T Nation

Muscle and Metabolism

While lying around this evening wishing I could sleep, I got to thinking about various topics related to muscles and metabolism…

In particular, since it was so damned warm, and I was sweating in proximity to some larger muscle groups, I got to thinking about how temperature increases blood flow and whether or not it would be a very cheap way to increase metabolism.


[i]The present work was aimed at measuring intramuscular oxygen consumption (O) as a function of temperature (T), in human forearm, during rest and aerobic isometric exercise (4% of the maximal voluntary contraction, MVC). Based upon results from in vitro experiments performed on isolated mitochondria of animal species, it was hypothesised that, during isometric exercise, the O-T curve should display a maximum for some ‘optimal’ T. Intramuscular T and measurements were performed using a combined deep body temperature/near infrared probe during muscle cooling. At rest, O increased non-linearly and monotonically as a function of T (n=8). increased ~2 times when going from 26 to 36C. A log()O-T plot or a log()O-1/T did not linearise the data.

During isometric contraction, O values at 26.8+/-0.6, 28.6+/-0.9, 31.9+/-0.9 and 35.9+/-0.9C were 3.04+/-1.26, 7.60+/-1.64, 4.43+/-1.95, and 6.64+/-1.37 mol 100 g−1 min−1, respectively (n=6). The O value at 28.6C was significantly higher (P<0.05) than that at 26.8 and 31.9C. The ‘sudden’ O change at 28.6C is compatible with the phenomenon observed at the mitochondrial level.[/i]

However, I really don’t know how different muscle temperatures are from core body temperatures in a resting state. If they do differ fairly significantly, than it would be easy to dress warmly and increase muscle temperature up to core body temperature.

At little Googling yields this snippet from some course material though, which is promising:

[i]There are 3 thermal zones:

superficial zone - skin and subcutaneous tissue
intermediate zone - skeletal muscle mass
deep zone - contents of cranial, thoracic and abdominal cavities.

It is only in the central parts of the body that the tissue temperature is kept high and relatively constant. The periphery of the body has a lower tissue temperature.

Or even this one…

[i]At rest there is a temperature distribution in the body and circulation.

1.Blood leaves the heart at about 37?C.
2.As it travels to the extremities, the temperature falls as much as 15?C or more without the subject feeling particularly cold.[/i]

And further in the same set of lecture notes…

[i]Heat loss is largely dependent upon the temperature difference between the body and the environment.

a.The heat exchange between the core and the skin largely controls skin temperature over the range 20 -28?C in ambient temperature.

b.Vasoconstriction and vasodilation by the sympathetic nerves can vary the skin surface between 21 and 29C.

c.Below 20C, internal heat production is increased.

d.Above 28C, sweating is used for increased heat loss.[/i]

Hmmm… a lot of muscle is obviously close to the skin.

Stretching was another strategy that came to mind. Anecdotally, people have stated that stretching is similar to exercise in some respects. It is known to prevent muscle wasting in the ill, for example.


A more general study, which may or may not be applicable shows that heat and stretching both have interesting effects on muscle tissue.


Effects of heat stress, mechanical stretching or a combination of both on the expression of heat shock proteins (HSPs) and total protein level were studied in a culture system. Rat skeletal muscle cells (L6) were cultured on flexible-bottomed culture plates. They were subjected to one of the four following conditions: (1) 97 h incubation at 37 degrees C, (2) 1 h incubation at 41 degrees C followed by 96 h incubation at 37 degrees C, (3) 1 h incubation at 37 degrees C followed by 96 h cyclic stretching (18% of initial length, 2-s stretch and 4-s release) at 37 degrees C or (4) 1 h incubation at 41 degrees C followed by 96 h cyclic stretching at 37 degrees C. The expression of HSP72 and HSP90 and total protein was determined in the crude homogenates, supernatant and pellets. Cellular protein concentrations in the homogenates and pellets were increased by heat stress and/or mechanical stress (stretch). A cumulative effect of the combination of heating and stretch on the protein concentration in the homogenates and in the pellets was noted. The expressions of HSP72 and HSP90 in the pellets were also increased by heat stress and/or stretch. However, HSP90 in the supernatant did not change following heat stress and/or stretch. The regulation of HSP72 and HSP90 expression in skeletal muscle cells may be closely related to total protein, the abundance of which is also stimulated by mechanical and heat stresses. These observations suggest strongly that heating and passive stretch of muscle may be useful as a means of increasing muscle mass, not only in athletes but also in patients during rehabilitation.

Also, I remember reading on this site somewhere some hints on achieving optimal muscle growth. One of those hints was to keep the muscles warm. I also recall a perhaps more recent article dealing with “Stretch Mark Mass” which talks about muscle growth via stretching and the importance of muscle volumization (stretching) as well.

So, where does this all lead, other than to me wishing I was asleep right now? To some questions or possible strategies.

  1. What would be the effect of being on a below maintenance calorie diet, consuming HOT-ROX and ensuring that you keep all the major muscle groups closer to core temperatures? The percentage resting O2 consumption increase described above is huge! No, let me put that in perspective, it is HUGE! Can we actually take advantage of some of that? Would HOT-ROX help ensure optimal fat utilization during increased muscle metabolism?

  2. Would non-specific stretches throughout the day also aid in raising muscle metabolism or growth/anti-catabolism?

  3. Is there some type of synergy to be obtained between various strategies involving workouts, nutrition, stretching and temperature control? For example, you probably don’t want to increase metabolism during a fasted or catabolic state.

Anyway, time for me to get some sleep… I wonder if these thoughts will be interesting under the light of day?

Other “interesting” thoughts:

  1. Thermic effect of food. It becomes interesting that protein has a larger thermic effect than other foods. Raising temperatures during digestion would stimulate blood flow to the extremeties and get that protein available to the muscles.

  2. Fat as insulation. Did you ever notice that if you get cool you are likely to suddenly feel hungry? If the effects in the first post are significant, then cooling off would directly lower metabolism and simultaneously signal a need for increased food consumption. The result, an insulating layer of fat to keep the body warmer.

Okay, perhaps I’m a bit of a geek, but I find it interesting when simple theories start to overlap and explain or reinforce each other. Of course, this can also be seeing patterns where there are none… :wink:

Thank vroom. Although insomnia sucks, I find this thread interesting.

As for the thermal effect of food…I can relate. I’m in the middle of a bulking cycle, and I’ve never been so freaking hot in my life.

And from when I was at the tale end of my Atkins phase, I wasn’t eating enough…even with the help of Ephedra, I was cold all the time, due to the lack of calories…I don’t recall being “hungry”, but when I started back with the carbs, I was ravenous for a few weeks.

I think that when I was on Atkins with under 20grams of carbs/day, the protein has full-effect, moreso than carbs…and when I started back with carbs (fruit, oatmeal, more veggies), my bodie started to overcompensate for my slow/cold metabolism.


But we also have the other side of the temp. control thing. In that by exposing ones self to LOW temps. the body inturn has to ramp up its processes in order to simply warm itself.

So it is kind of a double edged sword. Trying to find the the right amount of time in which to expose one self to cold temps in order to ramp up ones BMR and increase fat loss, but not to long as to create a reaction inwhich the body stores more BF for insulation.

So one would, in theory, keep ones self at a fairly high temp throughout much of the day inorder to keep growth and recovery high. Then brief exposure to cold temps. which will ramp up your BMR and rush blood to the muscles on the surface and further enhance recovery and growth. Kinda like contrats showers and such but longer term.

Boy sounds like a lot of work, lol. But it is fun to think about.

Stay warm,

Good point on the cooling Phill.

Perhaps we are looking at very different things when we talk about being cool within acceptable parameters and a possible drop in core temperatures, which of course the body won’t tolerate.

Some sort of chronic versus acute reaction depending on the ‘degree’ of temperature shift?

If we want to discuss this, which I am not sure many actually do, we’d probably have to distinguish between cooling of the extremities/skeletal muscle and potential lowering of core temperature.

Check out something on the oxygen debt theory. Oxygen debt is incurred during anarobic activity,like our favorite activity lifting. To recover from this oxygen debt, our metabolism kicks into high gear.With this metabolic jump comes a substantial increase in calories burned and a massive increase in heat output from the body.Just ask my girlfriend. She can’t even sleep next to me 6 hours after a good heavy workout.But thats not very scintific. A way to measure where you are at in recovery is to take your temprature regularly in a rest phase. This will give you a baseline measurement of your core temp. at rest.Then you can compare this to your body temp. post work out.The difference in temps is the difference in your metabolism. Measure intermitantly throughout the next several days to see where you are in the recovery cycle. when you cool back down, you are ready to incur more oxygen debt.This indirect method of measurement is a prety cool way to avoid overtraining. I read about it in Mclearry,Klatch,and Klatch of Boston Universitys’ physiology text. I can’t remember the exact name of the text, but I can retrieve that too, if you want. If you realy want to dive deep, the calculus formulae for an individual measurement are in there too.

Oh, yea, I almost forgot. One day snowboerding with the temp. around Zero,I can go through 5000 cal, without even flinching.7000 would probably be Ideal.That would present a great combinatorial problem to physiologists. There are also some great chapters in that book covering the thermic effects of food,Metabolic water production,Krebs and Cory Cycles, phosphorylation,yadayadayada.


I hear you on the effort versus recovery and metabolism deal. The extra heat output can be pretty insane at times.

One of the things I’m thinking about, with respect to INDEPENDENTLY increasing muscle temperature, is basically comfort. I’ve always preferred not to sweat unless I’m working for it. So, at the office I generally wear fairly light clothes and then usually only a single layer.

If I were going to be burning off hundreds of extra calories per day and enhancing the rate of anabolic activity I’d gladly endure some discomfort and wear a sweater to work, for example. Especially since the percentage of fat used for fuel is fairly high during periods of rest or NEPA.

For the sake of argument, lets assume 22 kcal per day per kilogram of muscle mass – which fits in well with John Berardi’s metabolism calculations. At maybe 75kg of muscle mass that represents 1650 kcal. If a 20% increase in energy expenditure due to thermally induced metabolic increases were possible it would equate to 330 kcal per day.

If this is something we can actually tap into in a significant way, it would have an impact.

However, I’m not thinking about trying to get any warmer while working out – heh, while talking to a friend of mine she had to raise the specters of dehydration and heat exhaustion.

I haven’t yet seen anything that indicates a relationship between staying warm or insulated and lipolysis, but that doesn’t mean it doesn’t exist.It can help to dehydrate you though.This is considered bad because it reduces the volume of most of your bodies cells,muscle included,but not fat cells.This reduction in muscle cell volume will manifest as reduced ability to perform and recover. With h2o as one of the main substrate of energy production,dehydration is generaly frowned upon.
It sounds like your goal is to loose fat. This is done by reducing the actual volume of the fat cells.Most folks that work with bodies agree that this is best done by aerobic activity,combined with an activity that will increase GH levels(like heavy lifting).The bonus oxygen debt and high metabolism also work to burn fat, because use of fat as fuel is part of the regular metabolic process. Increasing metabolism means increasing the exhaustion of those fat cells.
Good luck on your searching.An education is a fundamental element of a good well rounded T-Man. Sorry I didn’t include a works cited, the book was a loaner.


Lipolysis rates and dehydration should not be issues in an “at rest” scenario.

The question (that I am pondering) is whether the study, showing a relationship between muscle temperature and increased oxygen consumption by a warmer muscle (even at rest), is something that can be taken advantage of.

Will wearing warmer clothes raise skeletal muscle temperatures appreciably?

Are the results of the study reliable with respect to apparent metabolic effects on muscle (there are some questions about the efficacy of using near infrared probes to measure blood flow and metabolism)?

If so, will the increase in temperature affect enough muscle mass to make this worthwhile?

I’ve been Googling for a while and searching Pubmed, but I’m afraid I haven’t found answers to these questions. Most of the studies I can find are related to metabolic activity during exercise in various temperature conditions.

A few studies do refer to the first journal abstract quoted above though.

Well the topic is seeming to be sparking the interest of a few atleast. Just enough to keep it bumped up high enough for me to find it without having to dig. LOL

Another interesting point that has been bouncing around in my bean comes from the new topic of dehydration as a negative side effect.

It just may be possible that the dehydrating effect of keeping ones temp elevated MAY be beneficail. That is if you take the proper actions to keep yourself hydrated with extra fluid intake. This constant turn over of fluids should keep various nutrients and such shuttling into needed places, and constantly expelling waste and other unwanted by products of tissue breakdown and growth, etc…


HMM. Vroom this just gets more interesting with each addition. Lets just bundle you up for a few months and you can be our test subject. LOL


good thread

should i keep my sweater on at work but keep my hat off to allow my head to stay cool to allow some major heat escape while still keeping my muscles in a warm state? I’m one of those types that sweats easily even when i feel cold.

i also agree that dehydration should not be an issue since we all should be keeping up with our water intake all the time.

laters pk


I may just give it a shot in the spring when I plan to be cutting. It seems to me that being “warm” is somewhat of an appetite suppressant – and this might be helpful regardless of any other possible effects.

As for fluid replacement effects, once again, an unknown. I expect that fluids leaving via skin evaporation are fairly pure compared to regular elimination. At least rehydrating in this scenario shouldn’t lead to nutrient leaching.

Anyway, to recap, some things that might be affected by keeping muscles warmer (if they are indeed generally cool compared to core body temp)…

  • Blood flow through muscles.
  • Muscle metabolism.

An increase in muscle metabolism, at rest, would (if really present) lead us towards…

  • Increased protein turnover?
  • Faster recover rates?
  • Extra kcal expense without trauma!

It is easy to burn extra kcal, just lift weights or do some cardio or some NEPA. However, there are limits to how much of this you can do – due to cortisol, recovery or on the job/time demands.

Staying warmer, if useful at all, is something we could do perhaps 12 hours a day whenever we weren’t actually lifting, doing cardio or otherwise getting exercise.

Anyhow, whether or not any of this is actually achievable, it is at least plausible for heat to affect metabolism. Chemical reactions are generally accelerated by increased temperature – and what is our metabolism (with respect to kcal usage) but the sum total of all the energy used during chemical reactions occuring in the body over a period of time?