Kurt Niepraschk and Dr. Allen Parcell, Physical Education
Human muscle has important individual characteristics and variations. We have looked at these individual characteristics and more importantly, the specific muscle fibers. These muscle fibers can be divided into two major types; slow twitch (Type I) and fast twitch (Type IIa and IIb) fibers. On average most muscles are composed of 50 percent Type I fibers and 25 percent each of Type IIa and IIb fibers. It is these fiber types that help the researchers determine a variety of things about the subjects’ abilities to succeed in specific areas of sport. Each person has different percentages of these different muscle fiber types. For example, a person with a high percentage of slow-twitch fibers might have an advantage in prolonged endurance events, while a person with fast-twitch fibers may be better at short term and explosive events.
In our study we evaluated and determined the morphologic (size) changes that occur in muscle fibers with four weeks of training. We also assessed the contrast between fiber change in male and female subjects. We accomplished this by looking at the cross sectional areas and the levels of hypertrophy. Both males and females were included in the study since there is little known about the female muscle fiber and how it is affected by resistance training. We know that for the same amount of muscle there are no differences between the strength of sexes, however, men do experience a greater increase in size due to testosterone levels. In our study we focused mainly on the differences of hypertrophy and the cross sectional areas in muscle fiber.
We tested a group of 20 individuals, 10 each of males and females. The subjects had not done any weight training within the past year, but were overall healthy individuals. The subjects started their training by riding a stationary bike and then did two warm-up sets on the leg extension machine. This was then followed by four training sets of 6-8 repetitions. This routine was followed three times a week. We also had one day a week of testing where we measured strength levels and obtained muscle biopsies. The biopsies were taken from the subjects’ quadriceps muscle after the first, second and fourth week.
My main task was to aid in the process of fiber typing which begins by using a specially cooled machine (-25 degrees Celsius) called the Cryostat microtome. The Cyro was used to slice tissue into 10 mm thick sections. The sections were then mounted on glass cover slips. Next we stained each tissue section individually using two different methods. The first method used is the NADH stain, which is very useful in demonstrating a variety of disruptions of fiber architecture. The second method, ATPase fiber typing stain, is used next. This was used to determine the percent composition of the muscle fiber.
My hypothesis when starting this research was that males would experience greater hypertrophy than females during resistance training. Also that during training the Type I fibers will not incur any change and the Type II fibers will experience a small amount of change, since these are the fibers stimulated during resistance training. Overall, however, I was hoping to gain a better understanding of all these things and the differences that occur between males and females. The findings of this project were not as expected, which was slightly disappointing. Most of the data obtained was not statistically significant and was therefore of no great meaning as far as what we were hoping to find. Type IIa fiber was the only fiber type to demonstrate an increase during the training period. However, we were not able to calculate any differences between men and woman for fiber types, since there was no significant interaction of gender and time. Therefore, the date was combined for both genders to provide more meaningful results. The distribution of fiber types remained approximately the same with a slight increase in Type IIa and a slight decrease in Type IIb. Neither, unfortunately, reached statistical significance. The primary finding of this study, as noted by the head researcher, was that there are no differences between genders in the time course of adaptation to 4 weeks of progressive training in any of the variables studied in these previously untrained athletes.
We hope to further the research done in this area by taking a larger sample of subjects for both males and females. Also, we would like to increase the time period that the subjects train, thus making this a more long-term research project. By doing this, we hope to find data that may be of greater statistical significance. However, we realize that we may come up with the same results regardless of the increase of subjects and time.