Date of Award

Summer 2019

Document Type

Thesis Restricted

Degree Name

Master of Science (MS)

Department

Kinesiology

Committee Chairperson

Dr. Meghan Ramick

Committee Member

Dr. Melissa Reed

Committee Member

Dr. Melissa Whidden

Committee Member

Dr. Evan Matthews

Abstract

Fluctuations in estrogen and progesterone have been associated with changes in sympathetic and parasympathetic activity, with most research suggesting that in endurance trained females, the sympathetic nervous system tends to decrease overall HRV in the high hormone phase more so than the low hormone phase at rest. There is not much known about how hormonal oral contraceptives effect these measures during exercise recovery. The purpose of this study is to investigate how the female menstrual cycle effects both heart rate recovery and heart rate variability after exercise in females with natural cycles versus those on hormonal contraceptives. This study consisted of 2 trained females on hormonal oral contraceptives (OC group) and 4 trained females with natural cycles (NT group). Resting HR, post-exercise recovery HRV, and heart rate recovery were measure in both the low hormone phase (LoH) and the high hormone phase (HH). Subjects ran for 30-minutes at a HR previously determined to match 80% of VO2max and then recovered in a sitting position for 10-minutes post-exercise where R-R data was captured. This study found that there was a statistically significant difference in the SD1/SD2 ratio. The SD1/SD2 ratio was elevated more in the NT group than in the OC group in both phases. This indicates that there was greater SNS influence on the NT group than the OC group during exercise recovery. T30 (the time constant of HR decayed for the first time 30 s after exercise) was trending towards significantly longer in the NT group than in the OC group in both phases. This indicates that the OC group displayed an accelerated cardio-vagal reactivation as compared to the NT group.

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