Actively Recruiting
Timing of Energy Availability on Menstrual Cycle Function
Led by University of Colorado, Colorado Springs · Updated on 2026-05-01
64
Participants Needed
1
Research Sites
160 weeks
Total Duration
On this page
AI-Summary
What this Trial Is About
The primary aim of this clinical trial is to evaluate how fasted prolonged exercise may influence circulating reproductive hormones (i.e., estradiol, progesterone, luteinizing hormone) and menstrual cycle length when energy availability is maintained at or above 30 kcal/kg lean body mass/ day among women who regularly do running or cycling exercise. A secondary aim is to determine the effects of fasted prolonged exercise on serum leptin and cortisol. Participants will be asked to do the following over a \~3 month enrollment period: * attend a laboratory visit at the beginning of the study to have their resting metabolic rate, aerobic fitness, and body composition tested * monitor their menstrual cycle length, urine hormones, perceived stress levels, and diet for \~3 months * complete 3, 90-minute exercise sessions on a stationary bike or treadmill either fed (consuming a carbohydrate meal 1 h prior and 0.7 g carbohydrate/ kg body mass/ h during exercise) or fasted (consuming no meal prior and no carbohydrates during exercise) during month \~3 * saliva samples will be taken prior to and after 90-minute exercise sessions for quantification of leptin and cortisol
CONDITIONS
Official Title
Timing of Energy Availability on Menstrual Cycle Function
Who Can Participate
Eligibility Criteria
You may qualify if you...
- Participates in structured running or cycling exercise at least 30 minutes on 3 or more days per week
- Accustomed to exercising for 90 minutes or more
- Has regular menstrual periods every 21 to 35 days
- Has not used hormonal contraceptives for at least the past 6 months
- Is not currently pregnant, trying to become pregnant, or breastfeeding and has not been pregnant or breastfeeding in the past 12 months
- Does not have a diagnosis of major menstrual cycle disorders such as amenorrhea, polycystic ovary syndrome (PCOS), endometriosis, ovarian cancer, ovarian insufficiency, or uterine or endometrial cancer
- Does not have metabolic diseases including hypothyroidism, hyperthyroidism, Cushing disease, Addison's disease, diabetes, or congenital adrenal hyperplasia
- Does not have major cardiovascular or respiratory diseases
You will not qualify if you...
- Missing more than 7 consecutive days of aerobic activity like running, cycling, or cross training
- Having clinical low energy availability defined as less than 30 kcal/kg fat free mass
- Reporting menstrual cycle lengths shorter than 21 days or longer than 35 days during the first 2 months of monitoring
- Not showing expected rises in luteinizing hormone and progesterone during the first 2 months of monitoring
- Beginning hormonal contraceptive use during the study
- Becoming pregnant during the study
- Being diagnosed with menstrual cycle disorders such as amenorrhea, PCOS, endometriosis, ovarian cancer, ovarian insufficiency, or uterine or endometrial cancer during the study
- Being diagnosed with metabolic diseases including hypothyroidism, hyperthyroidism, Cushing disease, Addison's disease, or diabetes during the study
- Being diagnosed with major cardiovascular or respiratory diseases during the study
- Being unable to follow instructions for study procedures
AI-Screening
AI-Powered Screening
Complete this quick 3-step screening to check your eligibility
Trial Site Locations
Total: 1 location
1
William J. Hybl Sports Medicine and Performance Center
Colorado Springs, Colorado, United States, 80918
Actively Recruiting
Research Team
M
Marissa Baranauskas, PhD
CONTACT
How is the study designed?
Study Type
INTERVENTIONAL
Masking
NONE
Allocation
RANDOMIZED
Model
PARALLEL
Primary Purpose
BASIC_SCIENCE
Number of Arms
2
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