How this is calculated
Inspect the versioned inputs.
Input defaults that are not sourced measurements are illustrative planning assumptions. Exact unit definitions, the 52-week convention and algorithm details are in the shared methodology.
Worked example
An example you can inspect.
A user-entered 60 s hot + 15 s cold + 30 s rest repeated twice is 210 s. This arithmetic example is not an exposure recommendation.
Set a schedule without treating it as a prescription.
Enter the durations for the hot, cold and optional rest phases and choose a whole number of rounds. These settings create a sequence of intervals. The demonstration defaults are scheduling examples, not a sourced therapeutic contrast protocol or a declaration that either exposure is appropriate for you. Confirm the intended plan independently before starting. A zero rest interval omits the rest phase, while hot and cold intervals must be positive so the sequence has meaningful timed phases.
Understand start, pause and reset.
Starting records elapsed time against a monotonic clock. The displayed phase is derived from the complete interval sequence, rather than being advanced by assuming that every animation callback arrives exactly on time. Pausing preserves progress and stops elapsed accumulation. Reset returns the sequence to its initial state. Review the displayed settings before restarting after a reset. The timer is a convenience for a plan you chose; it does not sense temperature, immersion depth, symptoms or whether a person has actually moved between environments.
Check optional cues on the device you will use.
Audio and wake lock depend on browser support, permissions and the current device state. Enable sound through the visible control and check its audibility in your intended setting. A wake-lock request can be unavailable or fail; the interface reports that fallback rather than promising the screen will stay awake. Operating-system interruptions or a closed browser can still affect the experience. Keep an independent way to monitor the situation and do not rely on a browser sound as a substitute for attention to the environment.
Read elapsed time rather than chasing the display.
The large current-phase label, remaining time and round count make the schedule easier to read, and phase changes are announced through the page's live region. They are not real-time medical monitoring. Stop or change your own activity when circumstances require it, even if the scheduled interval has time remaining. Reloading starts a fresh page and does not restore an earlier run. If sharing the timer settings, verify the durations and rounds after opening the link; the link represents settings, not evidence that a previous session was completed.
Check the full sequence before starting.
Review the total sequence, including whether a rest phase follows the final cold phase. The round counter refers to the configured sequence rather than a sensor-confirmed transition. Changing settings while preparing the timer should be followed by a reset and a fresh review. If the page is interrupted, confirm the current state before continuing instead of assuming that the display still matches the intended activity.
Questions, considered
Questions about this tool
How should I interpret the contrast therapy timer result?
Abrupt cold exposure adds separate risks. The timer cannot monitor you, temperature or symptoms. Audio and wake lock require browser support; backgrounds and device sleep can limit them. Run your own hot, cold and rest intervals with accessible controls, optional audio and a supported-browser screen wake lock.
Which assumptions matter in the contrast therapy timer?
Build the entered phase sequence for each whole-number round. Track elapsed time using a monotonic clock rather than trusting interval callback counts. Pause preserves elapsed time; reset clears it. Announce phase transitions instead of reading every second to screen readers. The short default sequence demonstrates the timer only. No therapeutic or safe hot/cold protocol has been established by this tool.
Primary sources
Follow the source.
- Sauna Health Benefits: Are saunas healthy or harmful? ↗
May 14, 2020; general precautions
General precautions include avoiding alcohol, discussing heat-relevant medications, limiting visits to 15–20 minutes, gradual cooling, and avoiding sauna when ill. Symptoms during a visit mean leaving. Do not translate the text into a personal permission or treatment algorithm.
Checked 2026-11-08 - RNLI Water Safety — The Dangers Of Cold Water Shock ↗
Cold water shock explanation
Sudden cold-water exposure can disrupt breathing and cardiac function. A contrast timer supplies timing functions, not an endorsed cold-immersion protocol or protection from cold shock.
Checked 2026-11-08 - Published tool assumptions and preference scoring ↗
Editorial assumptions, input defaults, uncertainty and validation
Explicit site-authored conventions, not external scientific evidence.
Checked 2026-11-08