Train with CORE: Simple Heat Training for Runners

Once you have done a heat ramp test, identified your ideal temperature zones, and gained some heat awareness, you are ready to start heat training. Heat training is a simple technique that has been proven to boost VO2max, power at lactate threshold, and time trial performance by 5–8% in both hot and cool conditions. The physiological changes mostly involve creating more blood plasma and red blood cells, allowing greater delivery of oxygen to muscles. The gains from season-long heat training allow you to train at a higher intensity, which further boosts your race performance.

Basics of heat training

The article Heat Training for Sporting Performance gives details on heat training. But the basics involve doing 2–3 heat sessions per week, with each session having 45–75 minutes in your heat training zone. This amount of time accumulated in the heat training zone is known as thermal load, and it is easily tracked in the CORE mobile app.

Accumulating this amount of thermal load is easy with a typical runner’s training plan. The required thermal load should be reached each week. Missing 2–3 weeks of heat training will greatly diminish the extra blood plasma you have created.

Note that while some people will choose to do a heat training block (2–4 weeks of 6 days/week of heat training), to get their plasma gains immediately, most find it more convenient to accumulate those gains more gradually with something like the schedule below. If you do choose a heat training block, the below schedules can be used for season-long maintenance.

Runners usually find it easy to elevate their core temp into their heat training zone – even during winter by wearing some extra layers. These workouts are also very suitable for the treadmill.

Sample heat training schedule








Rest or easy run

VO2max intervals

Endurance run
(include 45–75 minute heat session)

Tempo run

Easy run
(45–75 minute heat session)

Endurance run
45–75 minute heat session)

Long run


Details of the heat sessions

Wednesday, endurance run

This is a relatively low intensity run, possibly with substantial time spent at a marathon pace. If your run isn’t long enough to give you 45–75 minutes in the heat training zone, sitting in a hot bath or sauna after you run can extend your heat session and give you the total thermal load you desire.

Friday, easy run

This is a recovery run, performed at an easy pace. If your run is not long enough to accumulate 45–75 minutes in the heat training zone, your heat session can be extended with a hot bath or sauna immediately after the run.

Saturday, endurance run

This is a repeat of Wednesday’s run.

Heat training during high intensity?

High intensity running while in the heat training zone causes a lot of stress to the body and is best avoided. Most runners have enough easy–moderate-paced workouts in a week to do their heat training during those lower intensity days.

Heat training during the long run?

While the long run presents a big block of time to do heat training, some runners do tempo intervals during their long run. It is best to have your core temp below the heat training zone during those intervals. Also, remember that once your core temp is elevated to the heat training zone, it can be challenging to lower it while running. Accumulating more than 75 minutes in the heat training zone is not recommended, as it may cause excess fatigue. In other words, plan carefully if you do a heat session during the long run.

Lower volume runners

The above schedule works easily for those running approximately 6 hours/week or more. Lower-volume runners may only be running 4–5 days/week, and seldom run for longer than 45 minutes. However, they can still accumulate enough thermal load by making the following adjustments:

  • Immediately following the Wednesday and Friday runs, enjoy a sauna or hot bath to extend the amount of time in the heat training zone.
  • Switch the weekend heat training session to the long run.

Tracking thermal load

The CORE mobile app makes it easy to track your thermal load. You can see how many heat training sessions you’ve done in a week or month, and also the cumulative time you’ve accumulated in that zone. Remember that athletes can also easily share their CORE mobile app data with their coach – it will be synced to the coach’s app as soon as the athlete uploads it to the CORE app (or if using a Garmin device, as soon as the workout syncs with the Garmin app).

Next steps

Once you’ve become accustomed to heat training, the next step in using CORE is learning how to pre-cool before a race or intense workout.