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Annual Meeting Abstracts: F-25 – Free Communication/Poster: Exercise and Fitness: General

Whole Body Substrate Oxidation in the Menstrual Phases During Exercise Relative to Ventilatory Threshold

Yasuda, Nobuo; Ruby, Brent C. FACSM; Gaskill, Steven E. FACSM

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Medicine & Science in Sports & Exercise: May 2004 - Volume 36 - Issue 5 - p S254
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Clarification of the effect of the menstrual phases on substrate use pattern to exercise remains to be elucidated with respect to exercise mode, intensity, and duration. PURPOSE: The purpose of this study was to determine the variations of substrate oxidation in the follicular (F) and luteal (L) phases for women during progressive arm and leg exercise at 70, 85, 100, and 115% of mode specific ventilatory threshold (Tvent). METHODS: Eumenorrheic recreationally active women (n = 10) served as subjects. Ventilatory equivalence, excess CO2, and modified V-slope methods were used to concurrently determine Tvent. All subjects performed 5 min exercise at each intensity of 70, 85, 100, and 115% of Tvent arm cranking (AC) and Tvent leg cycling (LC), once during the follicular phase (5–9 days after onset of menses) and once during the luteal phase (22–27 days after onset of menses). Total carbohydrate (CHO) and fat (FAT) oxidation were determined with indirect calorimetry. Significance was set at p<0.05. RESULTS: There were no significant differences between the two menstrual phases in relative contribution (%) of CHO during AC (70%Tvent: F = 52.1 ± 8.2, L = 50.7 ± 20.9; 85%Tvent: F = 60.0 ± 10.1, L = 59.0 ± 18.8; 100%Tvent: F = 66.3 ± 12.9, L = 64.0 ± 18.8; 115%Tvent: F = 71.2 ± 10.2, L = 69.1 ± 18.7) and during LC (70%Tvent: F = 51.6 ± 11.4, L = 53.5 ± 11.3; 85%Tvent: F = 58.0 ± 10.2, L = 60.9 ± 10.1; 100%Tvent: F = 64.0 ± 10.3, L = 63.1 ± 12.2; 115%Tvent: F = 68.9 ± 11.0, L = 68.5 ± 13.7). Similarly, there were no differences in %FAT contributions during AC or LC at any intensity across menstrual phases. It is noteworthy that as exercise intensity approached 100%Tvent, there was a tendency towards higher whole body CHO oxidation (expressed as g CHO•min−1, kJ CHO•kg−1•min−1, and μmol CHO•kg−1•min−1) in F vs. L during both AC and LC exercise. CONCLUSIONS: These findings indicate that whole body substrate utilization was similar during exercise in the follicular and luteal phases in recreationally active women. Whole body patterns of fuel utilization between the two phases may be more dependent on exercise mode, intensity and duration including individual variations in ovarian hormone concentrations.

©2004The American College of Sports Medicine