Muscle Physiology

The rapid growth of wireless communication technologies has caused public concerns regarding the biological effects of electromagnetic radiations on human health. Some early reports indicated a wide variety of non-thermal effects of electromagnetic radiation on amphibians such as the alterations of the pattern of muscle extractions. This study is aimed at investigating the effects of exposure to radiofrequency (RF) radiation emitted from mobile phone jammers on the pulse height of contractions, the time interval between two subsequent contractions and the latency period of frog's isolated gastrocnemius muscle after stimulation with single square pulses of 1V (1 Hz). Frogs were kept in plastic containers in a room. Animals in the jammer group were exposed to radiofrequency (RF) radiation emitted from a common Jammer at a distance of 1m from the jammer's antenna for 2 hours while the control frogs were only sham exposed. Then animals were sacrificed and isolated gastrocnemius ...

During the early period of running after cycling, EMG patterns of the leg are modified in only some highly trained triathletes. The majority of studies have analysed muscle EMG patterns at arbitrary, predetermined time points. The purpose of this study was to examine changes to EMG patterns of the lower limb at physiologically determined times during the cycle-run transition period to better investigate neuromuscular adaptations. Six highly trained triathletes completed a 10min isolated run (IR), 30min of rest, then a 20min cycling procedure, before a 10min transition run (C-R). Surface EMG activity of eight lower limb muscles was recorded, normalised and quantified at four time points. Oxygen uptake and heart rate values were also collected. Across all muscles, mean (±SD) EMG patterns, demonstrated significant levels of reproducibility for each participant at all four time points (α<0.05; r=0.52-0.97). Mean EMG patterns during C-R correlated highly with the IR patterns (α<0.0...

The deadlift exercise is commonly performed to develop strength and power, and to train the lower-body and erector spinae muscle groups. However, little is known about the acute training effects of a hexagonal barbell vs. a straight barbell when performing deadlifts. Therefore, the purpose of this study was to examine the hexagonal barbell in comparison with the straight barbell by analyzing electromyography (EMG) from the vastus lateralis, biceps femoris, and erector spinae, as well as peak force, peak power, and peak velocity using a force plate. Twenty men with deadlifting experience volunteered to participate in the study. All participants completed a 1 repetition maximum (1RM) test with each barbell on 2 separate occasions. Three repetitions at 65 and 85% 1RM were performed with each barbell on a third visit. The results revealed that there was no significant difference for 1RM values between the straight and hexagonal barbells (mean 6 SD in kg = 181.4 6 27.3 vs. 181.1 6 27.6, respectively) (p . 0.05). Significantly greater normalized EMG values were found from the vastus lateralis for both the concentric (1.199 6 0.22) and eccentric (0.879 6 0.31) phases of the hexagonal-barbell deadlift than those of the straight-barbell deadlift (0.968 6 0.22 and 0.559 6 1.26), whereas the straight-barbell deadlift led to significantly greater EMG values from the bicep femoris during the concentric phase (0.835 6 0.19) and the erector spinae (0.753 6 0.28) during the eccentric phase than the corresponding values for the hexagonalbarbell deadlift (0.723 6 0.20 and 0.614 6 0.21) (p # 0.05). In addition, the hexagonal-barbell deadlift demonstrated significantly greater peak force (2,553.20 6 371.52 N), peak power (1,871.15 6 451.61 W), and peak velocity (0.805 6 0.165) values than those of the straight-barbell deadlift (2,509.90 6 364.95 N, 1,639.70 6 361.94 W, and 0.725 6 0.138 m$s 21 , respectively) (p # 0.05). These results suggest that the barbells led to different patterns of muscle activation and that the hexagonal barbell may be more effective at developing maximal force, power, and velocity.

Background: Globalization is having a significant impact on health care and the demands put on the health professions are increasing day by day. In the healthcare sector, professions like those of Doctors and Nurses are well known than the other paramedical professions like Physiotherapy. Physiotherapy plays a major part in various conditions. The demand of the physiotherapy continues to increase with increase in aging population. Despite the tremendous growth in the field, researchers have documented that the public especially the students does not understand the different aspects of this profession. It is mandatory to give appropriate information about the various professions to the higher secondary students so that it would be useful in choosing their career pathway.
Methods: The study was Descriptive in nature. The samples were taken through the purposive sampling technique. The subjects were taken from various schools. 300 samples were collected. A detailed explanation of research and purpose of the study were given and the informed consent were obtained from all participants.
Results: The data was meaningfully assorted. The results came out positively proves that the high school students of Ludhiana had a great knowledge about the every aspect of physiotherapy.
Conclusion: Awareness of physiotherapy was found to be increasing amongst the science students who participated in the study. Mass media was considered to be the most influential source of information and many respondents cited television as the source of information.
Keywords: Physiotherapy, Awareness, Paramedical profession, Healthcare System, Musculoskeletal, Neurological conditions.

Complex interactions between the nervous, muscular, and
skeletal systems produce the wide variety of movements
available for human task execution. Each of these systems
is often studied in isolation, but movement scientists and
clinicians are forced to integrate the entire neuromusculoskeletal
system to understand functional limitations and prescribe viable
treatments. Although this approach is appropriate for clinical decision making, the details of each system are often overlooked, perhaps at the expense of accurate and/or innovative treatment approaches. The purpose of this paper was to describe the fundamental organization and physiology of the muscles controlling hip movement.

A motor unit is composed of a motor neuron and all the muscle fibers that are innervated by that motor neuron. In a persistent muscle contraction, multiple motor units are firing repetitively throughout the contraction of the muscle. The strength of a muscle contraction is related to the number of motor units in the muscle that are activated during the same time period. The electromyogram (EMG) recorded during the muscle contraction is seen as a burst of spike-like signals, and the duration of the burst is about equal to the duration of the muscle contraction.

Background. Self-myofascial release (SMR), a type of myofascial release is a popular therapy performed by the individual using a foam roller. The aim of the present study was to evaluate the immediate effect of SMR using a foam roller on electromyographic muscle activity during isometric contraction. Material and methods. Twenty healthy adults (17 men and 3 women; mean: age = 23 ± 2 years) volunteered for the study. The 16-channel modular Wi-Fi myon EMG system, compatible with myon ProEMG software, was used for the recording. The sEMG electrodes (Ag/AgCl) were distributed bilaterally on the skin overlaying VMO. The participants were instructed to assume a half knee bend position for 60 seconds. SMR was performed by the participants unilaterally in right anterior thigh in a prone position using The Grid Foam Roller. Second sEMG measurement according to the same protocol was performed immediately after SMR. Results. Significant differences in spectral median frequency (MF) the electrical activity of the VMO muscles before and after SMR of right VMO muscle was observed only on the left VMO muscle. In right VMO muscle, the analysis did not show a significant difference in spectral median frequen­cy between first and second sEMG measurement. Conclusions. Use of SMR affects the reduction of muscle fatigue tested with the spectral median frequency of EMG signal. Foam rolling could beneficial in enhances muscular recovery.

Esta es una guía fácil y didáctica que explicara de forma clara como poder aumentar el tamaño de los glúteos. Se considerara al lector una persona que con cierto nivel de conocimiento y previa experiencia entrenando, ante cualquier duda contactarse con el autor. Esta es una guía general que tiene el propósito de ser un reservorio de conocimiento para que luego lo apliques en base a tu criterio, es por ello que no usaremos un peso específico para cada ejercicio ni un número exacto de series y repeticiones, solo ciertos parámetros generales que podrías considerar para maximizar tus ganancias. Por ende es un compilado de normas generales que te ayudaran con tu meta.

Hay tres tipos de tejido muscular en el cuerpo: el músculo estriado (voluntario) o esquelético, el músculo no estriado (involuntario) o liso y el músculo cardiaco. La constitución química del músculo esquelético es la que ha sido más completamente estudiada: 75% es agua, 20% proteína y 5% restante está compuesto de material inorgánico, ciertas substancias orgánicas "extractas" y carbohidratos (glucógeno y sus derivados). Tejido excitable: el músculo 4 NRC: 10871 Equipo: 5

Jaringan otot atau biasa disebut otot telah dijumpai mulai dari invertebrata sampai vertebrata. Otot merupakan bagian terbesar dari tubuh manusia. Hampir setengah dari keseluruhan berat tubuh manusia disumbang oleh otot. Jaringan otot seperti jaringan yang lain memiliki sifat peka terhadap rangsangan (sifat iritabilitas), mampu merambatkan implus, mampu melaksanaan metabolisme, dan maampu membelah diri. Sifat jaringan otot yang khas adalah kemampuannya  untuk berkontraksi yang tinggi. Sifat kontraktilitas ini disebabkan sel – sel otot memiliki protein kontraktil,yaitu aktin dan myosin. Sistem otot adalah sistem tubuh yang memiliki fungsi untuk alat gerak, menyimpan glikogen dan menentukan postur tubuh. Terdiri atas otot polos, otot jantung dan otot rangka.

Effects of two different training regimens on the contractile properties of the quadriceps muscle were studied in six individuals with spinal cord injury. Each subject had both limbs trained with the two regimens, consisting of stimulation with low frequencies (LF) at 10 HZ or high frequencies (HF) at 50 HZ; one limb of each subject was stimulated with the LF protocol and the other with the HF regimen. Twelve weeks of daily training increased tetanic tension by ∼20%, which was not significantly different between training regimens. Interestingly, after HF but not LF training, the unusual high forces at the low frequency range of the force-frequency relationship decreased, possibly due to a reduced activation per impulse. After LF but not HF training, force oscillation amplitudes declined (by 33%) as relaxation tended to slow, which may have opposed possible effects of reduced activation as seen after HF training. Finally, fatigue resistance also increased rapidly after LF training (by 43%) but not after HF training. These results indicate that different types of training may selectively change different aspects of function in disused muscles.

Ever since it was first observed and especially so in recent years, the phenomenon of the so-called "sticking point'" in resistance training has attracted a substantial amount of sports and exercise science research. Broadly speaking the sticking point is understood as the position in the range-of-motion of a lift at which a disproportionately large increase in the difficulty to continue the lift is experienced. Hence the sticking point is inherently the performance bottleneck and is also associated with an increased chance of exercise form deterioration or breakdown. Understanding the aspects of lifting performance which should be analysed in order to pinpoint the cause of a specific sticking point and therefore devise an effective training strategy to overcome it, is of pervasive importance to strength practitioners and instrumental for the avoidance of injury and continued progress. In this paper we survey a range of physiological and biomechanical mechanisms which contribute to the development of sticking points, and led by this insight review and analyse the findings of the existing observational research on the occurrence of sticking points in three ubiquitous exercises: the bench press, the squat, and the deadlift. The findings of our analysis should be used to inform future research and current resistance training practice.

In the context of resistance training the so-called "sticking point"  is commonly understood as the position in a lift in which a disproportionately large increase in the difficulty to continue the lift is experienced.  If the lift is taken to the point of momentary muscular failure, the sticking point is usually where the failure occurs.  Hence the sticking point is associated with an increased chance of exercise form deterioration or breakdown.  Understanding the mechanisms that lead to the occurrence of sticking points, as well as different training strategies which can be used to overcome them is important to strength practitioners (trainees and coaches alike), and instrumental for the avoidance of injury and continued progress.  In this paper we survey and consolidate the body of existing research on the topic: we discuss different definitions of the sticking point adopted in the literature and propose a more precise definition, describe different muscular and biomechanical aspects which give rise to sticking points, and review the effectiveness of different training modalities used to address them.

Creatine supplementation has been found to significantly increase muscle strength and hypertrophy in young adults (≤ 35 yr) particularly when consumed in conjunction with a resistance training regime. Literature examining the efficacy of creatine supplementation in older adults (55-82 yr) suggests creatine to promote muscle strength and hypertrophy to a greater extent than resistance training alone. The following is a review of literature reporting on the effects of creatine supplementation on intramuscular high energy phosphates, skeletal muscle morphology and quality of life in older adults. Results suggest creatine supplementation to be a safe, inexpensive and effective nutritional intervention, particularly when consumed in conjunction with a resistance training regime, for slowing the rate of muscle wasting that is associated with aging. Physicians should strongly consider advising older adults to supplement with creatine and to begin a resistance training regime in an effort to enhance skeletal muscle strength and hypertrophy, resulting in enhanced quality of life.

The aim of this investigation was to determine the contractile properties of motor units within 3 segments of the gluteus maximus utilizing a laser-based mechanomyographic (MMG) technique. The intention was to determine whether there were segmental differences in motor unit contractile properties and whether these differences may be related to the muscle segment's function and its fibre type composition.

Ce texte vise à mettre en place une série d’éléments devant servir de fondement à une interprétation phénoménologique de la pesanteur, à savoir une caractérisation de la pesanteur telle qu’elle se montre et fait sens pour l’individu dans son rapport quotidien, « préréflexif », au monde. Bien que les réflexions ici proposées soient prioritairement à rattacher à la philosophie, nous convoquerons une série d’observations issues des sciences empiriques – au premier chef la psychologie – pour appuyer leur cheminement. Après avoir montré, sur la base d’un ensemble de résultats de la psychologie, que le poids d’un objet manipulé est spontanément évalué/perçu par l’individu sur la base de l’effort requis pour le soulever, et que l’amplitude de l’effort devant être fourni pour développer un niveau de force donné est elle-même proportionnée à la capacité de production de force variable dont dispose l’individu, nous proposerons une première caractérisation phénoménologique de la pesanteur. Nous chercherons à partir de là à mettre en lumière les structures qui, du côté du sujet percevant, rendent possible la manifestation de quelque chose de tel que le poids. Deux idées principales s’imposeront : d’une part, la pesanteur peut être comprise comme une des manières dont l’individu se rend intelligible son monde en référant l’objet qu’il manipule à la prise dont il dispose, au sens de la latitude de son pouvoir d’action ; d’autre part, parce que le poids n’est pas quelque chose que l’on voit mais quelque chose que l’on supporte, quelque chose qui pour être perçu doit être pris en charge, seul un percevant capable de se rapporter à soi comme à une puissance finie, un être en perpétuel épuisement, aura la conformation requise pour rencontrer quelque chose de tel que le poids – pour ouvrir un monde où règne la pesanteur.

We examined the expression and function of a gene we previously cloned from its downregulation in a muscle atrophy model. The encoded protein was named myodulin because of sequence homologies with the cartilage-specific chondromodulin-I (ChM-I) protein, its restricted expression in skeletal muscle tissue, and its modulating properties on vascular endothelial cells described here. We investigated the expression of myodulin in muscle fibers and cultured muscle cells. Myodulin RNA messengers were found in muscle fibers and their tendon extensions. Overexpression of myodulin fused to a FLAG peptide showed evidence of a muscle cell surface protein. Myodulin functions were assessed from similarities with chondromodulin-I. Coculture experiments using C2C12 mouse myoblasts or myotubes, which stably overexpress myodulin, with H5V mouse cardiac vascular endothelial cells revealed that myodulin had a very active role in the invasive action of endothelial cells, without any evidence of extracellular myodulin secretion. Our results suggest that myodulin may be a muscle angiogenic factor operating through direct cell-to-cell interactions. This role is consistent with the correlation between modulations in myodulin expression and modifications in muscle microvascularization associated with activity-dependent muscle mass variations.

Locomotory systems evolved through adaptive radiations in response to changing environments and behavioural challenges such as predation avoidance and foraging niches (Pontzer & Wrangham 2004; Marzke, et al. 2015). Locomotory behaviours such as quadrupedalism, brachiation, knuckle-walking and facultative bipedalism are commonly practiced by Great Apes in arboreal environments; however, terrestrial, habitual bipedality is practiced today solely by Homo. sapiens.
Interest in human-like bipedality has attracted a focus on musculo-skeletal structural comparisons of the upper limb (i.e. quadrupedal forelimb) (Kikuchi 2010; Myatt, et al. 2012) and lower limb (hindlimb) (DeSilva 2009; Oishi, et al. 2012) between extant apes and modern humans. Chimpanzees (Pan. troglodytes) are often selected for comparison with H. sapiens due to their close phylogenetic relationship (Young, Hallgrimsson 2005).
This paper has two goals: first, the serial homologous nature of the upper and lower limbs are discussed in relation to evolutionary developmental programs of modular musculo-skeletal structures for integrated evolution of muscle groups for specific functional roles. Secondly, the gross and functional anatomies of chimpanzees and humans are detailed in relation to locomotive functionalities.

The naturally occurring polyamines, spermidine, spermine, and their precursor putrescine, play indispensible roles in both prokaryotic and eukaryotic cells, from basic DNA synthesis to regulation of cell proliferation and differentiation. The rate-limiting polyamine biosynthetic enzymes, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase, are essential for mammalian development, with knockout of the genes encoding these enzymes, Odc1 and Amd1, causing early embryonic lethality in mice. In muscle, the involvement of polyamines in muscle hypertrophy is suggested by the concomitant increase in cardiac and skeletal muscle mass and polyamine levels in response to anabolic agents including b-agonists. In addition to b-agonists, androgens, which increase skeletal mass and strength, have also been shown to stimulate polyamine accumulation in a number of tissues. In muscle, androgens act via the androgen receptor to regulate expression of polyamine biosynthetic enzyme genes, including Odc1 and Amd1, which may be one mechanism via which androgens promote muscle growth. This review outlines the role of polyamines in proliferation and hypertrophy, and explores their possible actions in mediating the anabolic actions of androgens in muscle.

A novel approach has been developed for the quantification of total mechanical power output produced by an isolated, well-defined muscle group during dynamic exercise in humans at different contraction frequencies. The calculation of total power output comprises the external power delivered to the ergometer (i.e., the external power output setting of the ergometer) and the "internal" power generated to overcome inertial and gravitational forces related to movement of the lower limb. Total power output was determined at contraction frequencies of 60 and 100 rpm. At 60 rpm, the internal power was 18+/- 1 W (range: 16-19 W) at external power outputs that ranged between 0 and 50 W. This was less (P<0.05) than the internal power of 33+/-2 W (27-38 W) at 100 rpm at 0-50 W. Moreover, at 100 rpm, internal power was lower (P<0.05) at the higher external power outputs. Pulmonary oxygen uptake was observed to be greater (P<0.05) at 100 than at 60 rpm at comparable total powe...

Aim: Our work investigates the use of "external momentum" in the context of hypertrophy oriented training. This is momentum supplied to the load (such as a dumbbell) used in an exercise by means of action of muscles not inherently involved in the exercise. We challenge the general consensus that the use of such momentum often described as "cheating" is counterproductive.

Methods: We focus on the use of external momentum in the shoulder lateral raise and adopt a framework whereby exercise execution is simulated on a computer. This is achieved using a physical model of motion which is combined with anthropomorphic measurements and empirical data of muscular recruitment from previous work.

Results: The introduction of moderate momentum (producing initial angular velocities around 57.5 deg/s) increases the torque of the target muscles even without an increase in the load used. A moderate increase in the load and the use of momentum allows the torque to be increased even further. In contrast, excessive use of momentum results in lower demands on the target muscles, while an excessive increase of the load reduces the total hypertrophy stimulus by virtue of the decreased number of repetitions which can be performed successfully and thus the dramatically shortened time under tension.

Conclusion: Our results disprove the conventional belief that the use of external momentum necessarily reduces the overload of the target muscles. A moderate use of external momentum increases both the per-repetition peak torque and the total hypertrophy stimulus in a set.

Despite increasing use of whole body vibration during exercise an understanding of the exact role of vibration and the supporting physiological mechanisms is still limited. An important aspect of exercise analysis is the utilisation of oxygen, however, there have been limited studies considering tissue oxygenation parameters, particularly during dynamic whole body vibration (WBV) exercise. The aim of this study was to determine the effect of adding WBV during heel raise exercises and assessing changes in tissue oxygenation parameters of the lateral gastrocnemius using Near Infra Red Spectroscopy (NIRS). Twenty healthy subjects completed ten alternating sets of 15 heel raises (vibration vs. no vibration). Synchronous oxygenation and motion data were captured prior to exercise to determine baseline levels, for the duration of the exercise and 20 sec post exercise for the recovery period. Both vibration and no vibration conditions elicited a characteristic increase in deoxyhaemoglobin and decreases in oxyhaemoglobin, total haemoglobin, tissue oxygenation index and normalised tissue haemoglobin index which are indicative of local tissue hypoxia. However, the addition of vibration elicited significantly lower (p < 0.001) depletions in oxyhaemoglobin, total haemoglobin, normalised tissue haemoglobin index but no significant differences in deoxyhaemoglobin. These findings suggest that addition of vibration to exercise does not increase the cost of the exercise for the lateral gastrocnemius muscle, but does decrease the reduction in local muscle oxygenation parameters, potentially resulting from increased blood flow to the calf or a vasospastic response in the feet. However, further studies are needed to establish the mechanisms underlying these findings.

Vermilion is both a brilliant red or scarlet pigment, originally made from the powdered mineral cinnabar, and the corresponding color. It is commonly used in Hindu culture, primarily by women, and was widely used in the art and decoration of Ancient Rome, in the illuminated manuscripts of the Middle Ages, in the paintings of the Renaissance, and in the art and lacquerware of China, during the time it was said that China was the home land of Dragons.

The word vermilion came from the Old French word vermeillon, which was derived from vermeil, from the Latin vermiculus, the diminutive of the Latin word vermis or worm, wormlike creature like a snake or winged and flying serpent, as a dragon.
The name originated because it had a similar color to the natural red dye made from an insect, Kermes vermilio, which was widely used in Europe. The first recorded use of "vermilion" as a color name in English was in 1289.
The term cinnabar was used interchangeably with vermilion until the 17th century, when vermilion became the more common name. Now the term "cinnabar" is used in mineralogy and crystallography for the red crystalline form of mercury sulfide HgS. Thus, the natural mineral pigment is called "cinnabar", and its synthetic form is called "vermilion". In ancient times, the term "cinnabar" could also be applied to red lead.

related disease: mutations in nonmuscle MYH9 Mouse models of http://bloodjournal.hematologylibrary.org/content/119/1/238.full.html Updated information and services can be found at: (381 articles) Platelets and Thrombopoiesis Articles on similar topics can be found in the following Blood collections http://bloodjournal.hematologylibrary.org/site/misc/rights.xhtml#repub_requests

ABSTRACT: The influence of earthworm’s environment on its biology needs to be well understood. This study investigated the impact of sawmilling activities on the diversity, abundance and mineral composition of the tissues of earthworm species in Lafenwa, Sapon, Isale-Ake and Kotopo sawmills of Abeokuta (7o9’12’’N-3o19’35’’E). The arboretum of the Federal University of Agriculture, Abeokuta was used as control. Earthworms were sampled in the morning hours from four random samples of 25x25x30cm and carefully counted. Weight of the earthworms was taken and tissues mineral composition determined using Atomic Absorption Spectrophotometer. Average population of earthworms were significantly higher (P<0.05) (140–516 earthworms/m2) in the sawmill soils than in the soil of the control site (96 earthworms/m2). A total of five earthworm species were identified from the study locations. Mean weight of adult E. eugeniae from Sapon (1.18g) and Kotopo (1.21g) sawmills were significantly higher than that of the control site (0.92g). K and Na were higher in the tissues of earthworms from Sapon sawmill. Significantly lower (P<0.05) Ca and Mg concentrations were recorded in the tissues of E. eugeniae from the control site compared to those of Kotopo and Sapon sawmills. Sawmilling activities is therefore not totally detrimental to earthworms’ habitation.

Aim:  The present study investigated the energy cost of lengthening, isometric and shortening contractions in rat muscle (n = 19).Methods:  With electrical stimulation the rat medial gastrocnemius muscle was maximally stimulated to perform 10 lengthening, isometric and shortening contractions (velocity 25 mm s−1) under experimental conditions (e.g. temperature, movement velocity) that resemble conditions in human movement.Results:  Mean ± SD force–time-integral of the first contraction was significantly different between the three protocols, 2.4 ± 0.2, 1.7 ± 0.2 and 1.0 ± 0.2 N s, respectively (P < 0.05). High-energy phosphate consumption was not significantly different between the three modes of exercise but a trend could be observed from lengthening (7.7 ± 2.7 μmol ∼ P muscle−1) to isometric (8.9 ± 2.2 μmol ∼ P muscle−1) to shortening contractions (10.4 ± 1.6 μmol ∼ P muscle−1). The ratio of high-energy phosphate consumption to force–time-integral was significantly lower for lengthening [0.3 ± 0.1 μmol ∼ P (N s)−1] and isometric [0.6 ± 0.2 μmol ∼ P (N s)−1] contractions compared with shortening [1.2 ± 0.2 μmol ∼ P (N s)−1] contractions (P < 0.05).Conclusion:  The present results of maximally stimulated muscles are comparable with data in the literature for voluntary human exercise showing that the energy cost of force production during lengthening exercise is ∼30% of that in shortening exercise. The present study suggests that this finding in humans probably does reflect intrinsic muscle properties rather than effects of differential recruitment and/or coactivation.

Insulin resistance is defined as a reduced ability of insulin to stimulate glucose utilization. C57BL/6 mice fed with a high-fat diet (HFD) are a model of insulin resistance. In skeletal muscle, hydrogen peroxide (H 2 O 2 ) produced by NADPH oxidase 2 (NOX2) is involved in signaling pathways triggered by insulin. We evaluated oxidative status in skeletal muscle fibers from insulin-resistant and control mice by determining H 2 O 2 generation (HyPer probe), reduced-to-oxidized glutathione ratio and NOX2 expression. After eight weeks of HFD, insulin-dependent glucose uptake was impaired in skeletal muscle fibers when compared with control muscle fibers. Insulin-resistant mice showed increased insulin-stimulated H 2 O 2 release and decreased reduced-to-oxidized glutathione ratio (GSH/GSSG). In addition, p47 phox and gp91 phox (NOX2 subunits) mRNA levels were OPEN ACCESS

Force is transmitted from muscle fiber to bone via several pathways: (1) via the tendons (i.e. myotendinous force transmission), (2) via intermuscular connective tissue to adjacent muscles (i.e. intermuscular myofascial force transmission), (3) via structures other than muscles (i.e. extramuscular myofascial force transmission). In vivo, the position of a muscle relative to adjacent muscles changes due to differences in moment arm between synergists as well as due to the fact that some muscles span only one joint and other muscles more than one joint. The position of a muscle relative to non-muscular structures within a compartment is altered with each change of the length of the muscle.

The Smith machine is a pervasive weight training apparatus, used extensively by a wide population of weight trainers, from novices to high-level athletes. The advantages of using a Smith machine over free-weight resistance are disputed, with conflicting findings reported in the literature. In the present study we are interested in practical differences between three types of loading mechanisms found in modern Smith machines. In addition to the basic design comprising a constrained weighted barbell, alterations with a counterweight and a viscous resistance component are examined. The approach taken is that of employing a recently proposed representation of force characteristics that may be exhibited by a trainee and a predictive model of thus effected adaptation. A computer simulation is used to predict the effects of the three linear Smith machine designs in the framework of different exercise protocols. Our results demonstrate that each resistance component: vertically constrained load, counterweight and viscous, can be matched with a particular training context, in which it should be preferred. Thus, a number of practical guidelines for weight training practitioners are recommended. In summary: (i) at low intensities (55% - 75% of 1RM) used in strength-endurance training a viscous resistance containing Smith machine was found to offer advantages over both a constrained load only and counterweighted designs; (ii) at medium intensities (75% - 85% of 1RM) typically employed in hypertrophy-specific training, the counterweighted Smith machine design was found to offer the best choice in terms of high-force development and total external work performed; finally (iii) at high training intensity (90% - 100% of 1RM) the optimal prescription was found to be more dependent on the specific athlete's weaknesses, highlighting the need for continual monitoring of the athlete's force production capabilities. To ensure that appropriate adjustments are made to the athlete's training regiment, the practitioner should consider the full set of findings of the present paper and the accompanying discussion.

Pires-Oliveira M, Maragno AL, Parreiras-E-Silva LT, Chiavegatti T, Gomes MD, Godinho RO. Testosterone represses ubiquitin ligases atrogin-1 and Murf-1 expression in an androgen-sensitive rat skeletal muscle in vivo. Skeletal muscle atrophy induced by denervation and metabolic diseases has been associated with increased ubiquitin ligase expression. In the present study, we evaluate the influence of androgens on muscle ubiquitin ligases atrogin-1/MAFbx/FBXO32 and Murf-1/Trim63 expression and its correlation with maintenance of muscle mass by using the testosterone-dependent fast-twitch levator ani muscle (LA) from normal or castrated adult male Wistar rats. Gene expression was determined by qRT-PCR and/or immunoblotting. Castration induced progressive loss of LA mass (30% of control, 90 days) and an exponential decrease of LA cytoplasm-to-nucleus ratio (nuclear domain; 22% of control after 60 days). Testosterone deprivation induced a 31-fold increase in LA atrogin-1 mRNA and an 18-fold increase in Murf-1 mRNA detected after 2 and 7 days of castration, respectively. Acute (24 h) testosterone administration fully repressed atrogin-1 and Murf-1 mRNA expression to control levels. Atrogin-1 protein was also increased by castration up to 170% after 30 days. Testosterone administration for 7 days restored atrogin-1 protein to control levels. In addition to the well known stimulus of protein synthesis, our results show that testosterone maintains muscle mass by repressing ubiquitin ligases, indicating that inhibition of ubiquitin-proteasome catabolic system is critical for trophic action of androgens in skeletal muscle. Besides, since neither castration nor androgen treatment had any effect on weight or ubiquitin ligases mRNA levels of extensor digitorum longus muscle, a fast-twitch muscle with low androgen sensitivity, our study shows that perineal muscle LA is a suitable in vivo model to evaluate regulation of muscle proteolysis, closely resembling human muscle responsiveness to androgens.