Daily spot-checking versus chronobiologic monitoring of human differential surface (rib versus breast) temperature

A healthy, physically active woman, 35 years of age, living in Minneapolis, automatically monitored her skin surface temperature (ST) 3 inches above each nipple and on a rib below each breast for almost 3 months. In this paper a portion of that period is analyzed, namely, from October 24, 1984 (day 1 of menstruation) to November 16, 1984 (day 1 of next menstruation). On both sides, the differences between the skin surface temperature over the rib and over the breast (rib-breast DST) were calculated for each hour. The DST starts with a negative value on day 1, then becomes less negative up to around day 6, when the DST becomes positive. The means of DST during certain hours show extremely variable patterns. Even by using DST along with changes in activity and environmental temperature, circadian rhythms must be assessed. Around the clock monitoring is more reliable than a daily 1-hr mean check at a fixed time of the day. On the left side, DST mesors have a first macroscopic peak around days 8-10, another on day 14, and still others later in the cycle. On the right side, DST mesors follow a similar pattern, changing from negative to positive values. Peaking at day 10 is not as marked on the right side as on the left. The peak on day 14 is clear for both sides. With around the clock monitoring and the computation of the mesor of the differences between the temperatures at the two sites, an increase around the "estimated" ovulation time may be expected if care is also taken to account for the effects of periods of exercise and/or environmental changes.