July 7, 2010
Ah, water. We all know we need it, as it is one of the most essential components of the human body that makes up over half of our body weight. From ensuring the healthy functioning of internal organs to regulating body temperature and aiding in digestion, water is imperative to sustaining life. And when it comes to working out adequate hydration is key to ensuring optimal performance and overall health, as in one hour of exercise the body can lose more than a quart of water depending on the exercise intensity and air temperature.
How do I know if I’m dehydrated?
Dehydration is the lack of adequate fluids for the body to function normally, which can impair thermoregulatory function as well as muscle and nerve activity. The sensation of thirst typically coincides with a 1% dehydrated state (that is, a 1% loss of body weight). Research has shown that dehydration in excess of 2% of body weight impairs aerobic exercise performance and can increase the potential for heat illness.
Aside from the sensation of thirst, urine color can typically (unless taking vitamins, supplements or medications that affect urine color) be used as an accurate marker of hydration status. When the body is properly hydrated, urine will be clear to lemonade colored, where as when the body is dehydrated urine will be orange-yellow to apple juice colored.
How do I ensure that I stay properly hydrated?
Two to three hours prior to exercise, aim to consume 17-20 ounces of fluid. This amount allows sufficient time for urination prior to the start of activity, yet is an adequate amount in order to achieve optimal hydration. Once you’ve begun to exercise, aim to consume 7-10 ounces of fluid every 10-20 minutes. Following exercise, replace water equal to 120-150% of body weight loss. An example of this would be if 1lb of body weight (16 oz) is lost during exercise, to achieve optimal rehydration as quickly as possible replace the lost fluid with 19-24oz of water. When exercising at a moderate intensity for less than 60 minutes, water for the most part should be all that is needed to adequately rehydrate.
In addition to the above mentioned fluid-intake recommendations, keep in mind that other factors such as sweat rate, clothing, exercise intensity, air temperature and humidity, also play a role in determining specific rehydration needs.
Jessica Matthews, MS, E-RYTContributor
Jessica Matthews, M.S., E-RYT is assistant professor of exercise science at Miramar College. As a leading fitness expert, writer and educator Jessica is a regular contributor to numerous publications, including Shape and Oprah.com. She holds a B.S. in physical education teacher education from Coastal Carolina University and M.S. in physical education from Canisius College. She is a certified Personal Trainer, Group Fitness Instructor and Health Coach through the American Council on Exercise (ACE) as well as an Experienced Registered Yoga Teacher (E-RYT) through Yoga Alliance and trained stand-up paddleboard (SUP) yoga instructor. Prior to teaching at Miramar, Jessica worked full-time ACE, serving in a number of key roles including exercise physiologist, certification director and senior health and fitness editor. Her past work also includes serving as aquatics director at Conway Medical Wellness and Fitness Center and designing health and physical education curriculum for grades K-12. Full Bio Jessica Matthews »