BACKGROUND: The female reproductive hormone estrogen has been postulated to have antioxidant properties which may indicate a connection between estrogen and a shortened duration or lower intensity of delayed onset muscle soreness (DOMS). However, many studies have attempted to compare males and females’ reaction to DOMS after exercise to determine if estrogen has a protective effect on muscle damage, but fewer studies have attempted to compare women in different phases of the ovarian cycle and the intensity of DOMS. The ovarian cycle has a distinct phase of breakdown and rebuilding. Thus, if estrogen does influence DOMS, women in ovarian phases in which estrogen is high may have a shorter or possibly less intense period of DOMS. The purpose of this study is to determine the effect of estrogen on the intensity of DOMS during different phases of the ovarian cycle when endogenous levels vary. METHODS: We plan to recruit 15 untrained eumenorrheic (28-32 day cycles) females who have not taken oral contraceptives in the past 6 months and are between the ages of 18 and 25. The participants will be asked to run downhill for 20 minutes at a 12% decline at a speed of 5.0 mph to 5.5 mph. They will complete this run once in their early follicular phase, 2-5 days after onset of menses, and once in their mid-luteal phase, 4-8 days after expected ovulation. These phases will be estimated by past menstruation data reported by the participants. We will test passive knee flexion range of motion, pain perception using a Likert scale, force production using an isometric mid-thigh pull, and swelling with thigh circumference to determine the intensity of DOMS. The outcome measures will be evaluated four times for each run: immediately pre-run, immediately post-run, 24-hour post-run, and 48-hour post-run. ANTICIPATED RESULTS: We hypothesize that the data from the early follicular phase will show lower pain perception and swelling with greater force and range of motion by 48 hours after exercise.

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