Friday, August 12, 2011

Hydration Status? Are you dehydrated or over-hydrated?

Hydration Status? Are you dehydrated or over-hydrated?

In this blog post I represent myself as my client. It is important to understand the necessity of staying hydrated while competing or exercise to stay at your performance best. There is a lot of talk about drinking water when exercising in the heat. One thing that clearly is lacking in most new reports is some detail on how to determine your sweat rate. Does your sweat rate equal your water intake or are you sweating more water than you are consuming? Hopefully you will have a better understanding of sweat rate, water intake and electrolyte balance by the time you are finished reading this post.

Disclaimer: The results from this personal study are from 06-21-2011, but still are relevant today. However, the results might be different if the same methods were done today. At the time my client suffered an MCL sprain my client was informed by his physical therapist to refrain from moderate to intense exercise other than physical therapy and light cardio until 06-20-2011.


What is the first step in determining hydration status, and what should my daily intake of water be?

Prior to his exercise bout my client made sure to urinate prior to being weighed. He was also instructed to notice the color of his urine. I used the NATA's specific gravity color chart to determine the level of dehydration prior to exercise. His urine color was a light yellow, which would place him at  #4 on the NATA scale, just below well hydrated (Casa et al., 2000). It is important that all athletes start their training session well hydrated. Several studies recommend starting with 7-10oz of fluid at approximately 10-15 min prior to training is important, but it is important to maintain hydration throughout the day (Casa et al., 2000). Urinating prior to exercise and observing the color of the urine is a great and non-invasive method to determine hydration status (Silva et al., 2010). Studies have shown that there is a significant relationship between specific gravity (hydration status) and urine color, and that is why urine color was the method for determining pre-exercise hydration status (Maughan & Shirreffs, 2008). None of my sources were able to give a rational amount for daily intake, however, had a very useful formula to determine adequate intake. Here is the formula: 0.5 * body weight in lbs = required daily water intake in ounces. My client weighs 154 (0.5 * 154 = 77oz), so 77oz would be the required amount of fluids for daily intake. Since my client is athletic, though a little less right now due to injury, it would be important for him to consume approximately 8-10 oz of liquid every 15-20 min or the equivalent of weight loss during exercise, and beverages that have carbohydrates and electrolytes could promote better performance when the exercise bout is longer than 90 min or performed in extreme conditions (Maughan & Shirreffs, 2008; Casa et al., 2000; Montain, 2008; Silva et al., 2010). Also, my client is encouraged to replenish fluids based off of his weight loss from the exercise performed (Maughan & Shirreffs, 2008), so my client would be consuming more fluids than the average person. His weight was determined using a Detecto Standard Medical Scale. His weight prior to exercise was 154 lbs (70 kg) and 153 lbs (69.5 kg) after exercise. His weight was determined in the nude in a private weighing area before and nude after exercise making sure to towel off any sweat from his body as recommended (Maughan & Shirreffs, 2008).

Pre-exercise wt  in lbs - post-exercise wt in lb = weight lost during exercise 
154 - 153 = 1 lb
1 lb = 16 oz of water or fluid lost
Fluid lost in oz + Fluid consumed during exercise in oz = total fluid lost
16 oz + 16 oz = 32 oz

Sweat rate = total fluid lost / exercise time =  oz / 60min
Sweat Rate Calculation: 32 oz/50 min= X oz/60 min (remember cross multiplying?)
Sweat rate = 1920 / 50
Sweat rate = 38.4 oz per hour

% of body wt lost = post weight / pre weight
% of body wt lost = 153 / 154
% of body wt lost = 0.99 or 1%

He did a moderate exercise bout on a cycle ergometer for 40 minutes (pain tolerated) with a 10 minute stretching period afterward with a total exercise time of 50 min. He consumed 16 oz of water during the 50 minutes when desired and lost a total of 1 lb (0.45 kg) during the exercise time. He worked out in a climate controlled environment that was air conditioned and had fans strategically place throughout the facility. Using the provided formula my client lost 32 oz of fluid during exercise and has a sweat rate of 38.4 oz p/h. My client did not drink a beverage with carbohydrates or electrolytes, however, since the workout was less than an hour he did not feel that it was important to consume electrolytes or macronutrients during the exercise session (Sneli, Ward, Kandaswami, & Stohs, 2010). My client lost less than 1% of his body weight during his exercise session. According to the research provided his percent of body weight lost through exercise would not impair his performance. My client is a moderate sweater and it would be recommended that my client replenish 32 oz of liquid since water replacement should equal the amount of water lost from exercise (Shirreffs, Casa, & Cartter III, 2007) within an hour of exercising and to consume water throughout the remainder of the day. Drinking water or other non-caffeinated / low carbohydrate ratio liquids in increments throughout the day or training session would be more helpful in lowering gastrointestinal upset or discomfort, especially if a sports drink is consumed during activity (Shirreffs et al, 2007).
Hypothetically, my clients decides to spend the next 6 weeks in Miami Florida, and do all of the exercise outside between 8am and 12pm each day. How does this change his training or fluid intake? 


According to, in Miami, FL the average highs for the next six weeks will range from the upper 80s to the lower 90s with lows hanging around the mid 70s. The humidity for the area will range from 58% to 100% depending on the time of day and weather. My recommendations would remain for the most part similar based off research. There are some dangers with heat related illness that most people never experience when training indoors such as heat syncope, exhaustion and stroke. For this reason it would be important for my client to pay even closer attention to hydration. Fluid loss of up to 2% usually will not impair performance or increase the risk of fatigue (Maughan & Shirreff, 2008), however, exercise in high temperatures when combined with humidity can create some changes in mood, cognition and mental status even when dehydration is only at 1% (Shirreffs et al., 2007). Some other effects of dehydration or simple loss of fluids from exercising in the heat are changes in blood plasma volume, reduced coronary filling, increased heart rate to compensate for a decrease in stroke volume and core temperature increases (Sneli et al., 2010) Also, exercising in hot and humid environments can lead to over-hydrating from water alone and this can lead to  hyponatremia (low sodium levels in one’s plasma), for this reason a solution that has sodium, such as Gatorade, would be a viable source to maintain sodium levels over water (Montain, 2008). Adding a beverage that my client would enjoy, like Gatorade, would also encourage drinking therefore decreasing the risk of developing a heat related illness caused by dehydration. It would be advisable for my client to exercise as close to the 8 am marker to avoid exercising during the heat of the day.

Gatorade now markets Gatorade Endurance.  Powerade plans to bring a similar product to the market (it is currently available in some markets).  Is this just marketing hype, or is there actually a physiological benefit for active individuals to utilize these beverages compared to “traditional” Gatorade/Powerade/Cytomax/etc?


The nutritional facts:

Gatorade Endurance
Servings: 3      Serving size: 8 oz        Calories: 50     Carbohydrates: 14 g    Sodium: 200 mg          Potassium: 90 mg            Calcium: 6 mg             Magnesium: 3 mg

Gatorade Original
Servings: 4      Serving size: 8 oz        Calories: 50     Carbohydrates: 14 g    Sodium: 110 mg          Potassium: 30 mg

A study performed by Sneli et al., found that AdvoCare Rehydrate (a similar product to Gatorade Endurance, no study using Gatorade Endurance was available at the time) performed better than Original Gatorade when it came to time to exhaustion in cycle ergometer trials (Sneli et al., 2010). Like Gatorade Endurance, Rehydrate is made up of a blend of monosaccharides, sodium, potassium, calcium and magnesium with similar osmolities as to that of Gatorade Original (Sneli et al., 2010;, 06/21/2011). It is believed that the added potassium and sodium levels along with magnesium and calcium lead those subjects on Rehydrate to outperform those that hydrated with Gatorade Original, also there are two ingredients that Rehydrate has that Gatorade Endurance does not have and they are L-glutamin and L-arginine combined with a glucose-polymer which promotes the storage of CHO outside of the muscle tissue and enhances the abilities of pyruvate in gluconeogenesis (Sneli et al., 2010). Rehydrate was only compared to Gatorade Original, but the composition of electrolytes and monosaccharides were similar to that of Gatorade Endurance, so it is likely that Gatorade Endurance would outperform the Original in clinical trials. The price difference of Gatorade Original and Gatorade Performance is about $1 difference per bottle, so price might come into play. It should also be noted that Gatorade Endurance has one less serving per bottle when compared to the Original. Rehydrate is a powder that you mix with water and it has a significantly lower cost than Gatorade Endurance. I would suggest my client to experiment with Rehydrate to see if it truly holds up to the results of the study performed by Sneli et al. Sneli et al., did state that they did not receive any funding or support from Advocare (Sneli et al., 2010). It is clear that the added electrolytes in Gatorade Endurance or Rehydrate would help an ultra endurance athlete, but will most likely not be a benefit to an athlete workout <2 hours. For athletes working out 1 to 2 hours a normal sports beverage would suffice, and those working out 1 hour or less water is all you need to stay hydrated and maintain performance.                 


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. (2000). National athletic trainers' association position statement: Fluid replacement for athletes. Journal of Athletic Training, 35(2), 221-224

Maughan, R. J., & Shirreffs, S. M. (2008). Development of individual hydration strategies for athletes. International journal of sports nutrition and exercise metabolism, 18, 457-472.

Montain, S. J. (2008). Hydration recommendations for sport 2008. Current Sports Medicine Reports, 7(4), 187-192.

Silva, R. P., Mundel, T., Altoe, J. l., Saldanha, M. R., Ferreira, F. G., & Marins, J. C. B. (2010). Preexercise urine specific gravity and fluid intake during one-hour running in a thermoneutral environment - a randomized cross-over study. Journal of Sports and Medicine, 9, 464-471.

Shirreffs, S. M., Casa, D. J., & Carter III, R. C. (2007). Fluid needs for training and competition in athletes. Journal of Sports Science, 25(S1), S83-S91.

Sneli, P. G., Ward, R., Kandaswami, C., & Stohs, S. J. (2010). Camparitive effects of selected non-caffeinated rehydration sports drinks on short term performance following moderate dehydration. Journal of the International Society of Sports Nutrition, 7(28) 1-11.

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