September 18, 2026
In the past few years, cold exposure has gotten all the attention.
However, the reality is that the research is really poor for interventions such as ice baths having any real benefit to health, recovery, or fitness.
Heat, on the other hand, can have some real benefits.
I’ve more and more become of the opinion that this is something worthwhile to dedicate training time toward.
So, let’s talk about why that is:
Heat training (or "heat acclimation") just means systematically exposing yourself to hot environments during or after exercise to drive specific physiological adaptations.
Unbeknownst to many, your body can adapt to heat exposure; with these adaptations providing a variety of health and performance benefits.
There are many things that occur in your body when you expose yourself to heat over time.
The following are the most worthwhile to note.
As your body gets used to dealing with heat, it gets better at holding onto sodium when you sweat.
One study in elite cyclists found that 5 weeks of heat training reduced sweat sodium concentration by about 14 mmol/L. [1]
Practically, this means you can train and race in the heat with a lower risk of cramping, hyponatremia, or feeling drained from electrolyte loss.
Repeated heat exposure has a real, measurable effect on blood pressure long-term.
A 2021 meta-analysis of 15 studies found that heat therapy protocols (typically 8+ weeks) reduced both systolic and diastolic blood pressure by about 4 mmHg on average. [2]
That's roughly the same magnitude you'd expect from moderate aerobic exercise training.
Even more compelling, a long-term Finnish cohort study followed over 1,600 men for nearly 25 years and found that those who used a sauna 4-7 times per week had about half the risk of developing high blood pressure compared to once-per-week users. [3]
Heat exposure consistently lowers both your resting and exercising heart rate.
A 2025 meta-analysis pooling data from 211 studies found that heat acclimation drops exercise heart rate by about 17 beats per minute on average. [4]
This means your heart is doing less work to deliver the same amount of blood, which is a sign your cardiovascular system is becoming more efficient.
Plasma is the liquid portion of your blood.
When you expose yourself to heat regularly, your body expands the total amount of plasma circulating through your system.
The same 2025 meta-analysis showed an average plasma volume expansion of about 5-6% with heat acclimation.
More plasma means more blood volume to circulate, which supports better thermoregulation, lower cardiovascular strain, and (with enough exposure) eventually drives more red blood cell production.
That last point matters. A 2024 study in elite cyclists found that 5 weeks of heat training increased total hemoglobin mass by about 4%, which is the same kind of adaptation people chase by going to altitude. Just with sweat instead of thin air. [1]
Both your resting and exercising core body temperature drop with heat acclimation.
The 2025 meta-analysis found that resting core temperature decreased by about 0.2°C and end-exercise core temperature decreased by about 0.4°C on average.
This matters because performance in the heat starts to fall off when your core temperature climbs too high. By starting cooler and rising more slowly, you can sustain hard work for longer before hitting that ceiling.
In hot conditions: the benefit is clear and consistent.
Heat acclimation reliably improves time to exhaustion and time-trial performance in the heat by anywhere from 3-15%, depending on the protocol. [4]
In cool or temperate conditions: it depends.
This is where the research gets messier. Some studies show meaningful gains in cool weather performance. For instance, a study by Lorenzo et al. found that 10 days of heat acclimation improved VO2 max by 5% and time-trial performance by 6% in cool conditions. [5]
But other high-quality studies have shown no advantage over normal training.
The deciding factor seems to be whether the heat training is in addition to your normal training or instead of it.
If heat training forces you to drop your power output and reduce your overall training stimulus, the benefits in cool weather may wash out. If it adds stress on top of what you're already doing, the benefits tend to show up.
So: you should not seek to do ALL of your training in hot environments.
Heat training is likely only beneficial as an adjunct to your regular training; and may be detrimental if it is used as a substitution.
I am not listing them in any ranked order; which is the best option for you will depend on factors I can’t know without knowing you.
Here, we’re really just talking about some form of aerobic or endurance activity.
This form of training produces much more heat internally than something like strength training.
And, in every other respect, the adaptations your body makes from heat exposure are much more similar to the adaptations made from endurance training than strength training.
An example training session could go as follows:
30 minute run @ RPE 4-5.
Use a run/walk strategy if needed to keep RPE under control
Perform this session in one of the following conditions:
Outdoor at peak heat of day (or hottest part of day you can tolerate)
Wearing extra layers of clothes (hoodie, sweatpants, etc.)
Use this if it is a colder month or if you can only train in the early morning / late evening
Because the heat provides a stress stimulus to the cardiovascular system specifically, this can help shift the stress from a session to that system and away from the musculoskeletal system.
The result is that you can achieve an equal cardiovascular stimulus with less recovery time needed.
This can be helpful if you need to use your legs in a different training (lifting, hard run, etc.) the day after.
Passive heat exposure basically just refers sitting in a sauna, steam room, or hot tub.
To my knowledge, one is not better than the other.
This can be done as a stand alone intervention or done after a training session.
I would not recommend doing so before a training session; as that will only serve to impair whatever the session was.
Heat training drives meaningful adaptations: better sodium retention in sweat, lower blood pressure, lower heart rate, expanded plasma volume, and lower core temperature.
Performance gains in hot environments are large and consistent.
Performance gains in cool environments are benefited if heat training serves as an addition to your training; not a replacement.
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