Curr Rev Musculoskelet Med (2008) 1:131–136 before the level of dehydration reaches a point where the performer’s physical performance would normally be affected. Mild dehydration has been attributed to increased headaches and subjective decreased performance without change in objective measurements [53]. These deleterious effects are further exacerbated with increasing core tem- peratures [40 C. These subjective changes are more likely to affect team sports as this requires group cooperation. Although these changes have not been shown to increase the severity of injuries, Patel et al. [54] did show that the subjective measurements of the athletes indicated greater perceived symptoms. Therefore, the importance of pre- venting signiﬁcant dehydration in team sports is evident before the individual members of the team would begin to show performance deﬁcits. This contrasts with endurance events such as marathon runners who typically compete as individuals with a set objective of competing against the clock as well as the other runners. Many of the elite runners will attempt to acclimate to the race environment by either traveling to the race destination early or training in a similar environment to acclimatize to the conditions they are likely to see [27]. These elite athletes will typically ﬁnish their competition in approximately 2 h for a standard marathon. Maintaining adequate hydration is the prime focus for these elite run- ners, to minimize heat strain-related performance deﬁcits. The more casual runners such as those in the open mara- thons (New York, Chicago, etc.) are at greater risks for hyponatremia as they can potentially consume signiﬁcantly more ﬂuids than they need for such an event [55]. These risks appear to increase for athletes who require more than four hours to complete their event [38]. Ultra endurance events such as 100 km runners, triath- letes, and long distance cyclists all experience unique risks associated with their sports. Competitors of ultra endurance runs can be subjected to signiﬁcant heat strain depending on environmental factors, dehydration, and even hypona- tremia if they are not able to consume enough sodium to offset sweat losses. Hyperhydration is rarely encountered during these types of events [56]. The above risks begin to increase when the athletes enter their third hour of com- petition. Alternatively, long distance cyclists have the beneﬁt of always having ﬂuids available with caution needed to prevent hyperhydration with associated side effects. Ebert et al. [57], hypothesized that dehydration would beneﬁt cycling hill climbing by improving the power-to-weight ratio of the athletes. However, the dele- terious effects of dehydration were greater than any beneﬁt that could have resulted from the reduced weight during the competition. Triathletes experience a conglomerate of exercise-associated risks secondary to the long competition duration. As the athletes have no availability of drinkable water during that initial swim, dehydration is prevalent. 135 Research has shown that these same athletes have weights above baseline on completion of the bike leg of the race [6]. This actual increase in weight is related to the ad libitum ﬂuid availability while on the bike leg. Anecdotal reports from triathletes indicate that many of these com- petitors also consume signiﬁcant quantities of food that would cause gastrointestinal distress in most athletes, but is tolerated in this group as they train while eating these foods as well. Conclusion The keys to success during any competition are to indi- vidualize ﬂuid and electrolyte consumption to prevent both dehydration and hyperhydration. A simpliﬁed adjustment is to calculate sweat loss during training runs and distribute ﬂuid replacement during training and competition. Elite athletes can have sodium sweat concentrations and losses calculated and replaced with special individualized for- mulated electrolyte replacement drinks. Typical athletes can estimate that they lose a little less than 1 g of sodium for every liter of sweat. If they continue to experience cramping during training, they should attempt to increase electrolyte concentration to relieve symptoms and then adjust as necessary. However, the most important key to a successful com- petition is to avoid any new experimental training changes on the competition day. References 1. Benardot D. Ch 3: Fluids and electrolytes. In: Advanced sports nutrition. Champaign, IL: Human Kinetics; 2006. p. 75–100. 2. Guyton AC, Hall JE. Textbook of medical physiology. 10th ed. W.B. Saunders Company; 2000. 3. Medilexicon. http://www.medilexicon.com. Accessed 29 Sept 2007. 4. Bartok C, Schoeller DA, et al. Hydration testing in collegiate wrestlers undergoing hypertonic dehydration. 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