First published on the 5th April 2005
A Unique Challenge
Mountain marathons (MM) have a distinct place in the world of endurance adventure racing. External support – common in other types of adventure racing – is strictly forbidden, so competitors are completely self-sufficient throughout the two day event. Weight is a major concern and elite competitors often carry less than 4 kg in total. It is necessary to restrict food intake and there is therefore a compromise between the energy required to perform well and the weight penalty associated with carrying it.
Nutrition & Hydration
It is well established that carbohydrate ingestion enhances athletic performance. Carbohydrate (or glycogen) loading has been applied successfully in many sports, but it is a limited strategy. Muscle glycogen depletes within the first two hours of sustained exercise. To provide sufficient fuel for a two-day MM event, competitors must develop additional nutritional strategies for carbohydrate intake throughout the event.
Adequate fluid replacement is vital for optimal performance in endurance events. If muscles dehydrate by just 3%, performance begins to suffer. Thirst is a poor indicator of hydration status, so the early stages of dehydration often go unnoticed. If more severe dehydration occurs, symptoms might include muscle cramp, extreme fatigue, shortness of breath, headache, nausea and vomiting.
MM competitors often find it difficult to maintain fluid balance. It may be impractical or uncomfortable to drink sufficient fluid whilst running. Water availability is often low, especially during summer months when natural water sources on hillsides dry out. However, water is freely available at the overnight camp and this gives competitors chance to rehydrate before the second day.
We observed the nutritional strategies of 90 MM competitors during the UK 2003 season. Volunteers were recruited via the Internet, with assistance from the Event Organisers. Every event class and age group was represented in the sample.
Food intake and hydration status were recorded throughout the event and linked to performance (measured as a % of the winning time/score in the same class). Food intake before the event was not taken into account. Due to the difficulty of measuring fluid intake accurately, we used urine colour (at various stages) as an indicator of hydration status.
After analysing the food intake results, considerable variation became apparent, in terms of both amount and type of food consumed. Some competitors survived almost entirely on high-energy snacks, whereas others ate more substantial meals including muesli, porridge, pasta, cous cous or noodles.
“Eating two meals at the overnight camp is critical to my recovery – one soon after we arrive and another before we go to sleep.” Richard Parry, MM competitor.
Specialist high-energy products (drinks/bars/gels) were popular. 81% of our subjects used some type of sports energy drink. Favoured brands were Science in Sport, High Five, Isostar and Lucozade. The extent of use varied and some competitors preferred household items such as cereal bars, flapjacks and jelly babies.
“As I’ve become more experienced, I have learned to eat less during an event. I choose highly concentrated energy foods so my calorific intake hasn’t changed, but my performance has improved.” Shane Ohly, MM competitor.
We measured nutrient intake in units per kg body weight per hour. Total energy intake ranged from 2.72 to 8.80 kcal/kg/hour. Carbohydrate intake ranged from 0.53 to 1.76 g/kg/hour. Contribution of carbohydrate to total energy intake ranged from 24.7 to 79.3 %.
Total energy intake varied with class length – the distance covered during the event. Competitors in the longer classes (elite, A, long score) had the lowest nutrient intakes overall and carried lighter, more energy dense food than competitors in the shorter classes. This may suggest that these competitors carbohydrate loaded prior to the event, thus requiring fewer calories during the event. It may also suggest that more experienced competitors were prepared to sustain an energy deficit during the event, though this was not measured directly.
"We have consistently improved our position on day two – I put that down to eating properly and rehydrating at the overnight camp.” Shane Ohly, MM competitor.
There was strong correlation between carbohydrate consumption and performance – competitors who consumed more carbohydrate performed better. This trend supports existing sports nutrition knowledge. There was also a strong link between protein consumption and performance – competitors who consumed more protein performed better. This could be evidence for the role of protein in recovery.
“I know I don’t drink enough, but I find it hard to stop to drink when another team is five seconds behind us!” Iestyn Lewis, MM competitor.
The urine colour results were striking. The majority of subjects were moderately to severely dehydrated throughout the event, particularly on day two. It was clear that fluid consumption was insufficient and competitors did not rehydrate adequately at the overnight camp; indeed many started day two in a dehydrated state. However, we also noticed that subjects who performed best were the most dehydrated at the end of day two. Perhaps these competitors became less concerned about hydration towards the end of the event, as they raced towards the finish. Or perhaps top-performing athletes are simply more able (or more willing) to tolerate dehydration.
Graph showing hydration status at different stages of the events:
Heather R. Clark, Margo E. Barker & Bernard M. Corfe. Nutritional Strategies of Mountain Marathon Competitors – An Observational Study. International Journal of Sport Nutrition and Exercise Metabolism, 2005, Vol. 15 (2) p160-172.
Our thanks to the organisers of the Mountain Navigation Challenge, Lowe Alpine Mountain Marathon, Saunders Lakeland Mountain Marathon and Karrimor International Mountain Marathon.
Heather Clark, Bernard Corfe, Margo Barker.
Human Nutrition Unit
University of Sheffield