Does hyperplasia cause growth in human skeletal muscles?

September 19th, 2007 by Paul Johnson

The possible role of hyperplasia in muscle growth, is a big debate in excercise science and among bodybuilders. Most bodybuilders accept that it doesn't happen in human skeletal muscle. But are they too easy to dismiss overwhelming evidence?

Two types of muscle growth?

The traditional common belief in muscle growth is in hypertrophy. This theory says that each individual muscle fiber gets thicker due to increased protein retention(due to increased protein synthesis). The increase of size of many individual fibers, in turn makes the entire muscle bigger in diameter.

The opposite theory is hyperplasia. Hyperplasia theory says muscle fibers stay the same, but the muscle cells divide creating more fibers. More fibers at the same size increases the diameter of the muscle overall.

The argument:

No one is arguing that hyperplasia doesn't happen in smooth muscles like the intestines of humans. We have done studies on other animals and know it for certain happens in other animal's skeletal issues. The controversy for experts, comes down to whether the muscle hypertrophy exists in skeletal muscles of humans. The common belief has been that we are born with a certain specific amount of muscle fibers. They believe that muscle hyperplasia is only possible in very abnormal circumstances, such as muscular dystrophy or pregnant women's abdomen.

Studies supporting hyperplasia in animal skeletal muscles:

Dr. Gonyea put weights on cats to test for hyperplasia. His results showed a 20% increase in number of muscle fibers. The results were controversial because scientist said it couldn't apply to humans or because of the method he used to determine new muscle fibers. There have been other studies done on birds and rats that also support hyperplasia for them also.

Studies supporting hyperplasia theory for humans:

Muscle fibers contain tens of thousands of fibers. The problem with doing hyperplasia studies is it involves counting the fibers. Not to mention some of the studies that they do on animals, won't be considered as ethical or possible with humans. It would require the removal of muscle cells causing the tissue is partially destroyed. Luckily, you can still draw conclusions of hyperplasia by using proportions.

Scientists by the name Tesch and Larsson, in 1982 did a fine needle biopsy comparison of 3 groups of athletes: competitive bodybuilders, powerlifters, untrained individuals. Interesting enough the muscle fibers were found smaller in the competitive bodybuilders than in powerlifters and the same size as the untrained. The study was confirmed again when redone in 1986. If hyperplasia is not possible, then how can large bodybuilders have the same muscle fiber diameter as untrained individuals?

Another interesting study done by the American College of Sports Medicine's Medicine and Science in Sport and Exercise found it in powerlifters who use steroids.

Studies supporting muscle hypertrophy theory:

To make matters confusing, there have been multiple studies that show evidence for muscle hypertrophy instead of hyperplasia theory. Using similiar methods of measuring proportions as the previous studies, they found that muscle size increased without a change in muscle fiber number.


Why do the studies give such conflicting results? I personally am of the belief that both hyperplasia and hypertrophy happen. Hyperplasia probably happens only as a result of certain types of training or possibly only from steroid use. That is the only logical explanation I could see from why some studies give different results, yet are scientifically sound. If hyperplasia is possible in other animals and there is supporting research in humans, there is no reason not to strongly believe it happens in humans.

Training to stimulate hyperplasia:

If hyperplasia is possible, which seems highly likely, the next question is, how can we stimulate it? One study by the Journal of Applied Physiology in October 1996 Mechanical overload and skeletal muscle fiber hyperplasia: a meta-analysis seems to help possibly answer that question. They had mechanical overload into 3 groups on several animal species: stretch, excercise, and compensatory. The stretch group had by far the most hyperplasia and the excercise group had the second most.

This research and other studies suggest that emphasis should be put on the negative portion of the rep, especially at the bottom. Slow deliberate negatives on each rep could help stimulate hyperplasia. A much better way to induce hyperplasia however, would be to get a good stretch at the end of a negative rep and hold it. For example, after a few sets of chest excercises, position a weight at the bottom of a chest flye negative portion of rep. Hold the weight at the bottom for a good stretch of about 30 seconds to one minute.

After you are done with back excercises you can get a good long weighted stretch of the lats at the bottom of a negative rep for the bent over row or pullup. Make sure when you do these stretches that you don't overdo it and that you have a nice pump from previous sets. For shrugs you will have to hold the barbell weight behind your back and get a good stretch.

Arnold Schwarzennegar was known for holding the weight and getting a good squeeze when doing chest flyes after a good chest workout. He also was known for having one of the best chests ever. As you seen from this article, it probably was more than coincidental.

There is yet another reason why a good deep static stretch could be stimulating to muscle growth, besides stimulating hyperplasia. The answer is due to the fact it will also stretch muscle fascia. I wrote a article on the issue here: Muscle fascia stretching

  1. Naul on January 9th, 2010

    Very interesting, i will certainly try doing more negative reps with more weight.

  2. kris on March 29th, 2010

    what if you choose hypercontraction training?(look it up)
    wouldn’t that be the key to extraordinary muscle mass fast,i heard some very good things about it by bodybuilders
    this is a stretch exercise BEFORE you do your compound exercises so you have the maximum stretch at the beginning of a set
    they say because you do this before you train with max intensity you will engage 20% more fibers
    let me know what you think of this training style

  3. king mirgle mirgle on April 1st, 2010

    i hate your answer it suks!