As mentioned in the previous article, losing as little as 1 – 2% of your body mass can have a detrimental effect on your performance. Besides replenishing the fluid intake, we have to restore those electrolytes that are lost through sweat during our workout.
But wait, how do you know if you are dehydrated and how much water do you need to consume? One way to find out is to assess your hydration status. There are few methods available to assess hydration status. One of which includes urine specific gravity (USG), urine osmolality, and plasma osmolality (3). While these methods are accurate, it requires sending your urine sample to the laboratory for testing and analysis (which is impractical to do on a regular basis).
Thankfully, there is a much quicker and effective way to assess fluid loss and that would be to weigh yourself before and after your workout, then find the difference between your pre-workout bodyweight and post-workout bodyweight (2). Each 0.45kg (1 lb) of body weight loss is equivalents to 450 ml of water loss (4). A loss of 2% (or more) of body weight indicates that the individual is not hydrating themselves adequately. In addition, you can also check the color of your urine (refer to the chart below) to monitor your hydration level.
However, do take note that factors such as diet and medications can affect the color of the urine. For example, certain fruits such as beets, blackberries, food colorings (such as those found in some sports drinks), and medications can turn urine pink, red, light brown, and blue or green. Supplements such as B vitamins, carotenoids, and certain medications can turn urine dark yellow, bright yellow, or orange.
The best way to prevent dehydration is to avoid it from occurring. It is highly recommended to start exercising or training in a hydrated state, minimize water loss during exercise (less than 2% body weight loss) and rehydrate completely after exercise, before the next training session. As recommended, here are general guidelines on fluid intake as recommended by the American College of Sports Medicine (2007):
- Before training:
Hydrate yourself early! – If necessary, pre-hydrate at least 4 hours before exercise/ training (~5-7 ml/kg per body weight) to allow fluid absorption and for urine output to return to normal levels. Be mindful of signs such as thirst, body weight, urine color, and frequency of emptying the bladder.
- During training:
Don’t just drink water! – Consume beverages containing electrolytes (sodium and potassium) and carbohydrates (concentration of ~5 – 10 %) than just water alone. It helps to replace the electrolyte and energy losses during exercise. You can also get these components from non-fluid sources such as gels, energy bars, and other foods.
- After training:
Recover what you have lost! – Restore hydration and electrolyte losses through food and fluids. Consume approximately 1.5L of fluid (with electrolytes) for each kilogram of body weight loss if there is a significant loss of water or if there is a short recovery period before the next training (less than 12 hours). To maximize fluid retention, hydration should be done over time rather than drinking a large amount at once.
To learn more about hydration strategy and how you can managed your hydration before, during and after training, check out this article by thethoughtfuldietitian.
To ensure optimal performance, coaches should always make sure that athletes are given adequate time to drink and access cool fluids during training. Maintaining fluid balance during training and competition can be a challenge due to a wide variety of fluid and electrolytes losses among individuals. Therefore, it is recommended to monitor an individual’s fluid loss and intake on a regular basis to provide a better understanding of how your body regulates fluid. This allows an appropriate hydration strategy to be put in place. Fluid and electrolyte intake should be customized individually as much as possible and the general guidelines provided would be a good start to prevent excessive fluid loss.
References
1) Casa DJ, Armstrong LE, Hillman SK, et al. “National Athletic Trainers’ Association. Position statement: fluid replacement for athletes”. Journal of Athletic Training (2000).
2) Change in body mass accurately and reliably predicts change in body water after endurance exercise.
3) American College of Sports Medicine position stand-Exercise and Fluid Replacement (2007)
4) Exercise Physiology: Nutrition, Energy, and Human Performance By William D. McArdle, Frank I. Katch, Victor L. Katch – Page 78, “Water requirement in exercise”