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Editor: Dr. Lonnie Lowery Free ASEP-Newsletter email updates What's New... Articles Departments Editor's Corner ASEPNewsletter Growth Lowery, L. Advertisements Refer to the ASEP web pages. http://www.asep.org/ JEPonline Ask the EP... Dietary Fat Intake is not Associated with High Levels of Circulating Lipoproteins or Total Cholesterol (second on page) Brahler, C., et al. This month: Summer heat... Are you hydrated enough? Mike, J. PEPonline Why join ASEP? Power of a Vision Boone, T. View the new web page! You'll be glad you did! The ASEP Board of Directors Editor's Corner ASEPNewsletter Growth! Lonnie Lowery, PhD, MA, MS, RD, LD ASEPnewsletter Editor, ASEP Board of Directors As Editor, this month I'd simply like to share information on the growth of this Newsletter. The number of regular subscribers the the ASEPnewsletter has grown steadily despite a moderate number of bounces each month (old defunct email addresses on our list). These bounces, and the rare "unsubscribe", are regularly outpaced by several new subscribers each month - which is encouraging. For you web connoisseurs, other markers such as total number of separate openings and total number of clicks have roughly mirrored the subscriber growth. Is the growth modest by some standards? Yes. But as a young, "specialty group" specific to exercise physiology, the scale on which we operate is not surprising to this Editor. Of course, one could go on about the much larger number of total persons who periodically receive the Newsletter (now in the thousands) but, to me, it is most fair to discuss purposeful monthly subscribers. It is no secret that we are not a large, non-specific body of professionals, catering to the interests and needs of multiple professions. Instead, we are the dedicated, specific voice for Exercise Physiologists, championing their cause, from helping with jurisprudence issues to finding meaningful employment, to defining scope of practice standards, to providing a code of ethics, to providing a forum for research publications and professional papers. Having watched the ASEPnewsletter grow from essentially zero subscribers at its start, I can tell you that the steadiness of the growth had been gratifying. The slowness may be difficult for impatient persons but the increase in regular subscribers does suggest that the multitudes of exercise physiologists who have yet to hear about ASEP are catching a whiff. There are many exercise physiology-related professionals out there, from professors and clinicians who could contribute significantly to the mission, to recent graduates who are likely to feel a need for community when the excitement of graduation wares off and employment realities set-in. If you know someone like this, just forward this email or have them check out www.asep.org. They can easily subscribe in the "Register for FREE ASEP email updates" section of this Newsletter. So thank you, subscribers. You, along with an even larger number of professionals who support ASEP's mission in less direct ways, keep an essential source of change and resources alive. Ask the EP: Your Inside Scoop on Tough Questions Ask the Exercise Physiologist (EP) is intended for informational purposes only. It is not to be taken as healthcare advice. Please do not submit questions of a personal nature (e.g., fitness programs and nutrition advice solicitation). Thanks. Question: From a physiological perspective, what are some factors affecting fluid loss? The EP Answer by Jonathan Mike, MS, CSCS, NSCA-CPT Several factors affect the rate at which an athlete can produce sweat. Higher ambient temperatures result in a greater potential for sweat production. Higher humidity is also responsible for higher sweat production, but because the vapor pressure gradient and skin is low, the cooling potential (i.e., the rate of evaporation off the skin) is lower in humid environments. The same problem also exists with clothing that traps sweat against the skin (i.e., does not breathe). This type of clothing results in a reduced cooling efficiency that forces a greater sweat rate. (Sweat-soaked clothing doesn’t mean an athlete is effectively controlling body temperature, it just means he or she is losing water.) Some new materials designed for athletes actually wick sweat away from the skin to improve evaporative efficiency. Athletes with large body surface areas may also have an enhanced sweat production capacity and, therefore, an enhanced evaporative heat loss. But these athletes may also gain more heat from the environment through radiation and convection in hot weather. The conditioning or training state of an athlete makes a difference. Well-conditioned athletes have a higher sweat volume potential that results in an enhanced cooling potential. However, this higher sweat rate requires a greater during-exercise fluid consumption to avoid higher heat-stress risk. In addition, because sweat has a lower osmolality than does plasma (i.e., sweat is hypotonic), profuse sweating increases plasma osmolality. Whether or not this increased plasma osmolality affects body temperature or cooling capacity in an exercising individual is, as yet, unclear, but a sufficient change in osmolality and volume does stimulate the kidneys to excrete sodium and reduce urine output by producing more concentrated urine. An athlete’s state of fluid balance also plays a factor; the better the hydration state, the greater the sweat potential. As athletes become progressively dehydrated, the sweat rate is reduced, and body temperature rises. This is a problem because fluid consumption during activity is rarely greater than 2 cups (480 milliliters) per hour, or only 30 to 40 percent of the amount of fluid lost in sweat, an amount that will inevitably lead to the athlete’s becoming dehydrated. Consider that marathoners competing in a cool temperature of 50 to 54 degrees Fahrenheit (10 to 12 degrees Celsius) lose between 1 and 5 percent of total body mass. Marathoners competing in warm weather lose about 8 percent of total body mass, or between 12 and 15 percent of total body water. Why ASEP? ASEP offers a new web page that you should see: "Why Join ASEP?" Click the link then tell a friend! Don't forget to get on the free ASEP email list! ASEP Contact Information Please use this web page (click above) and new email address: contact@asep.org ASEP is a member of the Health Profession Network Check out the HPN Links! And keep in mind: For more information on professional scope of practice, professional standards and code of ethics for exercise physiologists, accreditation of academic programs, board certification examination, and other important tasks already completed by ASEP in establishing a profession, visit: www.asep.org Copyright ©1997-2007 American Society of Exercise Physiologists. All Rights Reserved. All materials posted on this site are subject to copyrights owned by the American Society of Exercise Physiologists (ASEP). Any reproduction, retransmission, or republication (in whole or in part) of any document or information found on this site is expressly prohibited, unless otherwise agreed to by ASEP and expressly granted in writing to consent to reproduce, retransmit, or republish the material. All other rights reserved.
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Ask the Exercise Physiologist (EP) is intended for informational purposes only. It is not to be taken as healthcare advice. Please do not submit questions of a personal nature (e.g., fitness programs and nutrition advice solicitation). Thanks.
Question: From a physiological perspective, what are some factors affecting fluid loss?
Several factors affect the rate at which an athlete can produce sweat. Higher ambient temperatures result in a greater potential for sweat production. Higher humidity is also responsible for higher sweat production, but because the vapor pressure gradient and skin is low, the cooling potential (i.e., the rate of evaporation off the skin) is lower in humid environments. The same problem also exists with clothing that traps sweat against the skin (i.e., does not breathe). This type of clothing results in a reduced cooling efficiency that forces a greater sweat rate. (Sweat-soaked clothing doesn’t mean an athlete is effectively controlling body temperature, it just means he or she is losing water.) Some new materials designed for athletes actually wick sweat away from the skin to improve evaporative efficiency. Athletes with large body surface areas may also have an enhanced sweat production capacity and, therefore, an enhanced evaporative heat loss. But these athletes may also gain more heat from the environment through radiation and convection in hot weather. The conditioning or training state of an athlete makes a difference. Well-conditioned athletes have a higher sweat volume potential that results in an enhanced cooling potential. However, this higher sweat rate requires a greater during-exercise fluid consumption to avoid higher heat-stress risk. In addition, because sweat has a lower osmolality than does plasma (i.e., sweat is hypotonic), profuse sweating increases plasma osmolality. Whether or not this increased plasma osmolality affects body temperature or cooling capacity in an exercising individual is, as yet, unclear, but a sufficient change in osmolality and volume does stimulate the kidneys to excrete sodium and reduce urine output by producing more concentrated urine. An athlete’s state of fluid balance also plays a factor; the better the hydration state, the greater the sweat potential. As athletes become progressively dehydrated, the sweat rate is reduced, and body temperature rises. This is a problem because fluid consumption during activity is rarely greater than 2 cups (480 milliliters) per hour, or only 30 to 40 percent of the amount of fluid lost in sweat, an amount that will inevitably lead to the athlete’s becoming dehydrated. Consider that marathoners competing in a cool temperature of 50 to 54 degrees Fahrenheit (10 to 12 degrees Celsius) lose between 1 and 5 percent of total body mass. Marathoners competing in warm weather lose about 8 percent of total body mass, or between 12 and 15 percent of total body water.
ASEP Contact Information Please use this web page (click above) and new email address: contact@asep.org
ASEP is a member of the Health Profession Network Check out the HPN Links!
And keep in mind: For more information on professional scope of practice, professional standards and code of ethics for exercise physiologists, accreditation of academic programs, board certification examination, and other important tasks already completed by ASEP in establishing a profession, visit: www.asep.org