Heat ramp test for runners

The heat ramp test was an early way of identifying each individual's core temperature range best suited for heat training. It has been replaced with Heat Zones that better predict heat adaptation. Also, please see the article Individuality of Heat Zones.

This heat ramp test is the version for indoor running on the treadmill. The test is very similar to the version for cycling.

Purposes of the Heat Ramp Test

The purposes of the heat ramp test are to:

  • identify an optimal heat training zone
  • establish a baseline using a repeatable test so that changes in power/pace output can be monitored following heat training.


If there are any heart rate irregularities or other issues such as poor sleeping or illness, the test should not be started. For repeatability’s sake, consistency is important. For example, coffee intake should not vary from normal, and each repeat of the heat ramp test should be at the same time of day.


After the slow ramp-up, focus on maintaining a constant heart rate during the test. It is expected that you will naturally need to gradually reduce your speed in order to maintain a steady heart rate. This is normal and correct.

Room and clothing

This test can be conducted on an indoor treadmill in a normal room temperature of 20–25º C/68–77º F, or a low-humidity room super-heated to 30ºC / 86ºF. In normal room temperatures, overdressing is important. Runners may need to wear more clothes than they would normally wear for a winter run. For your safety, avoid using waterproof attire that completely traps sweat.

Fans should not be used and draughts or airflow should be stopped as these can provide cooling. If your body is able to cool too much, this can cause the heat ramp test to fail. A test conducted in a room much cooler than 20–25º C/ 68–77º F will also likely fail.

This test can be very uncomfortable. For tests at room temperature, the warmer you dress, the shorter the test. For further information, we have a supplement for the heat ramp test for cycling which is worth reading in advance to ensure you get the best out of your test.

Heat ramp test protocol

The heat ramp test has 4 steps that will take 30–60 minutes to complete:

Step 1: Slow ramp-up. 15–20 minutes until core body temp reaches 38º C/100.4º F.

Step 2: Start of test. Maintain heart rate. During the next 15–40 minutes, speed gradually decreases.

Step 3: End of test. Stop running when speed decreases 20% from start of test. Note core body temperature.

Step 4: Continue to monitor. Core temperature may climb for 2–8 minutes more. Note maximum temperature.

Step 1 – Slow ramp-up

A gradual, 15 minute ramp-up ensures the core body temperature rises slowly rather than rapidly.

Use the following guidelines to plan your ramp-up, based on your maximum heart rate (max hr) for running.

Ramp up:

10 min at 60–70% max hr.

5 min at 70–80% max hr

Variations: The target heart rate may be lowered if needed for the effort to be sustainable. However, this will extend the total test time.

Step 2 – Start of test: 38º C/100.4º F

The moment core body temperature reaches 38º C/100.4º F, take note of your heart rate and speed. You may reach the 38º C/ 100.4º F checkpoint before you reach the target heart rate. Or you may reach your target heart rate and will need to maintain this until your reach 38º C/100.4º F. If you are struggling to reach this temperature, this could be related to your setup or your own individual thermoregulation; further information is available here.

Core temp = 38ºC / 100.4ºF

Heart rate 1 ____________

Treadmill speed 1 ______________

The test has now started; maintain a constant heart rate and cadence. Gradually lower treadmill speed as needed.

Step 3 – End of test

Stop running when:

  1. a) your speed drops 20% below Speed 1 or;
  2. b) it becomes too difficult to run or you feel unwell

Note the following:

Core temp 1 (CT1) ________________

Heart rate 2 (ideally, the same as HR1) _______________

Speed 2 (80% of Speed 1) ______________

It may be easier to calculate the 20% drop using speed (km/h or mph) rather than pace (minutes per km or mile). It helps to have an assistant to monitor speed and calculate the 20% drop.

Rest, but don’t use fans or extra cooling.

Step 4 – Continue to monitor

For the next 2–8 minutes, your core body temperature may continue to rise before peaking and cooling. Note the following:

Peak core temp________________

Minutes after test ended ___________

Heart rate 3 ________________

  • The peak core temp value is not used for calculation and this value does not indicate heat threshold. This value is solely being documented for comparison in future tests.

Calculating the heat training zone

The heat training zone is calculated from the core temp 1 (CT1) value.

Celsius calculation Fahrenheit calculation

Lower limit of heat training zone:

CT1 minus 0.5º C _______

Upper limit of heat training zone:

CT1 minus 0.3º C _______

For example, if core temp 1 is 38.9ºC, the heat training zone is 38.4ºC to 38.6ºC

Lower limit of heat training zone:

CT1 minus 0.9º F _______

Upper limit of heat training zone:

CT1 minus 0.5º F _______

For example, if core temp 1 is 102.0º F, the heat training zone is 101.1º F to 101.5.º F

Within the heat training zone, an athlete endures enough thermal stress to be beneficial (to prompt an increase in blood plasma) but retains a sufficient buffer against risks and detrimental impact.

Heat training zone

The temperature range for the heat training zone may be lower than anticipated. In contrast to other sports training workouts, in heat training, "more is not better". Going beyond the heat training zone will not increase the benefits.

Repeating the heat ramp test after heat training

After heat block training (and assumed improved heat adaption/conditioning), it would be expected that repeating the heat ramp test would show:

  • it takes longer for the athlete to reach 38º C/101.4º F
  • with the same effort, the test takes longer until the athlete reaches core body temperature 1
  • the athlete will maintain a higher comparable speed (and slower drop in speed) during the test

Download the Treadmill Heat Ramp Test Data Sheet