The Science of Run­ning

Canadian Running - - FEATURES - By Alex Hutchin­son

Out­leg­ging Back Pain; The Price of a Pound; Ul­tra Hy­dra­tion; Whither the Knees?

Out­leg­ging back pain

If your back hurts, you’d think the log­i­cal rem­edy would be to strengthen your back. And in­deed, that’s fairly stan­dard ad­vice. But a few years ago, re­searchers in Sin­ga­pore stud­ied run­ners with per­sis­tent lower back pain, and no­ticed a pat­tern: run­ners with back trou­ble were more likely to have weak quads com­pared to painfree run­ners. Could the weak quads lead to poor shock ab­sorp­tion while run­ning, and ul­ti­mately to more stress on the lower back, they won­dered?

To test this the­ory, they as­sem­bled 84 run­ners who were on a wait­ing list for phys­io­ther­apy to deal with per­sis­tent lower back pain, and as­signed them to one of three ex­er­cise groups. One group did ex­er­cises to strengthen their back ex­ten­sion mus­cles, like “bird dogs”; an­other group did bal­ance-fo­cused back sta­bi­liza­tion ex­er­cises; and a third group did leg ex­er­cises like sin­gle-leg squats and leg presses. Each group trained twice a week un­der su­per­vi­sion and were asked to com­plete ex­er­cises on their own on the other days, for a to­tal of eight weeks.

The re­sults, pub­lished in Medicine & Science in Sports & Ex­er­cise, showed that all three groups de­creased their re­ported pain by sim­i­lar amounts, but the leg ex­er­cise group re­ported a slightly big­ger im­prove­ment in their abil­ity to run com­fort­ably. Strength tests showed that all three groups – even the leg ex­er­cise group – im­proved their back strength to a sim­i­lar de­gree, while only the leg group im­proved leg strength.

With­out a cont rol g roup, it’s hard to know ex­actly how ef­fec­tive the ex­er­cise pro­grams were com­pared to just rest­ing and wait­ing. But the re­sults do sug­gest that sim­ple leg-strength­en­ing ex­er­cises can yield ex­tra ben­e­fits by keep­ing your back mus­cles and sta­bi­liz­ers strong too – a point that’s worth bear­ing in mind not just for treat­ing back pain, but per­haps also for pre­vent­ing it in the first place.

The price of a pound

Any­one who has ever tried run­ning with a back­pack knows that ex­tra weight slows you down. But how much, ex­actly? Back in 1978, re­searchers at the Uni­ver­sity of Ge­or­gia loaded run­ners down with a waist and shoul­der har­ness, and found that each kilo­gram slowed them by about 1.9 sec­onds per kilo­me­tre. In a study pre­sented ear­lier this year at the Amer­i­can Col­lege of Sports Medicine con­fer­ence in Den­ver, Greek re­searchers tried the op­po­site ap­proach, us­ing a sys­tem of pul­leys and up­ward-pulling ropes to sub­tract weight from their sub­jects. The ver­dict was sur­pris­ingly sim­i­lar, with a speed-up of about 3.3 sec­onds per kilo­me­tre for each kilo­gram re­moved. In real life, of course, the weight on your body doesn’t be­have ex­actly like weight added or sub­tracted with har­nesses. Mus­cle helps pro­pel you for­ward and keeps you in­jury-free, and even fat, be­yond a cer­tain level, plays an im­por­tant role in your over­all health. For the most part, your rac­ing weight should be a nat­u­ral con­se­quence of your train­ing rather than a sep­a­rate goal. Still, the re­sults of­fer a use­ful back-of-the-en­ve­lope tool for com­par­ing per­for­mances across dif­fer­ent weights – whether you’re try­ing to fig­ure out how fast you can com­mute to work with lunch and a change of clothes on your back, or forec ast ing f ut ure im­prove­ments as you round into shape.

Ul­tra hy­dra­tion

Ex­actly how much you need to drink dur­ing ex­er­cise has been a source of con­tro­versy for years now. One of the lesser known ele­ments of the de­bate is the fact that, dur­ing pro­longed ex­er­cise, you ac­tu­ally cre­ate new wa­ter within your body. As you burn car­bo­hy­drate and fat to fuel your mus­cles, the byprod­ucts of these metabolic re­ac­tions are car­bon diox­ide (which you breathe out) and wa­ter. More­over, your mus­cles store car­bo­hy­drates in the form of glyco­gen, which also locks away one to three grams of wa­ter for ev­ery gram of car­bo­hy­drate stored. As you burn through your glyco­gen stores, this wa­ter also be­comes avail­able for hy­dra­tion.

Over the course of a marathon, a 2007 study es­ti­mated that you could lose one to three per cent of your start­ing weight with­out any change in hy­dra­tion – a dra­matic de­par­ture from the usual ad­vice to avoid los­ing more than two per cent of your body mass. And the ef­fects are even more dra­matic in longer events, ac­cord­ing to a new anal­y­sis by ul­tra re­searcher Mar­tin Hoff­man of the Uni­ver­sity of Cal­i­for­nia Davis, pre­sented at the Medicine & Science in Ul­traEn­durance Sports con­fer­ence ear­lier this year. A typ­i­cal fin­isher at the 100-mile Western States En­durance Run, Hoff­man and his col­leagues cal­cu­lated, should ex­pect to lose 4.5 to 6. 4 per cent of his or her start­ing weight sim­ply to main­tain the same level of hy­dra­tion.

One of the rea­sons these find­ings are im­por­tant is be­cause Hoff­man and oth­ers have stud­ied real-life hy­dra­tion be­hav­iour at Western States, and found widely vary­ing ap­proaches. Some run­ners lose eight per cent of their weight; oth­ers gain an as­tound­ing 10 per cent, with the fastest run­ners tend­ing to lose slightly more weight. Hoff­man has put to­gether a set of hy­dra­tion rec­om­men­da­tions for ul­tra events, which fo­cus on drink­ing when you’re thirsty, ex­pect­ing to lose some weight, and car­ry­ing enough wa­ter be­tween aid sta­tions to al­low your­self to drink when­ever thirst strikes. The guide­lines are avail­able at ul­tra­sports­s­

Whither the knees?

Is os­teoarthri­tis re­ally a mod­ern epi­demic, or does it just seem that way be­cause we’re liv­ing longer (and car­ry­ing more weight) than we used to? To find out, a Har­vard Uni­ver­sity re­search team criss­crossed the con­ti­nent ex­am­in­ing about 2,500 skele­tons from peo­ple who died as long as 6,000 years ago and as re­cently as 2015. Signs of “ebur­na­tion,” a pol­ish­ing that oc­curs when your car­ti­lage wears away and the bones of your knee joint rub to­gether, re­vealed who did and didn’t have os­teoarthri­tis. For the 20th-cen­tury skele­tons, med­i­cal records in­di­cated the age and weight of the sub­jects when they died.

The sur­pris­ing re­sult? Even af­ter ac­count­ing for age and weight, knee os­teoarthri­tis was still about twice as com­mon in peo­ple born af­ter Se­cond World War than for those born ear­lier, ac­cord­ing to the anal­y­sis pub­lished in the Pro­ceed­ings of the Na­tional Academy of Sciences. While there are nu­mer­ous pos­si­ble ex­pla­na­tions (the fact that we spend so much time walk­ing on hard pave­ment now, for ex­am­ple), se­nior au­thor Dan Lieber­man and his col­leagues sus­pect the cul­prit is wide­spread in­ac­tiv­ity. Like mus­cles, joints and car­ti­lage are health­i­est when used reg­u­larly – so in­stead of wor­ry­ing about whether you’re wear­ing your knees out, make sure you’re tax­ing them enough.

Ul­tra run­ner Jim Walm­s­ley keep­ing hy­drated dur­ing the 100 mile Ter­aweira ul­tra­ma­rathon

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