Y.E.S. News

Sodium, Muscle Cramps and Sweat Losses

Over-hydration can be as dangerous to your health as under-hydration. So what does an athlete need to know about staying adequately hydrated?

According to Dr. Noakes, the sports drink industry has effectively marketed an overhyped product (salted sugar-water). Noakes believes that the sports drink industry has brainwashed athletes to overhydrate and this has created life-threatening problems. For example, between 1983 and 1998, more than 700 cases of exercise-induced hyponatremia (over-hydration that leads to low blood sodium, brain swelling, coma and even death) were documented in the Gatorade-sponsored Ironman Hawaii Triathlon.  Participants had been encouraged to drink copiously. Did that advice backfire?

Below are a few droplets of hydration information to help you quench your thirst, perform well, and stay out of the medical tent when you are doing extended exercise in hot weather.

  • Our bodies can deal with transient under-hydration that lasts from 4 to 8 hours. In contrast, chronic dehydration leads to health issues such as what happens when elderly people are trapped in hot apartments during a heat wave. Also, Reductions in fluids cause nerve endings to be squished together, overexcited, and spontaneously discharge. That spontaneous discharge is a muscle twitch, which can lead to a muscle cramp.
  • Most athletes feel thirsty at about 2% dehydration. At that point, they will start looking for water. Ultra-runners can maintain performance at 3% dehydration. (To determine your percent dehydration, weigh yourself naked before and after your workout. A one-pound drop equates to a loss of 16-ounces of sweat; 2% dehydration equates to a 3 pound sweat loss for a 150-lbs. person).
  • Thirst is a powerful fluid regulator. Noakes disapproves of the advice to drink before your are thirsty because that can create problems with over-hydration. Yet, others contend drinking on a schedule can help endurance athletes maintain proper hydration, as long as they do not aggressively overhydrate but rather replace fluids according to their sweat losses.
  • Exercise-induced hyponatremia (low blood sodium) occurs when athletes drink excessively during prolonged exercise. It can also occur when dehydrated endurance athletes lose significant amounts of sodium in sweat. Muscle cramps may occur when the concentration of sodium in the blood decreases; cramps can progress to a serious medical emergency when hyponatremia is not treated.
  • The amount of sodium lost in sweat varies from person to person. Some people are salty sweaters. Athletes accustomed to exercising in the heat retain more sodium than unacclimatized athletes.
  • Athletes lose relatively more water than sodium, so under standard conditions, the blood sodium level can actually increase during exercise; unless you overhydrate. But with abnormally high sodium losses, such as during an ultra-marathon, blood sodium can be low even in a dehydrated athlete. Hence, sodium replacement can be a wise idea.
  • The amount of sodium in a sports drink is small and unable to counter the dilution of body fluids that occurs with over-drinking. The 220 mg of sodium in 16 ounces of Gatorade is far less than the approximately 1000 mg sodium in 16 ounces of sweat loss.
  • Noakes says evidence is lacking to prove that athletes who cramp have low serum sodium or are more dehydrated than non-crampers. He suggests muscle cramps are related to fatigue, not sodium deficiency. If sodium deficiency was the problem, wouldn’t the entire body cramp, not just one muscle?
  • Exercise induced muscle cramps occur in muscles that perform repetitive contractions. Athletes who get cramps tend to be those who do high intensity exercise, as well as those who have a history of cramping. The science of camping lacks a clear consensus!
  • Stopping exercise to stretch resolves muscles cramping most of the time. (Stretching also resolves nocturnal cramps).
  • An athlete who collapses after the finish line is most likely experiencing blood pressure changes, not severe dehydration. When exercise stops, the heart stops pumping enough blood to the brain; the athlete collapses. It is advised to raise the athlete’s feet and pelvis above the level of the heart. This aids in the return of blood to the heart and rapidly corrects the situation without any IV fluid.
  • There is a finite amount of carbohydrate stored as glycogen in our muscles to provide the energy to exercise. When there isn’t adequate fuel circulating yet we continue to exercise and contract our muscles, muscle relaxation is impaired, and a cramp occurs.

So what is a sweaty endurance athlete supposed to do during prolonged exercise? Learn your sweat rate, drink accordingly and train appropriately. Acclimate yourself to the environment. Consume the right amount of fluids for your body to prevent dehydration. Consume salty foods such as salty pretzels, pickles or ham-cheese-mustard wrap to provide needed electrolytes. Prevent carbohydrate depletion by consuming carbohydrates before your workout. Just do not get too aggressive with water or sodium intake and have fun!

Resource: AAHF



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