When you lift weights and your muscles get larger, this is called muscular hypertrophy. You probably knew that though, but did you know there are two kinds? One type is called sarcoplasmic hypertrophy, and the other is called myofibrillar hypertrophy. Recognizing the difference between sarcoplasmic hypertrophy and myofibrillar hypertrophy can help you optimize muscular development.
Sarcoplasmic hypertrophy is the kind of size gained from performing higher repetitions, typically in the 10 to 15+ rep range. Higher rep schemes do yield size, however, such sizes stems from increased cellular liquid within the sarcoplasm. Essentially, one’s muscle mass is not gained from changes in the actual muscle fibers. Although the muscle mass itself shows as being a lot larger, this kind of hypertrophy is sometimes known as “air muscle,” “size without density,” or “all show, no go” as very little to no actual muscular growth happens. This type of hypertrophy is not advised for athletes as the added size does not link to increased performance. Athletes would be better served gaining size from myofibrillar hypertrophy, sometimes referred to as functional hypertrophy.
Myofibrillar hypertrophy is the kind of size gained from performing low to moderate repetitions, as low as 3 reps and as high as 8 reps. A myofibril is the contractile section of any given muscular fiber. Essentially myofibrils, are responsible for making our muscles contract and relax. When myofibrillar hypertrophy happens, one’s increased size comes from the an increased amount of myofibrils in the targeted muscle(s). Because of the lower rep and higher weight ranges used during training, myofibrillar hypertrophy also elicits strength and of course size but through increased muscular fiber density.
Although sarcoplasmic hypertrophy and myofibrillar hypertrophy are both useful in packing on size, consider using both in your quest for gains. As a strength and conditioning coach, I prefer myofibrilliar hypertrophy when working with traditional and tactical athletes. Sometimes I prescribe sarcoplasmic hypertrophy methods to facilitate increased muscular endurance but in general, I prefer athletes to have functional muscle mass and therefore generally lean towards myofibrillar hypertrophy methods in my programming.