If you think you know all there is to know about hy­drat­ing cor­rectly then think again be­cause trail run­ning has its own rules in the drink­ing game

Trail Running (UK) - - Contents - Words Rob Kemp

How, why and when to drink to max­imise your run­ning per­for­mance

When it comes to tak­ing on flu­ids there are a num­ber of key dif­fer­ences be­tween run­ning on road and off, some ob­vi­ous, some less so. Sure the side ef­fects of de­hy­dra­tion – fa­tigue, cramps, a gen­eral lack of en­joy­ment along the whole route – are pretty much the same whether you’re pound­ing pave­ments or tear­ing along trails. But there are more nu­anced, trail-spe­cific fac­tors to take into con­sid­er­a­tion when de­cid­ing how what to drink and how much of it. First off, as a trail run­ner it’s even more cru­cial that you mon­i­tor your fluid in­take and make mea­sur­ing it part of your run­ning regime. “A body wa­ter deficit of 2-3% of your weight is gen­er­ally de­fined as de­hy­dra­tion,” says Anita Bean, sport and ex­er­cise nu­tri­tion­ist. This can trig­ger a drop in blood vol­ume and in­crease in core body tem­per­a­ture puts stress on the heart, lungs and cir­cu­la­tory sys­tem, which means the heart has to work harder to pump blood round your body. “The strain on your body’s sys­tems caused by de­hy­dra­tion means that ex­er­cise feels much harder, your pace will drop, early fa­tigue de­vel­ops, all of which can amount to a drop in en­durance per­for­mance of 10-20%.”

In ex­treme cases the run­ner can col­lapse, weak­ened, dis­ori­en­tated and ex­posed to the el­e­ment. Trail run­ners, when train­ing espe­cially, need to drink to suit the con­di­tions.

“Run­ning in the deserts, where tem­per­a­tures are some­times up to 50°C you end up drink­ing much more than a run in the hills of Scot­land,” says Trail

Run­ning colum­nist Dr An­drew Mur­ray, Mer­rell brand am­bas­sador and consultant in Sports Medicine with the Univer­sity of Ed­in­burgh. He should know of course. An­drew com­pleted the first run across the mighty Namib desert, which skirts along the At­lantic coasts of An­gola, Namibia and South Africa, run­ning 340 miles over nine days in one of the hottest places in the world. He’s also run from Scot­land to the Sa­hara.

“Run­ning about 60km a day through sand dunes I tended to av­er­age about 10.5 litres per day so you needed to drink while you ran. If you are on your own, car­ry­ing all that wa­ter is hard work, but be­ing de­hy­drated in the mid­dle in the desert is much worse. And drink­ing your own pee isn’t the so­lu­tion!”

Cold de­hy­dra­tion

Trail run­ners of­ten make the er­ror of not drink­ing enough on cold days or on runs that will take them into higher, cooler al­ti­tudes. There are a num­ber of ways the cold can af­fect your hy­dra­tion.

SWEAT LOSS Those ad­di­tional cloth­ing lay­ers raise the core tem­per­a­ture. The body re­acts the only way it knows how, mak­ing you sweat more.


We lose the in­stinct to drink as the body goes into cold mode. Our thirst re­sponse can re­duce by as much as 40%.

FROZEN OUT In cold, dry con­di­tions air that’s breathed in needs to be warmed and hu­mid­i­fied. As that mois­ture is then lost with ev­ery breath out, our body is op­er­at­ing at a deficit.

PEE OFF A side ef­fect of vaso­con­stric­tion (the sur­vival mode in­stinct in which the brain nar­rows the blood flow canals in our ex­trem­i­ties, mak­ing the fin­ger­tips, toes and nose prone to frost­bite) is that our blood pres­sure will rise. Since the same amount of blood has less space to flow through, the kid­neys try to man­age this sit­u­a­tion by fil­ter­ing out some of the ex­cess fluid from the blood to re­duce its vol­ume. In short, we pee more. Think drink “De­hy­dra­tion can re­sult in a drop in stamina and run­ning pace,” says Anita. “In one study run­ning speeds over 5km and 10km dropped by 6-7% in run­ners

who were de­hy­drated (2% body weight loss) com­pared with full hy­dra­tion. But de­hy­dra­tion also leads to men­tal fa­tigue, a drop in con­cen­tra­tion and low mood,” adds Anita. This is espe­cially cru­cial for fell and trail run­ners.

Con­sider jock­eys for a mo­ment. Pro rac­ing jock­eys were among a group of ex­er­cis­ers tested to mea­sure the cog­ni­tive im­pact of not drink­ing enough flu­ids dur­ing in­tense ex­er­cise. Even at rel­a­tively low lev­els of de­hy­dra­tion – 2% body weight loss – the pro­fes­sional rid­ers were found to strug­gle when tested to mea­sure their speed of re­ac­tion and judge­ment. Th­ese guys have to make quick calls when trav­el­ling over un­sta­ble ter­rain in race con­di­tions, tak­ing eva­sive ac­tion to avoid in­jury… Sound fa­mil­iar?

“Elite run­ners may tol­er­ate slightly higher lev­els of de­hy­dra­tion than nonelite, per­haps as high as 3-4% body weight loss, be­fore ex­pe­ri­enc­ing neg­a­tive ef­fects on their per­for­mance,” says Anita.

“On a race day or long run I drink SiS gels ev­ery 6km – non-caf­feine ones for the first half of the race, caf­feinated for sec­ond,” says Dr An­drew Mur­ray. The caf­feine will help you fo­cus on those trip haz­ards as our body starts to tire.

Weights and mea­sures

The biggest trade off for trail run­ners when it comes to main­tain­ing proper hy­dra­tion sur­rounds the need to carry wa­ter – in­creas­ing your load in the process. Run du­ra­tion, con­di­tions, weather and your own train­ing lev­els all need to be fac­tored in when en­sur­ing that you’ve got enough fluid to keep you per­form­ing to the best of your abil­ity.

Cur­rent ad­vice is to drink to thirst not ahead of thirst. “Gen­er­ally, 400–800ml per hour when run­ning will pre­vent de­hy­dra­tion as well as over-hy­dra­tion,” sug­gests Anita. “It’s bet­ter to drink lit­tle and of­ten, say 100-150 ml ev­ery 15 min­utes, as this re­sults in greater re­ten­tion and less uri­na­tion. If you’re run­ning for less than 60-90min, drink wa­ter when you feel thirsty,” she says.

If you’re run­ning at a mod­er­ate or high in­ten­sity for more than 60-90min, then you may ben­e­fit from car­bo­hy­drate in your drink. Di­luted squash (1:6 di­lu­tion), an iso­tonic sports drink or co­conut wa­ter all pro­vide hy­dra­tion as well as an op­ti­mal con­cen­tra­tion of car­bo­hy­drate. For Dr An­drew Mur­ray a few hy­dra­tion hard truths have helped him:

The things that hy­drate you most are re­hy­dra­tion salts/tablets (SiS and HealthS­pan Elite have great prod­ucts), and skimmed milk.

Drink enough so that pee is clear or straw-coloured, and then only have a sip or two in the hour prior to a race. Try and force a pee out just be­fore rac­ing!

For a marathon, I’ll take small sips of­ten, and try and make sure I’m eat­ing some­thing with car­bo­hy­drates in it ev­ery 6km, start­ing at 6km.

You’ll no doubt find your own for­mula to stay hy­drated. We’ll drink to that!

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