Sports nutrition: Exercise and performance hydration

Dehydration (fluid loss) results in early fatigue, increased heart rate (cardiovascular stress), increased risk of heat illness and ultimately decreased performance.

Do you feel bloated and uncomfortable if you drink water during training, but if you donâ??t, you get headaches and feel tired quickly after exercise? Dehydration (fluid loss) results in early fatigue, increased heart rate (cardiovascular stress), increased risk of heat illness and ultimately decreased performance. Keeping up with fluid intake during the day, replacing fluids early and often during and after training runs, will help Marc, Lauren and Anne maintain top performance as they prepare for the Bayshore. Developing a fluid replacement plan will help them start and stay well hydrated as the days (eventually) warm up in Northern Michigan and they increase their training duration.

Goals of exercise and performance hydration are:

  • Delay fatigue and maintain focus

  • Regulate body heat, especially in hot environments

  • Satisfy thirst and prevent significant with loss from sweating

  • Improve ability to recover quickly from training and competition

High intensity exercise, such as running, requires increased blood flow to the large muscle groups to deliver oxygen and fuel (carbs), but blood must also flow to the skin to help cool the body. We know that we sweat to stay cool; the evaporation or water (sweat) from skin helps remove the heat generated by working muscles from the body and keep our core temperature around 98.6Ë?F. And when the air temperature in which weâ??re exercising is hot, fluid loss via sweat can be greater.

The amount and rate of fluid loss (sweat) is affected by genetics, body size, fitness level, environment and exercise intensity. Sweat rate can be calculated by weighing before and after exercise, accounting for fluids consumed during the exercise session and the time spent exercising. While sweat rates vary greatly between individuals, a fluid deficit of 2% or more of body weight reduces blood volume, which in turn reduces the bodyâ??s ability to regulate body temperature and exercise capacity.

On the flip side, people participating in endurance events should not drink so much that they gain weight during exercise. Drinking more fluid than is lost during exercise can dilute the blood (hyponatremia) leading to nausea, collapse, and loss of consciousness or even death. The Three Amigos should follow an individualized hydration plan based on fluid loss calculations and experiment during training to find the volume of fluid to drink that feels comfortable and allows them to perform at their best.

Along with water, electrolytes (sodium + chloride = salt) are lost from the body via sweat. As with total fluid loss, the sodium content of sweat varies greatly between individuals. Potassium, calcium and magnesium also appear in sweat, but in very small amounts. Studies have shown that including sodium with replacement fluids during and after exercise promotes sugar (carb) and water absorption with fluid retention for better fuel and fluid balance and helps maintain blood electrolyte levels for optimal performance and recovery.

Electrolyte supplements are powders, tablets or ready to drink products for targeted replacement of the electrolytes (sodium and potassium) lost through sweat. They can be used in place of sports drinks and in combination with carb sources (depending on supplemental carb needs) when sports drinks are not enough to replace large electrolyte losses during and after exercise. Electrolyte supplements may be important during ultra-endurance activities and in individuals with high rates of sweat loss and/or â??salty sweaters.â?? Individualised recommendations for sodium supplementation during exercise should be made under the supervision of a Sports Dietitian or Physician.

Marc, Lauren and Anne can include the following fluid sources and strategies to stay well hydratedand achieve their training and performance goals.

  • Start exercise well hydrated â?? drink fluids regularly throughout the day and 10- 12 ounces in the hour prior to starting exercise

  • Replace sweat losses â?? drink fluids throughout exercise

During exercise, drinking early and often (say every 15 minutes), in large gulps, helps fluid leave the stomach faster to increase comfort and promote fluid absorption

  • Replace fluid weight lost - rehydrate after exercise

A general guideline for fluid replacement is to drink 150% of weight lost (1 pound = 16 fluid ounces; if you lose 2 pounds of body weight during your run, aim to drink 48 ounces (6 â?? 8 oz cups) in the 2-4 hours after your run

  • For short duration ({<}60 minutes), moderate intensity runs, water is a good choice to drink before, during and after

  • For moderate to high intensity runs lasting longer than 60 minutes, sports drinks (6-8% carb) with sodium are good options

  • Choose cool fluids (60-70Ë?F)

Good sources of fluid, carb and sodium include:

  • Water + food

  • Sports and electrolyte drinks

  • Low fat plain or flavored milk

  • Fruit juices â?? diluted + pretzels

  • Tomato/vegetable juices

  • Soups/bouillon

  • Smoothies

  • Fruits and veggies

  • Vegemite sandwich + water or a sports drink

â??Salty sweatersâ?? can also eat salty foods such as pretzels or saltine crackers, before and after exercise.

Good hydration and electrolyte replacement for performance and your health is essential. Consider working with a registered dietitian who specializes in sports nutrition to develop an individualized hydration planbased on your body weight changes, thirst, taste preferences, and the varying conditions of your sport and exercise schedule. Contact Miranda Monroe via for a consultation to put the science of sports nutrition on your plate with a personalized plan and practical meal planning strategies to help you achieve your performance goals.

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