The Sci­ence of Run­ning

Do Soft Sur­faces Make a Dif­fer­ence?, Prep­ping for Alti­tude, Stress Frac­ture Signs, LCHF for En­durance

Canadian Running - - DEPARTMENTS - By Alex Hutchin­son

Aside from the scenery, one of the big­gest at­trac­tions of trail run­ning is the es­cape from con­crete. From an in­jury-pre­ven­tion stand­point, trails are thought to of­fer two key ad­van­tages over roads: softer, more for­giv­ing sur­faces, which re­duce the jar­ring im­pacts of each stride; and un­even ter­rain that forces your foot to land in slightly dif­fer­ent po­si­tions, re­duc­ing the repet­i­tive­ness of the im­pact. Prov­ing that these fac­tors re­ally re­duce in­juries, how­ever, has turned out to be sur­pris­ingly dif­fi­cult. The few stud­ies that have tested these claims have pro­duced con­flict­ing re­sults, and some re­searchers ar­gue that we au­to­mat­i­cally “tune” our mus­cles to pro­duce a sim­i­lar im­pact force no mat­ter what sur­face we’re run­ning on.

That makes the re­sults of a re­cent study by sci­en­tists in Bel­gium, pub­lished in the jour­nal Sports Biome­chan­ics, par­tic­u­larly in­ter­est­ing. In­stead of mea­sur­ing im­pact forces in a lab­o­ra­tory set­ting, they used tiny ac­celerom­e­ters at­tached to the shins of 35 vol­un­teers to mea­sure run­ning im­pacts on three dif­fer­ent real-life sur­faces: con­crete, a syn­thetic run­ning track and a wood chip trail. The re­sults showed that ver­ti­cal ac­cel­er­a­tion of the lower leg was in­deed re­duced on wood chips com­pared to the other two sur­faces, sug­gest­ing that it could – in the­ory, at least – lower in­jury risk.

So what about the role of vari­abil­ity? That’s much harder to quan­tify, but sim­i­lar ul­tra-light ac­celerom­e­ters may soon al­low re­searchers to col­lect data on that too. In 2015, as a proof-of-prin­ci­ple, re­searchers in France had top moun­tain trail run­ner Kil­ian Jor­net wear three of these ac­celerom­e­ters dur­ing a 45-kilome­tre trail race. They found that as the ter­rain var­ied, he made lib­eral use of three com­pletely dif­fer­ent foot-strike pat­terns: fore­foot, mid­foot and rear-foot. Whether that vari­abil­ity trans­lates to lower in­jury risk re­mains to be seen – but it cer­tainly seems to work for Jor­net.

Prep­ping for alti­tude

The chal­lenge of moun­tain trails isn’t just the rocky ter­rain, steep climbs and ver­tig­i­nous drop-offs. Once you get above about 1,000 m of el­e­va­tion – roughly Cal­gary’s level – the thin air be­gins to have mea­sur­able ef­fects on your aer­o­bic ca­pac­ity. By the time you get to Banff, at 1,383 m above sea level, the ef­fects are ob­vi­ous; at the 2,350 m sum­mit above Kick­ing Horse re­sort, where the na­tional moun­tain run­ning cham­pi­onships fin­ished a few years ago, you’ll be gasp­ing.

The best de­fence against alti­tude is weeks of ac­clima­ti­za­tion. But for those who don’t live in the moun­tains (and don’t own an ex­pen­sive alti­tude tent), are there any al­ter­na­tives? A se­ries of re­cent stud­ies have raised hopes that the sim­ple act of train­ing your breath­ing mus­cles – the seven to 11 lb. of mus­cle around your di­aphragm and ribcage – can im­prove high-alti­tude en­durance. A study of Bri­tish sol­diers trekking to­ward Makalu, in Nepal, found that those who had done four weeks of train­ing for their breath­ing mus­cles, which es­sen­tially in­volved re­peat­edly in­hal­ing against

re­sis­tance, had higher lev­els of oxy­gen in their blood.

That study used a de­vice called Pow­erBreathe. More re­cently, a Univer­sity of Buf­falo study pub­lished last year used a tech­nique that in­volved half an hour of con­trolled hy­per­ven­ti­la­tion, three times a week for four weeks, to boost en­durance in a cy­cling test to ex­haus­tion at a sim­u­lated alti­tude of 3,600 me­tres. The find­ings sug­gest that, since thin air forces us to breathe more heav­ily to get the oxy­gen we need, our breath­ing mus­cles are likely to fa­tigue pre­ma­turely at alti­tude. Train­ing those mus­cles in ad­vance pre­pares them to han­dle that ex­tra work with­out fa­tigu­ing as much. For now, the con­cept re­mains pre­lim­i­nary and re­quires more re­search – but it’s a promis­ing pos­si­bil­ity for flat­landers plan­ning a trip to the moun­tains.

Stress frac­ture warn­ing signs

It’s no se­cret that not get­ting enough calo­ries can lead to a spi­ral of health prob­lems, in­clud­ing weak­ened bones, in fe­male run­ners. But iden­ti­fy­ing who is re­ally at risk re­mains a chal­lenge. A con­sen­sus state­ment pub­lished in the Bri­tish Jour­nal of Sports Medicine in 2014 tried to quan­tify risk based on six cri­te­ria: in­ad­e­quate calo­rie in­take; low body-mass in­dex; ir­reg­u­lar pe­ri­ods; de­layed age of menar­che; low bone min­eral den­sity; and his­tory of stress frac­tures. Com­bin­ing these cat­e­gories pro­duces a risk score that is clas­si­fied as low, mod­er­ate or high.

But how re­li­able is this pre­dic­tion? Re­searchers at Stan­ford Univer­sity tracked 323 fe­male ath­letes, in­clud­ing 47 cross-coun­try run­ners – with sober­ing re­sults that were re­cently pub­lished in the Amer­i­can Jour­nal of Sports Medicine. About half the run­ners were iden­ti­fied as low-risk, and only three of these run­ners went on to de­velop stress frac­tures. But of the re­main­ing run­ners who were clas­si­fied as mod­er­ate- or high-risk, more than half of them suf­fered from sea­son-end­ing stress frac­tures, within an av­er­age time of a year. The risk score can be used to iden­tify run­ners who need di­etary changes and mon­i­tor­ing, says Adam Ten­forde, the study’s lead au­thor; and these ath­letes may also ben­e­fit from a switch to more low-im­pact cross-train­ing.

LCHF for en­durance

The claim that low-car­bo­hy­drate, high fat ( lchf) di­ets can boost en­durance per­for­mance has been hotly de­bated in re­cent years – but mostly with com­pet­ing anec­dotes. New re­sults pub­lished in the Jour­nal of Phys­i­ol­ogy, from re­searchers at the Aus­tralian In­sti­tute of Sport, of­fer some much­needed data. A group of 21 world-class Olympic race­walk­ers, in­clud­ing Cana­dian near-medal­list Evan Dun­fee, gath­ered in Aus­tralia last win­ter to com­plete a se­ries of three-week train­ing blocks. Some were fed a stan­dard diet with 60– 65 per cent car­bo­hy­drate, 15–20 per cent pro­tein and 20 per cent fat; oth­ers went lchf, with 75–80 per cent fat, 15–20 per cent pro­tein and less than 50 g per day of car­bo­hy­drate, scarcely more than a sin­gle can of Coke.

The re­sults showed a dra­matic in­crease in fat-burn­ing ca­pac­ity in the lchf group, nearly tripling their pre-in­ter­ven­tion lev­els. But it came at a cost: they were also less ef­fi­cient, re­quir­ing more oxy­gen to main­tain their goal race pace. As a re­sult, the lchf group per­formed worse than the con­trol group in the 10k race­walk tri­als used as a per­for­mance test. It’s still pos­si­ble that lchf di­ets may have ben­e­fits in other con­texts – for ex­am­ple, in re­duc­ing the need to re­fuel dur­ing ul­tra-events, par­tic­u­larly in ath­letes whose pri­mary goal is sim­ply to fin­ish rather than com­pete. And there may be other ways of com­bin­ing lchf and nor­mal di­ets to get an edge; Dun­fee and other race­walk­ers re­turned to Aus­tralia this win­ter for a fol­low-up study to test that idea. The de­bate, in other words, will con­tinue.

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