Nicolas
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Total Posts
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45
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Reward points
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10
- Joined: 4/17/2006
- Location: Perth, Western Australia
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Is hypohydration neccessary?
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Sunday, June 04, 2006 7:54 AM
Hi there, Is hypohydration neccessary, when exercising in excess of 2 hours?
The ideal temperature point for the human body is approximately 98.6 degrees Fahrenheit [1], converting to 37 degrees Celsius [2]. Should the internal temperature of the body become unstable, dire consequences can result [3], such as heat stroke, heat exhaustion and hyperthermia [4] [5], as well as illness, fever and hypothermia [6] [7]. In response to the many prospective problems that can result through mismanagement of body temperature regulation, there has been much attention placed on thermoregulation of athletes, in relation to exercise and sport [8]. Effective hydration techniques, core body temperature control and the effects of temperature extremes through the duration of exercise, are some examples of key focal points of athlete adaptations during a diverse range of settings and intensities [9]. As a result, this article will focus on the necessity of hypohydration during exercise, as a preventative method heat disease, through maintaining temperature regulation. It has long been believed that if athletes, through-out exercise, allow themselves to become dehydrated, they will then experience reduced sweat rates and elevated core body temperature, therefore increasing their risks of developing a life threatening heat disorder [10] [11] [12]. However, in recent years, the validity of these claims have been critically challenged, suggesting that aggressive hydration techniques are not associated with an increase in core body temperature to levels that are considered excessive [13] [14] [15] [16]. A recent study co-ordinated by Dr Paul Laursen, set out to test this critical view, was performed in a field setting of an Ironman triathlon event, as a result of most previous data being laboratory based [17]. This study monitored core temperature and hydration status in ten (10) well trained male Ironman athletes, during a 226km Ironman triathlon held in Busselton, Western Australia, with recordings performed pre-event, during the event and post-event. The conducted measurements were performed through the use of blood samples, skin folds of multiple areas, calibrated scales, a stadiometer, heart rate monitors, core temperature pill (ingestion) and also urine samples. These instruments were used to measure the ten (10) participant’s body mass; plasma concentrations of sodium, potassium and chloride; and their urine specific gravity. Once these results were tracked and recorded, the researchers used statistical analysis via applying the normative distribution “‘t’ test”, with multiple comparisons made through Tukey’s post hoc test [18]. Through-out this study, it was determined that aggressive hydration techniques are not required to maintain core body temperature. The ten (10) participants participated in high intensity exercise, in excess of ten (10) hours, in relative humidity; and as a result experienced a decrease in approximately 3% body mass, with only an average of 1°C increase in core body temperature. This conclusion of the study, therefore contradicts the hydration guidelines set forward by the ACSM (American College of Sports and Medicine) [19], and that of other professional bodies in the industry [20]. Through these recent studies, it can be seen that excessive hydration is not required, or indicative of core body temperature; which challenges many traditional views that claim otherwise. This is not to suggest that the athlete shouldn’t drink; rather that there is no need to panic, just drink when you are thirsty. Written & Researched by:- Nicolas Hart – (nhart@student.ecu.edu.au) BaSci (Exercise and Sport Science) – ECU Masters (Sports Administration) – Curtin Member (Australian Association for Exercise and Sport Science)
[1] Donatelle, R. J. (2006). Access to Health (9th ed.). San Fransisco, CA: Benjamin Cummings. Memmler, R. L., Cohen, B. J., & Wood, D. L. (1992). The Human Body in Health and Disease (7th ed.). Philidelphia: J. B. Lippincott Company. [3] Bowers, R. W., & Fox, E. L. (1992). Sports Physiology (3rd ed.): Wm. C. Brown Publishers.
[4] Donatelle, R. J. (2006). Access to Health (9th ed.). San Fransisco, CA: Benjamin Cummings.
[5] Martini, F. H. (2006). Fundamentals of Anatomy & Physiology (7th ed.): Pearson Education.
[6] Marieb, E. N. (2004). Human Anatomy & Physiology (6th ed.): Pearson Education.
[7] Memmler, R. L., Cohen, B. J., & Wood, D. L. (1992). The Human Body in Health and Disease (7th ed.). Philidelphia: J. B. Lippincott Company.
[8] Bowers, R. W., & Fox, E. L. (1992). Sports Physiology (3rd ed.): Wm. C. Brown Publishers.
[9] Brooks, G. A., Fahey, T. D., White, T. P., & Baldwin, K. M. (2000). Exercise Physiology. California: Mayfield Publishing Company.
[10] Convertino, V. A., Armstrong, L. E., & Coyle, E. F. (1996). American College of Sports Medicine Position Stand: Exercise and fuild replacement. Medicine and Science in Sports and Exercise, 28, i - vii.
[11] Sawka, M. N., & Coyle, E. F. (1999). Influence of body water and blood volume on thermoregulation and exercise performance in the heat. Exercise and Sport Science Review, 27, 167-218.
[12] Sawka, M. N., Latzka, W. A., & Matott, R. P. (1998). Hydration effects on temperature regulation. International Journal of Sports Medicine, 19, S108 - S110.
[13] Noakes, T. D. (2003a). Fluid replacement during marathon running. Clinical Journal of Sports Medicine, 13, 309-318.
[14] Noakes, T. D. (2003b). Overconsumption of fluids by athletes. British Medical Journal, 327(7407), 113-114.
[15] Noakes, T. D. (2004). Sodium ingestion and the prevention of hyponatraemia during execise. British Journal of Sports Medicine, 38, 790-792.
[16] Noakes, T. D. (2005). Can we trust rehydration research? In M. McNamee (Ed.), Philosophy and the sciences of exercise, health and sport: critical perspectives on research methods. (pp. 144-168). Oxford: Routledge.
[17] Laursen, P. B., Abbiss, C. R., Suriano, R., Quod, M. J., Lee, H., Nosaka, K., et al. (2005). Core temperature and hydration status during an Ironman triathlon. British Journal of Sports Medicine, 40, 320-325.
[18] Laursen, P. B., Abbiss, C. R., Suriano, R., Quod, M. J., Lee, H., Nosaka, K., et al. (2005). Core temperature and hydration status during an Ironman triathlon. British Journal of Sports Medicine, 40, 320-325.
[19] Convertino, V. A., Armstrong, L. E., & Coyle, E. F. (1996). American College of Sports Medicine Position Stand: Exercise and fuild replacement. Medicine and Science in Sports and Exercise, 28, i - vii.
[20] Casa, D. J., Armstrong, L. E., & Hillman, S. K. (2000). National Athletic Trainers' Association position statement: fluid replacement for athletes. Journal of Athlete Training, 35, 212-224.
Note: All sources of information, have been acknowledged.
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