Effects of electrical muscle stimulation on body composition, muscle strength, and physical appearance

Electrical muscle stimulation devices (EMS) have been advertised to increase muscle strength, to decrease body weight and body fat, and to improve muscle firmness and tone in healthy individuals. This study sought to test those claims. Twenty-seven college-aged volunteers were assigned to either an EMS (n = 16) or control group (n = 11). The EMS group underwent stimulation 3 times per week following the manufacturer's recommendations, whereas the control group underwent concurrent sham stimulation sessions. Bilaterally, the muscles stimulated included the biceps femoris, quadriceps, biceps, triceps, and abdominals (rectus abdominus and obliques). An identical pre- and posttesting battery included measurements of body weight, body fat (via skinfolds), girths, isometric and isokinetic strength (biceps, triceps, quadriceps, hamstrings), and appearance (via photographs from the front, side, and back). EMS had no significant effect on the any of the measured parameters. Thus, claims relative to the effectiveness of EMS for the apparently healthy individual are not supported by the findings of this study.     

Kinetics and thermodynamics of lactate dehydrogenases from beef heart, beef muscle, and flounder muscle.

The eight rate constants for a four-step ordered ternary-complex mechanism have been compared for lactate dehydrogenases (EC1.1.1.27) from three sources, beef heart, beef muscle, and flounder muscle. The rate constants were determined at temperatures ranging from 5 degrees C to 50 degrees C, and the corresponding activation parameters deltaG not equal to, deltaH not equal to, and deltaS not equal to were calculated. Significant differences are noted for the values for the three types of enzyme. The relative heights of the activation barriers are much the same in all three cases, differences in kinetic behavior resulting mainly from differences in the stable binary and ternary enzyme-substrate complexes. These complexes are, in general, at lower free-energy and enthalpy levels of the beef-heart and beef-muscle enzymes than for the flounder-muscle enzyme. A high degree of compensation is found between the enthalpies and entropies of activation, resulting in relatively small differences between the free energies (and rates) for homologous steps with different enzymes. Analysis of the results, on the assumption that the compensation effect is due to weak-bonding effects, suggests that there are fewer weak bonds in the stable complexes of the muscle enzymes.     

Somite subdomains, muscle cell origins, and the four muscle regulatory factor proteins

We show by immunohistology that distinct expression patterns of the four muscle regulatory factor (MRF) proteins identify subdomains of mouse somites. Myf-5 and MyoD are, at specific stages, each expressed in both myotome and dermatome cells. Myf-5 expression is initially restricted to dorsal cells in all somites, as is MyoD expression in neck somites. In trunk somites, however, MyoD is initially expressed in ventral cells. Myogenin and MRF4 are restricted to myotome cells, though the MRF4-expressing cells are initially less widely distributed than the myogenin-expressing cells, which are at all stages found throughout the myotome. All somitic myocytes express one or more MRFs. The transiently distinct expression patterns of the four MRF proteins identify dorsal and ventral subdomains of somites, and suggest that skeletal muscle cells in somites originate at multiple sites and via multiple molecular pathways.     

Histochemistry, immunocytochemistry, and biometry of muscle fibers and their innervation of the peroneus longus muscle]

The morphology of the peroneus longus muscle of the Chinese quail was studied in relation to partial behavorial characteristics. On the basis of the actomyosin ATPase reaction after alkaline and acid preincubation, three fiber types are revealed. The indirect immunofluorescence, using specific antibodies against 'slow' myosin from the human vastus lateralis muscle, provokes a strong reaction on the small fiber type. The characteristics of the innervation revealed by the cholinesterase activity, concentrated in the synaptic gutters and the direct study of the nerve fibres, show focal, mono-axonal 'en plaques' endings, typical of the phasic motor system.     

Comparative analysis of mesenchymal stem cells from adult mouse adipose, muscle, and fetal muscle

Recently, increasing evidence supports that adult stem cells are the part of a natural system for tissue growth and repair. This study focused on the differences of mesenchymal stem cells from adult adipose (ADSCs), skeletal muscle (MDSCs) and fetal muscle (FMSCs) in biological characteristics, which is the key to cell therapy success. Stem cell antigen 1 (Sca-1) expression of MDSCs and FMSCs at passage 3 was two times more than that at passage 1 (P < 0.0001). After 28-day myogenic induction, higher expression levels of skeletal muscle-specific genes were observed in MDSCs than FMSCs (P < 0.01), and the lowest expression levels were demonstrated in ADSCs among three cells (P < 0.01). Besides, M-Cad and MyHC expressions in ADSCs were not detected by immunofluorescence or real-time quantitative PCR. Furthermore, after 14 days adipogenic induction, PPARγ2, LPL and aP2 mRNA expressions were higher in ADSCs vs. MDSCs (P < 0.01). Besides, MSCs from adult or fetal muscle expressed higher OCN and OPN than ADSCs after 28 days osteogenic induction (P < 0.01). Taken together, our results suggested that cell source and developmental stage had great impacts on biological properties of mesenchymal stem cells, and proper consideration of all the issues is necessary.     

Resistance training induces qualitative changes in muscle morphology, muscle architecture, and muscle function in elderly postoperative patients.

Although the negative effects of bed rest on muscle strength and muscle mass are well established, it still remains a challenge to identify effective methods to restore physical capacity of elderly patients recovering from hospitalization. The present study compared different training regimes with respect to muscle strength, muscle fiber size, muscle architecture, and stair walking power in elderly postoperative patients. Thirty-six patients (60-86 yr) scheduled for unilateral hip replacement surgery due to hip osteoarthritis were randomized to either 1) resistance training (RT: 3/wk x 12 wk), 2) electrical stimulation (ES: 1 h/day x 12 wk), or 3) standard rehabilitation (SR: 1 h/day x 12 wk). All measurements were performed at baseline, at 5 wk and 12 wk postsurgery. After 12 wk of resistance training, maximal dynamic muscle strength increased by 30% at 60 degrees /s (P < 0.05) and by 29% at 180 degrees /s (P < 0.05); muscle fiber area increased for type I (+17%, P < 0.05), type IIa (+37%, P < 0.05), and type IIx muscle fibers (+51%, P < 0.05); and muscle fiber pennation angle increased by 22% and muscle thickness increased by 15% (P < 0.05). Furthermore, stair walking power increased by 35% (P < 0.05) and was related to the increase in type II fiber area (r = 0.729, P < 0.05). In contrast, there was no increase in any measurement outcomes with electrical stimulation and standard rehabilitation. The present study is the first to demonstrate the effectiveness of resistance training to induce beneficial qualitative changes in muscle fiber morphology and muscle architecture in elderly postoperative patients. In contrast, rehabilitation regimes based on functional exercises and neuromuscular electrical stimulation had no effect. The present data emphasize the importance of resistance training in future rehabilitation programs for elderly individuals.     

Comparative histology, histochemistry and innervation of striated muscle fibers of the greater pectoralis muscle and supracoracoid muscle in birds

The morphology of the pectoralis major muscle and the supracoracoideus muscle was compared in three Galliformes and five Passeriformes, in relation to partial behavioral characteristics. In all species, two fibres types are observed. The frequencies of these fibres are different, especially between Galliformes and Passeriformes, but also between Coturnix and other Galliformes. All fibres show phasic innervation. A relation of the extent between synaptic gutters and muscle activity is suggested.     

Polyamines, androgens, and skeletal muscle hypertrophy

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 β-agonists. In addition to β-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.     

Skeletal muscle acetylcholine receptor. Purification, characterization, and turnover in muscle cell cultures

Acetylcholine receptor has been purified from embryonic skeletal muscle cells grown and allowed to differentiate in tissue culture. The polypeptide composition of purified receptor has been determined by two-dimensional electrophoresis. The purest preparations are composed of a single Mr = 41,000 class of polypeptide which exhibits some charge heterogeneity. By high resolution two-dimensional electrophoresis a spot corresponding to acetylcholine receptor was localized among total proteins of muscle membrane extracts. Synthesis of this component is shown to be developmentally regulated. Quantitative analysis of receptor synthesis and degradation has led to the conclusion that receptor is one of a class of proteins whose synthesis is tightly regulated during terminal steps of myogenesis.     

Properties of particulate, membrane-associated and soluble guanylate cyclase from cardiac muscle, skeletal muscle, cerebral cortex and liver.

1. Guanylate cyclase of washed particles and plasma membranes showed S-shaped progress curves when titrated with either GTP or Mn2+ ions; similar results were obtained with Triton X-100-solubilized enzyme preparation from washed particles. Hill plots of these data revealed multiple metal-nucleotide and free-metal binding sites. 2. Guanylate cyclase of supernatant fractions displayed typical Michaelis-Menten properties when enzyme required excess of (free) Mn2+ (over GTP) for maximal activities; Ka (free Mn2+) was about 0.15-0.25 mM at subsaturating concentrations of GTP. 4 MnATP, MnADP, and MnGDP were found to increase the activities of both particulate and superantant enzyme, when MnGTP concentration was below saturation and free Mn2+ ion concentration was low (less than 100 muM); MnATP (50muM-1 mM) inhibited both these activities at high free Mn2+ concentration (1.5 mM) and inhibition of the particulate enzyme was greater than that of supernatant enzyme. 5. Ca2+ ions stimulated supernatant-enzyme activity; the stimulatory concentration of Ca2+ ions depended on the concentration of Mn2+ and GTP. 6. A modest stimulation of particulate guanylate cyclase by pyrophosphate (0.02-1 mM) was observed; the pyrophosphate effect appeared to be competitive with respect to GTP. At a higher concentration (2 mM), pyrophosphate produced a marked inhibition of particulate enzyme; the nature of inhibitory effect appeared complex. 7. Inorganic salts (e.g. NaCl, KCl, LiBr, NaF) produced inhibition of particulate enzyme; the degree of inhibition of Triton X-100-stimulated activity was less than that of unstimulated activity. 9. Treatment of sarcolemmal or microsomal membranes with either phospholipase C or trypsin decreased, whereas phospholipase A increased, the activity of guanylate cyclase.     

Comparison of muscle force,muscle endurance,and electromyogram activity during an expedition at high altitude

Handgrip force (HF), maximal pinch force (MF), muscle endurance (ME), and the median power frequency (MdPF) of the activity shown in the electromyogram (EMG) were studied at various altitudes in eight normal healthy subjects. MF and ME were measured between the index finger and thumb, and all measurements were obtained at altitudes ranging from 610 to 4860 m during an expedition in the Qinghai Plateau in China. With the change in altitude HF, ME, and MF showed no significant change. Compared to the MdPF at 2260 m on ascent, the MdPF at other altitudes showed a significant decrease (P<0.01). Thus, we conclude that muscle performance (HF, MF, and ME) was not affected by the environment at high altitude. However, MdPF was affected and the mean MdPF at 610 m after the expedition did not recover to initial values of MdPF. We suggest these results may have been affected by fatigue and chronic exposure to the hypobaric hypoxic environment, since the members of the expedition party expressed feelings of sluggishness and fatigue after the expedition.     

Influence of muscle geometry on shortening speed of fibre, aponeurosis and muscle.

The influence of muscle geometry on muscle shortening of the gastrocnemius medialis muscle (GM) of the rat was studied. Using cinematography, GM geometry was studied during isokinetic concentric activity at muscle lengths ranging from 85 to 105% of the optimum muscle length. The shortening speed of the distal fibre, the proximal aponeurosis and the muscle were determined, as well as the effect of rotation of the distal fibre and the proximal aponeurosis on the muscle speed of shortening. The results show that, due to the geometrical configuration, muscle shortening speed is not only determined by the speed of the fibre, but also to a large extent by the aponeurosis shortening speed. At optimum muscle length, the fibre and aponeurosis shortening speeds expressed relative to the muscle shortening speed amounted to 84% and 6%, respectively. At shorter muscle length, fibre speed relative to muscle speed decreased to values as low as 35%, whereas that of aponeurosis increased to values as high as 31%. Angular effects on the muscle speed of shortening can explain 10% of the muscle shortening speed at optimum muscle length and up to 34% of the muscle speed at shorter muscle length. In addition, a model was formulated to simulate the geometrical effects on muscle speed. This model, incorporating both fibre and aponeurosis length changes, contains a transfer function relating the shortening speeds of fibre and aponeurosis to muscle speed. The muscle shortening speed calculated using this transfer function demonstrated no significant differences with the speed measured experimentally.     

Effects of age on human muscle torque, velocity, and power in two muscle groups.

The purpose of this study was to test the hypotheses that, under isovelocity conditions, older compared with young humans would 1). be slower to reach target velocity and 2). exhibit a downward shift in the torque-velocity and power-velocity relationships in the ankle dorsiflexor and knee extensor muscles. We studied 12 young (26 +/- 5 yr, 6 men/6 women) and 12 older (72 +/- 6 yr, 6 men/6 women) healthy adults during maximal voluntary concentric contractions at preset target velocities (dorsiflexion: 0-240 degrees /s; knee extension: 0-400 degrees /s) using an isokinetic dynamometer. The time to target velocity was longer in older subjects in the dorsiflexors and knee extensors (both P 相似文献   

Proteasomal activity in skeletal muscle: A matter of assay design, muscle type, and age

The ubiquitin-proteasome system (UPS) is a major degradation system for regulatory and misfolded proteins. UPS function has been implicated to exert a central role in the pathogenesis of various human diseases. Because biochemical analyses are often hampered by the amount of available diseased tissue, we report on the establishment and validation of a luminescence-based proteasomal activity assay applicable to 5-mg quantities of skeletal muscle. We demonstrate that the specific proteasomal activity differs in individual muscle groups and decreases with aging. These findings warrant the use of appropriate controls and a careful interpretation of results in mammalian skeletal muscle pathologies.     

Morphology and organization of muscle fibres in the thoracic coxal muscle receptor organ and the associated promotor muscle, in a crayfish, Cherax destructor, and mud crab, Scylla serrata

Using confocal laser scanning and conventional light microscopy, the morphology and organization of the muscle fibres in a proprioceptor, the thoracic coxal muscle receptor organ (TCMRO), and the associated 'extrafusal' promotor muscle were investigated in two species of decapod crustacea, the crayfish Cherax destructor and the mud crab Scylla serrata . The diameter of the TCMROs was shown to increase distally, with an increase up to 350% recorded for the crayfish. The tapered shape of the crayfish TCMRO was demonstrated to amplify movements mechanically at the transducer region where the afferent nerves attach. Serial sectioning of the TCMROs, showed that the fibre number increased in the proximal to distal direction from 14 to 30 fibres in the crayfish and from 7 to 20 in the crab. Optical sectioning with the laser scanning confocal microscope revealed that the increase in fibre numbers was the result of muscle fibres branching in the distal third section of the TCMRO. The percentage of muscle tissue in the cross-sectional area in the TCMRO was found to be only 35.2% and 64.6% in the crayfish and crab, respectively. Longitudinal sectioning using laser scanning confocal microscopy revealed the average sarcomere length of the TCMRO muscle fibres of both species to be in the intermediate range for crustacean muscle fibres (4.1 ± 0.1 µm and 4.55 ± 0.34 µm for the crayfish and crab) compared with the long sarcomere muscle fibres in the associated promotor muscles (7.87 ± 0.2 and 10.6 ± 0.6 µm). The distinct morphology of the TCMRO muscle fibres – smaller diameter, intermediate sarcomere length and branching of fibres compared to the larger, long sarcomere promotor fibre muscle fibres – suggest that the TCMRO muscle fibres are specialized in their role of proprioception.     

Relation between cycling exercise capacity, fiber-type composition, and lower extremity muscle strength and muscle endurance

The aim of the study was to determine the relation between peak oxygen uptake V(O2)peak), peak work rate (WRpeak), fiber-type composition, and lower extremity strength and endurance during a maximal incremental cycle test. Thirty-nine healthy sedentary men, aged 30-46, participated in the study. Subjects performed a maximal incremental cycle test and isokinetic knee extension (KE) and flexion (KF) strength and endurance tests at velocities of 60 and 180° · s(-1). Muscle biopsies were taken from m. vastus lateralis and analyzed for fiber-type composition. A significant correlation existed between KE strength and V(O2)peak and WRpeak. Also, KF endurance correlated significantly to V(O2)peak and WRpeak. The KE endurance correlated significantly to WRpeak (rp = 0.32, p < 0.05) and almost significantly to V(O2)peak (rp = 0.28, p = 0.06). Stepwise multiple regression analyses showed that KE strength, KF endurance, and the percentage of type I fibers could explain up to 40% of the variation in V(O2) and WRpeak. The performance of sedentary subjects in a maximal incremental cycle test is highly affected by knee muscle strength and endurance. Fiber-type composition also contributes but to a smaller extent.     

Skeletal muscle IGF-binding protein-3 and -5 expressions are age,muscle, and load dependent

The purpose of the current study was to examine IGFBP-3, -4, and -5 mRNA and protein expression levels as a function of muscle type, age, and regrowth from an immobilization-induced atrophy in Fischer 344 x Brown Norway rats. IGFBP-3 mRNA expression in the 4-mo-old animals was significantly higher in the red and white portions of the gastrocnemius muscle compared with the soleus muscle. However, there were no significant differences in IGFBP-3 mRNA expression among any of the muscle groups in the 30-mo-old animals. There were no significant differences in IGFBP-5 mRNA expression in any of the muscle groups, whereas in the 30-mo-old animals there was significantly less IGFBP-5 mRNA expression in the white gastrocnemius compared with the red gastrocnemius muscles. Although IGFBP-3 and -5 proteins were detected in the type I soleus muscle with Western blot analyses, no detection was observed in the type II red and white portions of the gastrocnemius muscle. Aging from adult (18 mo) to old animals (30 mo) was associated with decreases in IGFBP-3 mRNA and protein and IGFBP-5 protein only in the soleus muscle. After 10 days of recovery from 10 days of hindlimb immobilization, IGFBP-3 mRNA and protein increased in soleus muscles from young (4-mo) rats; however, only IGFBP-3 protein increased in the old (30-mo) rats. Whereas there were no changes in IGFBP-5 mRNA expression during recovery, IGFBP-5 protein in the 10-day-recovery soleus muscle did increase in the young, but not in the old, rats. Because one of the functions of IGFBPs is to modulate IGF-I action on muscle size and phenotype, it is hypothesized that IGFBP-3 and -5 proteins may have potential modulatory roles in type I fiber-dominated muscles, aging, and regrowth from atrophy.