Training: Hypertrophy

What Is Hypertrophy?

Muscle hypertrophy refers to an increase in the size of a muscle. This is attributed to an increase in the cross-sectional area of a muscle or number of myofibrils within a muscle fibre. There are two types of muscle fibre; type I (slow twitch) and type II (fast twitch) - muscle hypertrophy can occur in both.

The Benefits Of Muscle Hypertrophy

Although muscular strength is not the only factor contributing to muscular hypertrophy and muscle hypertrophy is not the only factor contributing to muscular strength, there is a strong correlation between the two. In essence, generally, greater muscle mass creates greater potential for maximal strength development. In addition to increased potential strength, increased muscle mass and resistance training positively impact body composition. This is due to the positive influence of muscle and resistance training in addressing factors affecting energy expenditure.

Resting metabolic rate increases as a result of increased muscle mass due to a greater proportion of the body being comprised of metabolically active muscle tissue. Fat-free mass accounts for approximately 65-70% of an individual’s fasting metabolic rate. Resistance training is a form of physical activity, which results in energy expenditure whilst stimulating muscle growth - not only during exercise but in the 24-48 hours following activity. The outcome is improved body composition due to a reduction in body fat and an increase in muscle mass (without taking into consideration calorie consumption). Body composition is measured as percentage of fat-free mass to fat mass. An individual’s percent body fat can be decreased (improved) by inducing hypertrophy.

Inducing Muscle Hypertrophy

There are three primary factors that induce muscular hypertrophy…

• mechanical tension
• muscle damage
• metabolic stress

Mechanical Tension

Mechanical tension and the degree to which it is induced within a given training session is generally governed by intensity (amount of weight lifted) and time under tension (duration of load applied).

Muscle Damage

Muscle damage refers to the trauma within a muscle evoked by resistance training and progressive overload. A muscle is stimulated by overload, causing muscle damage and an inflammatory response. The result is potentiation of various growth factors which induce hypertrophy and a number of hormonal responses within the body.

Metabolic Stress

Metabolic stress arises from anaerobic training and training programs that rely heavily on the anaerobic system. High levels of anaerobic training decrease the pH level within a muscle (stimulating a build-up of lactic acid) and result in muscle fibre degradation. Despite there being multiple options in regard to inducing muscular hypertrophy, research suggests that performing multiple sets of a movement with a moderate load is optimal for muscle growth. The greatest elevation of testosterone and growth hormone has been identified through the employment of a repetition range between 6-12, using a load that equates to 65% to 85% of an individual’s one rep max. Heavier loads and lighter loads can be utilised, however, are less optimal when the objective is to induce metabolic stress.

Muscle hypertrophy is therefore induced by a combination of muscular tension, muscle damage, and metabolic stress which evokes an anabolic response. As a result, in order to recover, the body is required to super-compensate as a result of the resistance training stress.

Supercompensation refers to an increase in the ability of the body to manage and recover from stress of training. As a result of supercompensation, the body will repair itself above its previous baseline allowing it to perform at a level greater than its previous ability. Consequently, an individual will be able to perform at a higher level due to the adaptation that has taken place - the same workout will not cause the same amount of damage and will be perceived to be easier.

In order to continually evoke positive adaptations, a training program needs to systematically progress by modifying exercise variables (frequency, intensity, volume, rest periods, exercise selection).

In regard to hypertrophy, the most commonly adjusted variable is overall training volume. However, lifestyle factors such as sleep, and nutrition play a significant role in recovery and ultimately the body’s ability to undergo supercompensation. Sleep is important for the repair of damaged tissue which is vital for the recovery process of muscles and hypertrophy results. Research suggests that 7-9 hours of sleep usually suffices for individuals participating in intense activity like resistance training and seeking to optimise recovery and muscle gain. Nutrition is an important factor to consider and should be adjusted accordingly to an individual’s physiology, training goals and lifestyle. In addition to sufficient energy intake and a well-rounded, balanced diet composed of all three macronutrients, there should be a priority to ensure protein targets are set and adhered to. Protein provides the resources required to repair the muscular damage that is caused during resistance training. There is a general recommendation that individuals consume between 1.2-2.0 grams of protein per kilogram of bodyweight per day to optimise recovery from intense training. The recommendations for sleep and nutrition are general. In order to optimise these recovery factors, it is important to take an individualised approach.

Overall, muscle hypertrophy has a number of benefits. Muscular hypertrophy is induced as a result of the following stimulants: mechanical tension, muscle damage and metabolic stress. In order to optimise muscle growth, there needs to be sufficient recovery factors such as adequate sleep and nutrition which will allow the body to super-compensate and continue to progress muscle growth and development.