How To Know How Much To Hydrate

Did you miss Part 1 of this series, 7 Things to Know About Summer Exercise? If so, catch up here.

You may have heard the saying “drink to thirst”, is that really all it takes to stay hydrated? The short answer, yes. Unless you are an elite athlete performing ultramarathons or Ironman triathlons your body will guide you. Yet, sometimes preparing for a race everyone needs to be in the know to plan ahead.

Hydration is key to defend off hyperthermia, the body’s inability to cool itself. Dehydration leads to a multitude of cardiovascular complications including poor blood pressure regulation, increased strain on the heart and decreased capacity to exercise in the heat.

Do you know how to tell if you’re dehydrated? If you weigh yourself before and after exercise, it should vary less than 2% of your body weight. That is equivalent to roughly 2lbs for a 120lb individual or 4lbs for a 200lb person.

Is drinking water while exercising enough? It depends on the duration of exercise. For peak performance, athletes need to begin pre-exercise hydration days before. Within 2-3 days prior to an event and 2-3 hours prior to performance time water should be consumed to prevent muscle cramping from dehydration. Follow the chart below to see how much you should be consuming:



120 LBS                                                      5-6 oz

150 LBS                                                      6-7 oz

180 LBS                                                      8 oz

200 LBS                                                     9 oz

225 LBS                                                      10 oz


There is a lot of talk about electrolytes in regard to sports and exercise. What does the research say? Studies show sodium is the primary electrolyte lost. If an exercise session or event lasts more than 1 hour, athletes should consume a solution containing 0.5-0.7g of sodium per liter of water. If muscle cramping occurs, it should be increased to 1.5g sodium per liter of water.

Replenishing sodium can be achieved through food sources as well. If exercising for prolonged duration, 30-60g of carbohydrates should be consumed per hour. When the exercise session lasts greater than 2.5 hours, 90 g/hr of carbohydrates are necessary.

Fueling with food is also important, I cover that in-depth here if needed.

Endurance athletes benefit from consuming carbohydrates within 1 hour after exercise to ensure the highest rate of glycogen re-synthesis. Research shows the best drink post exercise contains 4:1 ratio of carbohydrates to protein. Chocolate milk is a great option.

So yes, drinking to thirst will allow you to perform. If you want to perform at your peak and avoid muscle cramping and cardiovascular effects, make hydration a priority following the guidelines above.

Good luck being the best you can. See you out there.


Dr. Shari

Orthopedic Physical Therapist

Exercise Scientist




Nielson et al 1993: Exercising daily at 60% VO2max in hot conditions for 9-12 consecutive days increases exercise capacity from 48 min to 80 min; elite athletes can adapt quicker

Houmard et al 1990: magnitude of adaptation depends on intensity, duration, frequency, number of heat exposures