Ask the Muscle Doc: Is Sarcoplasmic Hypertrophy Real?

Q: Is sarcoplasmic hypertrophy a real thing and, if so, is it affected by the type of training that I perform?

The sarcoplasmic hypertrophy theory has been around for decades and continues to be a source of controversy. The key to understanding it begins with a little muscle physiology.

Skeletal muscle is made up of approximately 75 percent water, with myofibrillar proteins (i.e., actin and myosin) and non-myofibrillar (i.e., sarcoplasmic) proteins comprising the balance. The fluid surrounding these proteins is the sarcoplasm, and it is critical for maintaining proper muscular function. The myofibrillar proteins are the ones responsible for carrying out muscle contraction.

It is generally accepted that lifting weights increases myofibrillar hypertrophy, which is a primary reason that building muscle is said to make you stronger.[1] During myofibrillar hypertrophy, there is a corresponding expansion of the sarcoplasm in which the ratio between myofibrillar protein and water remains relatively constant, thereby maintaining the integrity of the muscle cell. Still, it has been theorized that under certain conditions, growth of the sarcoplasm and increases in cellular components other than myofibrils can outpace that of the myofibrils—a phenomenon known as “sarcoplasmic hypertrophy.” The theory originally stemmed from research showing that differences exist