Friday, August 5, 2011

Hydration & Heat


Heat related illnesses are amongst one of the highest related causes of sports injury, illness and sometimes death. Summer can be an exceptionally hot period for both indoor and outdoor active individuals and athletes. So far during the summer of 2011 several high school players and coaches have either died from or experienced the symptoms of heat related illnesses caused from a deadly combination of dehydration and heat. Educating yourself is the first step, but you also have to learn how to listen to your body. 
·         Some physiological responses associated with dehydrated:
o   Increased heart rate & blood thickness causing an increase in the heart’s work load / An increase in muscle glycogen (sugar) usage leading to a decrease in energy for exercise and increased muscle cramping / Decrease in exercise capacity & performance leading to a shortened workout or even premature exercise exhaustion / Increased core temperature leading to excessive sweating and eventual sweat cessation (depleting the body’s natural ability to cool itself) / Decreased blood flow to organs and brain eventually leading to a systematic shut down / Increased injury risk due to lack of concentration

Signs and Symptoms (S/S), prevention and treatment of Common Heat Related Illnesses

o   Heat Syncope (Fainting)
§  S/S - Dizziness / Nausea / Fainting
§  Treatment - Lay down in a cool place with shade or go into an air conditioned building / Replace fluids
§  Prevention - Acclimatize to the heat (Acclimation may take as long as 10 days) / Begin exercise adequately hydrated

o   Exertional Heat Cramps
§  S/S - Muscle twitching and cramps / Usually the cramps are painful and occur in the legs, arms, or abdomen
§  Treatment - Ingest fluids with sodium and other electrolytes / Stretching / Ice massage the affected muscle
§  Prevention - Acclimatize to the heat / Drink adequate amounts of water prior to and during exercise / increase (calcium, sodium & potassium) electrolyte intakes

o   Exertional Heat Exhaustion
§  S/S - Excessive thirst, dry tongue and mouth / Fatigue and weakness / Mental dullness and incoordination / Elevated body temperature no higher than 103°F (temperature may appear normal or even low) / Profuse sweating and pale clammy skin
§  Treatment (may turn into a 911 emergency) - Rest in a cool room /Fluid replacement /Increase fluid intake to 6 to 8 l/d and keep a hydration journal / Keep record of pre and post exercise weight / IV if individual is unable to keep fluids down
§  Prevention - Drink adequate liquids prior to exercise /Allow for rest and cooling in between exercise sessions / Become acclimated to the heat before becoming a sports hero

o   Exertional Heatstroke
§  S/S - Headache, vertigo, and fatigue / Little to no sweating with flushed red skin / Rapid pulse rate and respiration / temperature ≥104°F / sensation of burning up / diarrhea and/or vomiting / physical collapse
§  Treatment - 911 emergency / sponge the body down with icy cold water or submerge in an ice bath / fan body / ice massage
§  Prevention - Drink adequate liquids prior to exercise /Allow for rest and cooling in between exercise sessions / Become acclimated to the heat before becoming a sports hero / educate athletes and active individuals about heat illness

o   Exertional hyponatremia (water poisoning or low sodium levels)
§  S/S - Progressively worsening headache, nausea and vomiting / swelling in the hands / lethargy or apathy / disorientation or lack of coordination
§  Treatment - 911 emergency / sodium levels must be increased and fluid levels decreased
§  Prevention - Hydration with sports drinks / fluid loss should = fluid intake / increase sodium intake

·         Hydration strategies
o   Pre- exercise hydration
§  Drink approximately 17 to 20 oz of water 2 hours before exercise and 8 to 10 oz of water or a sports drink (not an energy drink) 10-20 min before exercise
§  Weigh yourself before exercise

o   During exercise hydration
§  Consume 7 to 10 oz of water or sports drink every 10-20 min
§  Use a clear water bottle with volume measurements so you can see your water consumption
§  Water should be the beverage of choice for those exercising ≤ 1 hour, but those exercising ≥ 1 hour might want to supplement water or with a sports drink (no higher than an 8% concentration of carbohydrate) for extra energy and electrolytes
§ Over hydrating is just as dangerous as under hydrating – see exertional hyponatremia

o   Post-exercise
§  Weigh yourself / Subtract your post-weight from your pre-weight
§  1 lb of weight loss = 16 oz of water loss (3 lbs = 48 oz) / Replace your lost body weight in water within a two hour window.

Proper hydration is full of scientific formulas when done in the research facilities. But at the gym, field or court it is not so cut and dry. Remember, the moment you are thirsty you are already becoming dehydrated. Is not uncommon for athletes and active individuals to lose 2% of their body weight during exercise. Losing more than 2% can become detrimental to health and performance. There is better gastric emptying when larger quantities are consumed, so sipping is not necessarily better than drinking larger quantities. Prepare for your events; if you know that your next event will be somewhere that experiences extreme heat then train in the heat to acclimate yourself to those conditions. But play it smart, start out small with your outdoor exercise plan before going full force.

Please visit: Science of NFL Football: Nutrition, Hydration & Health to learn a little more about hydration and sports in the extreme heat. 

Casa, D. J., Armstrong, L. E., Hillman, S. K., Montain, S. J., Reiff, R. V., Rich, B. S. E., Roberts, W. O., & Stone, J. A. National athletic trainers' association position statement: Fluid replacement for athletes. Journal of Athletic Training, 35(2), 212-224.
Manore, M. M., Meyer, N. L., & Thompson, J. (2009). Fluid and electrolyte balance. Sports nutrition for health and performance (2nd ed., Chap. 8). Champaign, IL: Human Kinetics.
Prentice, W. E. (2010). Understanding the potential dangers of adverse environmental conditions. Essential of athletic injury (8th ed., Chap. 9). New York, NY: McGraw-Hill. 

Science 360. (2011). Science of NFL Football: Nutrition, Hydration, and Health. Retrieved from the Science 360 website at: 
Shirrefs, S. M. (2001). Restoration of fluid and electrolyte balance after exercise. Canadian Journal of Applied Physiology, 26(s), S228-S235.

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