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The Importance of HYDRATION

The Importance of HYDRATION. By Robert Robergs, Ph.D. , FASEP, EPC Exercise Physiology Laboratories Exercise Science Program Dep’t Physical Performance and Development The University of New Mexico. How Much Water is in the Body?. Total body mass. 100 %. 60 %.

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The Importance of HYDRATION

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  1. The Importance of HYDRATION By Robert Robergs, Ph.D., FASEP, EPC Exercise Physiology Laboratories Exercise Science Program Dep’t Physical Performance and Development The University of New Mexico

  2. How Much Water is in the Body? Total body mass 100 % 60 %

  3. How Much Water is Needed by the Body? INTAKE OUTPUT Metabolism 10% Sweat 8% 200 mL 250 mL Feces 4% Moist Foods 30% Skin and Lungs 28% 750 mL 700 mL 2500 mL Beverages = 60% 1500 mL 1500 mL Urine 60%

  4. Exercise or a Hot or Humid Environment? Normal OUTPUT Heat 8 L Sweat 200 mL Feces 700 mL Skin & Lungs 11.5 L 2.5 L 3 L 1500 mL Urine 500 mL

  5. Where is the Water Located? From Where is it Lost? Blood ~ 2.75 L Loss (%) Between Cells For ~ 4% dehydration ~ 12 L 50 40 Cells ~ 35 L Between Cells Cells 10 Blood Costill & Fink, 1976.

  6. Dehydration is quantified by the amount of body weight lost. For example Pre-exercise weight = 70.0 kg Post-exercise weight = 68.5 kg Weight Loss = 1.5 kg (1.5 / 70 ) x 100 = 2.1 %

  7. Heat Stroke Heat Exhaustion

  8. PROBLEM #1 It is very difficult to prevent a significant dehydration ~1200 mL/hr

  9. PROBLEM #2 It is very difficult to regulate the kidneys to maintain hydration GFR = 120 L/day ~ 99% of this water is reabsorbed For most beverages, increasing fluid ingestion causes a decreased effectiveness of water reabsorption

  10. Can Pre-exercise Hydration Be Increased? YES Robergs & Griffin. Sports Med. 26(3):145-167, 1998 ~ 400 – 700 mL

  11. How Does Glycerol Work? 1. Glycerol hyper-hydration is accompanied by a decrease in urine volume

  12. Recent Research (in-review) from Our Laboratory Study 1 • Compared, • Distilled water (DW) • 100 mEq/L NaCl (80 mEq), KCl (20 mEq) solution (EL) • Gatorade (CHO-EL) • Glycerol hyper-hydration (1.2 g/kg glycerol bolus + 26 mL/kg water) (GBol) • Glycerol solution (5.75 g glycerol/100 mL = 5.75 % glycerol) (GSol) • d + e (GG)

  13. Male Female Weight (kg) LBM (kg) BodyFat (%) 9 3 73.212.8 62.511.2 14.27.8 Subjects and Methods DW, EL, CHO-EL, GSol = 4.0, 6.4, 5.2, 5.2, and 5.2 mL/kg GBol = 40% glycerol, 6.4, 5.2, 5.2, and 5.2 mL/kg DW GG = 40% glycerol, 6.4, 5.2, 5.2, and 5.2 mL/kg GSol

  14. Results • Will be presented as two studies: • Comparing methods of glycerol ingestion to CHO-EL. • Comparing glycerol solution (Gsol) to EL, CHO-EL and DW

  15. Symptoms

  16. Osmolal Clearance

  17. Osmolal Clearance

  18. Free Water Clearance

  19. Free Water Clearance

  20. Change in Body Water

  21. Change in Body Water

  22. What we recommend to athletes: 4-5% (grams/100 mL) glycerol, 4 % CHO, 4 mEq/L Na+ and K+ eg: glycerol = 1.25 g/mL 1 L of 5% glycerol solution 50 g or 40 mL of glycerol, and add half strength Gatorade to equal 1 L Drink prior to exercise (1 to 2 L over 2 hrs) Drink as needed during exercise

  23. Thank you

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