Fuelling an Endurance World Record
Back in the winter we were asked to support Richard Thoday's attempt to break the 133-year-old Lands End to John O'Groats Penny Farthing record, raising money for Children In Need. It was a challenge so outlandish, we couldn't possibly turn it down. Over the last few months we applied all of the tools from our nutrition services to help him plan towards his record attempt, which he completed successfully on 24th July, finishing the 844 mile ride in 4 days, 11 hours and 52 minutes.
For any endurance event, and especially ultra-endurance races, fuelling is critical and without an effective plan in place it is often impossible to get to the finish, let alone break records. A common misconception amongst long-distance athletes is that it is simply a matter of eating as many calories as possible, regardless of where they come from. Fats and carbohydrates are the major sources of fuel used to power exercise and we can obtain these either from stores within the body, or by consuming foods during an event. Simply selecting ride foods based on the calories they contain lends itself to selecting high fat foods, as fats contain 9 kcal (37.7 kj) per gram and are the most energy dense component of our diet. By contrast carbohydrates provide just 4kcal (16.7 kj) per gram. Although this high fat strategy may seem intuitive given the vast number of calories likely to be burnt in such events (we estimate Richard burnt approximately 30,000 calories during his record attempt), it ignores important aspects of our physiology and is far from an optimal approach.
The body stores carbohydrates in the form of a glucose polymer called glycogen. Muscle is the biggest store providing approximately up to 700g of glycogen, while the liver is the other major store adding up to a further 160g. That gives a maximum total of around 860g or 3,440kcal. Assuming a 22% muscle efficiency and ignoring all other physiological requirements for glucose, fully expending his glycogen stores would have been enough to fuel Richard approximately 90 miles– not even out of Devon. By contrast we store fat throughout the body in adipocytes and even lean athletes have considerable fat reserves. A 70kg rider at 10% body fat for instance will have 7kg of fat, equating to 63,000 kcal. Making the same assumptions as above with carbohydrates, that would be enough energy to fuel Richard all the way to John O’Groats, then back to Lands End and still have some left to spare. We have a limited capacity to eat and there is simply no sense in prioritising refuelling the fuel source that isn't going to run out at the expense of the one that is.
A high fat strategy becomes even less appropriate when you consider how the two macronutrients are metabolised. Fats can only be used as a fuel source for aerobic respiration, meaning they cannot be the only fuel source when riding at higher intensities, carbohydrates by contrast can be burned both aerobically (low intensity) and anaerobically (high intensity). Although the majority of Richard’s ride would be at low intensity, much higher power outputs would be required for uphill sections – Penny farthings after all don’t give you the option to shift into a lower gear! Without maintaining his glycogen stores by consuming carbohydrates throughout his ride, these uphill efforts would soon become impossible. The fuelling strategy was for Richard to maintain a consistent low intensity of riding where possible and encouraging his body to burn fat, whilst ensuring glycogen stores were being maintained as much as possible by consuming target amounts of carbohydrate rich foods in the days prior to and during his record attempt.
A discussion we had very early on with Richard was how to obtain these carbohydrates. Although sports nutrition products such as gels are ideal for road racing, where riders need to be able to carry foods that can be eaten in seconds to provide energy for high intensity riding for 3-5 hours, the situation for someone riding at a low intensity for 16 hours a day is quite different. The major challenges are maintaining appetite and minimising gastric distress. With this in mind, we used our ride analysis tool to test and refine fuelling and hydration strategies on Richard’s training rides and quickly settled on a food-based snacking plan, combined with a maltodextrin / electrolyte drink and a larger, protein and carbohydrate rich meal at the end of each days riding. This provided scope for a wide variety of foods with differing flavours to help maintain appetite, ensured he remained well hydrated throughout and simultaneously made his hourly carbohydrate intake target obtainable for the long days of riding. Richard then spent subsequent months testing different foods which met our nutritional criteria in training and was able to create a menu from which he could select different items at each of his fuelling stops.
We followed Richard closely throughout his record attempt using the highly recommended MyWindsock to monitor his progress. Although we were confident from the start that he would complete the challenge, a sign of just how well he was riding came on day 4 when we had to increase his estimated power output for the model to keep up with him! A final sign that the nutrition plan had worked came on day 5 when he powered up the mile long 8% ramp out of Barriedale, just 40 miles from the finish.