Accelerated Muscular Development Programs
From birth to maturation, the mammalian heart undergoes a sixfold increase in mass. The normal heart body weight ratio is species-specific. The largest hearts relative to body size occur in animals with survival requirements that depend on sustained exercise rather than on burst activity.6 In humans, intense, prolonged exercise training can produce an increase in cardiac mass. Isotonic exercise, such as running, produces eccentric hypertrophy, characterized by a normal ratio of wall thickness to dimension, whereas isometric exercise, such as weight lifting, stimulated concentric hypertrophy, associated with an increased ratio of wall thickness to dimension.7 Senescent animals and humans free of organic heart disease develop mild concentric left ventricular hypertrophy as a consequence of age-related decreases in the distensibility of the peripheral vasculature.8 The molecular, biochemical, and physiologic changes associated with physiologic hypertrophy differ both qualitatively and...
Normally, the respiratory system does not limit exercise tolerance. In healthy individuals, arterial blood saturation with oxygen, which averages 98 at rest, is maintained at or near 98 in even the most strenuous dynamic or isometric exercise. The healthy response includes the ability to augment ventilation more than cardiac output the resulting rise in the ventilation-perfusion ratio counterbalances the falling oxygen content of mixed venous blood.
Within skeletal muscle, adaptations to training are specific to the form of muscle contraction. Increased activity with low loads results in increased oxidative metabolic capacity without hypertrophy, increased activity with high loads produces muscle hypertrophy. Increased activity without overload increases capillary and mitochondrial density, myoglobin concentration, and virtually the entire enzymatic machinery for energy production from oxygen (Table 30.6). Coordination of energy-producing and energy-utilizing systems in muscle ensures that even after atrophy the remaining contractile proteins are adequately
Molecular Regulation of Muscle Development Genes regulating muscle development have recently been identified. BMP4 and probably FGFs from lateral plate mesoderm, together with WNT proteins from adjacent ectoderm, signal the dorsolateral cells of the somite to express the muscle-specific gene MYO-D. BMP4 secreted by overlying ectoderm induces
Muscle wasting can have a multiplicity of different causes (see Table 6.20). In order to determine the anatomical cause of atrophy, it is necessary to assess its distribution whether it is focal or diffuse, primarily proximal or distal or whether or not the atrophy involves a peripheral nerve or a spinal segment. Conversely, muscle hypertrophy may be occupational or a manifestation of certain rare forms of muscular dystrophy (e.g. Duchenne).
Are needed to replace proteins, the excess amino acids are not stored as additional protein (one cannot build muscles simply by eating large amounts of protein). Rather, the amine groups can be removed, and the carbon skeletons of the organic acids that are left can be used for energy or converted to carbohydrate and fat.
Androgens effect changes in hair distribution, skin texture, pitch of the voice, bone growth, and muscle development. Hair is classified by its sensitivity to androgens into nonsexual (eyebrows and extremities) ambisexual (axilla), which is responsive to low levels of androgens and sexual (face, chest, upper pubic triangle), which is responsive only to high androgen levels. Hair follicles metabolize testosterone to DHT or androstenedione. Androgens stimulate the growth of facial, chest, and axillary hair however, along with genetic factors, they also promote temporal hair recession and loss. Normal axillary and pubic hair growth in women is also under androgenic control, whereas excess androgen production in women causes the excessive growth of sexual hair (hirsutism). drogens have multiple effects on skeletal and cardiac muscle. Because 5a-reductase activity in muscle cells is low, the androgenic action is due to testosterone. Testosterone stimulates muscle hypertrophy, increasing...
Basic Helix-Loop-Helix Factors and Muscle Development One of the initial, critical discoveries related to muscle development was the observation that a specific transcription factor, Myo-D, expressed in myoblasts19 is sufficient to convert a variety of mesodermal and nonmesodermal cell types to stable myoblasts with active muscle-specific gene
Endurance training does not increase the size of muscles. Muscle enlargement is produced only by frequent periods of high-intensity exercise in which muscles work against a high resistance, as in weightlifting. As a result of resistance training, type II muscle fibers become thicker, and the muscle therefore grows by hypertrophy (an increase in cell size rather than number of cells). This happens first because the myofibrils within a muscle fiber thicken because of the synthesis of actin and myosin proteins and the addition of new sarcomeres. Then, after a myofibril has attained a certain thickness, it may split into two myofibrils, each of which may become thicker as a result of the addition of sarcomeres. Muscle hypertrophy, in short, is associated with an increase in the size of the myofibrils, and then in the number of myofibrils within the muscle fibers.
With the four different classes of agents equally enhances the arterial barore-ceptor function through blood pressure reduction but not through specific depressor mechanisms at the early stage of hypertension. Ichikawa et al. 30 also examined the effects of long-term treatment with the four different classes of antihypertensive drugs on aortic baroreceptor activity in SHR with chronic hypertension. They found that (1) the four drugs induced baroreceptor resetting to a lower pressure level and that (2) baroreceptor sensitivity is augmented more by the calcium antagonist or the ACE inhibitor than by the diuretic agent or the (3-blocker. These findings might be explained as follows chronic hypertension induces changes in the aortic medial layers (such as smooth muscle hypertrophy and increased collagen content) that affect baroreceptor sensitivity through changes in vessel distensibility and or mechanical coupling of the baroreceptors to the vessel. Calcium blockers and ACE inhibitors...
Eccentric contraction-induced muscle damage and its subsequent response may be the essential stimulus for muscle hypertrophy. While standard resistance exercise involves a mixture of contraction types, careful studies show that when one limb works purely concentrically and the other purely eccentrically at equivalent force, only the eccentric limb hypertrophies. The immediate changes in actin and myosin production that lead to hypertrophy are mediated at the posttranslational level, after a week of loading, mRNA for these proteins is altered. Although its precise role remains unclear, the activity of the 70-kDa S6 protein kinase is tightly linked with long-term changes in muscle mass. The cellular mechanisms for hypertrophy include the induction of insulin-like growth factor I, and up-regulation of several members of the fibroblast growth factor family.
100-mg testosterone enanthate weekly x 16 wk, with or without resistance training placebo controlled 200-mg testosterone enanthate weekly, with or without strength training placebo testosterone treatment than with placebo Strength gains not significantly greater in testosterone or resistance training groups in comparison to placebo group Nandrolone 600 mg weekly alone or nandrolone plus resistance training exercise for 12 wk All subjects received resistance exercise training plus testosterone enanthate 100 mg weekly, and randomized to 20-mg oxan-drolone or placebo daily Placebo, 65 mg nandrolone weekly, or 200 mg nandrolone weekly Therefore, in a subsequent study (52) (see Figs. 1 and 2), the subjects returned to the exercise laboratory on two or more occasions until they were familiar with the equipment and technique and stability of measurement had been achieved. In this study, we determined the effects of testosterone replacement, with or without a program of resistance exercise,...
Unfortunately, fat calves often result from muscular hypertrophy. When performing liposuction of the calves the surgeon must have a lot of experience and be very careful to avoid causing dimples. For this reason caution must be exercised during liposuction of the calves and ankles. A 2-mm cannula with a vacuum that is not too high must be used (no higher than 0.6 at). After the operation immediate mobilization and the fitting of a compression girdle are advisable.
Muscular strength, power, and speed or endurance) (103,104). These agents are used by athletes involved in many sports. However, sports such as track and field (mostly in the throwing events), weight lifting, bodybuilding, and football report the highest prevalence of use (104-106). For the remainder of the discussion, anabolic-androgenic steroids will be referred to as anabolic steroids.
Although the enzyme 5-a-reductase is expressed at low concentrations in muscle (90), it is unknown whether conversion of testosterone to DHT is required for mediating the androgen effects on the muscle. Men with benign prostatic hypertrophy who are treated with the a 5-a reductase inhibitor do not experience muscle loss. Similarly, individuals with congenital 5-a-reductase deficiency have normal muscle development at puberty. These data imply that 5-a reduction of testosterone is not obligatory for mediating its anabolic effects on the muscle cells. Because testosterone effects on the prostate involve conversion to DHT, selective androgen receptor modulators that bind the androgen receptor but are not 5-a reduced would be attractive (91). Such agents could produce desirable anabolic effects on muscle without the undesirable effects on the prostate.
The most commonly recognized endocrine myopathy occurs as a feature of hypothyroidism it may antedate the diagnosis of hypothyroidism by several months. Symptoms and signs of this entity range from mild aches and pains, muscle cramps, and proximal weakness to apparent muscle hypertrophy and the mounding phenomenon, or myoedema (a transient focal ridging of muscle in response to percussing or pinching the muscle). In the usual form, proximal weakness may be observed, although atrophy is rare.
The prevalent view that testosterone produces muscle hypertrophy by increasing fractional muscle protein synthesis (46,83) is supported by several studies. However, as discussed below, recent observations suggest that increase in muscle protein synthesis probably occurs as a secondary event and may not be the sole or the primary mechanism by which testosterone induces muscle hypertrophy (84). The molecular mechanisms, which mediate androgen-induced muscle hypertrophy, are not well understood. Urban et al. (83) proposed that testosterone stimulates the expression of IGF-I and downregulates IGF-binding protein-4 (IGFBP-4) in the muscle. Reciprocal changes in IGF-1 and its binding protein thus provide a potential mechanism for amplifying the anabolic signal. duce muscle hypertrophy through an androgen-receptor independent mechanism, such as through an antiglucocorticoid effect (86). We cannot exclude the possibility that some androgen effects may be mediated through nonclassical binding...
There are likely to be many social influences that differentially influence male and female food intake and energy expenditure patterns. However, it is clear that biological and evolutionary components are also important factors underlying the differences in rates of obesity between the sexes. In all populations, from contemporary hunting and gathering groups to those in complex industrial countries, women have more overall fat and much more peripheral body fat in the legs and hips than men. In addition, there appears to be a tendency for females to channel extra energy into fat storage in contrast to men who utilize a higher proportion of the energy to make protein and muscle. These gender differences are believed to be associated with the need for adequate fat deposits to ensure reproductive capacity in females. Men have, proportionally, much more central body fat. They also have a higher proportion of lean muscle mass which leads to a higher basal energy expenditure.
Of particular relevance is the fact that recent estimates of obesity prevalence among patients with schizophrenia are 1.5 to 2 times that for the general population (Allison and Casey 2001 Allison et al. 1999a). The trend toward overweight and obesity was present among patients with schizophrenia, particularly females, prior to the advent of atypical antip-sychotics, but the concern has increased dramatically over the past 5 years due to evidence of profound weight gain with certain atypical antipsychotics, particularly olanzapine and clozapine, to an extent much greater than that achieved even with low-potency typical agents such as chlorprom-azine (Allison et al. 1999b Blackburn 2000 Meyer 2001a). Moreover, the weight gain from atypical antipsychotics is primarily in the form of greater adiposity, not increases in lean muscle mass (Eder et al. 2001).
A number of studies report national distributions for skinfolds and percent fat (8). However, nations that have a high prevalence of obesity do not serve as a reference source for healthy percent fat ranges. Thus it is possible to establish a subject's fatness relative to the population as a whole but there are no experimentally developed ranges set for optimum health. As a working alternative, our group and two others derived percent fat ranges in accord with the three BMI thresholds (6). Two methods for estimating fatness were applied as the reference, DEXA and four-compartment (4C). There were three groups of subjects, Caucasian, African American, and Japanese-Asian. Regression models were developed linking percent fat with BMI and other predictor variables. Two prediction models were developed, one for African Americans and Caucasians and the other for Japanese-Asians. The developed percent fat ranges are presented in Tables 6.6 and 6.7. A subject's measured percent fat can be...
An activity in which a muscle produces tension without a change in length is called an isometric exercise. For example, if you clasp your hands together and pull without actually moving them, you are participating in an isometric exercise. It has been shown that isometric exercises build muscle strength rapidly. On the other hand, the skeletomuscular system may still lack range of motion.
The male hormone testosterone and its derivatives actuate the reproductive potential in the adolescent boy. From puberty onward, androgens continue to aid in the development and maintenance of secondary sex characteristics facial hair, deep voice, body hair, body fat distribution, and muscle development. Testosterone also stimulates the growth in size of the accessory sex organs (penis, testes, vas deferens, prostate) at the time of puberty. The androgens also promote tissue-building processes (anabolism) and reverse tissue-depleting processes (catabolism). Examples of androgens are flu-oxymesterone (Halotestin), methyltestosterone (Oreton Methyl), and testosterone. Additional examples of androgens are given in the Summary Drug Table Male Hormones.
Infundibular stenosis is rare outside the setting of tetralogy of Fallot and is much less common than valvular PS. On 2D imaging, muscular hypertrophy is often visualized proximal to the pulmonary artery, while Doppler interrogation reveals increased flow velocities through the infundibulum.609 PS is reasonably common and may be either isolated or associated with other congenital lesions (such as VSD, transposition, and tetralogy of Fallot). Typical echocardiographic features include thickening of the leaflets, restricted leaflet motion, systolic doming of the valve, and elevated systolic flow velocity on Doppler610 (Fig. 13-85). As with other stenotic lesions, the gradient can be estimated using the modified Bernoulli equation. The pulmonic valve is best visualized in the parasternal short-axis view through the base (or a modified parasternal view of the RVOT). In children, the subcostal position frequently provides excellent visualization of the RVOT and pulmonic valve. When TTE is...
The anterior compartment is more commonly involved particularly the tibialis anterior and, to a lesser extent, the extensor digitorum longus, and the peroneus muscles 133 . Hernias can be associated with trauma or muscle hypertrophy and may be painful. 18 . When there is a history of trauma, it is usually from penetrating wounds or violent impact 133 . The diagnosis of a muscle hernia is generally a clinical one, based on symptoms and physical examination. A small superficial bump may be noted with the limb at rest, which will become more prominent with contraction of the associated muscle. If the clinical picture is not clear, an MRI may show a focal protrusion of muscle through the fascial defect, however dynamic imaging muscle contraction can make the herniation more conspicuous. It is critical for the interpreting radiologist to mark the area of concern with a vitamin E capsule or visually inspect the leg, as these findings may be subtle with MRI (Fig. 31)....
Gloves and sleeves are the simplest method of handling and are the method of choice provided that the work can be accessed. The maximum arm length of most operators is 700 mm, with a realistic limit to the working radius of 500 mm. The general weightlifting limit for working in sleeves is reckoned to be about 5 kg, and the absolute limit is 10 kg. A simple test to judge if a specific process can be handled when working in sleeves is to try out the process while seated at a bench. If the work can be handled reasonably comfortably in this way, without moving from the seated position, then it can probably be carried out in a glove isolator.
Natural muscle development can be exaggerated by both men and women who want to increase their maximum strength in athletic competition if they take synthetic andro-gens called anabolic steroids. However, anabolic steroids have serious negative side effects. In women, their use causes the breasts and uterus to shrink, the clitoris to enlarge, menstruation to become irregular, facial and body hair to grow, and the voice to deepen. In men, the testes shrink, hair loss increases, the breasts enlarge, and sterility can result. You can understand the causes of some of these side effects by considering the negative feedback effects of sex steroids on the production of LH and FSH. Other side effects are even more serious. Continued use of anabolic steroids greatly increases the risk of heart disease, certain cancers, kidney damage, and personality disorders such as depression, mania, psychoses, and extreme aggression. Most official athletic organizations, including the International Olympic...
In an effort to strengthen selected muscles after surgery and immobilization has led to muscle atrophy, isometric exercise is recommended. The intensity of isometric exercise is best quantified (D) Is substituted for isometric exercise 10.A 33-year-old woman embarks on an extensive program of daily exercise, with both strenuous dynamic and isometric exercise included. After two years, her maximal voluntary contraction of many major muscle groups and her maximal oxygen uptake, are both increased 30 . Predictably, pulmonary function tests show
Increases muscle gene transcription, including that of insulin-like growth factor (IGF)-I (21). In a related fashion, testosterone also decreases myostatin expression (transforming growth factor TGFJ-P family member and inhibitor of muscle development) (21). Testosterone also stimulates hematopoiesis and increases sodium reabsorption in the kidney. Finally, studies in animals reveal that testosterone also plays a role in increasing skeletal muscle glycogen synthesis and storage (17).
A variety of studies in animals have been undertaken to address the mechanisms leading to the evolution of the pulmonary vascular disease in association with hypoxia. It has been noted that at altitude severe pulmonary hypertension may in fact represent a maladaptive response related to the amount ofintrinsic muscle in the vessel wall. The llama, develops little acute or chronic pulmonary hypertension and has the least muscle pulmonary circulation of all species tested (49). In the rat, the development of structural changes and sustained pulmonary hypertension appears to occur after 3 days of chronic hypoxia (air at half atmospheric pressure, P02 approximately 40 mm Hg). Over the ensuing 2 weeks, pulmonary artery pressure progressively doubles and is associated with progressive extension of muscle into peripheral normally nonmuscular arteries, medial hypertrophy of normally muscular arteries, and reduction in arterial number, all proceeding in parallel, and right ventricular...
Athletes do have special nutrition needs. Primarily, these include increased energy needs, provided mostly from carbohydrate-rich food sources. The physical activity demands of sports create additional energy needs. Table 11-1 identities calorie demands with particular sports.1 A carbohydrate-rich diet serves to optimally fuel muscles for endurance and strength training. Athletes can usually meet their increased energy needs by following a nutrition plan of three meals and well-timed snacks. Table 11-2 identifies carbohydrate-rich food selections. It is recommended that a carbohydrate-based pre-practice or pre-event snack
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