Body State Explained
What is Body State?
Body State is a daily updated indicator that shows whether your body signals are stable and changing in step with your menstrual cycle. A stronger Body State over time usually means your period pattern is easier to read, which can support daily care and health management.
The system uses a personalized algorithm to analyze trends in the following metrics and compare them with the changes typically seen in cycle phases such as the follicular phase, ovulation, and luteal phase:
- HRV, or heart rate variability: changes significantly across cycle phases and reflects differences in autonomic nervous system regulation (PubMed).
- Resting heart rate (RHR): shows phase-based fluctuation across the cycle and can be used as a medium- to long-term trend reference (Nature).
- Body temperature or wrist temperature: the rise in temperature after ovulation is a classic signal for identifying cycle phase (PubMed).
By looking at several metrics together, Body State is less likely to be distorted by one stressful day, one poor night of sleep, or one hard workout. It gives a more balanced view of how your body has been running recently.
Why is Body State important?
The menstrual cycle is a body rhythm regulated by the hypothalamic-pituitary-ovarian axis and accompanied by hormone changes. These changes affect whole-body signals such as heart rate and body temperature (BioTrade).
When multiple metrics change steadily with cycle phase, your body pattern is easier to read. If they stay out of sync with typical trends, it may suggest that your body is temporarily off its usual rhythm and that sleep, stress, daily routine, and overall health deserve attention.
Continuous tracking of Body State can help you:
- Identify whether your cycle pattern is easy to read
- Observe long-term improvement or fluctuation
- Adjust daily care strategies
- Improve the reliability of period prediction
How to use and interpret it
- Updated daily: the score reflects the overall pattern of recent cycle signals and does not depend on one single value.
- Long-term trends matter: short-term fluctuation is common, while a long-term high score is more meaningful.
- Health reference tool: it supports personal health self-management and does not replace clinical diagnosis.
Main references
- Changes in resting heart rate variability across the menstrual cycle. Matthew S Tenan, R Matthew Brothers, Andrew J Tweedell, Anthony C Hackney, Lisa Griffin (PubMed)
- A Novel method for quantifying fluctuations in wearable derived daily cardiovascular parameters across the menstrual cycle. Summer R. Jasinski, David M. Presby, Gregory J. Grosicki, Emily R. Capodilupo & Victoria H. Lee (Nature)
- Menstrual Cycle Variations in Wearable-Detected Finger Temperature and Heart Rate, But Not in Sleep Metrics, in Young and Midlife Individuals. Elisabet Alzueta, Marie Gombert-Labedens, Harold Javitz et al. (PubMed)
- Comprehensive review of the menstrual cycle as a vital sign (BioTrade)