Responses of muscle mass, strength and gene transcripts to long-term heat stress in healthy human subjects
The present study was performed to investigate the effects of long-term heat stress on mass, strength and gene expression profile of human skeletal muscles without exercise training. Eight healthy men were subjected to 10-week application of heat stress, which was performed for the quadriceps muscles for 8 h/day and 4 days/week by using a heat- and steam-generating sheet. Maximum isometric force during knee extension of the heated leg significantly increased after heat stress (~5.8%, P < 0.05). Mean cross-sectional areas (CSAs) of vastus lateralis (VL, ~2.7%) and rectus femoris (~6.1%) muscles, as well as fiber CSA (8.3%) in VL, in the heated leg were also significantly increased (P < 0.05). Statistical analysis of microarrays (SAM) revealed that 10 weeks of heat stress increased the transcript level of 925 genes and decreased that of 1,300 genes, and gene function clustering analysis (Database for Annotation, Visualization and Integrated Discovery: DAVID) showed that these regulated transcripts stemmed from diverse functional categories. Transcript level of ubiquinol-cytochrome c reductase binding protein (UQCRB) was significantly increased by 10 weeks of heat stress (~3.0 folds). UQCRB is classified as one of the oxidative phosphorylation-associated genes, suggesting that heat stress can stimulate ATP synthesis.
These results suggested that long-term application of heat stress could be effective in increasing the muscle strength associated with hypertrophy without exercise training.
5 comments:
Doesn't really surprise me.
One of the big factors for release of growth hormone from the pituitary (IIRC) is heat from exercise. The more intense the exercise, the higher the body's internal temperature and the more GH released.
While that doesn't specifically deal with muscles in this case, a lot of the same processes which are stimulated for release of heat shock proteins are released much in the same manner as exercise does it (to a certain extent). The body is perceiving a threat/damage to the muscles; it compensates with higher amounts of internal anabolic processes.
The fact however that there is both a significant increase of hypertrophy and strength is pretty interesting though.
The growth hormone responds to exercise isn't the cause of growth. I have seen a published study examine the effect of post training limb cooling. This annihilated the normal training responds completely. One could speculate that the heat increase seen with intense exercise is a part of the growth signal.
Andreas
I know the growth hormone response to exercise isn't the cause of growth of the muscles themselves. Growth hormone isn't really the cause of muscular hypertrophy rather regenerative effects in most other tissues. (Although the study you seem to mention in question I have looked at the full text, and I am not too convincecd based on that study alone).
It seems pretty clear why limb cooling would destroy exercise response though -- significant decreased blood flow. Our tissues aren't as adaptive to cooling as they are to heating though so that may be a reason.
Very interesting that heating would have such a large effect though.
Why are all the World's Strongest Men competitors from Nordic (cold) areas and none are from near the equator?
MAS
South Africa, Australia and new Zealand are some not so cold countries who had decent strongman competitors. Denmark and Germany and The Netherlands are not that cold either! Think that climate is of lesser importance when it comes to strongman success. Access to AAS is of much more importance!
Andreas
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