A study determined if anaerobic power, isometric strength, and isometric endurance are affected by the menstrual cycle and if endurance trained females and untrained females are affected in the same manner on these performance parameters. Subjects were healthy, normally menstruating females, ages 18-34 years who were classified as either trained (n=23) or untrained (n=24). Each subject was tested once during four phases of one complete menstrual cycle. Anaerobic power was determined via the Margaria-Kalamen power test. Isometric strength and endurance of the non-preferred forearm flexor muscle group were determined using a cable tensiometer and strength bench. Study results indicated that there was no significant difference in anaerobic power, muscular strength, or muscular endurance as a result of the menstrual cycle. Additionally, there was no significant difference between the fluctuation patterns of the two groups studied. (Author/JD)