Since the early 1970's muscle biopsy has been a popular topic. Such
testing involves taking a small plug of muscle from a site in the body, then preparing it
for microscopic examination. Depending on the fixative and staining techniques applied,
biopsies were used for varying purposes, the most common being to identify muscle fiber
types. Recently, they seem to be a less popular test.
Biopsy is not a reliable way to assess an individual's fiber type for a number of reasons:
The biopsy is not consistent with respect to the location of the muscle cells extracted.
Staining is highly specific and biases the histology tech's interpretation for typing. The
procedure is invasive and somewhat destructive of muscle tissue. Muscle fiber typing is a
qualitative procedure that relies on the quantitative assumption that histology techs can
accurately and consistently - with one another - count pertinent organelles - particularly
mitochondria - in the muscle preparation.
Dependent upon the staining technique applied, various muscle typing schemes have been
advanced since 1970. One proffered the red vs. white fibers. Others said fast twitch vs.
slow twitch. Another suggested that humans have four distinct fiber types with several
intermediate types. I have heard references in other animals to as many as nine different
fiber types.
We know enough to conclude that humans indeed do have different muscle fiber types. This
is consistent with the summation that is thought to occur nervously as progressively
greater contraction intensity is willed by the subject. So what. This information alone
does not infer any suggestions regarding exercise mode, intensity, or amount.
Muscle fiber typing has been used as a basis for designing exercise programs specific to
said typing or as a measurement to gauge the success at changing the athlete's fiber type.
It may come to pass that the exercise repetition range ideally selected for an individual
is due to fiber type requirements - more likely indicative of muscle innervation -
although this might be loosely determined from the training experience of the individual.
Biopsy is not superior for this purpose. However, any attempt to change inherited fiber
type distribution is a fantasy amont many coaches and exercise physiologists.
On this last point, Peter Gollnick, MD, visited Nautilus in 1980. At that time he boasted
the best team of histology and cytology techs in the country. Gollnick defied any of them
to count mitochondria accurately.