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Resistance training Resistance training typically produces a combination of the two different types of hypertrophy; contraction against 80-90% of the one repetition maximum for a lower number of repetitions causes myofibrillated hypertrophy to dominate (as in powerlifters, olympic lifters and strength athletes), while several repetitions (generally 12 or more)against a sub-maximal load facilitates mainly sarcoplasmic hypertrophy (professional bodybuilders and endurance athletes). 'Neural Response' The first measurable effect is an increase in the neural drive stimulating muscle contraction. Within just a few days, an untrained individual can achieve measurable strength gains resulting from "learning" to use the muscle. Genetic Response As the muscle continues to receive increased demands, the synthetic machinery is upregulated. Although all the steps are not yet clear, this upregulation appears to begin with the ubiquitous second messenger system (including phospholipases, protein kinase C, tyrosine kinase, and others). These, in turn, activate the family of immediate-early genes, including c-fos, c-jun and myc. These genes appear to dictate the contractile protein gene response. Protein Synthesis Finally, the message filters down to alter the pattern of protein expression. It can take as long as two months for actual hypertrophy to begin. The additional contractile proteins appear to be incorporated into existing myofibrils (the chains of sarcomeres within a muscle cell). There appears to be some limit to how large a myofibril can become: at some point, they split. These events appear to occur within each muscle fiber. That is, hypertrophy results primarily from the growth of each muscle cell, rather than an increase in the number of cells. Muscular hypertrophy through anaerobic training Experts and professionals differ widely on the best approaches to specifically achieve muscle growth (as opposed to focusing on gaining strength, power, or endurance), it is generally considered that doing anaerobic strength training consistently will result in hypertrophy in the long term (as well as strength and endurance gains). Because testosterone is one of the body's major growth hormones, men tend to find hypertrophy much easier to achieve than women. Taking additional testosterone will increase results, but the psychological and physiological side-effects can cause health issues, and it is considered a performance-enhancing drug, and could thus get one suspended from sporting events, in addition to being illegal in most countries. In order to get the best gains out of training sessions, experts agree on some basic principles, however some are contradicted by other research: Microtrauma, which is tiny damage to the fibres, is seen as the basis for hypertrophy. When microtrauma occurs (from weight training or other strenuous activities), the body responds by overcompensating, replacing the damaged tissue and adding more, so that the risk of repeat damage is reduced. This is why progressive overload is essential to continued improvement, as the body adapts and becomes more resistant to stress. Because microtrauma is physical damage to the muscle, rest and recovery are just as important as training. Leave at least 48 hours before training a muscle group again. Also stretch after training, as well as on rest days, to maintain/improve flexibility and range of motion. Experts agree that nutrition is very important to hypertrophy, especially a diet high in protein, as protein is used to build more muscle. Some recommend protein supplements (such as shakes and bars), but some say these are unnecessary with appropriate meal planning and a diet high in lean meat, such as chicken, fish, beef and lamb. Carbohydrates are also important, as they are "protein sparing", which means carbs can be used for body fuel while the protein is free to be used for muscle growth. Also, carbs release insulin, which is an anabolic hormone, as opposed to glucagon, which is catabolic and turns protein into glucose when the body is deprived of carbs. Remember that the controversial "low carb diets" are designed for weight (fat) loss, not muscle gain, but sugary foods and drink should be avoided to limit fat gain. Ventricular hypertrophy See main article Ventricular hypertrophy The ventricles are the chambers in the heart responsible for pumping blood either to the lungs (right ventricle) or the rest of the body (left ventricle). Increased ventricular mass is an adaptation by the ventricle(s) of the heart to increased stress, such as chronically increased volume load (preload) or increased pressure load (afterload). It is a physiological response that enables the heart to adapt to increased stress; however, the response can become pathological and ultimately lead to a deterioration in function. For example, hypertrophy is a normal physiological adaptation to exercise that enables the ventricle to enhance its pumping capacity. Aerobic training results in the heart being able to pump a larger volume of blood through an increase in the size of the ventricles. Anaerobic training results in the thickening of the myocardial wall to push blood through arteries compressed by muscular contraction. This type of physiologic hypertrophy is reversible and non-pathological, increasing the heart's ability to circulat eblood. Chronic hypertension causes pathological ventricular hypertrophy. This response enables the heart to maintain a normal stroke volume despite the increase in afterload. However, over time, pathological changes occur in the heart that lead to a functional degradation and heart failure. If the precipitating stress is volume overload (as through aerobic exercise, which increases blood return to the heart through the action of the skeletal-muscle pump), the ventricle responds by adding new sarcomeres in-series with existing sarcomeres (i.e. the sarcomeres lengthen rather than thicken). This results in ventricular dilation while maintaining normal sarcomere lengths - the heart can expand to receive a greater volume of blood. The wall thickness normally increases in proportion to the increase in chamber radius. This type of hypertrophy is termed eccentric hypertrophy. In the case of chronic pressure overload (as through anaerobic exercise, which increases resistance to blood flow by compressing arteries), the chamber radius may not change; however, the wall thickness greatly increases as new sarcomeres are added in-parallel to existing sarcomeres. This is termed concentric hypertrophy. This type of ventricle is capable of generating greater forces and higher pressures, while the increased wall thickness maintains normal wall stress. This type of ventricle becomes "stiff" (i.e., compliance is reduced) which can impair filling and lead to diastolic dysfunction. | ||||||||||
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