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Sources like this: http://www.cancerresearchuk.org/about-cancer/causes-of-cancer/physical-activity-and-cancer/how-physical-activity-prevents-cancer point out that we can reduce our risk of some cancers by exercising.

But it seems to just be hypothetical, like "scientists think insulin can turn on signals that tell cells to multiply", and

"This can lead to the cells multiplying much more frequently than usual, to replace dead and damaged cells, increasing the chances of mistakes that could lead to cancer"

But human metabolism significantly increases during and after exercise, implying high rate of cellular division! Therefore, these 'hypotheses' seem questionable in their attempt at saying, "cells don't divide as much". I believe that these may be contributing factors, but I don't believe they're the main cause of most cancers in general. I am deeply skeptical that muscle inflammation requires less cell division than colon inflammation.

I have a hypothesis that exercise simply reduces cancer in the following manner: increase cellular movement, which increases the probability of the following:

1) t-cells tag foreign pathogens 2) white blood-cells capture foreign pathogens 3) damaged cells are repaired/found/killed faster

Statistically, increasing the entropy of a system would allow the individual components to cover a larger area in a shorter amount of time. Since the number of pathogens introduced into the system remains relatively constant while the interal system speeds up, it's like running a high-pressure jet stream of water and soap through pipes to clean them out. The soap (t-cells) and pressure (contractions of heart/blood vessels) together help clean the system effectively.

I'm having trouble finding evidence/support for this hypothesis, so if someone could point out the flaws in my hypothesis or point me to some sources to find out more, I'd be deeply appreciative.

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  • $\begingroup$ Check mTor downregulation during exercise. $\endgroup$ – Graham Chiu Mar 13 '18 at 3:57
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    $\begingroup$ I think the only answer here is "nobody really knows why, it's something that's been discovered through statistical studies". $\endgroup$ – jamesqf Mar 13 '18 at 5:11
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    $\begingroup$ Come on, comments aren't for answers, people... $\endgroup$ – arboviral Mar 13 '18 at 9:00
  • $\begingroup$ No one knows, it's just a line of research $\endgroup$ – Graham Chiu Mar 13 '18 at 17:01
  • $\begingroup$ Can you cite any evidence at all that exercise does any of the list you have? $\endgroup$ – Graham Chiu Mar 14 '18 at 7:28
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Vigorous exercise (even for five minutes) causes increased DNA damage http://www.ncbi.nlm.nih.gov/pubmed/20839226. The increased DNA damage would stimulate the defenses including the immune system (e.g. natural killer cells) http://www.ncbi.nlm.nih.gov/pubmed/16618710, and the boosted immune system would eliminate cancer cells, reducing cancers based on the immune suppression model of cancer http://www.ncbi.nlm.nih.gov/pubmed/27928220. The reduction of cancers with increased exercise (physical activity) has indeed been observed http://www.ncbi.nlm.nih.gov/pubmed/18506190.

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    $\begingroup$ You did notice that your last link offers a completely different MOA then the one you put together? $\endgroup$ – swbarnes2 Apr 27 '18 at 20:47
  • $\begingroup$ Welcome. It's good practice to give the full citations, just in case the link goes down. Nice referenced answer +1 $\endgroup$ – AliceD Apr 27 '18 at 21:11
  • $\begingroup$ This answer gives good information, but doesn't really answer the question because if individual organisms could just stimulate the immune system without an adverse effect, why would they need exercise to do it? $\endgroup$ – sterid Apr 28 '18 at 1:50

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