Every summer and early into football season when the Texas temperature is beyond cantankerous, we hear about athletes getting hyperthermia and worse, life threatening heat stroke. Ideally, nobody would be exercising after 8:00 AM, because it’s just too hot and humid. Realistically, athletes are out at all times of the day.
There’s no denying that a serious shortage of fluids can cause problems. Research over the past 30 years suggest that the body’s temperature-regulating mechanism is affected even at one – two percent dehydration. For a 150-pound man, that would mean losing no more than 3 pounds of fluid (and ideally, much less) during a workout. When fluid loss jumps up to 6 – 8% of body weight, the athlete is in big trouble. One way to make sure the athlete does not succumb to the blistering heat, is to make sure he/she stays hydrated or at least does not loss too much fluid.
Warning signs of Excess Loss of Fluids
The primary reasons for a football player to overheat on the field are intensity and duration of practice, the environment, and the uniform. Parents, players, and coaches should all be aware of the warning signs and symptoms of dehydration and heat illness:
- Headache and dizziness
- Muscle cramping and unusual fatigue
- Nausea and/or vomiting
- Confusion and change in personality
Athletes should weigh each day before and after practice and weight charts checked. Generally a three percent weight loss through sweating is considered safe and over a three percent weight loss is in the danger zone. Over a three percent weight loss the athlete should not be allowed to practice in hot and humid condition until they have adequately replaced their weight.
Recommendations for fluid replacement have changed recently which has led to some confusion. Emphasis to drink while exercising can lead to another dangerous situation called hypo-hydration (overhydration and a diluting of blood-sodium levels). In our heat, you would really have to be guzzling the liquids in order to take in fluids faster than losing fluids but it can happen and it is life-threatening. Fluid replacement drinks containing electrolytes may help delay the development of hyponatremia, because the sodium in such drinks can assist in maintaining healthy blood sodium levels. One way to make sure the athlete gets the proper amount of fluids is to know sweat rate.
Know Sweat Rate
The most accurate method for determining personal fluid needs is to take the sweat-rate test, which will help the athlete and coach develop an individualized strategy for fluid replacement.
1) Weigh nude right before a workout.
2) Practice for one-hour, keeping track of how much fluid is consumed (in ounces) during the training session.
3) After the workout, strip down, towel off any sweat, and weigh nude again.
4) Subtract post-weight from your pre-weight and convert to ounces. Then add to that number however many ounces of liquid consumed during practice. (For example, if a pound was lost and 16 ounces of fluid was consumed, the fluid loss is 32 ounces.)
5) To determine how much to drink about every 15 minutes, divide hourly fluid loss by 4 (in the above example it would be 8 ounces).
6) Because the test only determines sweat losses for the environmental conditions that day, retesting on another day, when conditions are different is important for accuracy. The test should also be done during different seasons, because the environments will be different.