Sweat, sodium, and scales…


I asked a friend of mine, Beth Gabhart, an accomplished triathlete and nutritional guru to let me re-post this article she wrote regarding sodium and knowing how much you need to accomplish or endurance goals.  This has been a particular issue for myself over the last couple years of training and racing.  I think it spells out very well.


Sweat, Sodium and Scales……
To start, let’s clarify sodium and salt. Sodium is an electrolyte needed by the body for vital functions. Salt is a carrier of sodium, but sodium is added in other products such as sport gels and drinks. How the levels of sodium can vary: To consume 1 gram (1000mg) of sodium, you would need to drink more than half a gallon (2.18 liters) of Gatorade. To get 1 gram of sodium from table salt, you’d need 2.5 grams that includes 1.5 grams of chloride. A teaspoon of table salt is around 6.6 grams.
Balance sodium levels are important for endurance athletes is due to the impact of long training sessions on sodium loss. It’s increasingly important during hot weather due to increased sodium loss through sweat as the body attempts to cool itself. Being knowledgeable of your sweat rate is an important metric to calculate, especially if you plan on racing during the summer months. Our rates can be influenced by hormones, gender, weight, medications, hydration and other factors. Every “body” is different. For example, seasoned and heat acclimated triathletes usually have less than 900mg of sodium per liter of sweat. In recreational or un-acclimated athletes, the sweat rate is typically higher, but some highly trained triathletes can have “salty sweat” as high as 1400mg per liter. If these individuals also have a high sweat rate, they can have significant sodium loss during long training sessions or events. Sodium losses in lab studies range from 450-1800mg per liter of sweat. This reflects how individualized our needs are.
Sodium concentration in the body has several life-sustaining functions and its blood levels are kept in close check by the body through various means. If the body is unable to compensate for an imbalance, that’s when bodily functions can deteriorate and even death can occur. Imbalances are defined as hyponatremia (low sodium concentrations) and hypernatremia (too much sodium). It’s very difficult to induce hypernatremia because the body has safety mechanisms (hormones, adjustment of other electrolytes, kidney function) and even our taste buds help by curb intake by their “salty” sensors. Ingesting too much salt can cause GI disturbances, so we need to have an idea on how much we have lost and focus on replacing it. If we don’t address the imbalance known as hyponatremia, the risks are much higher as is evidenced in the chart below. The lower the blood levels, the more dangerous it becomes:

Blood Sodium Levels Symptoms:
136-142 mmol/L Normal levels
125-135 mmol/L No obvious symptoms or mild gastrointestinal upset such as bloating and nausea
Below 125 mmol/L Symptoms are more severe including headache, vomiting, wheezing, swollen hands and feet, unusual fatigue, confusion, and disorientation
Below 120 mmol/L Seizure, coma, brain swelling with brain damage and death are more likely

Estimating sweat losses: This simple formula can estimate sweat losses in hot weather season. Urine losses affect this equation, as would weight gain from solid foods consumed. Your goal is to at least replace losses, but also to stay a little ahead of the game .
⦁ Weigh yourself before and after training often so that you can better calculate approximate weight loss and plan how much fluid to have ready. Remember, it’s almost impossible to catch up once behind on fluid intake, so assume you will have at least a 1-2 lb. loss in moderately intense training workouts lasting longer than an hour or if heat or humidity is present. Here’s an example of the equation:
-165 lb. (pre-workout) to 162 lb. (post-workout)= 3 lbs. weight loss during training
⦁ Know the amount of fluid that you consumed during the training session. 30 oz. of fluid weighs 2 pounds.
-Consume 60 oz. (1800 ml) of fluid during a 3-hour bike ride. This fluid weighs 4 lb.
⦁ Add the answers in 1 & 2.
-3 lb. + 4 lb. = 7 lb.
⦁ 7 lb. equals 105 oz. fluid divided by 3 hours = 35 oz. per hour for sweat losses.
⦁ Remember to count your solid food intake. You may think that your fluid loss is less if you don’t take this into consideration. Therefore, you will be under in your estimated fluid replacement needs.
Here’s another chart that explains the role of other electrolytes that are important to athletes, but may not get the attention of the more relevant ones that are discussed more often. A well balanced diet should give you what you need, but endurance athletes may need additional supplementation. If your diet is lacking, a multivitamin may be needed to ensure more balance.

Sweat chart1

Knowing your fluid losses and electrolyte needs are just as important as other metrics (power, watts, pace, etc.). Sport drinks, gels and other electrolyte or fluid replacement products can vary. So, tailoring your needs according to personal fluid losses, type of sport and how long the event or training is can impact what you may need.

Sweat chart2


Sweat chart

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