Hydrating and Why It’s So Important

By Coach Ashlynne

Proper hydration is critical for maximizing performance during physical activities. Water plays a crucial role in maintaining blood volume, regulating body temperature and aiding in muscle contraction. During physical exertion, water is lost through sweat and must be replenished. If the water lost is not replenished properly it causes a decrease in effective muscle function and physical performance. A loss of sweat equal to 2% of body weight causes a noticeable decrease in physical and mental performance.  Losses of 5% or more of body weight during physical activities may decrease the capacity for work by roughly 30% (sports cardiology). 

The biggest mechanism affecting maximal performance is cardiac output. Dehydration affects cardiac output because less water in the bloodstream means lower blood volume. During peak intensity, these changes decrease the amount of blood returning back to the heart. This directly affects the ability of the heart to refill as fully and quickly, therefore, decreasing its ability to circulate as effectively. During exertion, muscles need even more blood circulation, because they need more oxygen. 

Hydration is also important post workout to help muscles rebuild. Research from the University of Connecticut tested athletes’ muscle growth during resistance training over a period of three different states: hydrated, moderately dehydrated (2.5% of body weight) and critically dehydrated (5% of body weight). Molecules correlated to muscle growth was measured by obtaining blood samples. The dehydrated state athletes had an increased level of cortisol, this affects testosterone levels which is the primary hormone required for muscle hypertrophy. Cortisol interferes with testosterone levels because cortisol competes for the enzymatic receptors in the body reducing testosterone’s ability to repair and build the muscle. 

The Institute of Medicine has set an approximate ideal volume of water that people should consume daily. Male adults 18 and above should consume about 4 liters per day while females above the age of 18 should drink about 3 liters of water (sports cardiology). 

Water is important for the proper function of the body systems and is especially critical for athletic performance and recovery.

“The Effects of Hydration on Athletic Performance.” SportsCardiologyBC, 1 Apr. 2016,


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