As spring fades into summer and temperatures rise, we get a lot of questions from athletes about how much they should drink to stay hydrated. Hydration is a big topic for athletes and it’s crucial for athletic performance, so I’m going to break it down into several smaller, more digestible posts as part of a hydration series. This post helps you answer the question: how much do you need to drink?
Staying hydrated depends on a lot
The truth is, how much fluid you need to stay hydrated depends on numerous variables, including:
- ambient temperature
- sweat rate
- salt intake
- the phase of your menstrual cycle
8 Glasses of 8 oz…Total Myth
The recommendation to drink 8 glasses of 8 oz of water a day came from an old Japanese marking campaign to get people to buy more bottled water. There’s no biological basis for this number. While it’s not harmful, we can do better when it comes to more accurate hydration recommendations.
Can You Drink To Thirst?
It depends. Most people can get away with drinking to thirst during workouts of less than 2 hours. Ladies, if you are in the luteal phase of the menstrual cycle (2nd half of the cycle, the time between ovulation and your period) you likely can’t rely on thirst. Estrogen and progesterone affect the hypothalamus, the part of the brain that handles thirst, so we don’t feel as thirsty. Our hypothalamus responds to (up to 8%) lower plasma volume. Basically, we get more dehydrated before we start to feel thirsty. Older adults (over the age of 50) may have a harder time sensing thirst. If you’re a master, you might want to get a hydration plan in place rather than waiting to drink when you feel thirsty.
Generally, 0.10 oz/lb of body weight per hour in 75 degrees F or cooler is a good starting point. As I mentioned above, it depends on a lot so you’ll need to tailor this to your circumstances. If it’s warmer than 80 degrees F, 0.15 oz/lb should help maintain blood volume. Don’t exceed 25-27 oz of plain water per hour in a temperate environment, you’ll dilute your electrolytes.
Workouts Longer than 2 Hours
If your workout is over 2 hours long, aim for 0.08-0.16 oz/lb body weight/hour. Again, you will likely need to make adjustments, but this is a good starting point. Weigh yourself before and after your workout and drink 24 oz for every pound lost.
Hopefully, this clarifies how much to drink. Wondering what to look for in a sports drink, check out this blog post. Cheers!
Athletes need to individualize their hydration strategy based on several varialbes and environmental factors. Ambient temprature and workout duration are two key factors to consider in order to optimize hydration.
About Dr. A’nna
Dr. A’nna strives to inspire people to optimally fuel their body to achieve their best and have a positive impact on the world. She is the only combined Ph.D./RD specializing in sports performance nutrition in the world with all Ivy League degrees and the Chief Research Officer at AthleteBloodTest.
Dr. A’nna aims to cultivate a world of healthy athletes who understand nutrition and know how to leverage their physiology to get the best results in sports and life. You can reach her at [email protected] or on Instagram @drannaroby.