Study: Strenuous physical exercise may lead to cognitive –not just physical– fatigue

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Too Much Exer­cise Can Tire Our Brains Out, Too (Dis­cov­er Mag­a­zine D‑brief):

“For years, the Nation­al Insti­tute of Sports, Exer­cise and Per­for­mance (INSEP) in France had been study­ing an unusu­al phe­nom­e­non. If an athlete’s work­out reg­i­ments were ramped up, it didn’t always lead to a bet­ter per­for­mance — even if that ath­lete felt like they were work­ing hard­er than before.

The orga­ni­za­tion called this phe­nom­e­non over­reach­ing, and knew what the phys­i­cal symp­toms were. But the orga­ni­za­tion want­ed to know if any symp­toms of fatigue were appear­ing in the brain, too. New research says yes. Too-intense work­outs can make ath­letes more impul­sive, accord­ing to a study pub­lished today in Cur­rent Biol­o­gy … This insight is rel­e­vant even for peo­ple who don’t work out for a liv­ing, he says. Not only does the research indi­cate it’s best to avoid dif­fi­cult deci­sions after par­tic­u­lar­ly stren­u­ous work­outs, but “if you’re work­ing out hard and start feel­ing exhaust­ed, annoyed, or are more impul­sive, you could be on the path to over­train­ing,” he says.

The Study:

Neu­ro-com­pu­ta­tion­al Impact of Phys­i­cal Train­ing Over­load on Eco­nom­ic Deci­sion-Mak­ing (Cur­rent Biology).

  • Sum­ma­ry: Over­train­ing syn­drome is a form of burnout, defined in endurance ath­letes by unex­plained per­for­mance drop asso­ci­at­ed with intense fatigue sen­sa­tion. Our work­ing hypoth­e­sis is that the form of fatigue result­ing from phys­i­cal train­ing over­load might share some neur­al under­pin­nings with the form of fatigue observed after pro­longed intel­lec­tu­al work, which was pre­vi­ous­ly shown to affect the cog­ni­tive con­trol brain sys­tem. Indeed, cog­ni­tive con­trol may be required to pre­vent any impul­sive behav­ior, includ­ing stop­ping phys­i­cal effort when it hurts, despite the long-term goal of improv­ing per­for­mance through intense train­ing. To test this hypoth­e­sis, we induced a mild form of over­train­ing in a group of endurance ath­letes, which we com­pared to a group of nor­mal­ly trained ath­letes on behav­ioral tasks per­formed dur­ing fMRI scan­ning. At the behav­ioral lev­el, train­ing over­load enhanced impul­siv­i­ty in eco­nom­ic choice, which was cap­tured by a bias favor­ing imme­di­ate over delayed rewards in our com­pu­ta­tion­al mod­el. At the neur­al lev­el, train­ing over­load result­ed in dimin­ished acti­va­tion of the lat­er­al pre­frontal cor­tex, a key region of the cog­ni­tive con­trol sys­tem, dur­ing eco­nom­ic choice. Our results there­fore pro­vide causal evi­dence for a func­tion­al link between endur­ing phys­i­cal exer­cise and exert­ing cog­ni­tive con­trol. Besides, the con­cept of cog­ni­tive con­trol fatigue bridges the func­tion­al con­se­quences of exces­sive phys­i­cal train­ing and intel­lec­tu­al work into a sin­gle neu­ro-com­pu­ta­tion­al mech­a­nism, which might con­tribute to oth­er clin­i­cal forms of burnout syndromes.

The Study in Context: