Much research has been done regarding proper nutrition and hydration prior to and after exercise or athletic performance. The majority of studies done on nutrition and hydration during exercise has slanted toward hydration. However, physical activity can be enhanced with the consumption of nutrients while engaged in activity lasting 60 minutes or more. Optimal performance hinges on adequate intake of nutrients and water during physical activity.
Benefits of Carbohydrates
Consuming carbs has been shown to improve performance, especially endurance activities. Stamina can be increased significantly with the intake of 150 to 200 calories (30 to 60g) after the first hour. The exposure to additional carbs during low-intensity activity increases the uptake of and utilization of skeletal muscle glucose (glycogen). This increased uptake leads to increased muscle performance. As intensity increases, muscle glycogen becomes depleted. Blood glucose becomes primary for sustaining energy. Ingesting a carb during this time provides sugar for instant energy.
Sources of Carbs
The aforementioned rationale gave birth to the massive sports drink industry. Well-known drinks hit the market proclaiming instant replenishment of blood sugar levels for sustained performance. Also touted in these claims are replenishing sources of electrolytes (sodium, potassium and chloride) necessary for proper muscular contractions. Bananas, energy bars, gels and sports drinks are typically chosen as fuel sources by many athletes during performance.
Theories of Water Intake
For years the misconception proliferated that if you drink water during exercise or athletic performance, you would develop cramping. Any merit to this assertion would be based on the fact that an individual began the activity underhydrated, did not hydrate at adequate intervals, and waited until severe thirst had set in before deciding to drink water, leading to over-consumption. Realistically, water should be ingested approximately every 15 minutes during exercise and not when a feeling of thirst is recognized. By the time thirst is recognized, you could have potentially lost 1 to 3 percent of body weight. This reduction in body weight can hinder performance and force the heart to beat an additional three to five times per minute.
Significance of Water
Exercise can generate heat in muscle upwards of 20 times its normal temperature. The body uses water to reduce core temperature in efforts of maintaining a constant 98.6 degrees F temperature. This is done by sending water to the skin's surface, or sweating. Sweat evaporates and cools the skin, and, subsequently, the blood. The hotter the internal environment becomes, the greater the need for water to be escorted to the skin. This negatively impacts physical performance because available blood is needed to transport water to the sweat glands. This minimizes the blood available for working muscles, thus, minimizing nutrient transport to the working muscle. Adequate hydration during exercising reduces the core temperature and the need for excess water, by way of sweat, to be transported to the surface of the skin.
Considerations
Weighing yourself prior to and immediately after exercise provides sufficient information pertaining to your hydration status. The goal is to minimize acute weight loss during a bout of exercise. Experiment with the quantity you ingest in the recommended 15-minute intervals. Also, the color of your urine during or following exercise is a clear indicator of your hydration status. The darker the urine, the less hydrated you are. Ideally, there will be a pale, yellow hue to the urine. Carbs containing glucose, maltodextrins, maltose, sucrose and amylopectin are broken down and utilized more rapidly than those containing fructose, amylose or galactose. However, be mindful that a high sugar content in the stomach due to over-consumption can slow water absorption in the body.
References
- "Nancy Clark's Sports Nutrition Guidebook," Nancy Clark; 2003.
- "Sports and Fitness Nutrition," Robert Wildman and Barry Miller; 2004.
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