FIGURE 2.

Menstrual cycle characteristics of naturally cycling athletes (n = 8). Each row represents a complete menstrual cycle. Red squares represent bleeding days, yellow squares represent a rise in urinary estrogen (as claimed by the manufacture), and green squares represent ovulation. A “?” is placed where an ovulation kit was not used, but a rise in estrogen concentrations was expected based on prior/subsequent day measures. Gray bars represent the point at which tracking was ceased during the last cycle. n = 3 naturally cycling athletes were removed from this figure: two subjects collected <2 cycles worth of data (see Fig. 1) and 1 athlete had indissociable menstrual cycle characteristics due to recent HC use.