In this study, women will be required to wear a chest heart rate monitor and wrist heart rate monitor daily and collect daily early morning urine samples for the duration of one complete menstrual cycle. This will enable comparisons between data collected from the heart rate monitor and hormone analysis in urine samples to be made.

This study is a prospective observational study of women's heart rate and heart rate variability throughout one complete menstrual cycle. A minimum of 10 volunteers aged 18 years of age or over will be recruited via a variety of methods according to the criteria detailed in section 9. They will be required to wear a chest heart rate monitor and wrist heart rate monitor for 1 hour each day, and throughout the night for one menstrual cycle. In addition, a daily early morning urine sample will be collected throughout the study.

Urine samples will be returned to SPD on a regular basis for measurement of urinary hormones related to pregnancy and fertility. Data collected via the monitors including heart rate and heart rate variability will be downloaded for comparison.

Inclusion Criteria:

• Aged 18 years of age and over
• Regular menstrual cycles (23-35 days in length)-

Exclusion Criteria:

• Taking any hormonal medications
• Taking any medications that may affect heart rate
• Known heart condition or use of a pacemaker
• Skin condition where there is sensitivity to wearing a skin monitor
• Currently suffering with anxiety or panic attacks
• Pregnant or breastfeeding
• Undertaking any frequent travel or long-haul flights during the course of the study
• Does not have access to an Apple iPhone or iPad with Bluetooth 4.0 (or later) and iOS 10.0 (or later)

Adult female

Healthy volunteers