Hypertrophy: What is it?

Arnold was quite successful at stimulating hypertrophy of the biceps.

What we’re really talking about is muscular hypertrophy. “Hypertrophy” – used both as a verb and a noun – is Latin for “grow larger”. So, when we talk about hypertrophy, we’re talking about anything that makes your muscle mass increase.

Muscles can get bigger – or hypertrophy – in several ways:

  • Hyperplasia – an increase in the number of muscle cells that make up a muscle.
  • Sarcoplasmic Hypertrophy – an increase in the volume of muscle cells caused by fluid retention within the cell. In effect, the cell swells up.
  • Myofibrillar Hypertrophy – an increase in the amount of contractile protein contained in the muscle cells.
  • Swelling – not really hypertrophy; this is the “pumped up” look you get after exercise. It disappears in a few hours.

Hypertrophy: How do I get it?


Muscular hyperplasia is different from muscle hypertrophy, but because it increases muscle mass, plenty of people want it. Unfortunately, it’s difficult to get. The only sure-fire way to stimulate hyperplasia is with Human Growth Hormone (HGH) supplementation, which usually requires a physician’s prescription and a reason other than the purely cosmetic. There is no definitive conclusion about whether it’s possible to stimulate hyperplasia; research is scant, inconclusive, and often contradictory.  Suffice it to say that hyperplasia is best left to professional bodybuilders and movie stars.

Sarcoplasmic Hypertrophy

Fluid retention in the muscle cells is fairly easy to achieve.

Supplementation with creatine – which seems almost de rigueur among even the most casual of bodybuilders – is a transitory way to achieve modest sarcoplasmic hypertrophy.

Bodybuilding magazine (and the web writers who learned their trade from these magazines) will have you convinced that bodybuilders generate massive amounts of sarcoplasmic hypertrophy by lifting weights with relatively high repetitions – 10 reps or more. Whether this is true is debatable. Most bodybuilders bulk up just like everyone else: they use low reps and heavy weight. It is only during contest prep phases that bodybuilders increase the reps.

Sarcoplasmic hypertrophy is the mechanism responsible for maximum hypertrophy. That is, if you want to be really big, you want maximum sacroplasmic hypertrophy.

Myofibrillar Hypertrophy

Stuffing a muscle cell full of contractile protein – the myosin/actin pairs known as myofibrils – causes myofibrillar hypertrophy. Unfortunately, it’s not possible to achieve the same sort of muscular size with this mechanism as it is with sarcoplasmic hypertrophy.

Lifting heavy weights with low reps stimulates myofibrillar hypertrophy. It also builds strength levels past the point possible with sarcoplasmic hypertrophy, even though the muscles may be smaller overall.


Various activities cause muscles to swell. None of these is considered hypertrophy, but since they result in a (temporary) increase in the size of muscles, I’ll include them here for the sake of completeness.

Lifting, especially in the high-rep ranges, “pumps up” your muscles. The capillaries that supply blood to the muscle cells dilate, filling the muscle with blood and fluid. This pump disappears within hours.

Micro-trauma caused by heavy exercise results in an immune response. This swelling may be barely-noticeable, and it generally takes at least a day to develop. The increase in muscle size is negligible.

Creatine supplementation forces water into the muscle cells. This semi-permanent swelling mimics sarcoplasmic hypertrophy. It quickly fades after supplementation ceases.

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