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How Exercise Fuels the Brain By GRETCHEN REYNOLDS

ShannonStapleton/ReutersDoes exercise keep your brain running?

Moving the body demands a lot from the brain. Exercise activates countless neurons!hich generate receive and interpret repeated rapid"fire messages from the nervoussystem coordinating muscle contractions vision balance organ function and all of thecomplex interactions of bodily systems that allo! you to take one step then another.

#his increase in brain activity naturally increases the brain$s need for nutrients but untilrecently scientists hadn$t fully understood ho! neurons fuel themselves duringexercise. %o! a series of animal studies from &apan suggest that the exercising brain

has uni'ue methods of keeping itself fueled. (hat$s more the finely honed energy balance that occurs in the brain appears to have implications not only for ho! !ell the brain functions during exercise but also for ho! !ell our thinking and memory !orkthe rest of the time.

)or many years scientists had believed that the brain !hich is a very hungry organsubsisted only on glucose or blood sugar !hich it absorbed from the passing

bloodstream. *ut about +, years ago some neuroscientists found that speciali-ed cellsin the brain kno!n as astrocytes that act as support cells for neurons actually containedsmall stores of glycogen or stored carbohydrates. nd glycogen as it turns out iscritical for the health of cells throughout the brain.

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1n petri dishes !hen neurons !hich do not have energy stores of their o!n are starved

of blood sugar their neighboring astrocytes undergo a complex physiological processthat results in those cells$ stores of glycogen being broken do!n into a form easily

burned by neurons. #his substance is released into the space bet!een the cells and theneurons s!allo! it maintaining their energy levels.

*ut !hile scientists kne! that the brain had and could access these energy stores theyhad been unable to study !hen the brain$s stored energy !as being used in actual liveconditions outside of petri dishes because brain glycogen is metaboli-ed or burneda!ay very rapidly after death2 it$s gone before it can be measured.

#hat$s !here the &apanese researchers came in. #hey had developed a ne! method ofusing high"po!ered micro!ave irradiation to instantly free-e glycogen levels at deathso that the scientists could accurately assess 3ust ho! much brain glycogen remained inthe astrocytes or had recently been used.

1n the first of their ne! experiments published last year in #he &ournal of hysiologyscientists at the 4aboratory of *iochemistry and %euroscience at the 5niversity of#sukuba gathered t!o groups of adult male rats and had one group start a treadmillrunning program !hile the other group sat for the same period of time each day onunmoving treadmills. #he researchers$ aim !as to determine ho! much the level of

brain glycogen changed during and after exercise.

5sing their glycogen detection method they discovered that prolonged exercisesignificantly lo!ered the brain$s stores of energy and that the losses !ere especiallynoticeable in certain areas of the brain like the frontal cortex and the hippocampus thatare involved in thinking and memory as !ell as in the mechanics of moving.

#he findings of their subse'uent follo!"up experiment ho!ever !ere even moreintriguing and conse'uential. 1n that study !hich appears in this month$s issue of #he&ournal of hysiology the researchers studied animals after a single bout of exerciseand also after four !eeks of regular moderate"intensity running.

fter the single session on the treadmill the animals !ere allo!ed to rest and feed andthen their brain glycogen levels !ere studied. #he food it appeared had gone directlyto their heads2 their brain levels of glycogen not only had been restored to !hat they had

been before the !orkout but had soared past that point increasing by as much as a 6, percent in the frontal cortex and hippocampus and slightly less in other parts of the brain. #he astrocytes had 7overcompensated 8 resulting in a kind of brain carbo"loading.

#he levels ho!ever had dropped back to normal !ithin about 9: hours.

#hat !as not the case though if the animals continued to exercise. 1n those rats that ranfor four !eeks the 7supercompensation8 became the ne! normal !ith their baseline

levels of glycogen sho!ing substantial increases compared !ith the sedentary animals.

http://well.blogs.nytimes.com/tag/phys-ed/http://topics.nytimes.com/top/features/style/fashionandstyle/series/faster_higher_stronger/index.htmlhttp://health.nytimes.com/pages/health/nutrition/index.htmlhttp://www.ncbi.nlm.nih.gov/pubmed/21521757http://www.ncbi.nlm.nih.gov/pubmed/21521757http://www.ncbi.nlm.nih.gov/pubmed/21521757http://well.blogs.nytimes.com/tag/phys-ed/http://topics.nytimes.com/top/features/style/fashionandstyle/series/faster_higher_stronger/index.htmlhttp://health.nytimes.com/pages/health/nutrition/index.htmlhttp://www.ncbi.nlm.nih.gov/pubmed/21521757http://www.ncbi.nlm.nih.gov/pubmed/21521757http://www.ncbi.nlm.nih.gov/pubmed/21521757

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