The Marathon is a 26 mile 385 yard long-distance running event and one of the ultimate challenges in sport. Endurance events that require extreme volumes of training, such as the Marathon, have seen an ever-increasing reliance on nutritional strategy. Stellingwerff (2013) suggested that this explosion of marathon performance may be due to a “perfect storm” of factors including; physiology, biomechanics, training advances and anthropometrics. However, modern day approaches to nutritional physiology and periodization must also be appreciated beyond these factors. Nutrition plays a key role in ensuring an athlete is sufficiently prepared prior to a sporting event (Burke, Millet & Tarnopolsky, 2007). An athlete’s quest for marathon success can be facilitated by an individualised and periodized nutritional strategy and training approach (Stellingwerff, 2012). An athletes’ pre-competition diet must efficiently supply essential nutrients and the adequate fuel needed to optimize their recovery and training performance (Burke et al, 2007).
Fluids
Starting any form of exercise in a euhydrated state is vital, as dehydration can compromise performance levels. Heat loss can only occur through evaporation of sweat from the surface of the skin, when ambient temperature exceeds skin temperature (Tarnopolsky, Gibala, Jeukendrup & Phillips, 2005). Convertino et al. (1996) recommended an athlete drink 400-600 ml of fluid 2 hours prior to exercise, allowing adequate hydration and time for the excretion of excess ingested fluid. During training runs >1hr, the use of a Carbohydrate electrolyte drink (4-8g per 100ml-1) can simultaneously replace fluids and carbohydrates (Burke et al, 2007). Maughan, Leiper and Shirreffs (1997) suggested that when the sodium lost in sweat is replaced after exercise, then effective re-hydration can be achieved. Athletes should therefore consume re-hydration drinks that also contain sufficient sodium without compromising fluid intake (Tarnopolsky et al. 2005).
Carbohydrate
The availability of carbohydrate (CHO) as a substrate for muscles becomes a limiting factor in sporting performance (>90minutes) of submaximal or intermittent high-intensity exercise (Burke, Kiens & Ivy, 2004). Therefore optimizing the intake and delivery of CHO is of maximal importance during training (Stellingwerff, 2013). Increased CHO intakes are encouraged during competition preparation and recovery stages in order to maximise the glycogen stores (Burke et al. 2007). According to Fallowfield and Williams (1993) a high intake of CHO enhances performance of a single bout of distance running, the recovery process and the performance of the subsequent bout of running. This was supported by a study conducted by Tarnopolsky et al. (2005) where athletes on a high CHO diet (65% CHO) maintained energy levels and performance over an 11 day period, in comparison to those on a low CHO diet (41% CHO) whose performance levels and self-reported fatigue levels decreased. According to sports nutrition guidelines (Burke et al. 2004), a marathon runner’s diet must provide sufficient CHO to restore glycogen between training sessions and cover the fuel costs of their individualized training programs.
Carbohydrate Loading
An effective technique used to adequately prepare fuel stores for distance events is carbohydrate loading (Burke et al. 2007). This technique allows an athlete to run at optimum pace for a longer period of time before fatiguing, therefore enhancing marathon performance. Distance race performances that would otherwise be limited by fatigue due to glycogen depletion, can be improved by CHO loading. A protocol was modified which does not include a severe glycogen stripping phase, as it used to include, and merely consists of 3 days of high CHO intakes (10-12g/kg/day), resulting in the super-compensation of an athlete’s glycogen stores (Burke et al. 2007).
Fat-loading with Carbohydrate loading
A study by Lambert et al. (2001) examined the effects of a ten-day high-fat diet followed by a three-day carbohydrate loading protocol on the fat-burning capacity of endurance athletes. The study proved that fat-loading would increase the body’s reliance on fat and decrease reliance on glycogen as fuel, with athletes completing a time trial 4.5% faster after this intervention. Subsequent CHO loading would then maximise glycogen stores without the negating effect of fat loading, by reversing the depletion of muscle glycogen stores. Therefore this would decrease the chances of an athlete ‘hitting the wall’ and consequently improve their performance, as there would be a greater percentage of glycogen available and less glycogen being used.
Conclusion
Elite marathon performance is heavily influenced by the application of effective nutritional strategies and the dedication to handle large training loads.
In summary, the pattern of intake and meeting the total energy requirements during pre-competition training are of upmost importance to marathon success. Athletes must also devise a diet plan which is both practical and comfortable to fit around their training schedule. An elite marathon runner should tailor their daily diet to reflect their training loads – a higher intake on harder training days, lower intake on easier/recovery days for example.
Carbohydrates, fats and fluids have been identified as the key nutritional aspects in an elite marathon runner’s diet. The research provided suggests general guidelines and therefore further research needs to be made into how elite athletes can adapt their diet plans according to their genetics, anthropometrics and training schedules.
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