Riley Ables
My name is Riley Ables, and I am a junior here at Indiana University. I am studying exercise science with a minor in chemistry. I have been in the exercise physiology lab for a year now and have really enjoyed the experience especially when seeing the relevance to real world situations and individuals. My future ambitions include attending medical school and hopefully pursing a career in surgery with an involvement in research.
Fluid Balance is Unlikely Modified by the Menstrual Cycle when Ad Libitum Drinking is Permitted During Physical Work in the Heat
Purpose: The female menstrual cycle is characterized by fluctuations in estrogen and progesterone, such that elevations in these ovarian sex hormones may modify fluid regulation by both reducing urine output and promoting fluid intake. It is unknown if body fluid balance during occupationally relevant heat stress scenarios is altered across the menstrual cycle. We tested the hypothesis that during physical work in the heat women will be more dehydrated during the early follicular (EF) phase, compared to the late follicular (LF) and mid-luteal (ML) phases of the menstrual cycle.
Methods: Eight healthy, eumenorrheic, women completed three trials consisting of 4h exposure during the EF, LF, ML phases of their menstrual cycle. Each hour participants walked on a treadmill for 30min at an intensity evoking a rate of metabolic heat production of ~430W. Participants drank a cool flavor preferred non-caloric sport drink ad libitum throughout each trial.
Results: Changes in internal temperature did not differ between menstrual cycle phases (EF:0.3±0.2°C, LF:0.5±0.5°C, ML:0.3±0.3°C, p=0.544). Sweat loss (EF:2628±1504mL, LF:2804±1204mL, ML:2817±1267mL, p=0.762) and urine output (EF:864±494mL, LF:955±540mL, ML:925±480mL, p=0.725) also did not differ between phases. There were no differences in fluid intake between phases (EF:1764±1039mL, LF:1849± 694mL, ML:1892 ±883mL, p=0.785). Thus, %BWL did not differ between phases (EF:-0.3±0.7%, LF:-0.1±0.7%, ML:-0.3±0.8, p=0.530).
Conclusions: When cool, flavor preferred fluids are freely accessible, fluid balance in women likely does not differ across three distinct phases of the menstrual cycle.
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