Today, the modern ultra-endurance athlete is acutely aware of the need for sustenance in order to recover and prepare for upcoming training and racing. Rehydration and recovery of fluid balance after exercise, together with the timing and method of increased food intake to cope with heavy training, are essential for optimal performance. Furthermore, specific activities may present unique challenges in administering the appropriate strategy. During an ultra-mountain bike race for example, it is much more difficult to meet nutritional demands than during a road biking or running race due to the nature of the event.

Caloric Replacement

Caloric replacement is one of the key fundamentals of sustenance for ultra-endurance athletes. Some events report caloric expenditure ranging from 8500 to 11,500 kcal. The caloric intake must be adequate to maintain the activity.

Ultra-endurance events require energy contributions from all three macronutrients (carbohydrates, protein, and fat) as indicated by the duration of the event and the lower intensity. The relative contribution of these macronutrients is also affected by the intensity of the performance, or frequency of intensive bouts dictated by terrain and race strategy.

The higher the intensity, the more reliance there is on carbohydrates. Carbohydrate diets range from 5 to 7 g/kg/d to 7 to 10 g/kg/d three to four days before competition.

During prolonged running events, usage of 40 to 80 g/h have been reported, whereas usage of more than 90 g/h is not uncommon during cycling events.

Most endurance athletes report better performances and less gastrointestinal discomfort using liquid carbohydrates.

Research has shown that liquid ingestion of 30 to 70 g of carbohydrate per hour or 0.2 to 0.6 g/kg body weight/h can maintain blood glucose oxidation and delay fatigue. A liquid composition prescribed at 7.5% to 12% solution has been shown to minimize the chances of hypoglycemia but maximize performance as glycogen levels deteriorate.

A critical factor in the rate of carbohydrate ingestion is individual gastric emptying physiology. Absorption occurs in the duodenum but particle size can affect the rate at which the substrate enters. Entry via the pylorus is gained only if the particle size is no larger than 1mm in diameter.

Other factors that must be taken into consideration include dietary fiber, meal volume, meal temperature, and osmolarity. Exercise intensity and environmental stress can affect the blood flow to the small intestine consequently affecting gastric emptying and distress. The athlete must have alternate feed plans to accommodate the state of digestion and absorption.

It is important that the athletes implement these feeding strategies during training at the same relative intensity and if possible under the same environmental conditions as the race. Unfortunately, it is difficult to simulate race anxiety and the affect it may have on the gastrointestinal system, but often, the more race experience the athlete has, the less likely they will be affected. Liquid meal feeding has been shown to be superior when compared with solid food.

But for some, solid food will satisfy athlete hunger and allow for more variation, which can help ensure ingestion of caloric requirements. Again, this concept should be investigated individually as taste fatigue is a real concern in ultra-endurance events. In addition, gastric emptying can be enhanced when the feeding solution contains sodium and other electrolytes. Cooler liquids tend to be more readily absorbed, but this element may not be controllable during longer training sessions. In some races that allow support teams or provide aid stations, athletes will freeze their feed bottles and have them several hours later ensuring better liquid temperatures. In ultra-endurance events and training, evidence suggests that protein is an essential nutrient to assist in energy requirement, tissue repair, and glycogen replenishment. Furthermore, Zawadzki et al. provided evidence that a ratio of 3 g of carbohydrate to 1 g of protein can enhance glycogen resynthesis, although other studies have indicated that immediate carbohydrate ingestion remains the most important factor in recovery. What seems to be the common principle for ultra-endurance training and racing is that immediate ingestion of carbohydrate or carbohydrate-protein solution is necessary to replenish muscle glycogen. Some nutritional strategies have tried to promote fat oxidation for sparing muscle glycogen in order to enhance performance. In extreme ultra- endurance events in which tremendous caloric use occurs, foods high in fat tend to be appropriate not only to provide caloric dense options, but to satisfy taste and satiety. Often athletes in these ultra-events need small rewards to maintain pace. Reward foods that do not support the tradition views of performance can be used. Variations can be used to meet the athlete's desires, such as salty fat foods, or sweet savory foods. As long as the athlete is fulfilling the fundamental requirements for continued exercise, these strategies can be quite advantageous for longer events.

Fluid Replacement

Adequate fluid and electrolyte replacement is critical in ultra- endurance performance and training. Dehydration increases core temperature and cardiac drift occurs when the body losses excessive amounts of fluids due to perspiration. Water loss can be as high as 2L/h in hot weather particularly if the event pushes the athletes above 70% of VO2max. In ultra-endurance events, modifications in fluid and electrolyte ingestion have been suggested to avoid hyponatremia. Researchers recommend 500 to 800 mL/h during the 180-km bike portion and 300 to 500 mL/h during the marathon run, with smaller men and women advised to drink lower rates. Oral sodium supplementation has been shown to assist in maintaining hydration balance during ultra-endurance events. An increasing proportion of athletes develop either hypernatremia or hyponatremia in ultra-endurance events that last 6 hours or more. According to Sharwood et al., conservative drinking policy can be advocated for those Ironman triathlons that are held in moderate environmental conditions similar to those at the South Africa Ironman Triathlon, without risking the health of the athletes.

Prevention of Injuries

In order for an athlete to complete an ultra-endurance event, countless hours of physical preparation are required. Consistent training relies heavily on the athlete's tolerance to repetitive strain. According to Egermann et al., most injuries (81.3%) occur during triathlon training hours compared with 18.7% during actual competitions. But considering the hours spent training in relation to competitions, there is a sixfold higher incidence for injury during competitions. This implies that athletes tend to push their bodies to their limits during competition even beyond structural tolerance. Treatment of soft tissue after training and racing incorporates ice and cold water therapy to control inflammation. This practice along with proper rehydration and fuel replacement should be the focus immediately following extreme physical training. Repeated recovery care will ensure successful training sessions in the immediate future.

Overtraining

Overtraining is an additional potential problem for ultra-endurance sports performers. Athletes who exhibit performance incompetence, prolonged fatigue, or an inability to train at expected levels are said to be suffering from overtraining. Overtraining occurs when an excessive training load is not compensated by a sufficient amount of recovery for a sustained period of time. Overload training, a few days of hard training followed by short-term fatigue, is an essential part of all athletes' training. Overload training can, however, result in overreaching if recovery of 3 to 5 days has not resulted in performance recovery. Overreaching is characterized by a transient performance incompetence, which is reversible within a short recovery period of 1 to 2 weeks, and can be rewarded by a state of supercompensation. However, if recovery is inadequate or the training load is unmanageable, over-reaching can progress to overtraining and recovery may take weeks or months. External factors that may contribute to prolonged fatigue may include excessive intensity or volume of training, incorrect sequencing of training or competitions, a lack of training background, and inadequate structural tolerance. A progressive increase in intensive training volume with a considerable increase in training volume is the strongest cause, including an imbalance between an athlete's adaptive capacity and the recovery time required. Furthermore, issues such as social or economic factors, food intake, or sleep may play a role in leading to overreaching or overtraining. In reality, it is likely that significant inter-individual variability in recovery potential, exercise capacity, nontraining stress factors, and stress tolerance may explain the different vulnerability of athletes to training under identical training stress conditions. Diagnosis of overtraining is very difficult and no exact criterion exists. A diagnosis should be based on several points, including patient history, ruling out of other diseases, laboratory findings, and careful examination of the athlete's training log, paying particular attention to the sequence and load of training. A blood marker that shows promise as an indicator of overreaching/overtraining is the glutamine/glutamate rati0. A lowering of the ratio in conjunction with a decline in performance and altered mood state may be a useful tool for diagnosis [48]. A common feature of overtraining is the inability to sustain intense exercise. A performance test that has been used to distinguish overtrained athletes, involves exercise associated with the individual anaerobic threshold (IAT). The duration of this stress test, an all-out short-term duration exercise test performed at an intensity of 110% above IAT, has been observed to be one of the most sensitive single objectifiable criterion in diagnosing overtraining. At this time, there are no clear early warning signs of overtraining and it is suggested that the best treatment is prevention through periodization with sufficient recovery built into the program.

Conclusions

Successful ultra-endurance performance is characterized by the ability to sustain a higher absolute speed for a given distance than other competitors.

The training required is no different than for other sports with respect to the underlying principles. Successive stresses must be applied to the body over time in order to provide a stimulus to initiate adaptation so that subsequent training or performance is accomplished at a higher absolute intensity or for a longer period of time. The sequence in which a series of training blocks is applied is critical to the final outcome for an ultra-endurance athlete. How the loads are applied is dependent on training periodization, which is a training concept in which the year is divided into large, medium and small training blocks that are referred to as macro-, meso-, and microcycles. The design of a periodized plan should incorporate the following principles: all-around development, overload, specificity, individualization, and consistent training. Furthermore, structural tolerance is a concept that suggests that the body needs time to adapt to a training load and tolerance is built up through years of general and specific training. The modern ultra-endurance athlete requires sustenance in order to recover and prepare for upcoming training and racing. Rehydration and recovery of fluid balance after exercise, together with the timing and method of increased food intake to cope with heavy training, are essential for optimal performance.