Basics to Staying Hydrated

By Paula Poh


Hi Gals! Are you drinking enough fluids after your workouts? Or even on a daily basis? Here are some quick and easy tips to assess your hydration throughout the day, and rehydrating after exercise.

By the time your brain, specifically the hypothalamus, signals to you that you’re thirsty, your body is already two percent dehydrated. So if you think about it, we’re already dehydrated by the time we’re thirsty, which can adversely affect your mood and energy (think “hangry” but for water). An easy way to assess your hydration is your urine output; a larger urine output means you’re well hydrated, while a smaller urine output means you’re dehydrated. Simple enough, right? Another way, that’s been scientifically tested and validated, is the urine color chart. If your urine color matches colors 1-4, you’re hydrated. If your urine color matches colors 5 and above, you should drink more fluids throughout the day (but don’t overdo it) and continue monitoring your urine color.  It’s important that you slowly increase your fluid intake versus chugging large volumes in one sitting. Not only is that uncomfortable, but can dilute the sodium in your blood, which can lead to nausea and headaches—medically referred to as hyponatremia.

Now that you have the tools to monitor your hydration on a daily basis, let’s shift our focus to hydrating, or rehydrating after exercise. Since you’re losing more fluid (i.e., sweat), you should be drinking more to minimize the risk of thermal injuries and impairments to your exercise performance. While water is a great before, during and after a workout, sometimes it may not be enough, and a sports drink is needed. The added carbohydrates in sports drinks help maintain blood glucose concentration and delay the onset of fatigue, while the addition of electrolytes (i.e., salt) enhances palatability and reduce the chances of hyponatremia. Here are four instances when you should opt for a sports drink:

  1. Workouts more than 60 min (e.g., half/full marathon, triathlon); workouts less than 60 min, water is fine
  2. Continuous exercise utilizing your fast twitch muscles (e.g., sprints, plyometrics)
  3. Having a pre-existing carbohydrate deficiency (e.g., being on a low-carb diet)
  4. Having a pre-existing sodium deficiency; highly unlikely due to the heavy amount of sodium in our foods #murica

To ensure that we are taking care of our body post-workout and in preparation for our upcoming workout, fluid replacement should be equivalent to fluid loss (i.e., sweat). So how can we determine how much fluid we’re losing from a workout? I hope you like math! Grab a scale and calculator, and we’ll find out!

  1. Weigh yourself pre-workout in kilograms (kg)
    • To convert pounds (lb) to kg, divide by 2.2 (example: 150lb/2.2 = 68.2kg)
    • For the most accurate calculation it’s best to be nude (to reduce the weight of sweat trapped in clothes)
    • But if you prefer to stay clothed, just take note of what you’re wearing
  2. Work out for at least one hour at a moderate intensity
    • If you drink or use the restroom during your workout, estimate the amount of fluid consumed/voided in milliliters (to make the math easier, it’s best to not drink or pee during this workout)
    • Use the “talk test” to determine if your workout is at the right intensity: for moderate intensity, you should be able to carry a conversation, but you can’t sing. Try to stick with a cardio-type workout (e.g., rowing, spinning)
  3. Weigh yourself post-workout in kg
    • Make sure to weigh yourself in the same condition (e.g., nude, fully-clothed) as you did for your pre-workout weight
  4. Calculate!

__________________   ­              __________________ =                __________________

Pre-workout weight (kg)               Post-workout weight (kg)             Weight change (kg)

__________________ * 1000 =                  __________________

Weight change (kg)                                         Weight change (g)

______________+          ______________ -          ______________ =                    _____________

Weight change (g)           Fluid intake (mL)              Urine output (mL)                         Total (mL)

_____________ /            _____________ =            _____________

Total (mL)                           Exercise time (h)              Amount of fluid loss per hour of exercise (mL/h)

Convertino et al. (1996) ACSM: Position stand on exercise and fluid replacement.