September 23, 2025 • 14 mins
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Speaker 1 (00:09):
Hey everyone, welcome to another edition of Wisdom Wednesdays. Before
we get into the podcast, quick announcement. My new book,
The Hardiness Effect, How to Grow From Stress, Optimize your
health and live Longer, is now forcel on Amazon dot
Com or Amazon dot Com do au and it actually
has for a short period of time about a twenty
(00:31):
five percent discount, So now is the time to go
in and pre order The Hardiness Effect and get yourself
a bit of a discount. Now onto the podcast. Today,
we are going to talk about the interaction between exercise
and heat exposure. So some of you may know or
may have heard that getting in a sauna after doing
(00:55):
particularly resistance training can spike growth hormone by a significant
amount three to four fold increase, and some studies have
shown and a new study just out followed a bunch
of cyclists, male cyclists who were pretty fit. They had
(01:15):
an average VO two max of sixty middle leaders per
kilogram per minute, which is pretty damn fit. But it
was a randomized control trial and they all performed high
intensity interval training for three weeks and then did hot
water immersion after exercise. Now, some of the research has
suggested that getting into a hot bath for at about
(01:40):
forty degrees for twenty minutes can actually mimic the effects
of the sauna and spike growth hormone and lead to
better performance games after exercise. So let's dig into this study.
So they did nine high intensity interval training sessions over
three weeks, so that was three sessions per week, and
(02:01):
immediately after exercise, they took a thirty minute bath in
either hot water at forty two degrees centigrade which is
one hundred and eight degrees firenheit or thermonutral kind of
body temperature ish so thirty four degrees centigrade or seventy
five degrees fahrenheit. And before and after the interventions, the
(02:22):
researchers collected muscle biopsies. So these guys are pretty game.
I don't know if you've ever seen a muscle biopsy
or had a muscle biopsy, but they basically use a massive,
thick needle like device and take a pinch of your muscle.
That's about the size of a rice crispy or rice
(02:43):
bubble depending on what country you're in, So it's pretty
dam sore. But anyway, so these guys were donating a
little bit of their muscles to science, and what they
wanted to look at was the adaptations in the mitochondria.
And then the performed a time to exhaustion test and
(03:04):
a twenty kilometer time trial on a cycle orgometer, and
the time trial performance improved to a similar degree in
both the hot water and the thermal neutral water groups
during the study, whereas the mitochondrial adaptations were unchanged in
both groups. So this is a bit of a damp
(03:25):
squid in terms of this idea that going into a
sauna or exposing yourself to heat and can improve exercise adaptations.
But a couple of things to dig into. So firstly,
let's look at a big picture. So repeated heat exposure
(03:46):
that is sufficiently stressful to elevate core temperature and that's
critical actually results in a number of physiological adaptations, so
you get overall heat acclimation. But what actually happened is
there's their plasma volume. The amount of plasma increases or expands,
(04:06):
you get reduced heart rate and core temperature at rest,
and during exercise you get higher sweat output earlier onset
of sweating and increased amounts of hemoglobin or hemoglobin mass.
And that heat acclimation is something that athletes do, that
military guys do as well, and it can it has
(04:28):
been shown quite unequivocally to improve aerobic exercise performance in
hot environments, especially performance on time to exhaustion tests. Now,
on the other hand, and some studies have shown mixed
results with respect as to whether heat acclimation improves aerobic
exercise performance in normal environments, so when it's not too hot,
(04:51):
and according to a meta analysis, heat acclamation can improve
vot max to a small degree when testing occurs in
a temperate environment, so not that hot, and the magnitude
of improvement is greater when VO two max is tested
in a hot environment, which kind of makes sense because
you're adapting to the heat. Now, alow, VO two max
(05:14):
is a strong predictor of aerobic exercise performance, Several other
physiological factors also play a role, such as your lactate threshold.
So there's a whole heap of stuff of adaptations that
actually go on in a number of these different studies.
And you can induce this heat acclamation by either exercising
(05:36):
in the heat or exercising in a thermal neutral environment
and wearing a heat suit or thermal clothing. And it
can also be induced, and this is where this study
comes in through passive methods like sona bailing or hot
water immersion. So some of these adaptations occur pretty quickly,
such as plasma volume expansion that can take only three
(06:00):
or four days, but we know that some longer interventions,
generally about five weeks or so, are needed to increase
your red blood cell volume and hemoglobin mass. Now, although
it has been suggested that the different protocols whether you
(06:20):
do sauna post exercise, hot water post exercise, or you
exercise in the heat, although some of the previous research
has suggested that they stimulate similar adaptations, Ultimately, this study
didn't find a beneficial effect of the hot water immersion
on exercise performance. And one potential reason for this is
(06:45):
that the exercise tests were performed in a temperate environment,
and as discussed above, those adaptations and generally have the
biggest impact when you're exercising in hot environments. But there's
another thing that's really important here, and I think why
(07:05):
this study didn't enhance the exercise adaptations, and it's probably
because the protocol wasn't stressful enough. During the last five
minutes of hot water immersion, core temperature was approximately thirty
seven point eight degrees, which is about one hundred degrees fahrenheit. Now,
the evidence suggests that core temperature should be raised to
(07:28):
at least thirty eight point five degrees that's one hundred
and one point three degrees fahrenheit. So it was almost
a one degree centigrade, almost one degree centigrade lower than
it needed to be to maximize heat acclimation adaptations. And
here's the thing. Why all of this happens, or why
(07:50):
a lot of this happens, and particularly the changes are
the increased adaptations are because of stress response proteins, and
a lot of the research around SONA bathing is shown
that we get a lot of the positive adaptations, not
(08:11):
all of them, but we certainly get a lot of
positive adaptations because that heat can activate these stress response proteins.
These are my favorite proteins in the body, and they
are nature's agents of hardiness. So when you exercise vigorously,
(08:34):
or you are in the heat enough to increase your
core body temperature by about one degree, or you have
significant amounts of cold exposure, you will release these stress
response proteins, and in cold exposure you get both heat
shok proteins and cold shock proteins, whereas in the heat
(08:56):
you only get heat shock proteins. But these proteins actually
stimulate lots of different adaptations, and it's basically nature's way
of going Jesus, this is a stressful environment, so we
had better toughen up the body in case we encounter
this environment again. And I think this is probably why
(09:20):
this study didn't show the improvement that other studies have,
because they didn't increase the core body temperature. And I'm
not sure how quickly they got into the water, but
I certainly know. So to add a bit of color
onto this, when I was deciding whether or not to
(09:42):
have when I got my sauna, whether or not to
have a traditional finish sauna or an infrared sauna, what
I was really interested in. I did a whole heap
of research on the heat shot proteins and find that
generally you need to stimulate or increase your core body
temperature by about one degree or to that threshold of
(10:05):
thirty and a half degrees in order to stimulate those
heat chock proteins. And I find that actually the infrared
sauna did increase my core body temperature by one degree
if I was in it for at least twenty minutes,
and it was on seventy degrees and especially it did
it quicker after exercise. I won't go into too much
(10:28):
detail about how I worked, how much my core body
temperature was increasing. I will just leave that to the imagination.
So there's a couple of other three week studies, and
it's important to compare the time that looked at post
exercise sauna building. And one had male football players in
Spain that did their usual training program and then performed
(10:51):
three forty minutes ona sessions a week, and it was
four bouts of ten minutes each with a little break
in between, at a temperature of a undred degrees centigrade
or two hundred and twelve degrees firenheat, which is pretty
damn hot. And they had that as I said, they
did ten minutes and the end a few minutes of
recovery and then ten minutes again and at the end
(11:11):
of the study there are time to exhaustion and their
VO two max improved more in the solar group than
the control group. And another study which has a crossover design,
which is what you do that the first, whether it's
the control group some one group does that first and
the other does the intervention and then they switch over.
This is probably the best design that there is that
(11:33):
had meal distance runners and triathletes sit in the sauna
at ninety degrees centigrade or one hundred and ninety degrees
fahrenheit immediately after exercise for about thirty minutes, result in
a total of about thirteen SAW sessions during the study
and the end of the study their performance on a
time to exhaustion test was better when they incorporated the
(11:54):
SAWA sessions. And there are actually numerous studies that show
that you get improvements in our increased stimulation from strength
training if you then get into the sauna afterwards. But
it would appear in all of these studies that you
(12:14):
need to increase your core body temperature by about one degree. Now,
if you are working out intensely and then you get
straight into the sauna, you're going to have a quicker
impact on your core body temperature. So, particularly if you've
worked out to the point where you're sweating and you're hot,
and then you just jump into the sauna, some of
(12:38):
the research shows that about twenty minutes in there at
any degree centigrade. Now that's in a traditional sauna, and
I think you get away with less in a near
infrared sona because, as you may be aware, that heats
you from the inside as well, and I certainly sweat
much more at the same temperature on an infrared song
(13:00):
than I do on a traditional finished sona. But anyway,
it would appear to be that you gotta increase that
core body temperature by one degree in order to get
those real additional effects on a muscle mass and muscle
stimulation from strength training, but on this one improvements and
(13:21):
exercise performance if you're doing cardiovascular training. So the take
on with all of this is that if you want
to optimize your adaptations to exercise, whether that's through strength
training or cardiovascular training, both sauna and hot baths would
appear to be a good way to actually do that
(13:42):
if you have access to them and you have the
time to be able to do that. That's it for
this week, folks, Catch you next time.
Hey everyone, welcome to another edition of Wisdom Wednesdays. Before
we get into the podcast, quick announcement. My new book,
The Hardiness Effect, How to Grow From Stress, Optimize your
health and live Longer, is now forcel on Amazon dot
Com or Amazon dot Com do au and it actually
has for a short period of time about a twenty
(00:31):
five percent discount, So now is the time to go
in and pre order The Hardiness Effect and get yourself
a bit of a discount. Now onto the podcast. Today,
we are going to talk about the interaction between exercise
and heat exposure. So some of you may know or
may have heard that getting in a sauna after doing
(00:55):
particularly resistance training can spike growth hormone by a significant
amount three to four fold increase, and some studies have
shown and a new study just out followed a bunch
of cyclists, male cyclists who were pretty fit. They had
(01:15):
an average VO two max of sixty middle leaders per
kilogram per minute, which is pretty damn fit. But it
was a randomized control trial and they all performed high
intensity interval training for three weeks and then did hot
water immersion after exercise. Now, some of the research has
suggested that getting into a hot bath for at about
(01:40):
forty degrees for twenty minutes can actually mimic the effects
of the sauna and spike growth hormone and lead to
better performance games after exercise. So let's dig into this study.
So they did nine high intensity interval training sessions over
three weeks, so that was three sessions per week, and
(02:01):
immediately after exercise, they took a thirty minute bath in
either hot water at forty two degrees centigrade which is
one hundred and eight degrees firenheit or thermonutral kind of
body temperature ish so thirty four degrees centigrade or seventy
five degrees fahrenheit. And before and after the interventions, the
(02:22):
researchers collected muscle biopsies. So these guys are pretty game.
I don't know if you've ever seen a muscle biopsy
or had a muscle biopsy, but they basically use a massive,
thick needle like device and take a pinch of your muscle.
That's about the size of a rice crispy or rice
(02:43):
bubble depending on what country you're in, So it's pretty
dam sore. But anyway, so these guys were donating a
little bit of their muscles to science, and what they
wanted to look at was the adaptations in the mitochondria.
And then the performed a time to exhaustion test and
(03:04):
a twenty kilometer time trial on a cycle orgometer, and
the time trial performance improved to a similar degree in
both the hot water and the thermal neutral water groups
during the study, whereas the mitochondrial adaptations were unchanged in
both groups. So this is a bit of a damp
(03:25):
squid in terms of this idea that going into a
sauna or exposing yourself to heat and can improve exercise adaptations.
But a couple of things to dig into. So firstly,
let's look at a big picture. So repeated heat exposure
(03:46):
that is sufficiently stressful to elevate core temperature and that's
critical actually results in a number of physiological adaptations, so
you get overall heat acclimation. But what actually happened is
there's their plasma volume. The amount of plasma increases or expands,
(04:06):
you get reduced heart rate and core temperature at rest,
and during exercise you get higher sweat output earlier onset
of sweating and increased amounts of hemoglobin or hemoglobin mass.
And that heat acclimation is something that athletes do, that
military guys do as well, and it can it has
(04:28):
been shown quite unequivocally to improve aerobic exercise performance in
hot environments, especially performance on time to exhaustion tests. Now,
on the other hand, and some studies have shown mixed
results with respect as to whether heat acclimation improves aerobic
exercise performance in normal environments, so when it's not too hot,
(04:51):
and according to a meta analysis, heat acclamation can improve
vot max to a small degree when testing occurs in
a temperate environment, so not that hot, and the magnitude
of improvement is greater when VO two max is tested
in a hot environment, which kind of makes sense because
you're adapting to the heat. Now, alow, VO two max
(05:14):
is a strong predictor of aerobic exercise performance, Several other
physiological factors also play a role, such as your lactate threshold.
So there's a whole heap of stuff of adaptations that
actually go on in a number of these different studies.
And you can induce this heat acclamation by either exercising
(05:36):
in the heat or exercising in a thermal neutral environment
and wearing a heat suit or thermal clothing. And it
can also be induced, and this is where this study
comes in through passive methods like sona bailing or hot
water immersion. So some of these adaptations occur pretty quickly,
such as plasma volume expansion that can take only three
(06:00):
or four days, but we know that some longer interventions,
generally about five weeks or so, are needed to increase
your red blood cell volume and hemoglobin mass. Now, although
it has been suggested that the different protocols whether you
(06:20):
do sauna post exercise, hot water post exercise, or you
exercise in the heat, although some of the previous research
has suggested that they stimulate similar adaptations, Ultimately, this study
didn't find a beneficial effect of the hot water immersion
on exercise performance. And one potential reason for this is
(06:45):
that the exercise tests were performed in a temperate environment,
and as discussed above, those adaptations and generally have the
biggest impact when you're exercising in hot environments. But there's
another thing that's really important here, and I think why
(07:05):
this study didn't enhance the exercise adaptations, and it's probably
because the protocol wasn't stressful enough. During the last five
minutes of hot water immersion, core temperature was approximately thirty
seven point eight degrees, which is about one hundred degrees fahrenheit. Now,
the evidence suggests that core temperature should be raised to
(07:28):
at least thirty eight point five degrees that's one hundred
and one point three degrees fahrenheit. So it was almost
a one degree centigrade, almost one degree centigrade lower than
it needed to be to maximize heat acclimation adaptations. And
here's the thing. Why all of this happens, or why
(07:50):
a lot of this happens, and particularly the changes are
the increased adaptations are because of stress response proteins, and
a lot of the research around SONA bathing is shown
that we get a lot of the positive adaptations, not
(08:11):
all of them, but we certainly get a lot of
positive adaptations because that heat can activate these stress response proteins.
These are my favorite proteins in the body, and they
are nature's agents of hardiness. So when you exercise vigorously,
(08:34):
or you are in the heat enough to increase your
core body temperature by about one degree, or you have
significant amounts of cold exposure, you will release these stress
response proteins, and in cold exposure you get both heat
shok proteins and cold shock proteins, whereas in the heat
(08:56):
you only get heat shock proteins. But these proteins actually
stimulate lots of different adaptations, and it's basically nature's way
of going Jesus, this is a stressful environment, so we
had better toughen up the body in case we encounter
this environment again. And I think this is probably why
(09:20):
this study didn't show the improvement that other studies have,
because they didn't increase the core body temperature. And I'm
not sure how quickly they got into the water, but
I certainly know. So to add a bit of color
onto this, when I was deciding whether or not to
(09:42):
have when I got my sauna, whether or not to
have a traditional finish sauna or an infrared sauna, what
I was really interested in. I did a whole heap
of research on the heat shot proteins and find that
generally you need to stimulate or increase your core body
temperature by about one degree or to that threshold of
(10:05):
thirty and a half degrees in order to stimulate those
heat chock proteins. And I find that actually the infrared
sauna did increase my core body temperature by one degree
if I was in it for at least twenty minutes,
and it was on seventy degrees and especially it did
it quicker after exercise. I won't go into too much
(10:28):
detail about how I worked, how much my core body
temperature was increasing. I will just leave that to the imagination.
So there's a couple of other three week studies, and
it's important to compare the time that looked at post
exercise sauna building. And one had male football players in
Spain that did their usual training program and then performed
(10:51):
three forty minutes ona sessions a week, and it was
four bouts of ten minutes each with a little break
in between, at a temperature of a undred degrees centigrade
or two hundred and twelve degrees firenheat, which is pretty
damn hot. And they had that as I said, they
did ten minutes and the end a few minutes of
recovery and then ten minutes again and at the end
(11:11):
of the study there are time to exhaustion and their
VO two max improved more in the solar group than
the control group. And another study which has a crossover design,
which is what you do that the first, whether it's
the control group some one group does that first and
the other does the intervention and then they switch over.
This is probably the best design that there is that
(11:33):
had meal distance runners and triathletes sit in the sauna
at ninety degrees centigrade or one hundred and ninety degrees
fahrenheit immediately after exercise for about thirty minutes, result in
a total of about thirteen SAW sessions during the study
and the end of the study their performance on a
time to exhaustion test was better when they incorporated the
(11:54):
SAWA sessions. And there are actually numerous studies that show
that you get improvements in our increased stimulation from strength
training if you then get into the sauna afterwards. But
it would appear in all of these studies that you
(12:14):
need to increase your core body temperature by about one degree. Now,
if you are working out intensely and then you get
straight into the sauna, you're going to have a quicker
impact on your core body temperature. So, particularly if you've
worked out to the point where you're sweating and you're hot,
and then you just jump into the sauna, some of
(12:38):
the research shows that about twenty minutes in there at
any degree centigrade. Now that's in a traditional sauna, and
I think you get away with less in a near
infrared sona because, as you may be aware, that heats
you from the inside as well, and I certainly sweat
much more at the same temperature on an infrared song
(13:00):
than I do on a traditional finished sona. But anyway,
it would appear to be that you gotta increase that
core body temperature by one degree in order to get
those real additional effects on a muscle mass and muscle
stimulation from strength training, but on this one improvements and
(13:21):
exercise performance if you're doing cardiovascular training. So the take
on with all of this is that if you want
to optimize your adaptations to exercise, whether that's through strength
training or cardiovascular training, both sauna and hot baths would
appear to be a good way to actually do that
(13:42):
if you have access to them and you have the
time to be able to do that. That's it for
this week, folks, Catch you next time.
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