Ava utilizes temperature and other physiological parameters to determine whether the cycle’s physiological parameters conform to the literature reported biphasic patterns (Shilaih et al. 2016, 2017). It is therefore possible that the shift can’t be seen in parameters such as temperature but it was recognized in other parameters related to progesterone.
Shilaih M, Goodale BM, Falco L, Kübler F, De Clerck V, Leeners B. Modern fertility awareness methods: Wrist wearables capture the changes of temperature associated with the menstrual cycle. Bioscience reports. 2017 Nov 24:BSR20171279.
Shilaih M, de Clerck V, Falco L, Kübler F, Leeners B. Pulse Rate Measurement During Sleep Using Wearable Sensors, and its Correlation with the Menstrual Cycle Phases, A Prospective Observational Study. Scientific Reports. 2017 May 2;7(1):1294.