Hyperplasia - formation of new musclefibers

Discussion in 'HST FAQ' started by Blade, Apr 2, 2003.

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  1. Blade

    Blade Super Moderator Staff Member

    Note: There is still an ongoing debate in the scientific community of whether hyperplasia occurs in humans. The evidence that it does happen, is heavily critized by others. We encourage people to do form their own opinions based on the available research.

    Quoting from Kelly (Kelley 1996), "The results of this investigation are similar to a recent narrative review that concluded that muscle fiber hyperplasia 1) consistently occurs as a result of chronic stretch, 2) rarely occurs with overload in the form of compensatory hypertrophy, and 3) has produced mixed results when overload in the form of exercise is employed."

    You will hear the term "compensatory hypertrophy" used in stretch overload studies. What this means is that the stretch overload is progressively applied, rather than all at once (i.e. chronic stretch).

    What this tells us is that fiber splitting is dependant on the degree of strain (strain = load + microtrauma) experienced by the fibers as a factor of time. In compensatory hypertrophy models, the tissue is allowed to adapt to a lighter load before a more severe load is applied. With chronic stretch the max load is applied all at once and isn’t changed throughout the observation period.

    Intermittent stretch is similar to chronic stretch in that the max load is applied all at once, however, it is “intermittently” applied. So it is applied then it is removed, and then reapplied, etc. This has tended to result in hypertrophy without fiber splitting.

    It used to be thought that muscle fibers would only split after they have hypertrophied, almost as a result of the hypertrophy itself. But a recent study which I just read the other day but can’t seem to find at the moment, demonstrated fiber splitting can occur before fiber hypertrophy.

    1: Kelley G. Mechanical overload and skeletal muscle fiber hyperplasia: a meta-analysis. J Appl Physiol. 1996 Oct;81(4):1584-8.

    2: Antonio J, Gonyea WJ. Muscle fiber splitting in stretch-enlarged avian muscle. Med Sci Sports Exerc. 1994 Aug;26(8):973-7.

    3: Antonio J, Gonyea WJ. Progressive stretch overload of skeletal muscle results in hypertrophy before hyperplasia. J Appl Physiol. 1993 Sep;75(3):1263-71.

    4: Antonio J, Gonyea WJ. Role of muscle fiber hypertrophy and hyperplasia in intermittently stretched avian muscle.

    J Appl Physiol. 1993 Apr;74(4):1893-8.
    "Title: Effects of anabolic steroids on the muscle cells of strength-trained athletes.

    Researchers: Kadi F, Eriksson A, Holmner S, Thornell LE Department of Integrative Medical Biology, Umea University, Sweden.

    Source: Med Sci Sports Exerc 1999 Nov;31(11):1528-34


    Athletes who use anabolic steroids get larger and stronger muscles. How this is reflected at the level of the muscle fibers has not yet been established and was the topic of this investigation. METHODS: Muscle biopsies were obtained from the trapezius muscles of high-level power lifters who have reported the use of anabolic steroids in high doses for several years and from high-level power lifters who have never used these drugs. Enzyme-immunohistochemical investigation was performed to assess muscle fiber types, fiber area, myonuclear number, frequency of satellite cells, and fibers expressing developmental protein isoforms.

    RESULTS: The overall muscle fiber composition was the same in both groups. The mean area for each fiber type in the reported steroid users was larger than that in the nonsteroid users (P < 0.05). The number of myonuclei and the proportion of central nuclei were also significantly higher in the reported steroid users (P < 0.05). Likewise, the frequency of fibers expressing developmental protein isoforms was significantly higher in the reported steroid users group (P < 0.05). [these researchers found embryonic fiber development in the nonsteroid using group as well...just not as much as in the group using.]

    CONCLUSION: Intake of anabolic steroids and strength-training induce an increase in muscle size by both hypertrophy and the formation of new muscle fibers (hyperplasia). We propose that activation of satellite cells is a key process and is enhanced by the steroid use. The incorporation of the satellite cells into preexisting fibers to maintain a constant nuclear to cytoplasmic ratio seems to be a fundamental mechanism for muscle fiber growth. Although all the subjects in this study have the same level of performance, the possibility of genetic differences between the two groups cannot be completely excluded."

    So, there is really no argument anymore among groups up to date on their muscle physiology...that includes people into HST.

    - Bryan
  2. Blade

    Blade Super Moderator Staff Member

    What percentage of muscle growth is due to hyperplasia, and what percentage is due to hypertrophy?

    It depends on the type of training stimulus.

    Ultimately, ALL permanent muscle growth is due to hyperplasia. This is evidenced by the fact that biopsies of bodybuilders often don't show any difference in fiber CSA than non-trained individuals. In other words, the increase in muscle size is attributed to a greater number of fibers.

    Muscle fiber hypertrophy is temporary and only remains as long as the loading is consistent. When training stops for long periods, hypertrophy will reverse. Nevertheless, if training has been maintained for years, some size stays until sarcopenia sets in later in life.

    Will HST promote hyperplasia more than traditional programs?

    The average serious bodybuilder will experience hyperplasia whether they try to or not.

    Hyperplasia is more likely to occur when the loading stimulus is abrupt and frequent (or constant).

    HST will contribute to hyperplasia more so than other programs insofar as the muscle is loaded heavily (5s-negs) and frequently. Microtrauma seems to be highly correlated with hyperplasia.

    Hyperplasia does not interfere with hypertrophy. Not only that, but hyperplasia is preferable to hypertrophy.

    A muscle’s size has no real bearing on hyperplasia. It is the stimulus and how it is applied that dictates when and to what extent hyperplasia occurs.

    If hyperplasia is a fact, why shouldn't we embrace the notion that "muscle shaping" is possible ? Perhaps we can create a "peak" in the biceps after all?

    You can’t control where the most tension will be experienced in a muscle when the sarcomeres are arranged in series. It’s like hooking a bunch of identical rubber brands together, then pulling from each end and expecting anyone rubber band to experience more tension than any other. The load will be evenly distributed from end to end over all the rubber bands equally. The is why you can’t “shape” a muscle with training. Why do you think Synthol is so popular among IFBB pros?

    (Just for the sake of detail, the fibers arranged towards the distal end of the muscle converge on the tendon. As a result of their converging orientation there is often more microtrauma experienced in those fibers than other deeper and/or more proximally oriented fibers.)

    But don’t lose hope, all you need to do to have a bigger peak on your biceps is build bigger biceps.

    - Bryan
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