than men. A separate three-way mixed model ANOVA that included a repetition factor showed that perceived exertion ratings increased similarly across the first 30 repetitions in all exercise conditions. Significant partial correlations were found between mean RPE during the eccentric exercise bout, and the mean intensity of delayed-onset muscle pain measured from 12- to 72-h postexercise after controlling for the relative exercise intensity (r12.3 = 0.28) or the maximum concentric strength of the elbow flexors (r12.3 = 0.33). 1) for both women and men, there is a positive association between the intensity of eccentric exercise performed with the elbow flexors and RPE; 2) perceived exertion ratings increase significantly then plateau when repeated eccentric muscle actions are performed at constant, submaximal absolute intensities; 3) women rate eccentric exercise performed at the same intensity (relativized to MVC-C) as being less effortful compared with men; and 4) RPE during eccentric exercise can account for a small but significant amount of variability in delayed-onset muscle pain after statistically controlling for differences in strength or relative intensity.
Article
Full-text available
BACKGROUND: Eccentric contractions (ECC)-induced muscle damage and activation pattern are not fully understood.OBJECTIVE: To investigate the activation level and damage in each muscle and site after ECC.METHODS: Eleven men performed 30 isokinetic ECC of the elbow flexors. Maximal voluntary isometric contraction (MVC) torque, range of motion of the elbow joint (ROM), delayed onset muscle soreness (DOMS), transverse relaxation time (T2), and cross-sectional area (CSA) were measured immediately before, immediately after, and 1, 3, 5 days after ECC.RESULTS: MVC and ROM significantly decreased while DOMS significantly increased until 3 days after ECC. The CSA of the brachialis significantly increased after ECC. The T2 in biceps brachii and middle and distal brachialis increased significantly at post (p< 0.01) day 1 (middle; p< 0.01, distal; biceps brachii, p< 0.05, brachialis, p< 0.01), and day 3 (middle; p< 0.01, distal; biceps brachii, p< 0.05, brachialis, p< 0.01). In addition, after 5 days only the distal brachialis has shown a significant increase (p< 0.01).CONCLUSIONS: Following maximal ECC the activation pattern and muscle damage differ among the elbow flexors depending upon the individual muscle and site of recording.
Article
In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of NMR in biomedicine. Each bibliography is divided into 9 sections: 1 Books, Reviews ' Symposia; 2 General; 3 Technology; 4 Brain and Nerves; 5 Neuropathology; 6 Cancer; 7 Cardiac, Vascular and Respiratory Systems; 8 Liver, Kidney and Other Organs; 9 Muscle and Orthopaedic. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted.
Article
This thesis uncovers the rational and Romantic assumptions about the relationship between objects and identity that are embedded in occupational therapy, and critiques current practice from that perspective. It is based on an initial assumption that there is in fact a relationship between people's identity and the objects they make, have, use and are associated with. This assumption is explored through an interpretive examination of the fields of literature that are commonly identified as informing occupational therapy, supplemented by selected popular literature. The exploration takes a philosophical approach, guided by notions from philosophical hermeneutics, including pre-understandings, the hermeneutic circle and fusion of horizons. The conclusion reached is that people informed by Western philosophies interpret the identity meanings of objects in both rational and Romantic ways. To inform the study, the nature of rationalism and Romanticism are then explained, and the implications of these philosophical traditions in relation to objects and identity are teased out. This interpretation is guided by a history of ideas methodology, which entails approaching historical texts from a new perspective, in this case the identity meanings of objects. Thus informed, occupational therapy literature, primarily that published in Britain between 1938 and 1962 is examined from the perspective of objects and identity. What is revealed is that rational and Romantic understandings of objects, and of patients' and their own identity are clearly discernible. Such understandings afforded early occupational therapists both ways to organise their growing knowledge of the therapeutic application of crafts and the transformative outcomes of occupational therapy intervention. Gradually however, factors both internal and external to the profession served to undermine therapists' Romanticism. Primary amongst these were World War II, which saw a redeployment of occupational therapists from mental health to physical rehabilitation settings; advances in rehabilitative medicine, which brought a reduction in secondary complications and the adoption of teamwork; and the development of new practice areas including domestic rehabilitation using gadgets to enhance function and pre-vocational rehabilitation. As a result, tensions between rational and Romantic understandings crystallised around two long-standing controversies. These were whether or not craft equipment such as weaving looms should be adapted to serve specific remedial purposes, and whether it was the process of making a crafted object or the quality of the finished product that was more important. In the event, these contested ideologies became largely irrelevant as craftwork was sidelined from mainstream practice. With it, occupational therapists' Romantic vision of transforming people's lives through creative activity also slipped away. Several reasons for this loss of one of the profession's founding philosophies are proposed. They include the substantial absence of the professions' philosophical foundations from its education, and the paucity of theory and research methodologies that might have informed the nature and process of transformative change that earlier occupational therapists had observed and reported. The thesis concludes by arguing for the importance of recovering a balance between rationalism and Romanticism. A call to action is issued, addressing change in educational practice, concerted research effort to identify and articulate transformative processes within occupational therapy, and political action focusing on the inclusion of Romantic perspectives within policy and strategic documents.
Article
Full-text available
Background: Localized cooling has been proposed as an effective strategy to limit the deleterious effects of exercise-induced muscle damage on neuromuscular function. However, the literature reports conflicting results. Purpose: This randomized controlled trial aimed to determine the effects of a new treatment, localized air-pulsed cryotherapy (-30°C), on the recovery time-course of neuromuscular function following a strenuous eccentric exercise. Study design: Controlled laboratory study. Methods: A total of 24 participants were included in either a control group (CONT) or a cryotherapy group (CRYO). Immediately after 3 sets of 20 maximal isokinetic eccentric contractions of elbow flexors, and then 1, 2, and 3 days after exercise, the CRYO group received a cryotherapy treatment (3 × 4 minutes at -30°C separated by 1 minute). The day before and 1, 2, 3, 7, and 14 days after exercise, several parameters were quantified: maximal isometric torque and its associated maximal electromyographic activity recorded by a 64-channel electrode, delayed-onset muscle soreness (DOMS), biceps brachii transverse relaxation time (T2) measured using magnetic resonance imaging, creatine kinase activity, interleukin-6, and C-reactive protein. Results: Maximal isometric torque decreased similarly for the CONT (-33% ± 4%) and CRYO groups (-31% ± 6%). No intergroup differences were found for DOMS, electromyographic activity, creatine kinase activity, and T2 level averaged across the whole biceps brachii. C-reactive protein significantly increased for CONT (+93% at 72 hours, P < .05) but not for CRYO. Spatial analysis showed that cryotherapy delayed the significant increase of T2 and the decrease of electromyographic activity level for CRYO compared with CONT (between day 1 and day 3) in the medio-distal part of the biceps brachii. Conclusion: Although some indicators of muscle damage after severe eccentric exercise were delayed (ie, local formation of edema and decrease of muscle activity) by repeated air-pulsed cryotherapy, we provide evidence that this cooling procedure failed to improve long-term recovery of muscle performance. Clinical relevance: Four applications of air-pulsed cryotherapy in the 3 days after a strenuous eccentric exercise are ineffective overall in promoting long-term muscle recovery. Further studies taking into account the amount of exercise-induced muscle damage would allow investigators to make stronger conclusions regarding the inefficiency of this recovery modality.
Article
Muscle functional magnetic resonance imaging (mfMRI) is an innovative technique that offers a noninvasive method to quantify changes in muscle physiology following the performance of exercise. The mfMRI technique is based on signal intensity changes due to increases in the relaxation time of tissue water. In contemporary practice, mfMRI has proven to be an excellent tool for assessing the extent of muscle activation following the performance of a task and for the evaluation of neuromuscular adaptations as a result of therapeutic interventions. This article focuses on the underlying mechanisms and methods of mfMRI, discusses the validity and advantages of the method, and provides an overview of studies in which mfMRI is used to evaluate the effect of exercise and exercise training on muscle activity in both experimental and clinical studies.
Article
Full-text available
This study examined acute hormone and recovery responses to resistance exercise with slow movements. Six men performed three types of exercise regimens (five sets of knee extension exercise): (1) high-intensity resistance exercise with normal movement (HN; 1 s for lifting action, 1 s for lowering action), (2) low-intensity resistance exercise with slow movement (LS; 3 s for lifting action, 3 s for lowering action), and (3) low-intensity resistance exercise with normal movement (LN; 1 s for lifting action, 1 s for lowering action). The intensity in the first set was set at approximately 80% of 1RM for HN and 40% of 1RM for LS and LN. In the HN and LS, the subjects performed each exercise set until exhaustion. In the LN, both intensity and number of repetitions were matched with those for LS. The total work volume in the HN showed approximately double the value of LS and LN (P < 0.05). Electromyography (EMG) data indicated that LS showed sustained EMG signals throughout the exercise. During the exercise, the HN and LS showed lower muscle oxygenation levels. After the exercise, LS caused significantly greater norepinephrine and free testosterone responses (delta value) than in the HN and LN (P < 0.05). However, no significant difference was observed in the recovery of maximal isometric strength, isokinetic strength, and jump performance between the HN and LS. These results indicate that slow movements during the resistance exercise are important for the enhancement of hormonal responses, especially catecholamine and free testosterone, but they do not affect muscle strength recovery.
Article
Full-text available
Eccentric (lengthening) muscle actions involve the forced lengthening of active muscles. Compared with concentric (shortening) muscle actions subjected to the same relative work load, eccentric actions have lower oxygen consumption requirements, fewer activated motor units, and less lactate production. This study was conducted to determine if T2-weighted MR could show any difference in muscles performing these specific types of actions and, therefore, be useful for physiologic investigations of eccentric and concentric actions. Five subjects performed exhaustive exercise by doing isolated concentric actions (raising a dumbbell, flexing at the elbow) and eccentric muscle actions (lowering a dumbbell, extending the contralateral arm). T2-weighted MR images of the arms were obtained immediately before and after exercise. Muscles that performed concentric actions had increases in signal intensity, whereas muscles that performed eccentric actions showed little or no change. T2 relaxation times increased significantly (p less than .01) in all volunteers, but T2 relaxation times for the muscles that performed concentric actions were significantly higher than those for muscles that performed eccentric actions (p less than .01). Therefore, T2 times increased with both concentric and eccentric actions, but the images failed to show the changes in the muscles that performed the eccentric actions. These data demonstrate that assessment of T2 values can be used to distinguish between muscles that perform concentric actions and those that perform eccentric actions, and this phenomenon may be useful for further physiologic investigations of these specific types of muscle actions.
Article
Full-text available
Exercise is known to produce changes in the amount and distribution of water in skeletal muscle. Because MR imaging is highly sensitive to changes in water distribution, these changes should be detectable under appropriate imaging conditions. Imaging of the forearms and/or legs was performed in 16 volunteers at 0.35 T, before and after exercise. Exercises included finger flexion and extension, wrist flexion, ankle plantar flexion, and great toe extension. In the case of handgrip exercise, the level of exertion was quantitated. Individual muscles were frequently indistinguishable on preexercise scans. After exercise, active and inactive muscles could be clearly distinguished. For example, in the flexor digitorum profundus, finger flexion resulted in an increase in the image-derived estimate of T1 (T1 postexercise was 1037 +/- 162 msec vs T1 preexercise of 590 +/- 49 msec, p less than .001). T2 also increased (T2 postexercise was 35 +/- 2 msec vs T2 preexercise of 28 +/- 1 msec, p less than .001). Relative spin density also increased (p less than .001). T1, T2, and spin density subsequently decreased with time but were still increased above baseline at 10 min postexercise (p less than .005). Signal changes correlated moderately with the level of exertion (r = .63) and fatigue (r = .45). Vascular occlusion did not prevent intensity changes. Thus, changes in skeletal muscle MR signal intensity occur with exercise and appear to parallel known alterations in water distribution.
Article
Full-text available
The peripheral adaptation process associated with repeating eccentric training over a longer period of time was studied in m. vastus lateralis of eleven healthy males aged 24 +/- 4 years. The maximal dynamic concentric muscle strength was only slightly improved after 8 weeks of training. However, eccentric work capacity was dramatically increased (375%). A maximal eccentric stint immediately after fulfilled 8 weeks of training caused a selective glycogen depletion from the type 28 fibers. An increased number of type 2C fibers was observed. The ultrastructure analysis showed an essentially well-preserved fine structure. Volume density of mitochondria was somewhat higher in all fiber types after training. Z-band widths were not affected by eccentric training. It is concluded that skeletal musculature adapts itself in a functional manner to the extreme tension demands put on them. Improved coordination and reorganization of the contractile apparatus of muscle fibers are the determining mechanisms of this adaptation.
Article
Full-text available
Muscle soreness that has a delayed onset is a common feature among both athletes and untrained individuals who engage in unusual exercises. This study was designed to provide additional morphological data to assess the relevance and significance of our previous findings that the sore muscles contain fibers with disorganized myofibrillar material. Muscle biopsies were obtained from 12 males (mean age 25 +/- 7 years), who suffered from severe soreness in their thigh muscles 18--72 h following eccentric bicycle exercise. Their strength performance were tested in parallel. Knee extensor strength was decreased at all angular velocities soon after exercise but gradually increased over the subsequent days although slower at the fastest contractions. Disturbances of the cross-striated band pattern were constantly observed. They originated from the myofibrillar Z-band, which showed marked streaming, broadening and, at places, total disruption. The disturbances were found in every second to every third fiber up to 3 days after exercise and in one tenth of the fibers 6 days following the exercise. Type 2 fibers were predominantly affected. Thus, the eccentric exercise gives rise to muscles soreness and influences, on mechanical basis and selectively with regard to fiber type, the fine structure of the contractile apparatus.
Article
Full-text available
The fine structure of muscle fibres from m. vastus lateralis of nine healthy males (mean age 26 years) was investigated. Four individuals constituted non-exercised controls while five subjects participated in a two-months eccentric muscular training program. Specimens from the controls showed a well-preserved, regular myofibrillar band pattern while changes in the myofibrillar architecture were constantly found in specimens taken after the training program. These changes consisted of Z-band alterations, Z-bands being out of register, extra sarcomeres, Z-band extensions and bisected Z-bands. Between the separated Z-band halves, thin and thick myofilaments as well as abundant glycogen particles and/or ribosomes, were observed. Type-2 (fast-twitch) fibres were predominantly affected. Contrary to the controls the trained individuals constantly showed a greater variation in sarcomere lengths in Type-2 fibres than in Type-1 fibres. It is concluded that muscular work of high tension can induce fine-structural alterations. When repeated over a long period of time, extreme tension demands seem to initiate reorganization in the muscle fibres, predominantly in the, ultrastructurally defined, Type-2 fibres. This adaptation probably results in a better stretchability of the muscle fibres, reduces the risk for mechanical damage and brings about an optimal overlap between actin and myosin filaments.
Article
Samples of skeletal muscle were taken from 50 sites in each of 6 previously normal male autopsy subjects aged between 17 and 30 years. The respective percentages of Type I and Type II fibres were calculated and showed that there was a wide variation in fibre type proportions between the 6 samples in almost all the muscles studied. Examination of the mean fibre type proportions of each muscle revealed that predominantly tonic muscles had a high percentage of Type I fibres and predominantly phasic muscles had a high percentage of Type II fibres. Most of the muscles studied were known to fulfil both tonic and phasic functions, however, and showed no striking preponderance of either fibre type.The spatial distribution of the fibre types was examined in order to determine whether this was random or not. The number of “enclosed” fibres observed in the actual samples was compared statistically with the number expected to occur in a hexagonal lattice model, assuming a random distribution. In the great majority of muscles, the distribution of the fibre types was in fact random, though isolated instances of grouping of fibres of uniform type were noted in some distal muscles and more regularly in extensor digitorum brevis.The methods used in the quantitative assessment of the proportions and spatial distribution of the respective fibre types in normal muscle have obvious applications in the study of neuromuscular disease.
Article
Twelve physically active women underwent a 3-week program involving eccentric, isotonic arm flexion at 120 to 180% of their maximal isometric arm flexion strength (MVC). They then performed 5 trials at 120, 140, 160, and 180% MVC. High-speed video ascertained the mean eccentric angular velocity of each trial. Bipolar surface electrodes recorded mean integrated electromyographic activity (IEMG), mean frequency and peak amplitude of electromyographic activity (EMG), and rate of occurrence of isolated, high-amplitude spikes to identify differences in recruitment patterns at different angular velocities. A one-way MANOVA suggested that all variables responded differently to the increasing loads, thus two-way ANOVAs were conducted for each variable. Mean angular velocity increased significantly from 120 to 140% MVC and then tended to plateau. Peak amplitude was significantly greater for 120% MVC than for the 3 higher load categories. Mean IEMG, mean frequency, and rate of spike occurrence did not differ significantly across conditions. These results were equivocal as to whether there were significant differences in recruitment patterns for maximal eccentric arm flexions for speeds between 0.18 and 0.25 rad·s-1.
Article
An ischemic clamp model of exercise was used to evaluate the potential role of blood flow in mediating changes in the magnetic resonance imaging appearance of skeletal muscle. Proton relaxation times of muscle were serially estimated in 10 healthy subjects (a) before exercise, (b) after exercise in the presence of vascular occlusion (VO1), (c) during vascular reocclusion after 1 minute of reperfusion (VO2), and (d) after reinstitution of continuous flow. T1 and T2 of active muscles were increased during VO1. During VO2, there were additional increases in relaxation times of active muscles. Reinstitution of continuous flow was associated with a continuous decrease in the T2 of exercised muscle. Hence, blood flow was not required for increases in T1 and T2 with exercise. Additional relaxation time increases occurred after a brief period of reperfusion; however, continuous flow was associated with a decrease in T2.
Conference Paper
Signal changes in skeletal muscle immediately following exercise have been reported in the literature, and are prominent on T2-weighted spin echo, gradient echo and inversion recovery (STIR) images. In the present experiments, we set out to determine the time course of such muscle activation as well as to understand better the basis of the signal changes, by measurement of T1, T2, proton density and diffusion. These data indicate that the signal intensity change seen in MR images following exercise is due almost solely to changes in T2. The fact that no change in either T1 or spin density were detected is contrary to published literature and may reflect variations in experimental and data analysis protocols. The most likely mechanism for these large signal changes remains the previously described increase in the extracellular water fraction following exercise, which is presumed to reflect an increased volume fraction of water with relatively long relaxation time. It is notable in this context that the data indicate no evidence of multiexponential decay with TE or of D variations, and thus do not support this conclusion directly.
Article
The hip abductor muscles are considered important for gait and biomechanics of the hip joint; however, their specific function has not been defined precisely. The intensity of magnetic resonance imaging signals in skeletal muscle has been reported to increase immediately after exercise. Making use of this phenomenon, we evaluated the hip abductor muscles. Magnetic resonance imaging was performed after isometric exercise of the hip abductor in three positions (20 degrees of abduction, neutral, and 20 degrees of adduction). The abduction force of the hip was measured with a dynamometer, and electromyographic measurements were made simultaneously for the same hip positions. Additionally, magnetic resonance imaging was performed after one-legged stance. As the hip was more adducted, the signal intensity increased on the scans. The values for muscle force, as evaluated with the dynamometer and integrated electromyography, also supported the results. The increase in signal intensity of the gluteus minimus at 20 degrees of abduction and after one-legged stance was significantly greater than that of the gluteus medius (p < 0.0001 and p < 0.0001, respectively). The results of this study indicate that the gluteus minimus muscle, along with the gluteus medius, plays an important role in hip abduction, gait, and stabilization of the pelvis.
Article
Electromyography (EMG) is commonly used to determine the electrical activity of skeletal muscle during contraction. To date, independent verification of the relationship between muscle use and EMG has not been provided. It has recently been shown that relaxation- (e.g., T2) weighted magnetic resonance images (MRI) of skeletal muscle demonstrate exercise-induced contrast enhancement that is graded with exercise intensity. This study was conducted to test the hypothesis that exercise-induced magnetic resonance (MR) contrast shifts would relate to EMG amplitude if both measures reflect muscle use during exercise. Both MRI and EMG data were collected for separate eccentric (ECC) and concentric (CON) exercise of increasing intensity to take advantage of the fact that the rate of increase and amplitude of EMG activity are markedly greater for CON muscle actions. Seven subjects 30 +/- 2 (SE) yr old performed five sets of 10 CON or ECC arm curls with each of four resistances representing 40, 60, 80, and 100% of their 10 repetition maximum for CON curls. There was 1.5 min between sets and 30 min between bouts (5 sets of 10 actions at each relative resistance). Multiple echo, transaxial T2-weighted MR images (1.5 T, TR/TE 2,000/30) were collected from a 7-cm region in the middle of the arm before exercise and immediately after each bout. Surface EMG signals were collected from both heads of the biceps brachii and the long head of the triceps brachii muscles. CON and ECC actions resulted in increased integrated EMG (IEMG) and T2 values that were strongly related (r = 0.99, P < 0.05) with relative resistance.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
Clinical evaluation of the locomotor system has long been hampered by difficulty in assessing the morphologic and functional integrity of skeletal muscles. Diagnostic imaging represents a major advance in the diagnosis and management of patients with locomotor dysfunction through the possibility of probing beyond overlying soft tissues to identify muscle lesions, determine their extent, characterize their composition, direct invasive procedures, and monitor therapies. Magnetic resonance imaging (MRI) appears to be the most promising of available imaging methods, because of its great sensitivity to changes in muscle water distribution and fat content. Also, it can distinguish between individual deep and superficial muscles. Serial evaluations of many muscles are practical because of the safety of MRI. While the cost effectiveness in the workup of locomotor dysfunction remains to be determined, the scientific and practical clinical information now available merits further investigation by clinicians and radiologists alike. The purpose of this review is to describe the potential role of skeletal muscle MRI in evaluating the locomotor system.
Article
1. We have investigated the possibility that voluntary muscle lengthening contractions can be performed by selective recruitment of fast-twitch motor units, accompanied by derecruitment of slow-twitch motor units. 2. The behaviour of motor units in soleus, gastrocnemius lateralis and gastrocnemius medialis muscles was studied during (a) controlled isotonic plantar flexion against a constant load (shortening contraction, S), maintained plantar flexion, or dorsal flexion resisting the load and gradually yielding to it (lengthening contraction, L), (b) isometric increasing or decreasing plantar torque accomplished by graded contraction or relaxation of the triceps surae muscles, (c) isometric or isotonic ballistic contractions, and (d) periodic, quasi-sinusoidal isotonic contractions at different velocities. The above tasks were performed under visual control of foot position, without activation of antagonist muscles. The motor units discharging during foot rotation were grouped on the basis of the phase(s) during which they were active as S, S + L and L. The units were also characterized according to both the level of isometric ramp plantar torque at which they were first recruited and the amplitude of their action potential. 3. S units were never active during dorsal flexion; some of them were active during the sustained contraction between plantar and dorsal flexion. Most S + L units were active also during the maintenance phase and were slowly derecruited during lengthening; their behaviour during foot rotations was similar to that during isometric contractions or relaxations. L units were never active during either plantar or maintained flexion, but discharged during lengthening contraction in a given range of rotation velocities; the velocity of lengthening consistently influenced the firing frequency of these units. Such dependence on velocity was not observed in S + L units. 4. A correlation was found between the amplitude of the action potential and the threshold torque of recruitment among all the units. In addition, the amplitudes of both the action potential and the threshold torque were higher in the case of L units than in the case of S and S + L units. Most L units could be voluntarily recruited only in the case of ballistic isometric or isotonic contraction. 5. Occasionally, L units were directly activated by electrical stimulation of motor fibres and their conduction velocity was in the higher range for alpha-axons. In contrast, nerve stimulation could induce a reflex activation of S and S + L units.(ABSTRACT TRUNCATED AT 400 WORDS)
Article
1. Raw or rectified and integrated electromyograms (integrated EMGs) of the leg muscles were recorded during (a) isotonic ramp shortening or lengthening contractions consisting of foot plantar flexions against a constant load, or dorsal flexions accomplished by braking the load and yielding to it, respectively, and (b) isometric increasing or decreasing plantar torques accomplished by graded contractions or relaxations of the triceps muscles. 2. During plantar flexions or increasing torques, the EMG of soleus, gastrocnemius lateralis, medialis, and peroneus increased in parallel. During decreasing torques, motor unit derecruitment took place gradually and simultaneously. The tibialis anterior was silent. During dorsal flexions, one of two characteristic patterns was observed in different subjects: (a) soleus was abruptly derecruited at the beginning of the task, while gastrocnemius lateralis (or medialis) exhibited a large recruitment lasting throughout the lengthening contraction; (b) soleus remained active during the task, showing large motor unit potentials, while the gastrocnemius lateralis recruitment was of a lesser extent than in (a). Peroneus derecruitment was gradual and tibialis anterior activity was absent in both cases. 3. The EMG patterns observed during plantar flexions or in increasing and decreasing torques, and the two patterns observed during shortening or lengthening contractions, were closely reproduced during sinusoidal oscillations of the foot or in isometric contractions and relaxations. 4. When recruitment of the gastrocnemius lateralis was present during dorsal flexion, the slope of its integrated EMG envelope was steeper, the higher the velocity of lengthening contraction. The most rapid and the slowest tasks, however, did not require its activation. Gastrocnemius lateralis integrated EMGs of an amplitude similar to those occurring during lengthening contractions were observed only during ballistic plantar flexions. 5. The two patterns of triceps activation occurring during lengthening contraction could be traced to different mechanical characteristics of the soleus muscles, the gastrocnemius lateralis being activated preferentially in subjects with long soleus half-relaxation times, and the soleus in subjects with short soleus half-relaxation times. 6. The soleus and gastrocnemius lateralis H reflexes were tested during shortening and lengthening contractions.(ABSTRACT TRUNCATED AT 400 WORDS)
Article
Six subjects performed one-legged dynamic knee-extension. Blood samples were drawn from the femoral artery and vein, and muscle biopsies were obtained from the quadriceps muscle. Leg blood flow was measured by the thermodilution technique, and 3H-inulin was infused for determination of extra- and intracellular muscle water shifts. During the submaximal work load (S) muscle lactate increased, whereas muscle pH remained almost constant; after maximal exercise (M) the values markedly increased for lactate and decreased for pH. Except for a release of lactate from the exercising muscles, K was continuously released throughout S, and this release increased during M. Immediately when the muscles relaxed, the K release was converted to a K re-uptake. The calculated K loss, based on v- a and flow values, agreed with the decrease in muscle K content from 458 mmol/kg dw at rest to 414 mmol/kg dw at exhaustion (P less than 0.05), as analyzed on the muscle biopsies. Muscle water content increased during S mainly because of an increased extracellular H2O, whereas during M the largest increase occurred in intracellular H2O (H2Oi). Because of the simultaneous K loss and H2Oi increase in the exercising muscle the intracellular [K] was calculated to decrease from 165 mM at rest to 129 mM at exhaustion. This decrease and an increase in extracellular [K] from 4.5 mM at rest to greater than 6.0 mM at exhaustion affects the muscle membrane excitability. Muscle fatigue may thus not only be caused by changes within the cell, affecting energy metabolism or actin-myosin reaction, but may be located at the membrane protecting the cell against overload.
Forearm flexor muscles of 5 male subjects were loaded during 40 repeated maximum concentric and eccentric contractions of constant velocity in different test sessions. Muscle tension and 'integrated' electromyographic activity (IEMG) were registered for every contraction and oxygen consumption was measured during the whole work period of 12 min. The results indicated first that the muscle tension decreased to about 50% in eccentric and to 80% in concentric work when the last contractions were compared with the first ones. Second, IEMG activity of the studied muscle declined continuously during the entire work period, and the pattern of this decrease was the same in both types of work. The oxygen consumption was similar also in the 2 fatigue conditions reaching a value of about 0.8 l/min at the end of the work periods. It is suggested that the neural input and energy requirement are equal in maximal concentric and eccentric work, but the difference observed in the fatigue effects on muscle tension may be of mechanical origin emphasizing the extreme loading of the elastic components of muscle during the high tension eccentric contractions.
Article
A series of experiments was performed to measure the relationships between the integrated surface EMG and the mechanical state of the cineplastic biceps muscle of one subject. The muscle was studied during static and dynamic isometric contractions at different muscle lengths and during constant velocity isotonic contractions at different loads. The cineplastic biceps results are compared with results obtained from the intact biceps.
Article
Many exercise protocols used in physiological studies assume homogeneous and diffuse muscle recruitment. To test this assumption during a "standard" wrist flexion protocol, variations in muscle recruitment were assessed using MRI in eight healthy subjects. Variations were assessed by comparing the right to the left forearms and the effect of slight (15 degrees) pronation or supination at the wrist. Postexercise imaging showed focal regions of increased signal intensity (SI), indicating relatively strong recruitment, most often in entire muscles, although occasionally only in subvolumes of muscles. In 15 of 26 studies, flexor carpi radialis (FCR) showed more SI than flexor carpi ulnaris, while in 11 studies SI in these muscles increased equivalently. Relatively greater FCR recruitment was seen during pronation and/or use of the nondominant side. Palmaris longus, a wrist flexor, did not appear recruited in 4 of 11 forearms in which it was present. A portion of the superficial finger flexor became hyperintense in 89% of studies, while recruitment of the deep finger flexor was seen only in 43%. Inter- and intraindividual variations in forearm muscle recruitment should be anticipated in physiological studies of standard wrist flexion exercise protocols.
Article
To examine the effect of strenuous exercise on the magnetic resonance imaging (MRI) characteristics of the rotator cuff tendon. A second objective was to define an optimal time to image the rotator cuff and possibly eliminate exercise-induced false positives. Five male subjects from 24 to 38 years old with normal rotator cuffs by history, physical examination, and screening MRI underwent a rotator cuff exercise session on the Biodex System 2 (Biodex, Shirley, New York). The exercise sessions were followed by sequential MRI scans of the exercised shoulder. These were performed immediately and at 8 h and 24 h after exercise. The rotator cuff tendon and subacromial-subdeltoid bursal signal remained unchanged from the pre-exercise through the 24-h post-exercise scans. The rotator cuff muscle signal was increased in five of five subjects on the immediate post-exercise fat-suppressed T2-weighted images. This signal returned to baseline by the 8-h scan. Positive findings of rotator cuff pathology on MRI after strenuous athletic activity should not be discounted as normal exercise-induced changes. Also, diagnostic MRI scanning may take place after a practice session without an increased risk of false positives.
This study examined hypertrophy after head extension resistance training to assess which muscles of the complicated cervical neuromuscular system were used in this activity. We also determined if conventional resistance exercises, which are likely to evoke isometric action of the neck, induce generalized hypertrophy of the cervical muscle. Twenty-two active college students were studied. [mean (SE) age, weight and height: 21 (1) years, 71 (4) kg and 173 (3) cm, respectively]. Subjects were assigned to one of three groups: RESX (head extension exercise and other resistance exercises), RES (resistance exercises without specific neck exercise), or CON (no training). Groups RESX (n = 8) and RES (n = 6) trained 3 days/week for 12 weeks with large-muscle mass exercises (squat, deadlift, push press, bent row and mid-thigh pull). Group RESX also performed three sets of ten repetitions of a head extension exercise 3 days/week with a load equal to the 3 x 10 repetition maximum (RM). Group CON (n = 8) was a control group. The cross-sectional area (CSA) of nine individual muscles or muscle groups was determined by magnetic resonance imaging (MRI) of the cervical region. The CSA data were averaged over four contiguous transaxial slices in which all muscles of interest were visible. The 3 x 10 RM for the head extension exercise increased for RESX after training [from 17.9 (1.0) to 23.9 (1.4) kg, P < 0.05] but not for RES [from 17.6 (1.4) to 17.7 (1.9) kg] or CON [from 10.1 (2.2) to 10.3 (2.1) kg]. RESX showed an increase in total neck muscle CSA after training [from 19.5 (3.0) to 22.0 (3.6) cm2, P < 0.05], but RES and CON did not [from 19.6 (2.9) to 19.7 (2.9) cm2 and 17.0 (2.5) to 17.0 (2.4) cm2, respectively]. This hypertrophy for RESX was due mainly to increases in CSA of 23.9 (3.2), 24.0 (5.8), and 24.9 (5.3)% for the splenius capitis, and semispinalis capitis and cervicis muscles, respectively. The lack of generalized neck muscle hypertrophy in RES was not due to insufficient training. For example, the CSA of their quadriceps femoris muscle group, as assessed by MRI, increased by 7 (1)% after this short-term training (P < 0.05). The results suggest that: (1) the splenius capitis, and semispinalis capitis and cervicis muscles are mainly responsible for head extension; (2) short-term resistance training does not provide a sufficient stimulus to evoke neck muscle hypertrophy unless specific neck exercises are performed; and (3) the postural role of head extensors provides modest loading in bipeds.
Article
The effect of different types of exercise upon echo planar (EP) magnetic resonance (MR) images was examined during and after both dynamic and isometric dorsi-flexion exercises at matched workloads and durations. Healthy untrained subjects performed either dynamic exercise through a full range of motion and against a constant resistance or isometric exercise at the center of the range of motion and against a constant resistance at 25 or 70% their measured maximum voluntary contraction (MVC). EP MR images were acquired at 1.5 T every 4 s before (4 images), during (27 images), and after (29-65 images) exercise. A spin echo EP sequence was employed with TE = 30 ms, TR = 4000 ms, FOV = 20 x 40 cm, 64 x 128 matrix. The changes in proton transverse relaxation rate (deltaR2, [s(-1)]) relative to values obtained before exercise were calculated from individual images at different times during and after exercise. At both 70 and 25% of MVC, the maximum deltaR2 after dynamic exercise (-8.38+/-0.32 s(-1) (70%), -6.47+/-1.23s(-1) (25%)) was significantly greater (P < or = 0.05) than after isometric exercise (-5.91+/-0.67 s(-1) (70%), -3.80+/-0.87s(-1) (25%)). Throughout the period that recovery was monitored, the recovery patterns of deltaR2 following isometric and dynamic exercise at both workloads remained parallel. We conclude that exercise-induced changes in MR images are influenced not only by workload and exercise duration but also by the type of exercise, and we postulate that these differences result from the different physiological responses elicited by the different types of exercise.
1.1. The integrated electromyogram parallels tension in human muscle contracting isometrically.2.2. No quantitative relation between EMG and tension exists when a muscle is allowed to change in length.3.3. No quantitative relation between EMG and muscle power exists.4.4. The amplitude of the EMG characteristically diminishes in large human muscles when they are stretched. This phenomenon has not been fully explained.5.5. It is shown that a lag of approximately 0.08 ± 0.02 sec. exists between peak electrical activity and peak tension of human muscle, which should be taken into account in the analysis of rapid movements.
Specificity of resistance training responses in neck muscle size and strength Acute effects of exercise on MR imaging of skeletal muscle in normal volunteers
  • M S Conley
  • M H Stone
  • G A Dudley Fleckenstein
  • R C Canby
  • R W Parkey
CONLEY, M. S., M. H. STONE, M. NIMMONS, and G. A. DUDLEY. Specificity of resistance training responses in neck muscle size and strength. Eur. J. Appl. Physiol. 75:443– 448, 1997. 9. FLECKENSTEIN, J. L., R. C. CANBY, R. W. PARKEY, and R. M. PESHOCK. Acute effects of exercise on MR imaging of skeletal muscle in normal volunteers. AJR 151:231–237, 1988.
Selective recruitment of high threshold human motor units during voluntary isotonic lengthening of active muscles Isometric and dynamic exercise studied with echo planar MRI
  • A Nardone
  • M Price
  • R P Kennan
NARDONE, A., C. ROMANO, and M. SCHIPPATI. Selective recruitment of high threshold human motor units during voluntary isotonic lengthening of active muscles. J. Physiol. 409:451– 471, 1989. 23. PRICE, T. B., R. P. KENNAN, and J. C. GORE. Isometric and dynamic exercise studied with echo planar MRI. Med. Sci. Sports Exerc. 30:1374 –1380, 1998.
Relationship of human electromyogram to muscular tension
  • H J Ralston
  • C M Saunders
  • E W Wright
INMAN, V. T., H. J. RALSTON, C. M. SAUNDERS, FEINSTEIN B., and E. W. WRIGHT. Relationship of human electromyogram to muscular tension. EEG Clin. Neurophysiol. 4:187, 1952.
Therapeutic Exercise: Foundations and Techniques
  • L A Colby
KINSER, C., and L. A. COLBY. Therapeutic Exercise: Foundations and Techniques. Philadelphia: F. A. Davis, 1991, pp. 1-107.