Daily Hydration Needs For Athletes

BY Cindy Stonesmith

Coach Cindy Stonesmith tells us the importance of staying hydrated, explains how to calculate the amount of water you need, and gives some great tips on how to make sure you get it all in.

Most people think my job as a running endurance coach is to motivate my clients to complete their prescribed daily workout. However, I often find myself motivating my clients to take the time throughout the day to fully recover and be prepared for the next day’s training run. One of your first lines of defense for recovery is to hydrate properly throughout the day. 

The human brain is made of 70% fluid and the human body is made up of 60-70% fluid; one could say we are mostly made up of fluid. You can’t live two days without consuming some form of fluid. The need to balance the fluid in our body is a daily activity, one that is often over looked, even by athletes. On a rest day you’ll lose 1-3 liters of water due to insensible fluid loss, depending on your size, age, athletic ability, and gender, through respiration, renal filtration, and metabolic processes.

If you want to train and race to the best of your abilities, proper daily hydration is imperative. Researchers concur that with as little as a 3% fluid loss, athletic performance is hindered, pace decreases and perceived effort increases. In laymen’s terms…we bonk! This is not a new concept for athletes; you know you need to drink fluid during your races, but do you know how much fluid you need daily?

“With as little as a 3% fluid loss, athletic performance is hindered, pace decreases and perceived effort increases.”

A good rule of thumb for calculating how much fluid you need to replenish daily is to divide your body weight by 2.2 to get your weight in kilograms. Your weight in kilograms is how many ounces of fluid you need to consume daily. For example if you weigh 150lbs/2.2 = 68kg/body/wt. A 68kg person will need 68oz of daily fluid to replace what the body uses at rest.

Think that number is a lot to swallow? You’re not alone; most of us don’t come close to hydrating ourselves daily. Let’s look at some of the variables that help or hinder us from reaching a topped off tank for a fluid balanced state:Sleep: During sleep we can lose up to 0.5 liter of fluid. This happens through respiration, skin evaporation, and renal filtration. Many of us go to bed dehydrated and wake up even more so.


All liquids count in your daily fluid balance, but some are better than others.

  • Consuming a healthful diet high in fresh fruits and vegetables can provide up to 20% of your daily fluid needs.
  • Caffeinated drinks have a slight diuretic effect on your body. A cup of coffee or tea in the morning will count toward your total daily fluid but if you continue to reach for the coffee pot or caffeinated sodas throughout your day you’ll have a negative balance on your total hydration status.
  • Social beings we are, and where there is a party there is alcohol. Alcohol consumption has an undisputed dehydration effect. The more you consume the greater the net loss in total hydration. If you do find yourself having more than an occasional drink, consuming a glass of water for every alcoholic drink may offsetting the net fluid loss.


Many factors affect hydration status for athletes: ambient temperature (cold, heat, arid, humid), altitude, mode, intensity and duration of exercise, fitness level, size and gender to name a few. Due to all these variable sweat rate becomes an experiment of one. Research suggests an absorption rate of 12-25oz of fluid will fulfill most athletes’ hydration requirements in most conditions. drink water In order to calculate your individual absorption rate, weigh yourself pre and post activity to understand how your body reacts to these many variables. At TrainingPeaks, my athletes track their pre and post workout weight with the daily metrics data pod. For example: a 150lb athlete goes on an hour run. He runs a tempo run, at high altitude, with an ambient temperature of 80?F. While running he consumes 12oz of fluid. Post workout he weighs 149.5lbs, equaling a 0.5lb loss. The first line of defense for this athlete is to offset the 0.5loss by hydrating with 8oz post workout. For every 1lb loss post workout, an athlete needs to ingest 16oz of fluid. The 0.5lb loss during his workout also suggests that this athlete needs to increase his fluid intake during similar running to 20oz/hr.

So how much fluid does this 150lb athlete who runs an hour a day need?


68oz for daily metabolic replacement – 20% from diet high in fruits and vegetables + 12oz during 1hour workout + 8oz for a 0.5lb loss post workout = 81.2oz of daily fluid needs.

Getting it Consumed

It’s important to sip throughout the day, because ingesting a large amount of fluid over a short time will over activate the kidneys leaving you more dehydrated. In order to manage the total daily fluid needs during your day, divide total ounces into hours, i.e. 89.2oz/12hr = 7.4oz/hr. That’s less than a cup an hour, now that’s a number we can all ingest.

Follow these simple guidelines and you’ll find yourself well hydrated and ready mentally and physically for your next workout or race!

Reasons to Hydrate

  • To improve performance.
  • To promote dissipation of heat from working muscles.
  • To promote detoxification-flushing out bad toxin while bringing good nutrients into cells.
  • To keep joints and muscles lubricated and moving.
  • To promote mental clarity for training and race day.
  • To keep blood pressure in normal range.
  • To promote healthy digestive processes, makes you regular!

Tips to Increase Daily Hydration 

  • Take fluid on every run, and set your watch to remind you to drink every half mile.
  • Take a water bottle with you to work.
  • Eat fruits and vegetables that are laden with water, i.e. watermelon, oranges, and celery.
  • Drink a glass of water before and during every meal.
  • Fill a container full of water that matches your recommended daily fluid in the morning. Then calculate your success every evening.
  • Take a glass of water with you to bed and sip throughout the night.
Avatar1501767210 7
About Cindy Stonesmith

Cindy Stonesmith ACSM HFS, is a Running Endurance Coach with’Ultrarunner Training. You’ll find her – most days -training in the foothills of Boulder, Colorado.