The runner's guide to race fuel

Drinks? Gels? Bars? How much? How often? There are so many questions in the search for optimum in-race fuelling. RW’s Tobias Mews embarks on a quest for the answers.

by Tobias Mews

I should be pretty clued up on in-race nutrition. I’ve twice run the infamous Marathon des Sables, raced across mountain ranges, sweated through Amazon jungles and clocked countless road marathons. And, unsurprisingly, there have been moments when my body definitely needed an extra kick. But I have a confession: I had never fully understood the intricacies of in-race fuelling. Not knowing exactly what my body needed (and when), put off by the taste and what I’ll delicately call some ‘digestive incidents’, bamboozled by the array of gels, powders and bars on the market, I had stumbled through, trial and error – with an emphasis on the latter.

Sound at all familiar? However, if you’re anything like me, you’ll still be inexorably drawn to the tantalising promise that getting in-race nutrition right will boost energy and performance, lower your times and increase your enjoyment. So I set out to find that magic formula.

Do we really need fuel?

Having not gone near a biology textbook since Britpop was a twinkle in Damon Albarn’s eye, I enlisted an independent expert to point me in the right direction. ‘The first question you should ask yourself is whether or not you require fuel during the race,’ says Dr Ricardo Costa, ex- professional Ironman triathlete turned senior lecturer and researcher in sports dietetics at Coventry University. ‘For runs of up to 90 minutes, water should suffice provided you’re following a good, varied diet. Eat sufficient carbs for a couple of days before an event, and you should have enough stored in your body for shorter races such as 5-10Ks.’

And when the distance goes up? ‘For longer runs, such as a marathon, maximising carbohydrate supplies becomes very important if we are to avoid “hitting the wall”,’ says Costa. ‘This generally occurs at 18-20 miles when you’ve basically got no more carbs in storage to support the high level of muscle contraction and glucose levels in your blood start to drop. When the carbs run out, the body needs to refuel.’ But with such a plethora of energy products to choose from, what should that fuel be?

To answer this question, I went to meet Tim Lawson, former national-level cyclist, sports scientist and founder of Science in Sport (SiS). With a heritage of groundbreaking research and product launches, and a client list that has included Chris Boardman and Sir Chris Hoy, SiS is a leading sports nutrition provider and takes its science very seriously. A fact I’m immediately conscious of on entering its Lancashire Innovation Centre. It’s more high-tech lab than food factory, with white lab coats, blue plastic shoe covers and hairnets the look du jour.

I’m hoping for a simple answer to the bars, gels or drinks conundrum. But Lawson tells me there’s no one-size-fits-all solution. ‘What you want from an energy source is something that is easy to take, that empties efficiently, will be light on your stomach, and will allow you to continue running – while delivering the maximum amount of carbohydrates when you need it.’

There are some clear points of difference in the options, though. ‘Although an energy bar has carbohydrates, it comes in a different source from a gel,’ says Lawson. ‘The energy will still be digestible but will take longer to come through.’ He explains that bars take longer to be broken down in the stomach and small intestine, and so need more time to be absorbed into the bloodstream. This may be a disadvantage in shorter races, but can work in your favour when running longer distances. As you may have learned from experience, bars can be more palatable than gels, too.

Gels, on the other hand, are already liquid so don’t have to be changed from a solid as part of the digestive process. That means less effort and blood diverted to your digestive system, and quicker delivery of energy. ‘Think of a gel as a more concentrated version of an energy drink,’ says Lawson. 

But what if you can’t stomach gels or bars? ‘Isotonic [energy] drinks with electrolytes tick all the boxes,’ Rin Cobb, a clinical dietitian and sports nutritionist, tells me later. ‘Not only are you getting 30g of carbs per 500ml, you’re also replacing fluids lost in sweat – whereas gels are not a good fluid source, and generally need to be taken with water, with the exception of isotonic gels such as SiS’s Go.’

This raises another consideration. While isotonic gels don’t need to be taken with water, ‘with other gels, there is a risk of dehydration, as the rate of gastric emptying [leaving the stomach] of a gel without water intake will be slower’, says Lawson. You not only risk dehydration, but the rate at which you absorb the energy will be slower. It’s like clogging your sink. The thicker and more gooey the gel, the less water it has, and the more important it is to have a drink with them. So, if you don’t want to carry water or rely on water stations, non-isotonic goo isn’t for you.

How much fuel do we need?

This obviously depends on various factors, including how long you’re running and at what intensity. ‘Get carried away and go too hard, too early, and you start to use increasing chunks of your carbohydrate stores,’ Lawson explains. It’s akin to the difference between driving a car in economy mode to conserve petrol, or putting your foot down and using up more fuel.

Another key factor is how much fuel you start your race or run with, in terms of grams of carbohydrate stored in the body. ‘This depends upon size, weight and gender,’ says Costa. But as an example, ‘if a fit 11st man were to carb-load over a long scheduled period, he should have 500-600g of carbohydrate stored in his muscles and liver – enough for approximately 90 minutes of intense exercise.’ 

Clearly, if we’re going to go longer, we’re going to need to top up. But another factor to consider is how much fuel your body is actually capable of absorbing on the run. ‘Think of the absorption of nutrients into the body like a bucket with a hole at the bottom,’ suggests Costa. ‘There is a maximum amount of carbs that can pass through that hole – ie a maximum capacity of carbohydrates that the stomach can empty and that the intestines can absorb.’ During exercise, ‘the maximum amount of carbohydrates from glucose sources that your body can absorb and utilise is approximately 60g per hour,’ says Cobb. So bearing in mind that most gels contain 20-30g of carbs, you should take one every 20-30 minutes. Take in more, and it will sit in your stomach rather than being delivered to, and used by, your muscles.

What ingredients should you go for?

If you’ve ever studied the ingredients list on a typical gel or other sports nutrition product and don’t happen to be a professor of biochemistry, you may have found yourself flummoxed. Thankfully my questioning produced a basic consensus from the experts on the roles played by the main ingredients, and so what you’ll want to consider before buying.

Firstly, all gels include a primary source of carbohydrate, usually in the form of maltodextrin (which is usually derived from corn or wheat starch).Unlike complex carbs such as brown rice and wholewheat pasta, maltodextrin is rapidly and incredibly easily digested, delivering energy fast and minimising the chance of bloating, wind and other digestive issues. Also look for the combination of fructose (which is a type of fruit sugar) and glucose: because fructose is taken into your system through a different route, it means your body can absorb more carbohydrates per hour.

Secondly, look for electrolytes to replace the vital salts lost through sweating – particularly sodium. If you’re a ‘salty sweater’ (look for white residue on your kit), you’ll want to find a product with higher sodium levels to counter this.

Going further down the list, consider whether you want the performance-enhancing, perceived exertion-lowering effects of caffeine, which is contained in many products. Research suggests that you need 3mg per kilogram of bodyweight to attain a measurable effect – and remember that it takes approximately an hour to reach its peak so time your dose accordingly. You’ll also find the amino acid L-carnitine in a number of gels, which can help your body to burn fat. Then there are nitrates, offered in some products and known to aid the delivery of oxygen and essential nutrients to your muscles. The catch with these is they need to be taken for a few days before your race. (For more on ingredients, see Recipe for success, above).

Practice makes perfect

While the right product for you varies from individual to individual depending on your chosen event and the particular needs of your body, all the experts agree that it’s vital to test out gels gradually on your longer runs to see how your digestive system reacts and allow it to adapt. Never try anything new on race day.

‘If you haven’t practiced with gels in training, it’s unwise to use them on the day,’ says Costa. ‘They could cause gastrointestinal [GI] distress.’ This advice may sound obvious but when I speak to 34-marathon veteran Nick Gracie of sports nutrition retailer, he assures me it’s a common mistake. ‘I have worked at the London Marathon expo the last couple of years and it always amazes me the number of people who come to me the day before the marathon saying, “Should I be taking gels at the race?” and I say, “Yeah you should – but it’s too late now.”’ 

Another reason to start early is that – in addition to ensuring there are no nasty digestive surprises on race day – using gels, bars and energy drinks during your training can actually train your body to be capable of absorbing more carbohydrate.

Something else to consider pre-race is researching whether or not sports nutrition products will be on offer at your chosen event, and if so, which. Just about every major marathon has a nutrition sponsor –Lucozade if you’re running London Marathon for example, or Clif if you’re doing Brighton (see Aid-station savvy, below, for more). Find out what’s on offer, consider experimenting with that particular product beforehand as it could save you carrying your own supplies.

A final practical lesson I learned through experimenting with dozens of gels from various manufacturers is that no matter how perfect the grams of carbohydrate, the hit of caffeine or the balance of electrolytes, if you can’t stand the flavour you won’t want to use it. Which leads back to the most important point of all: there is no one ‘perfect’ product. Once you have the info, and you’re able to choose options that should work in theory, it’s down to experimentation to discover what works best for you in practice. That’s the key to ensuring that come race day you’re hunting down PBs rather than Portaloos.

Armed with all this newfound theoretical and practical fuelling knowledge, I toe the start line of the inaugural 100K Race to the Stones. I start my fuelling early, rather than waiting until I feel like I need a gel (my previous strategy), taking two per hour from the start of the race. To avoid taste fatigue, I take different flavours and textures, all of which I have experimented with on training runs; to avoid dehydration and cramping I wash down the non-isotonic gels with water containing electrolyte tablets. The results are pretty conclusive: although it’s the hottest day of the year, there is no sign of a wall at the 42K mark and I push on through the race, holding pace and with no digestive disasters, to cross the finish line in second place. Which just leaves me wondering what could happen if I were to train my body to tolerate three gels an hour…   

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