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Long runs and endurance events warrant special consideration with both nutrition and hydration. The cliché "you are what you eat" or in the case of this discussion, you will perform better depending on what you eat and drink both before and during exercise, holds true. Hydration and nutrition are an important part of optimum performance with exercise but especially as the weather gets warmer and with exercise that lasts more than 60 minutes.
Our body weight is made up predominantly of water. A 150 pound man may have between 10-12 gallons of water in his body. Water is essential for our health and maximum athletic performance. Water transports oxygen, glucose and essential electrolytes to our working muscles during exercise. It helps to maintain electrolyte levels at normal concentration. On the opposite end it helps to transport waste such as lactic acid from muscle and metabolic waste from the kidneys.
Water also serves to cool us transporting heat from working muscles in the form of sweat that leads to evaporative cooling. Exercising muscles can generate up to 15-20 times more heat than muscles at rest. Men tend to sweat more profusely than women who sweat less and cool more efficiently.
The volume of fluid needed to avoid dehydration can be difficult to measure. In an exercising individual, especially one who is in good physical condition, thirst cannot be used to measure proper hydration. Athletes and children may have a delayed thirst reflex putting them at risk for dehydration. Thirst is initiated by the serum (or blood) level of sodium concentration. Water loss through sweat and respiration can lead to increase in sodium levels which would trigger thirst. This reflex is not immediate and by the time an individual is sensing thirst they may be dehydrated already. Consuming the correct amount of fluids to keep sodium levels at a normal level will ensure adequate hydration status.
Being well hydrated before exercise is important especially for more enduring activities lasting more than 60-90 minutes. It is generally recommended to drink 16 oz of appropriate fluid 60-90 minutes prior to exercise to allow for absorption and the elimination of excess.
During prolonged exercise early hydration before thirst will help maintain a better late stage effort of exercise. Between 8-10 oz of fluid should be consumed every 15-20 minutes. Other factors can predispose the athlete to dehydration such as sodium depletion. Sodium depletion is seldom a problem unless the athlete is participating in a prolonged event such as a marathon or ultra distance event. Usually adequate sodium is ingested with meals to stave off hyponatremia (low blood/serum sodium level). Sodium can be replaced by the use of sport drinks although the absorption may be slow to benefit during a race event or prolonged workout.
The optimal fluid to hydrate with is by far water. Natural diluted fruit juices are also effective and may provide small amounts of electrolytes. Sport drinks can provide good hydration options during prolonged exercise and provide a source of glucose to working muscles. Sport drinks are often over consumed and loaded with calories. Soft drinks or soda both regular and diet should be avoided at all costs. Energy drinks with large doses of caffeine should also be avoided.
Calorie consumption both before and during exercise depending on duration and intensity is important and may improve athletic performance. Pre workout calories high in carbohydrates will help to prevent hypoglycemia (low sugar level), fatigue, and poor judgment. They will also help to preserve glycogen stores and provide an immediate source of energy to working muscles.
If you will be exercising greater than 60 minutes, you will want to consume carbs with a low glycemic index to provide a more steady energy source to muscles. Foods such as sweet potato, baked potato, pasta, yogurt and bananas are examples of foods with low glycemic index. It is best to avoid foods high in simple sugars as they have a high glycemic index and can lead to feeling fatigued after the initial rush of energy.
While exercising greater than 60 minutes it is recommended to consume between 100-300 calories of carbohydrates every hour to maintain energy stores and to help to maximize performance.
With these basic recommendations, proper training techniques and acclimatization to warm weather exercising in the heat for healthy individuals can be safe and rewarding.
