2006 Meek, Katie
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Meek, Katie Lynn The Effect of Dosage on the Rate of Change in Young Adults With Tight Hamstrings Faculty Mentor: Dr. Brent Feland, Exercise Science A variety of methods have been used to increase the range of motion and length of the hamstring muscles (Bandy et al. (1997), Feland et al. (2001), Graham, et. al. (year unknown), Johnson et al. (1997), Sherry et al. (2004), Willy et al. (2001)). The purpose of this study was to determine which method of total time and dosage was most effective in increasing the range of motion and flexibility of the hamstring muscle. After discussing methods used to study the hamstring muscles, Dr. Feland, Wayne Johnson, and I decided that dosage should be studied more. Dosage, in physical therapy, is defined as the segment of time a muscle is stretch. For instance, if a muscle is stretched for a total time of 30 seconds and those 30 seconds are split up into 10 second segments, then the dosage would be 310. We decided on two dosages, 910 and 330, using 90 seconds as our total time. We decided on these two dosages because they are those most frequently used by physical therapist and other health professionals. A control group was also used in this study. They came to stretching sessions and lay supine for a total time of ninety seconds. It was hoped that this study would determine which method was a more effective stretch. This study was conducted over a six-week period. Before the stretching regime was conducted all participants were randomly placed into groups by drawing a one, two, or three out of a hat. Initial range of motion was obtained with an inclinometer, (Dasco Pro, Angle Finder Plus level, model AF100) having a manufacturer’s reported error of ½ of 1 degree (Dasco Pro Inc. Rockford, IL) Participants then underwent a pre- measurement to determine that they were not too flexible. To be considered too flexible participants would have to have a measurement greater than 11 using an inclometer (Figure 1). A post-measurement was also taken at the end of the six-week period to see the change in stretch from week one to six. Both pre- and post-measurements were performed by a proctor who was blind to the distribution of each participant into groups one, two, or three. We hypothesized that the 330 group would have a greater rate of change from week one to six than would participants in the 910 group. There were a total of fifty subjects at the beginning of the study. Two subjects did not qualify for the study, as they were too flexible in the initial pre- stretch trial. Twelve subjects either dropped out of the study early for various reasons, or did not meet stretching criteria throughout the course of the six-week period. Subjects had to meet certain standards in order to participate. Participants completed a subject-information questionnaire, which listed inclusion and exclusion criteria. One of our greatest challenges was not having enough participants in the study. Ultimately, 25 males and 11 females ages 18 to 25 fully participated as subjects in this study. Due to not having enough participants to begin with, dropouts, and not having all participants follow stretching protocol the study was not as valid as it could have been including a larger sample size. The results of our study indicated that there was a difference in the amount of stretch between the control group, and the 10-second and 30-second stretch group (F=19.77, p = 0.999). A Post-hoc analysis showed a difference between the control group and the two experimental groups. There was no significant difference from pre- to post-measurements between groups two and three. The mean for group two was 13.285, while the mean for group three was 11.538. The first test measured the differences between all pre-measurement ROM, and the second test measured the differences between all post-measurement ROM for the control group (one), the 10-second group (two), and the 30-second group (three). Alpha was set at p<0.05. The results of the ANOVA test resulted in a p<0.05. The means of group two and three are close enough to show no statistically significant difference in stretching method. Once again showing that the different methods of stretching, whether it is nine times ten seconds for group two or three times thirty seconds for group three are not statistically significant enough to prove that either method is better than the other. Studies in the past have not established an effective standard whereby length in hamstring can be increased using different dosages all using a set amount of time. The goal of this study was to see dosage could produce results equivalent to previous studies, which were successful in increasing hamstring length and ROM. In this study no methods other than 9x10 seconds and 3x30 seconds were used. Future studies might focus on different combinations of dosage and methods, although the outcome is likely to be the same. Future research should experiment with changing the length of each dose. After final revisions are completed I will submit my thesis to “Physical Therapy” and other professional journals for review in the hope of being published. This will take place after I have made my final copies for the Honors department to be bound and placed in the HBLL and the Exercise Science department. I will take the knowledge I have gained from this study to help those I work with as I begin a lifetime devoted to improving the areas of health and human performance. Figure 1 - Measurement of range of motion with inclinometer References Bandy, W.D., Irion, J.M., & Briggler, M. (1997). The effect of time and frequency of static stretching on flexibility of the hamstring muscles. Journal of Physical Therapy, 77, 10901096. De Weijer, V.C., Gorniak, G.C., & Shamus, E. (2003). The effect of static stretch and warm-up exercise on hamstring length over the course of 24 hours. Journal of Orthopaedic & Sports Physical Therapy, 33, 727733. Feland, J.B., Myrer, J.W., Schulthier, S.S., Fellingham, F.W., & Measom, G.W. (2001). The effect of duration of stretching of the hamstring muscle group for increasing range of motion in people aged 65 years or older. Journal of Physical Therapy, 81, 11101117. Graham, D.J., Draper, D.O., Feland, B., & Eggett, D. (Year Unknown). The long term effects of short-wave diathermy and long-duration static stretch on hamstring flexibility. Department of Exercise Science. Brigham Young University, Provo, Utah. Johnson, W. Kennedy, J., & Mortensen, B. (1997). Effect if repetition on the rate of change in muscle length in females with tight hamstrings using an active stretch. School of Health Related Professions. University of Alabama at Birmingham, Birmingham, Alabama. Sherry, M.A., & Best, T.M. (2004). A comparison of 2 rehabilitation programs in the treatment of acute hamstring strains. Journal of Orthopaedic & Sports Physical Therapy, 34, 116125. Willy, R.W., Kyle, B.A., Moore, S.A., & Chleboun, G.S. (2001). Effect of cessation and resumption of static hamstring muscle stretching on joint range of motion. Journal of Orthopaedic & Sports Physical Therapy, 31, 138144.