Purpose This study aimed to test the hypothesis that aerobic exercise performance is impaired in the midluteal (ML) compared with the midfollicular (MF) phase of the menstrual cycle. Methods Twelve recreationally active eumenorrheic women (25 ± 6 yr) completed exercise sessions during the MF and the ML phases. Each session consisted of an 8-km cycling time trial that was preceded by 10 min of cycling performed at a constant power below and above gas exchange threshold. Heart rate, ventilation, and oxygen uptake were continuously measured. RPE and ratings of fatigue were assessed during the time trial using visual analog scales. Total mood disturbance was calculated from the POMS questionnaire administered before and 20 min postexercise. Results Salivary progesterone concentration was 578 ± 515 pg·mL−1 higher in ML compared with MF phase (P < 0.01), whereas estradiol concentration did not differ between phases (167 ± 55 vs 206 ± 120 pg·mL−1, P = 0.31). Total mood disturbance before exercise was greater during the ML phase compared with the MF phase (P < 0.01), but this difference was abolished postexercise (P = 0.14). Mean power output was lower during the ML phase (115 ± 29 vs 125 ± 28 W, P < 0.01), which led to a slower time trial in the ML phase (18.3 ± 2.0 min) compared with the MF phase (17.8 ± 1.7 min, P = 0.03). Ratings of fatigue were greater during the ML phase from 2 to 8 km (P ≤ 0.01), whereas no differences in RPE were observed. Heart rate (P = 0.85), minute ventilation (P = 0.53), and oxygen uptake (P = 0.32) did not differ between phases during the time trial. Conclusion Aerobic exercise performance is worse in the ML phase compared with the MF phase in recreationally active women, which was accompanied by a more negative mood state preexercise and increased ratings of fatigue.

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Gas-collection masks are used as a comfortable alternative to the traditional mouthpiece and noseclip during exercise testing protocols in human performance laboratories. However, these masks may introduce potential problems which could affect metabolic and ventilatory parameters, including gas leaks and added dead space. Therefore, the purpose of this study was to compare breathing mechanics, gas exchange variables and ratings of perceived breathlessness (RPB) during highintensity exercise between a mouthpiece and face mask. Fourteen men [V ̇O2 peak = 55.3 ± 7.3 ml•kg −1 •min −1 ] were recruited to perform 6 min of cycle ergometry (Velotron Pro, RacerMate, Inc., Seattle, WA) at a work rate corresponding to 90% of V ̇O2 peak while breathing on either (1) a mouthpiece (Hans Rudolph, KC, KS) with nose clip, or (2) a face mask (7450, Hans Rudolph, KC, KS). The difference in V ̇E between the mouthpiece (156.8 ± 23.3 L/min) and face mask (153.3 ± 21.8 L/min) was not significant (p = 0.534). Similarly, there were no significant differences in breathing mechanics, gas exchange variables or RPB. These data suggest that the facemask can continue to be used interchangeably with the mouthpiece and may even be a more comfortable alternative during high-intensity exercise.