hypertrophy

Hypertrophy is the increase of the size of an organ. It should be distinguished from hyperplasia which occurs due to cell division; hypertrophy occurs due to an increase in cell size rather than division. It is most commonly seen in muscle that has been actively stimulated, the most well-known method being exercise.

This is most effectively done by undertaking resistance training, though it can also occur during other high anaerobic exercises such as interval training, rowing, cycling and sprinting.

For hypertrophy to occur in the skeletal muscles, the muscle must be directly stimulated. Hypertrophy can be pathological in many organs; for example in the heart hypertrophy of the left ventricle can be associated with up to a four fold risk of dying over the following 5 years. In skeletal muscle, it is usually helpful and increases strength.

Two different types of hypertrophy are common; Sarcoplasmic hypertrophy, in which sarcoplasmic fluid in the muscle cell increases rather than the contractile protein, and hence no increase in contractile strength. Myofibrillar Hypertrophy, in which there is an increase in myofibrils, and hence increase in muscular contractile strength.

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.

Achieving muscular hypertrophy through resistance 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 resistance 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 you suspended from sporting events, as well as being illegal in most countries.

In order to get the best gains out of your training sessions, experts agree on some basic principles, however some are contradicted by other research:

• Resistance Training: it is doing "weights", targeting specific muscle groups, that best stimulates muscle growth, as opposed to aerobic training. Even though runners, swimmers and cyclists have all been known to be very muscular, it is generally the shorter distance / sprinters that tend to develop muscle, so the type of training they do could be seen as a type of "resistance training", and is mostly anaerobic, as opposed to long distance swimmers/runners/cyclists, that tend to be slim and lean.

• Progressive overload is considered the most important principle behind hypertrophy, so increasing the weight, reps and sets will all have a positive impact of growth. Some experts create complicated plans that play around with weight, reps and sets, increasing one while decreasing the others, to constantly shock the body into growing. Keeping the sets and reps the same while just increasing weight will lead to growth, but will focus more on developing muscular strength; keeping the weight the same but doing more sets, or doing a few extra reps, may be more effective at stimulating growth for a few weeks, before a rise in weight is necessary. It is generally believed that with more than 15 repetitions per set, the weight will be too light to stimulate growth. Also leave about 45-60sec rest between sets.

Microtrauma, which is tiny damage to the fibres, is seen as the basis for hypertrophy. When microtrauma occurs (from weight training or other 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.

• Some scientific research on hypertrophy training is contradictory. For instance some studies have found that the anabolic stage lasts only 36-48 hours after a workout, while others have found that the body is still making adaptive changes after 1-2 weeks. Which study one chooses to believe will affect the training regime, for instance working a muscle group once a week in a 3 day split, or 3 times a week in a full body program. Therefore trying both types of programs for a few months each may help one determine which is better for the individual.

• Seek the advice of a professional trainer, especially trainers that have already achieved the results you wish to achieve, but be wary of those that use/recommend anabolic steroids, as these are illegal and entail potential health risks.

• There are plenty of legal supplements that can help one get results quicker. The three considered most effective are glutamine, creatine, and the humble multivitamin. The body needs vitamins and minerals to process the protein, carbohydrates, and fat that it gets from food, and getting enough vitamins will help the body function more efficiently and build more muscle. Glutamine is an essential amino-acid for building muscle, and taking supplements replenishes the stores that may be used up in heavy training. Creatine is used by the body to convert ADP back into ATP in the first 10-20 seconds of exertion, as is limited by the amount of creatine stored in your muscles. As a set in weight training doesn't usually last more than 10-15 seconds, this energy system is the dominant one, and so taking supplements will increase the amount of creatine available and can greatly increase muscular endurance, meaning one can do more reps and sets, fatiguing more muscle fibres.

Ventricular hypertrophy (The Heart)

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 training that enables the ventricle to enhance its pumping capacity. This type of physiologic hypertrophy is reversible and non-pathological. Chronic hypertension causes 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, the ventricle responds by adding new sarcomeres in-series with existing sarcomeres. This results in ventricular dilation while maintaining normal sarcomere lengths. 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, 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.

External links

• University of California Muscle Physiology Home Page: Hypertrophy