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