Muscular hypertrophy (i.e. simply, the growth and enlargement of muscle), is a very common training goal. The aim of hypertrophy training is to increase the size of an individual muscle, or a group of muscles. This additional muscle mass is best gained through the combination of increased resistance training volume and appropriate nutrition. The development of additional muscle mass can be for aesthetic or performance goals. However, each of these goals can have slight differences in the method of mass accumulation. In all hypertrophic training, it is essential to ensure that net protein synthesis (i.e. the formation of new proteins) is increased in order to facilitate the development of new muscle tissue. This can be achieved through increased protein synthesis, reduced protein degradation (breakdown) or a combination of both.

Types of Muscle Growth

Muscular growth is the process of increasing the size and volume of your muscles. This can be achieved by two main processes: (1) fibre hypertrophy or (2) fibre hyperplasia.

(1) Muscle fibre hypertrophy is based on the concept that muscle fibre number remains constant throughout life, and so for hypertrophy to occur there must be an increase in the size of the individual contractile units, connective tissue and sarcoplasm (the largest constituent of the muscle cell).

(2) Hypertrophy from fibre hyperplasia is a consequence of the splitting of a single muscle fibre. This splitting of the muscle fibre comes from the presence of extremely high intensity weight training (training at high % of 1RM), the split fibre results in two new fibres both the same size as the parent cell. Therefore hyperplasia hypertrophy is an end result of an increase in the number of muscle fibres within a whole muscle.

Common Hypertrophy Methods

High repetition hypertrophy is a result of high volume resistance training at a lower % of 1RM (50-80% 1RM). The range of repetitions used is typically 8-12 repetitions, with multiple exercises of 3-6 sets. This type of training results in what is referred to as sarcoplasmic hypertrophy. Sarcoplasmic hypertrophy results in increased cellular fluid. This training also elicits what is commonly called a muscle “pump”. The pump is not an actual increase in muscle size, but rather a transient response to increased high volume contractile activity. The training that results in this type of adaptation typically results in low additional strength gains as the repetitions used usually result in a low percentage of 1RM being used as a training load.

Myofibrillar hypertrophy comes as a result of high intensity training at high % of 1RM (85-95% 1RM). This training type utilises a lower repetition range than sarcoplasmic hypertrophy (typically 2-6 reps) again with multiple exercises of 3-6 sets. This type of training results in increases in the function of contractile parameters within muscle cells. These changes facilitate greater increases in maximal strength, as a high percentage of 1RM load is used. However, this type of training is associated with smaller increases in muscle mass compared to high repetition hypertrophy.

Both sarcoplasmic and myofibrillar hypertrophy rarely happen independently of each other. While typically one type may predominate, there may be a balanced contribution of both training responses. The high tension applied to the muscle fibre is ultimately the mechanism that facilitates the accumulation of muscle. The application of tension to the muscle allows for a muscle building signalling pathway to be evoked.

Early increases in strength induced by resistance training in novice athletes are primarily due to modifications in neural function that facilitate adaptation to the training loads. Hypertrophy itself is typically associated with prolonged training in intermediate to experienced weight training athletes. Therefore, a specific hypertrophy training goal should be set after an initial period of resistance training, subsequent to enhanced neural adaptation.

In addition to the tension being applied to the muscle as a regulator of the hypertrophic response, muscle fibre type also plays a role in the hypertrophic response. The total volume of training must be high using either high repetition (8-12) with a lower % of 1RM (50-80%) OR lower repetition (3-6) with higher % of 1RM (85-95%). Type 2 fast twitch fibres respond more favourably to hypertrophic training despite there being no difference in protein synthesis between muscle fibre types. The tempo used should be a kept constant at 4-0-1: i.e. four seconds through the eccentric phase and as quick as possible through the concentric phase. Throughout all movement strict form should be maintained.


The type of training that facilitates hypertrophy results in micro-trauma to the muscle tissue. This micro-trauma is in essence a miniscule injury in the muscle, which is normally not perceptible on a whole body level. If training for hypertrophy on consecutive days, a split or alternate routine can be utilised. The inclusion of a split routine can facilitate training on consecutive days by training specific body parts or muscles during training. The subsequent training sessions will avoid targeting of previously trained muscles until sufficient recovery has occurred. For whole body hypertrophy, particularly in novice trainers, 48 hours rest between sessions working a particular body part is essential to maximise progression. If insufficient recovery occurs between training times the risk of potential injury is increased. Although not an injury, some athletes may experience delayed onset muscle soreness (DOMS). DOMS is a result of the eccentric overload in the working muscles, which causes a temporary disruption to the architecture of the muscle fibres that is mildly to moderately painful, but should not be a cause for concern. The pain felt will subside over 2-4 days with active recovery, and the eccentric action will produce a protective effect for the muscle for future activity.


Hypertrophy occurs in response to the presence of an appropriate training stimulus sufficient to elicit an adaptive response in the muscle cells. The relative contribution of either type of hypertrophy (fibre hypertrophy/fibre hyperplasia) is as yet unclear. To train for increases in muscle mass with slight increases in strength, a high repetition count should be used, 3-6 sets of between 8-12 repetitions. For lesser hypertrophy with greater strength gains lower repetition counts should be used, 3-6 sets of between 2-6 repetitions. For all hypertrophy, sufficient rest should be given between sessions. If using a split routine, an ideal rest period of 48 hours should be given before re-training a particular body part.