For this weeks blog, we thought we would talk a little about marathon fueling. There is a danger when running the marathon of “hitting the wall” which is probably a term you’re all familiar with. In technical terms, it refers to the point in the marathon when your muscles and liver are depleted of glycogen which is the main storage form of glucose in the body. When we ingest a carbohydrate rich meal, the body breaks down most of the carbohydrate and stores it in the liver and muscles as glycogen. In times of need (e.g during exercise) the body will break down the stored glycogen and convert it to glucose to be used as energy. Glucose is the easiest and most readily available fuel source to burn when exercising, so the body prefers it. When you run low on glucose and glycogen, the body’s reflex is to go into shut down to preserve energy, even the brain wants to shut down, which leads to the negative thinking that comes along with hitting the wall.
Although glucose is the quickest source of energy for the body, most of the time we we burn a combination of both glucose and fat for fuel. However, the ratio of these two fuels changes with the intensity of the activity. For example, during an intense speed session, glycogen is the main source of fuel, however on a long slow run you would burn a higher percentage of fat and a lower percentage of carbohydrate. Every athlete is different though, and in a marathon, depending on how you’ve trained, some athletes may burn a higher percentage of fat than others. However, regardless of this no athlete is immune to hitting the wall!
Most elite male distance runners store approximately 2000-2400 kcal (or 400g) of glycogen in their muscles and liver. However the cost of running a marathon at a super fast 2:12 pace for example can be considerably higher (up to approx. 3,000 kcal) depending on how the individual utilises their fuel source and the way they have trained. Working out how the athlete fuels (are they primarily a fat burner or carbohydrate burner?) can be done in a lab or simply by trial and error in training. Every runner has different and specific nutritional needs for optimal performance. The best ways to find out what works for you are by experimenting through trial and error and making fueling practice a regular part of your marathon-specific workouts. But as a general rule, if no carbohydrate is taken on during the race the body would run out of its glycogen stores by around the 20 mile mark and unfortunately, the side effect of dwindling glycogen stores is hitting the metaphorical wall with a reduction in running speed and what is likely to be a painfully slow last few miles!
The way to get around this is fueling, which may sound simple, however, getting fluids down when running 5 minute miles is easier said than done! So it helps to have something that at least tastes nice! We are fortunate and proud at Team NB MCR, to be supported by Science in Sport (SiS). The SiS GO gels and the SiS Go Electrolyte Powder are coming in particularly handy for Jonny who is currently in training for Berlin marathon. On his long runs he uses a combination of the SiS Go Gel (87kcal in 60ml (22g CHO) and the Go Electrolyte powder (40g (36g CHO) mixed into 500ml water for a 7% Carbohydrate solution. It’s important to work out what suits you , there is no one rule for everyone. SiS suggest that you aim for 60-90g of carbohydrate per hour. Experiment during long runs to see what works and then once you’ve found something that works stick to it and use it for race day. It is easy to over complicate things but staying hydrated and fueled by drinking every 3 miles or 5km keeps a regular input of calories and fluid going into the working muscles. Don’t rush it either, carry the bottle or gel with you and take your time rather than gulping down and feeling sick!
There is one final trap that’s possible to fall into…….you’ve done the training and have worked out when and what gels/drinks your going to take on during the race. If you’ve tapered well, the likelihood is that you will be feeling fresh and quite good for the first half of the race. It’s easy in these situations to fall into the trap of thinking that you don’t need to fuel because you are feeling good, far better than you usually do at this point in training, so you skip a few feeding stations. However, in a marathon this is likely to come back to bite you! Not fueling adequately during the first half is likely to be a recipe for a painful and slow second half, so I guess the message is don’t just save the gels and drinks for when the going gets tough….as it is often too late!
SiS products are available from their website http://www.scienceinsport.com/uk/