Monday, August 18, 2014

Hydration = Improved Performance

According to Gutyon's Textbook of Medical Physiology "the total amount of water in a man of average weight (70 kilograms or 155 pounds) is approximately 40 liters, averaging 57 percent of his total body weight.”   Specifically, lean muscle tissue contains about 99% water by weight, blood contains almost 70% water, body fat contains 10% water and bone has 22% water.  The human body is about 60% water in adult males and 55% in adult females.  Knowing that 50-60% of the human body is composed of water, then it makes sense why hydration is so important for tissue health.  But, did you know that hydration is also a critical part of every chemical reaction that takes place in the human body?  Knowing all this, it is surprising that it is rarely addressed in the medical and rehabilitation literature when considering those with injuries or for improvements in performance. 

According to research published in the Chan et al in American Journal of Epidemiology 2002 showed that nearly 50% of the American population is considered clinically dehydrated.  Part of this has to do with not taking in enough water while simultaneously taking in too much caffeine.  Since caffeine is a diuretic, it makes you urinate and hence loose water.  Therefore, for every milligram of caffeine over the recommended daily dose means it is adding to an increased need in hydration.  Therefore you need to consider how much water you are losing when looking at your recommended daily dose of water.   The recommended daily dose of caffeine is 420mg/day while the average American gets between 800 and 1600 mg/day, or nearly 2-3 times the recommended dose.  According to Chan's study, if caffeine consumption is kept within recommendations and enough water is consumed, an individual’s risk of heart disease is reduced by 46% in men and 59% in women.  Although this is an older study, the information that is gained is critical and still applicable to today's athlete!  Why is this the case?

The human body is constantly undergoing a complex set of chemical reactions. These are not only essential for basic physiological purposes but also for soft tissue repair.  All chemical reactions are highly dependent on blood pH.  There is some disagreement among researchers about what constitutes a healthy pH in humans, but most agree it ranges from 6.1 to 7.5.  A healthy blood and body pH is essential in order to allow chemical reactions in the body to take place.  The rate limiting step for chemical reactions in the human body is dependent on enzymes.  Enzymes are activated and deactivated by pH levels.  If pH levels are higher or lower than “optimal”, then chemical reactions are slowed or do not occur at all.  These reactions are critical for maintaining normal physiological function, soft tissue repair and force generation. 

Water is essential to maintain a proper pH balance and hence is essential to facilitate these reactions at the proper rate.  When taken into the body, water (H20) has a hydrogen molecule cleaved off, which leaves H + HO.  This free hydrogen ion aids in making the body’s pH more neutral.  This allows chemical reactions to take place more readily.   Therefore, proper hydration is believed to have the following critical effects in humans: 

1.      Improves muscle repair  by creating a chemical environment more conducive to protein synthesis and repair of muscular tissue torn down during injury.  This allows for improved response to training stimulus and aids in reducing risk for overtraining.

2.      Improves the efficiency of chemical reactions for both aerobic and anaerobic metabolism.  This increases speed and availability of energy which has direct impact on performance.

3.      Improves viscosity of the blood

a.      Allows improved oxygen and nutrient transport to muscle tissue.  Direct impact on both soft tissue repair as well as performance.

b.      Decreases stress on the heart by increasing stroke volume - improves cardiac output.

4.      Improves elasticity of muscle and ligament tissues – which improves tolerance to the high force demands of work related activity.  This improves overall endurance and also reduces the risk for injury and overtraining.

Gatorade Sports Science Institute has shown that as little as 1% dehydration can result in a 10% decrease in performance in athletes.  Although all the mechanisms are not completely understood, it is suspected that the above effects are some of the causes.  This not only has a negative impact on performance but endurance as well as increased susceptibility to injury. So, if simply reducing caffeine intake and increasing water intake has a direct impact on your performance, why would you not take that into consideration.  It is one of the easiest and quickest ways to directly impact health and performance. 

That being said, there is some variation in recommendations for water consumption, and requirements are highly dependent on activity, environmental conditions and individual needs.  Current recommendations in the literature range from .5 to 1.0 oz/kg of body weight.  To calculate, you would convert your weight to Kg and multiply by the .5 to 1.0.  So, if you weight 180 lbs., this would equate to:

Converting pounds to kilograms
180 / 2.2 = 81.8 kgs

Converting Kg to water intake needed
81.8 kg x.5 to 1.0 oz =
41 oz to 82 oz per day

When considering your own water needs, it is typically best to measure your current intake and gradually work your way up to a recommended range, all while paying close attention to what “feels” best for you. But the key indicator of whether you are hydrated enough or dehydrated is the color and odor of your urine.  Keep in mind, certain foods and vitamins will alter the odor and color of your urine (vitamin packs and asparagus to name a few), but outside of that, it is the best indicator of your hydration.  So, using the attached chart, you can easily see how you are positively or negatively impacting your athletic performance.

When you consider the impact of hydration on performance and the impact movement has on performance, these are two relatively easy ways to see significant impacts to overall performance.  So, whether you are an athlete or recovering from an injury or looking to improve your performance, hydration plays a critical role in your success.

Trent Nessler, PT, MPT, DPT:  CEO/Founder ACL, LLC | Author | Innovator in Movement Science and Technology.  Dr. Nessler is a physical therapist and CEO/Founder of ACL, LLC.  He is the researcher and developer the Dynamic Movement Assessment™, Fatigue Dynamic Movement Assessment™, 3D-DMA™, author of the textbook Dynamic Movement Assessment: Enhance Performance and Prevent Injury, and associate editor for International Journal of Athletic Therapy & Training.


2.      Guyton, A; Hall, J.  Textbook of Medical Physiology.  Saunders and Elsevier.  2010.

3.      Bergeron, M; Mack, G.  Hydration and Physical Activity: Scientific Concepts and Practical Applications. J Appl Physio. 65:325-331.  1996.

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