Dissertations, Theses, and Capstone Projects

Date of Degree


Document Type

Capstone Project

Degree Name



Physical Therapy


Milo N. Lipovac

Subject Categories

Physical Therapy


Many human physiological functions, including muscle flexibility, exhibit a pattern over a 24-hour period, known as circadian rhythm. Muscle flexibility and its circadian rhythm have been researched, though much more information is needed, especially regarding the hamstring muscle group. The object of this study was to determine if stretching at different times of the day results in differences in hamstring flexibility. Since muscles and joints are most flexible at night, greater ranges of motion should be available, allowing for a greater degree of stretching to take place. We hypothesize that when utilizing the optimal type, duration, and frequency of stretch, subjects who stretch later in the day will have more significant increases in hip range of motion post intervention, as compared to subjects who stretch in the morning. The study was a randomized trial parallel-group research design; with hamstring flexibility being the outcome measure. Ten subjects between the ages of 21 to 40 years old were randomized into two intervention groups, one stretched between 0600 to 0900 the other between 1800 to 2100. Both intervention groups participated in active and passive knee extension stretches, performed for 5 days a week for 6 weeks. Pre and post intervention hamstring flexibility measurements were recorded, via manual goniometry of the hip angle while undergoing a passive straight leg raise. Data Desk Software was used to analyze the data, utilizing a 2-sample T test and one way v ANOVA, the results of this study were found to be insignificant for all variables. There is no significant difference in gains in hamstring flexibility with relation to Circadian Rhythm. Those who stretched in the evening did not have greater gains in ROM following a six week stretching protocol than those who stretched in the morning group.