The toll of ex­er­cise on the heart

Since Phei­dip­pi­des ran the pur­ported first marathon thou­sands of years ago in Greece and then col­lapsed and died, peo­ple have won­dered if stren­u­ous ex­er­cise is dan­ger­ous.

The Hamilton Spectator - - FOCUS - GRETCHEN REYNOLDS

Does spend­ing years run­ning marathons or cy­cling for long dis­tances po­ten­tially strain some­one’s heart?

Two ma­jor new stud­ies of ath­letes and their coro­nary ar­ter­ies sug­gest that the an­swer may be a qual­i­fied yes. Both stud­ies find that en­durance ath­letes, es­pe­cially men, who spend years train­ing and com­pet­ing show a sur­pris­ingly high in­ci­dence of plaques in their ar­ter­ies, which can be a hall­mark of car­dio­vas­cu­lar dis­ease.

But the stud­ies also find that these plaques seem to dif­fer some­what in their makeup from the kinds of plaques found in less ac­tive peo­ple’s hearts and so may not be a cause for much con­cern.

Prob­a­bly at least since Phei­dip­pi­des ran the pur­ported first marathon thou­sands of years ago in Greece and then promptly col­lapsed and died, peo­ple have won­dered whether stren­u­ous ex­er­cise is dan­ger­ous for the heart.

There have been in­di­ca­tions, both anec­do­tal and sci­en­tific, that it might be. One study from 2011 of long­time, elite, male en­durance ath­letes found that a dis­pro­por­tion­ate num­ber had scar­ring within their heart mus­cles.

Other stud­ies since have in­di­cated that marathon run­ners, par­tic­u­larly men, seem to have a greater risk of de­vel­op­ing plaques in­side their coro­nary ar­ter­ies than peo­ple who ex­er­cise less or not at all. Such plaques are wor­ri­some, since if they break free from the artery walls, they can block blood flow, caus­ing a heart at­tack. But most of these past stud­ies have been small, of­ten in­volv­ing fewer than a dozen par­tic­i­pants.

So for the new stud­ies, which were pub­lished in the July 11 is­sue of Cir­cu­la­tion, sci­en­tists set out to ex­am­ine far more hearts than in ear­lier ex­per­i­ments. For one of the stud­ies, re­searchers at Rad­boud Univer­sity in the Nether­lands and else­where re­cruited 284 men who had ex­er­cised through­out their adult lives. For the other, car­di­ol­o­gists from St. Ge­orge’s Univer­sity in Lon­don and other institutions gath­ered al­most 300 men and women, about half of whom were mas­ters run­ners and cy­clists with long his­to­ries of train­ing and com­pet­ing, while the other vol­un­teers were mostly seden­tary. None had any his­tory of heart dis­ease.

The vol­un­teers in both stud­ies com­pleted ex­ten­sive ques­tion­naires about their life­long ex­er­cise his­to­ries, de­tail­ing the time, if any, that they had spent train­ing for and com­pet­ing in en­durance sports since ado­les­cence.

The re­searchers in each of the stud­ies then scanned their vol­un­teers’ hearts, us­ing a va­ri­ety of tech­niques. While most ear­lier stud­ies of ath­letes’ hearts had re­lied pri­mar­ily on ba­sic CT scans of the heart and blood ves­sels that re­veal how much plaque ex­ists in some­one’s ar­ter­ies, the new stud­ies also de­ployed ad­di­tional tech­niques that pin­point the com­po­si­tion of those plaques.

And the makeup of plaque tis­sue mat­ters. Car­di­ol­o­gists know that if plaques are dense and heav­ily cal­ci­fied, they tend also to be sta­ble and un­likely to break free from artery walls. If, on the other hand, the plaques are fatty and some­what loose, they can more eas­ily rupture from the wall and ini­ti­ate a heart at­tack.

In both stud­ies, a long his­tory of heavy ex­er­cise was linked to hav­ing ar­te­rial plaques. In the Dutch study, the men who had ex­er­cised — mostly by run­ning — for more than about four hours per week through­out their adult lives were far more likely to have plaques in their ar­ter­ies than the men who had run for less than about an hour per week dur­ing that time. The cor­re­la­tion was strongest among the men who had run the most in­tensely, ac­cord­ing to their train­ing and race times.

Sim­i­larly, in the Bri­tish study, while a ma­jor­ity of the par­tic­i­pants had clear ar­ter­ies, those mas­ters ath­letes whose scans did show plaques tended to have far more of them than the seden­tary vol­un­teers did.

But in both stud­ies, the more ac­tive some­one was, the more likely that his (and in rare in­stances, her) plaques were cal­ci­fied and dense. Less-ac­tive peo­ple had fat­tier, more-prob­lem­atic plaques.

To­gether, these stud­ies sug­gest that “there may be an as­so­ci­a­tion be­tween high vol­umes of ex­er­cise and coro­nary cal­ci­fi­ca­tion,” said Dr. Ben­jamin Levine, a pro­fes­sor of car­di­ol­ogy at the Univer­sity of Texas South­west­ern Med­i­cal Cen­ter and di­rec­tor of the In­sti­tute for Ex­er­cise and En­vi­ron­men­tal Medicine at Texas Health Pres­by­te­rian in Dal­las. He was a co-au­thor of an ed­i­to­rial in Cir­cu­la­tion that ac­com­pa­nied the stud­ies.

“But if you dig into the mor­phol­ogy of the plaques,” he con­tin­ued, “they ap­pear to be more be­nign” than in peo­ple who ex­er­cise less.

Of course, these stud­ies can­not tell us whether peo­ple’s ex­er­cise habits di­rectly cause plaques of any kind to de­velop in their hearts, only that the two are re­lated. They also can­not ex­plain why ex­er­cise might con­trib­ute to plaques, or whether, over time, the ath­letes with plaques are at any greater risk than other peo­ple of ex­pe­ri­enc­ing a heart at­tack.

Levine and his col­leagues have just be­gun a long-term study, he said, that will fol­low mas­ters ath­letes for years, track­ing changes within their ar­ter­ies and med­i­cal out­comes.

But for now, he said, the avail­able data, in­clud­ing these new stud­ies, sug­gest that pro­longed, in­tense en­durance ex­er­cise may al­ter your ar­ter­ies, but does not seem likely to harm them.

If, how­ever, you are con­cerned about your car­diac health, ob­vi­ously con­sult a doc­tor, he said, and do not hes­i­tate to err on the side of cau­tion.

“If you want to run a marathon, fine, run a marathon,” he said. “But if your goal from ex­er­cise is sim­ply to be healthy, a half-hour of jog­ging will do.”

JA­SON O’BRIEN, GETTY IM­AGES

Go­ing for a pleas­ant short run of say 30 min­utes is good for you, but the ben­e­fit of marathons may be de­bat­able long-term for peo­ple with car­diac prob­lems.

AS­SO­CI­ATED PRESS FILE PHOTO

AS­SO­CI­ATED PRESS FILE PHOTO

Run­ning in ex­treme heat is bad for ev­ery­one, es­pe­cially for those who push the lim­its of their own phys­i­cal en­durance. Al­ways stay hy­drated, es­pe­cially dur­ing marathons.

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