LIGHT FAN­TAS­TIC

We shine a light on the force, in all its forms, that pow­ers us to be bet­ter trail run­ners

Trail Running (UK) - - Contents -

How the sun pow­ers your run­ning

Words Paul Larkins

Early one spring morn­ing, I found my­self float­ing along the tow­path in west Lon­don with a trail run­ning mate of 20 years, Pro­fes­sor John Brewer. We had agreed to meet to chat about a va­ri­ety of sci­ence­type topics as well as to put the world to rights, but as the sun slowly rose above the Thames our con­ver­sa­tion quickly turned to one sub­ject: light. Could it be the rea­son run­ning is so much eas­ier and more fun this time of year?

Your our mus­cles feel looser and your spir­its soar, even on the wettest of July days. For­get true grit and brav­ing the el­e­ments, trail run­ning is so much more re­ward­ing (and, (and as it turns out, out ben­e­fi­cial for you) right now. And, more of­ten than not, it’s more mem­o­rable than a late Novem­ber af­ter­noon out­ing in a chill­ing driz­zle.

I can eas­ily re­call plenty of such runs thanks to their feel-good na­ture – be it a group run with cross coun­try col­lege team­mates on the rolling trails around cam­pus, or slightly more re­cently one par­tic­u­larly mem­o­rable 10-miler while on hol­i­day in Hawaii. There I was, mind­ing my own busi­ness, in the ho­tel lobby of a Waikiki Beach Ho­tel, pon­der­ing whether to head out of the door left or right, when four-time Olympic cham­pion Lasse Virén tapped me on the shoul­der and asked me if I was go­ing for a run and could he join me? ‘Of course,’ was my non­cha­lant, but hugely proud re­ply. Here was the leg­end of my youth,

win­ner of the 1972 and 1976 5000m and 10,000m golds ask­ing me if he could join me. When do we start? Enough of the 6am de­lay­ing tac­tics, sud­denly I couldn’t get out of the door quickly enough. I didn’t want him chang­ing his mind and opt­ing for a Star­bucks in­stead.

Ef­fort­lessly we cov­ered 10 or so miles in no time at all, chat­ting about his ca­reer, his thoughts on the world of run­ning, and about a 5km road race that was planned that week­end. I still have in pride of place on my desk the pic­ture a pho­tog­ra­pher took of me run­ning along the beach that evening as the sun set.

A few years ago, I got an in­vite to go along to the Outrun the Sun event in Cha­monix that in­volved, as you’d ex­pect, rac­ing the sun from sun­rise to sun­set, over 150km, around Mont Blanc. Of course, that was a won­der­ful event with views and mem­o­ries aplenty, but the sun dip­ping be­hind Mont Blanc is some­thing spe­cial, be­lieve me.

Cer­tainly, the sub­ject of ‘light’ got John and I chat­ting, cov­er­ing five miles in the blink of an eye! Just why is light so im­por­tant to us? Be­ing a pro­fes­sor of sports sci­ence, he had the an­swer.

“Light brings many ben­e­fits, not the least of which is the ob­vi­ous one of greater safety and the abil­ity to see and be seen,” says John, in­creas­ing the pace just marginally, as if to em­pha­sise his point. “Head torches have made trail run­ning pos­si­ble, even in the dark­est and wettest of nights, but the ten­dency for rugged ter­rain and un­ex­pected haz­ards means that good vis­i­bil­ity and quick re­ac­tions are es­sen­tial to re­duce the risk of in­jury.

“It’s all too easy to over­look the im­por­tance of be­ing seen by oth­ers, espe­cially when run­ning near roads,

and, while high-viz run­ning gear is al­ways ad­vis­able, the risk of ac­ci­dents is clearly less when run­ning in day­light.”

More to power to you

But, safety aside, light is so much more than that. It has all sorts of phys­i­o­log­i­cal roles to play. “Stud­ies have shown that Vi­ta­min D de­fi­ciency is much more preva­lent in the pop­u­la­tion than once thought and one of the most com­mon rea­sons for this is lack of ex­po­sure to sun­light,” says John “Al­though Vi­ta­min D can be ob­tained from di­etary sources, such as oily fish and red meat, the best source is sun­light – which, of course, is of­ten se­verely lack­ing in the north­ern hemi­sphere dur­ing the win­ter months. From mid-March un­til Oc­to­ber, most peo­ple who spend time out­doors, with skin ex­posed to the sun­light, can get am­ple Vi­ta­min D, which is es­sen­tial for the health of our bones and mus­cles.” Of course, this sun­light comes with a health warn­ing, as too much ex­po­sure to the harm­ful ul­tra-vi­o­let rays can in­crease the risk of skin cancer.

Light is the most im­por­tant stim­u­lus for set­ting the body’s in­ter­nal clock, which in turn in­flu­ences many hu­man func­tions in­clud­ing sleep pat­terns, di­ges­tion and en­ergy lev­els – col­lec­tively known as our cir­ca­dian rhythms. For many run­ners, this has an im­pact on the best time of the day for train­ing and rac­ing. For those who run at the same time each day, it is likely that their body will ad­just to this and sub­con­sciously learn to pre­pare for a run. Con­versely, run­ning at an un­usual time of the day can feel much tougher. So, if you know there is an im­por­tant race com­ing up, at a time of the day when you are not used to run­ning, it

‘Light is the most im­por­tant stim­u­lus for set­ting the body’s in­ter­nal clock’

is sen­si­ble to pre­pare for this in ad­vance by train­ing at this ‘new’ time of the day.

Light and shade

A study pub­lished in 2015, in the British

Jour­nal of So­ci­ol­ogy, sug­gested that fell run­ners who were able to ex­pe­ri­ence and see the land­scape they were run­ning in soon be­came an in­te­gral part of it – blend­ing in with the scenery in a way that makes them as much a part of the hills as the sheep and the trees! Changes in light cre­ate a dif­fer­ent en­vi­ron­ment, with lev­els of sun­light, dark­ness and shad­ows al­ter­ing the run­ning ex­pe­ri­ence. We also know, from many stud­ies, that one of the rea­sons peo­ple stop ex­er­cis­ing is bore­dom. And, there are many who cite their aver­sion to the sport of run­ning as bore­dom. But, when a land­scape is il­lu­mi­nated with light, the va­ri­ety that this creates will soon add in­ter­est to any run – espe­cially one on trails or in the hills.

A grow­ing num­ber of run­ners can be seen wear­ing sun­glasses and, while the sci­en­tific ev­i­dence for their ben­e­fit is lim­ited, they will of course re­duce glare and block ul­tra vi­o­let rays. You’ll not only pro­tect your eyes, but, with the right lens se­lec­tion, vis­i­bil­ity will im­prove – im­por­tant on tech­ni­cal trails, where you need to be able to see ev­ery rock and piece of wood. Al­ways look for hy­dropho­bic lenses, which re­duce glare and en­hance sharp­ness – espe­cially handy when you’re on the trail in dap­pled sun­light. Some run­ners and man­u­fac­tur­ers of sun­glasses sug­gest they can also re­duce ten­sion in the head and neck, since squint­ing in bright light in­creases ten­sion. This helps to main­tain re­lax­ation, and – it is sug­gested – can im­prove run­ning ef­fi­ciency. Of course, for some, they are an im­por­tant fash­ion state­ment as well!

Weight for it…

But this isn’t the only way light, or in­deed, light­ness can help us as run­ners. Most of us burn be­tween 100 and 120 calo­ries for each mile that we run. This of course de­pends on the ter­rain – for ex­am­ple a muddy, hilly trail run will burn more calo­ries per mile than a steadily down­hill road run. But, in ad­di­tion to the ter­rain, sci­en­tists

have also found that the other biggest fac­tor that in­flu­ences en­ergy ex­pen­di­ture is the weight of a run­ner. Lighter run­ners use less en­ergy than those who are heav­ier. Of course, this makes sense – en­ergy is al­ways needed to move any weight over a given dis­tance. But, since the amount of en­ergy we burn is also re­lated to oxy­gen up­take, lighter run­ners (who use less en­ergy), will also re­quire less oxy­gen per mile, and, as a re­sult, their run­ning will feel much eas­ier – or they can run more quickly at the same in­ten­sity. Be­ing a light run­ner – or even a lighter run­ner – is there­fore likely to give a per­for­mance ben­e­fit to run­ners of all abil­i­ties, and prob­a­bly give even greater ben­e­fits when run­ning in the hills, on un­even ter­rain, and in heavy mud. But don’t con­fuse be­ing light with a lack of mus­cle strength – leg strength and core strength are es­sen­tial to deal with the ever-chang­ing forces and move­ment that oc­cur when trail run­ning. And, be­ing able to deal with this will re­duce the risk of in­jury and im­prove run­ning ef­fi­ciency.

Each time a run­ner’s foot hits the ground, a force of at least two or three times their body weight will be ab­sorbed through their foot and leg. While this will de­pend on the run­ner’s speed and the ter­rain, the lighter the run­ner, the lower this force will be. So, for ev­ery kilo a run­ner is over­weight, 2 or 3 ex­tra ki­los of force will pass through their lower body – us­ing more en­ergy, plac­ing ex­tra pres­sure on the mus­cles, ten­dons and lig­a­ments, and in­creas­ing in­jury risk.

Stud­ies have also sug­gested that lighter run­ners may be less at risk of ther­mal stress, over­heat­ing and de­hy­dra­tion, espe­cially in hot and hu­mid con­di­tions. Ex­tra body fat can act as a layer of in­su­la­tion, keep­ing heat in, rather than al­low­ing it to es­cape. As a con­se­quence, their core tem­per­a­ture will rise – to lev­els that can im­pact on per­for­mance or even be dan­ger­ous. Lighter run­ners with less body fat will find heat loss eas­ier, and are bet­ter able to main­tain a sta­ble core tem­per­a­ture while ex­er­cis­ing.

Move to the sun!

Fi­nally, hav­ing re­viewed both mean­ings of ‘light’, it is prob­a­bly worth con­sid­er­ing a homonym co­nun­drum; can the light help to make you light – or at least a bit lighter? The ev­i­dence would sug­gest that the an­swer to this is ‘yes’. When con­di­tions are lighter, most run­ners tend to run more of­ten – the day­light hours make run­ning eas­ier and safer, and the day­light should cre­ate an en­vi­ron­ment which is more con­ducive to en­joy­ing the ex­pe­ri­ence of run­ning. This can en­cour­age run­ners to run more of­ten and for a bit longer. Af­ter all, who doesn’t love a post-work leg-stretch of a sunny evening? Or a Sun­day morn­ing stride out in the first rays of sun­shine?

Fur­ther­more, light stim­u­lates the pro­duc­tion of vi­ta­min D, which helps to keep run­ners health­ier and less prone to ill­ness – and, there­fore, more likely to train on a reg­u­lar ba­sis. As a re­sult, if you’re get­ting a good vit D fix, you will prob­a­bly burn more calo­ries, shed more body fat, and see your body weight drop.

The light, and be­ing light, may well be linked, but for all run­ners the most im­por­tant thing is to ex­pe­ri­ence and en­joy the en­vi­ron­ment, re­gard­less of the con­di­tions – know­ing that ev­ery mile you run, whether in the light or dark, will im­prove phys­i­cal and men­tal health, burn calo­ries, and make a ma­jor con­tri­bu­tion to a more ac­tive and healthy life­style.

Paul’s Per­fect Day, run­ning on Waikiki Beach as the sun set

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