Heart rate by water temperature
TheoreticalContrast’s own measure. It rests on known physiology but hasn’t been tested in a study, so read it as a personal trend.
- What it is
- Every hot bath and plunge on one chart: your settled heart rate against the water's temperature. Recent weeks are solid, earlier ones faded, so you can see the curve move.
- How it is measured
- For each bath or plunge of 2½ minutes or more: the median heart rate from minute 2 to minute 4, against the median water reading after the first 30 seconds. The last 30 days are drawn solid.
- How to read it
- Heart rate isn't a straight line with temperature. Cool water around 20–32 °C lowers heart rate below its level in air, colder water nudges it back up, and hot water raises it steeply. A cloud that sits lower at the same temperature than it used to is the picture of the heat strain and cold settle trends.
- What it cannot tell you
- Contrast's own view, not a validated marker. Depth, how long you've been in, and what you did just before all move a point.
Sources
Every one of these ships inside the app, with the finding written out so you do not have to open the paper to know why it is there.
Šrámek P, Šimečková M, Janský L, Šavlíková J, Vybíral S. Human physiological responses to immersion into water of different temperatures. European Journal of Applied Physiology, 2000.
Head-out immersion at 32 °C and 20 °C lowered heart rate by about 15%, while 14 °C raised it about 5%.
doi.org/10.1007/s004210050065Mourot L, Bouhaddi M, Gandelin E, et al. Cardiovascular autonomic control during short-term thermoneutral and cool head-out immersion. Aviation, Space, and Environmental Medicine, 2008.
Heart rate was 81 bpm in air, 68 bpm in 35 °C water and 55 bpm in 26 °C water.
doi.org/10.3357/ASEM.2147.2008