When you lift weights and your muscles get bigger, that is muscular hypertrophy. But did you know there are two types? The first type is called sarcoplasmic hypertrophy, and the other is called myofibrillar hypertrophy. Knowing the difference between them can help you maximize your muscle growth.
Sarcoplasmic hypertrophy is an increase in muscle cell fluid within the sarcoplasm. Imagine grabbing a handfull of licorice vines. Each licorice vine represents a bundle of muscle fibers. Between the bundles is a fluid-filled space called the sarcoplasm. During sarcoplasmic hypertrophy, the sarcoplasmic fluid volume increases, but the muscle fiber mass does not, essentially creating larger, less dense muscles. No actual muscle growth occurs and no strength is really gained, but the muscle itself appears much larger.
Sarcoplasmic hypertrophy occurs from higher rep schemes (10-15+ reps) associated with bodybuilding, where building muscle size is the main goal. It is why some people in the gym appear large and muscular but are relatively weak.
For most athletes, training for sarcoplasmic hypertrophy is not beneficial. Only high-impact sport athletes like football and rugby players should add this type of training to their programs—to gain the additional benefit of size to help reduce injuries due to impact. Most other athlete programs should focus on myofibrillar hypertrophy.
Myofibrillar hypertrophy is essentially muscle fiber growth. A myofibril is the contractile portion of a muscle fiber. Without myofibrils, our muscles could not move. When myofibrillar hypertrophy takes place, the number of myofibrils in a muscle increases, which in turn increases the muscle fiber density and strength.
Again using the example of licorice vines, if you have five vines in your hand, each one representing a myofibril within a muscle fiber, you have five contractile units within that muscle fiber. Now add three more pieces of licorice, or three more myofibrils. This represents myofibrillar hypertrophy. The muscle fiber itself has grown by adding more contractile units, making it bigger and stronger.
Myofibrillar hypertrophy occurs from heavier loads and lower rep schemes (3-5 reps). Because it involves the addition of more contractile units to the muscle cells, myofibrillar hypertrophy is more beneficial to most athletes than sarcoplasmic hypertrophy. More myofibrils means greater strength and power production.
Although both types of hypertrophy can benefit athletes, myofibrillar hypertrophy is preferred because it leads to increased strength and power as well as central nervous system stimulation.
However, neither occurs solely on its own. Even when you lift heavy, a small amount of sarcoplasmic hypertrophy occurs, and when you lift for more reps, a small amount of myofibrillar hypertrophy occurs. So when planning a program, consider your goals. If you want to build size, focus on sarcoplasmic hypertrophy and perform higher rep schemes. If strength and power are your goals, aim for myofibrillar hypertrophy with heavy weight and low rep schemes.
Here's a sample lower-body training routine designed to prioritize myofibrillar hypertrophy for added power, strength and muscle density with some sarcoplasmic hypertrophy focus to increase overall muscle volume.
- Dynamic Warm-Up
- Power Clean - 4x3
- Squat - 3x5 at 80% max
- Walking Lunges - 3x10 each leg