Training

What’s the Difference Between Hypertrophy and Hyperplasia?

Written by:

Julien Raby

Last updated:

A man bulking his arm to show the difference between hypertrophy vs. hyperplasia

You might have heard of hypertrophy and hyperplasia if you’ve stuck around the weight-lifting scene. There are countless debates on hypertrophy vs. hyperplasia and whether hyperplasia happens in humans.

But what’s the difference between the two, and can you induce muscle hyperplasia to grow new muscle cells? Here’s what you need to know. 

What Is Muscle Hypertrophy?

Simply put, muscle hypertrophy refers to the increase in the size or growth of skeletal muscle fibers. The process occurs as a response to certain stimuli, like resistance training or weight lifting

There are three mechanisms of muscle hypertrophy, and your training regimen will likely include a combination of the three:

  • Mechanical tension
  • Metabolic stress
  • Muscle damage

During resistance training, microtrauma occurs within the muscle fibers, resulting in damage to the muscle tissue. The body responds to this damage by initiating a repair and adaptation process.

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Specialized cells outside the muscle fibers known as satellite cells activate, starting the repair and growth process. These cells fuse to the existing muscle fibers, donating their nuclei and promoting protein synthesis.

The increase in protein synthesis leads to an accumulation of contractile proteins, such as actin and myosin, within the muscle fibers. This causes the muscle fibers to grow in size, resulting in muscle hypertrophy.

A man showing his muscle hypertrophy

The Types of Muscle Hypertrophy

There are two kinds of muscle hypertrophy: myofibrillar and sarcoplasmic

When you lift weights, you can lift heavy weights for low repetitions or light weights for several reps. Depending on how you choose to exercise, you will either initiate myofibrillar or sarcoplasmic muscle hypertrophy.

Myofibrillar Hypertrophy

Myofibrillar hypertrophy involves an increase in the amount and size of myofibrils, the contractile units of muscle fibers. It occurs when you lift more than you are used to, applying trauma to individual muscle fibers. 

The body increases the volume and density of the myofibrils during the recovery process—leading to an increase in muscle strength and speed

Myofibrillar hypertrophy requires you to lift heavy weights. It’s recommended to lift weights in the 3–8 rep range with more extended rest periods to increase muscle strength. 

H3 Sarcoplasmic Hypertrophy

Sarcoplasmic hypertrophy involves an increase in the fluid-filled sarcoplasm within the muscle fibers, resulting in a larger muscle size. This type of hypertrophy contributes more to muscle endurance and overall muscle size.

Sarcoplasmic hypertrophy, or fatigue training, requires you to lift lighter weights for more repetitions. It’s recommended to lift weights for 10–15 reps with shorter rest periods. 

What Is Muscle Hyperplasia?

Muscle hyperplasia refers to an increase in the number of muscle fibers or cells within a muscle. Unlike muscle hypertrophy, which involves an increase in the size of existing muscle fibers, hyperplasia consists of the generation of new muscle fibers.

The research is lacking for humans, but it appears hyperplasia is greatest in animals when there are specific types of mechanical overload from stretching

Muscle hyperplasia is a contentious topic, as some sides believe it happens in humans and others do not.

A couple training

Is Muscle Hyperplasia Real?

Muscle hyperplasia is real, but we lack solid evidence of whether it occurs in humans and to what degree. However, there have been several animal studies showcasing muscle hyperplasia in birds, cats, mice, and fish.

Several studies involving birds have displayed strong evidence for muscle hyperplasia. One study attached weights to the wings of quail, ranging from 10–35% of the bird’s mass. The weights were attached for 28 days, not including rest days.

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The results were significant, especially after 28 days—muscle mass increased by 318%, Muscle length by 51%, mean fiber area by 39%, and fiber number by 82%. 

But, most lifters don’t hang weights from their limbs for extended periods of time. So, does muscle hyperplasia occur in humans?

Does Muscle Hyperplasia Occur in Humans?

It’s difficult to say for sure whether muscle hyperplasia occurs in humans, as the research is lacking. But, several studies have compared individuals to see if muscle hyperplasia occurs. 

One study compared the biceps of elite bodybuilders, intermediate bodybuilders, and age-matched control individuals. There was a wide range of individual muscle fibers between the groups.

Individuals with the largest muscles tended to have the most muscle fibers, but there were similarly trained subjects with fewer than normal fibers. This makes it difficult to say whether the bodybuilders had more fiber due to training or genetics. 

Other studies have reported that evidence supporting hyperplasia in humans is “scarce.” 

Another study stated that if hyperplasia does occur, it may account for less than 5% of muscle growth.

A muscular guy with a great muscular hypertrophy

Can You Induce Muscle Hyperplasia?

So, muscle hyperplasia may not play a significant role in human muscle growth. One review stated that it may account for less than 5% of total gains. But is it possible to induce muscle hyperplasia in your training regimen?

It may be possible, but it would take a very long time—potentially decades.

Hyperplasia may occur when your muscle fibers reach a training limit but don’t have enough cell space to continue growing. If you kept training, the fibers would have to split apart, creating new fibers and restarting the hypertrophy process.

Training Strategies

Although it may take decades to induce muscle hyperplasia, you may consider including acute training strategies in your program. How would you achieve this?

Extreme mechanical overload at long muscle lengths—or weighted stretching, stretch pause techniques, and intraset stretching

One method would be to execute a stretch while holding light weights for an extended period of time. 

Or, you might perform stretches between sets of regular lifts, like chest or overhead presses. Alternatively, you can perform a standard lift, pause for a short period, and finish the rep. 

Keep in mind that these methods only work well for the shoulders, lats, chest, hamstrings, and calves. The other joints in the body do not have enough range of motion for mechanical overload. 

A strong man with big biceps

Hypertrophy vs. Hyperplasia: Frequently Asked Questions (FAQ)

What Is the Difference Between Hypertrophy and Hyperplasia?

To put it simply, hypertrophy is the increase in the size of muscle cells. On the other hand, hyperplasia is the increase in the number of cells. Both are methods to increase muscle mass and size.

What Comes First, Hyperplasia or Hypertrophy?

It’s believed that hypertrophy comes before hyperplasia. The muscles are put under stress, reaching their growth limit, and new muscle cells are created. This process may take decades of consistent training to achieve.

Does Weight Lifting Cause Hyperplasia?

The research is inconclusive. Some studies claim that hyperplasia may account for a maximum of 5% of muscle growth. That said, hyperplasia is most common in animals during periods of extreme stretching. Weight lifting may not induce hyperplasia comparatively.

About Julien Raby

My name is Julien Raby and I’m one of the owner of BoxLife. Here’s my background on LinkedIn if you want more info. I’ve been active pretty much my whole life and I discovered Crossfit about 7 years ago. I want to help you improve your Crossfit performances by giving tips on specific movements, workouts and equipment. You have a question? Get in touch!