Muscle development

Objective: To compare the effects of different resistance training programs on measures of muscle strength and hypertrophy. Methods: Sixty-seven untrained subjects were randomized to one of two groups: Split Workout Routine (n=35), in which muscle groups were trained twice per week in an A/B split consisting of eight sets per session, or Full-Body Workout Routine (n=32), in which muscle groups were trained four times per week with four and eight sets per session. Both groups performed eight to 12 repetition maximum per set, with 60 seconds of rest between sets. Maximal strength and muscle thickness were assessed at baseline and after eight weeks of training. Results: A significant main effect of time (pre versus post) was observed for maximal strength in the bench press and squat exercises and thickness of the elbow extensor, elbow flexor and quadriceps femoris muscles. Selected variables did not differ significantly between groups. Conclusion: Resistance training twice or four times per week has similar effects on neuromuscular adaptation, provided weekly set volume is equal.

Atypical swallowing is a myofunctional problem consisting of an altered tongue position during the act of swallowing. High incidence in population, multifactorial etiology and the recurring connection with the presence of malocclusions made it a topic of strong interest and discussion in science. The purpose of this review is to illustrate the current orientation on the topic of atypical swallowing, trying in particular to answer two questions: 1) what kind of connection is there between atypical swallowing and malocclusion; 2) what kind of therapy should be used to solve it. This review was conducted on the Medline database [www.ncbi.nim.nih.gov/pubmed] searching for the keywords "atypical swallowing" and "tongue thrust". We examined all the documents from the year 1990 onwards, excluding the ones about syndromic cases of the central motor system. The causal relation between the two problems seems to be biunique: some authors affirm that this oral habit starts a...

Muscle injury induces strong changes in muscle cells and extracellular matrix. Muscle regeneration after injury has similarities to muscle development during embryogenesis and seems to follow the same procedure. The initial phase of muscle repair is characterized by inflammation and degeneration of the damaged tissue. Almost simultaneously, previous quiescent myogenic cells, called satellite cells, are activated, proliferate, differentiate and fuse to form multinucleated myofibers. Other non-muscle stem cells may also take part in this process. Secreted factors, such as hepatocyte growth factor (HGF), fibroblast growth factors (FGFs), transforming growth factor-betas (TGF-betas), insulin-like growth factors (IGFs), tumour necrosis factor alpha (TNFalpha) and others, are released during muscle repair and guide muscle regeneration, however, their exact functions and effects on muscle remodeling remain unknown. Intensive research is currently addressing the regenerative mechanisms whic...

Strenuous exercise is characterized by an increased oxygen consumption and disturbance of intracellular prooxidant-antioxidant homeostasis. At least three biochemical pathways, that is, mitochondrial electron transport chain, xanthine oxidase, and polymorphoneutrophil have been identified as potential sources of intracellular free radical generation during exercise. These deleterious reactive oxygen species pose a serious threat to the cellular antioxidant defense system, such as diminished reserve of antioxidant vitamins and glutathione, and have been shown to cause oxidative damage in exercising and/or exercised muscle and other tissues. However, enzymatic and nonenzymatic antioxidants have demonstrated great versatility and adaptability in response to acute and chronic exercise. The delicate balance between prooxidants and antioxidants during exercise may be altered with aging. Study of the complicated interaction between aging and exercise under the influence of reactive oxygen species would provide more definitive information as to how much aged individuals should be involved in physical activity and whether supplementation of nutritional antioxidants would be desirable.

This article reviews the complexity, expression, genetics, regulation, function, and evolution of the avian myosin heavy chain (MyHC). The majority of pertinent studies thus far published have focussed on domestic chicken and, to a much lesser extent, Japanese quail. Where possible, information available about wild species has also been incorporated into this review. While studies of additional species might modify current interpretations, existing data suggest that some fundamental properties of myosin proteins and genes in birds are unique among higher vertebrates. We compare the characteristics of myosins in birds to those of mammals, and discuss potential molecular mechanisms and evolutionary forces that may explain how avian MyHCs acquired these properties.

Computational identification of non-coding RNAs (ncRNAs) is a challenging problem. We describe a genome-wide analysis using Bayesian segmentation to identify intronic elements highly conserved between three evolutionarily distant vertebrate species: human, mouse and zebrafish. We investigate the extent to which these elements include ncRNAs (or conserved domains of ncRNAs) and regulatory sequences. We identified 655 deeply conserved intronic sequences in a genome-wide analysis. We also performed a pathway-focussed analysis on genes involved in muscle development, detecting 27 intronic elements, of which 22 were not detected in the genome-wide analysis. At least 87% of the genome-wide and 70% of the pathway-focussed elements have existing annotations indicative of conserved RNA secondary structure. The expression of 26 of the pathway-focused elements was examined using RT-PCR, providing confirmation that they include expressed ncRNAs. Consistent with previous studies, these elements ...