No Effect Of Monophasic Oral Contraceptives On Fixed Intensity And Self-paced Cycling Performance In The Heat: 1003

Fluctuations in sex steroids are thought to affect performance and exercise capacity. Therefore it is important to understand the effect of oral contraceptives (OC) on exercising women. OC are most widely used by sportswomen. In addition to being highly effective in preventing pregnancy, female athletes may also choose to use OC to manipulate the menstrual cycle during training and competition and for control of premenstrual symptoms. PURPOSE: To examine the effect of monophasic OC on fixed and self-paced exercise in HOT (32.04±1.1°C, 65.8±1.7% relative humidity) and COOL (20.09±0.5°C, 47.9±2.7% rh) conditions. METHODS: Ten healthy, active female subjects (21.89±4.08 years), on monophasic OC for at least 6 months, completed a 30 min fixed power cycling followed by a 30 min self-paced time trial (TT) with 30 s sprints during each stage at 9.5 min interval. The study was controlled according to menstrual cycle phase and the groups are referred to as: week 1 of OC, in a COOL environment (DAY8), week 3 of OC, in a HOT environment (DAY 18) and day 1 of menstruation, also in a COOL environment (MENS). RESULTS: There was no significant difference in distance cycled for the fixed power output trial (15.72 vs 15.85 and 15.32 km, for DAY8, DAY18 and MENS, respectively, p < 0.05) nor for the self-paced performance trial (10.82 vs 10.90 and 11.08 km, p < 0.05). There was also no difference in distance cycled during each 5 min interval in any condition. Core temperature (Tc) increased significantly over time for each condition during the fixed-power trial. However, Tcwas significantly higher for DAY18 during the self-paced trial compared to MENS (38.48°C vs 38.18°C, respectively, p < 0.05). Skin temperature increased significantly during DAY18 to ∼ 36.0°C and was significantly different from DAY8 and MENS (∼29.8°C and 29.65°C, respectively, p < 0.05). Rating of thermal sensation increased over time for both fixed-power and TT but was significantly higher for DAY18. Heart rate increased similarly for each condition during the sprints in both the fixed-power and TT. Perceived exertion (RPE) increased in each condition and peaked during the sprints but was significantly higher for TT compared to the fixed-power at the end all trials. CONCLUSION: These findings suggest that the use of a monophasic oral contraceptives do not alter the ability to perform self-paced exercise in either hot or cool conditions.