Importance of Hydration

Even though summer is coming to a close, it is still important to maintain hydration! It may seem like you’re sweating less because of the cooler temperatures, but exercise still affects the body’s fluid levels. Be aware that even small loss in body weight due to fluid loss (via exercise) may affect your exercise performance and endurance capacity, and larger losses in % body mass can even be dangerous. Also keep in mind that the symptom of thirst is delayed. The body sends a stimulus to the brain relaying the message that there is a fluid/electrolyte imbalance which induces thirst. By the time that there is a fluid/electrolyte imbalance, the body is already in dehydrated state. If exercise is added into the mix, there could be problems.

Severe dehydration causes shifts in plasma and thus blood volume, and can affect the efficiency of the heart. Dehydration can also lead to a decreased sweat rate which contributes to dangerous increase in core temperature, less blood flow to the skin (decreasing heat release), changes in the rate of perceived exertion (exercise seems more difficult), and in extreme cases – heat illnesses and loss of organ function (1). This is all easily prevented by staying hydrated! Make sure to replace the fluid that is lost through exercise, even in the winter months, so you don’t start your next exercise bout in a dehydrated state. Keep in mind that environmental conditions also play a role in hydration! ACSM’s guidelines indicate that active individuals should consume at least 1 pint  of fluid for each pound of body weight lost through exercise (2).


1. Noakes T. Fluid replacement during exercise. In: Exercise and sport sciences reviews. Philadelphia, PA: Williams & Wilkins, 1993:297-330.

2. American College of Sports Medicine. In: Thompson WR, Gordon NF, Pescatello LS, Eighth ed. ACSM’s guidelines for testing and prescription. Philadelphia, PA: Lippincott Williams & Wilkins, 2010

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