Does Dehydration Impair Exercise Performance? - She Runs Eats Performs

Episode 46

Published on:

11th Mar 2021

Does Dehydration Impair Exercise Performance?

Does Dehydration Impair Exercise Performance?

Do you pay attention to your fluid intake? Do you find you sometimes forget to drink? Have you ever thought about what impact your hydration levels may have on your running performance?

 In this episode we explore all these questions and more. We delve into the scientific research to gain an understanding of the current thinking around hydration and exercise performance as well as consider the impact of poor hydration on exercise performance.   

 We also endeavour to help you understand WHY appropriate hydration (euhydration) is important for YOUR running performance and give you lots of hints and tips on how to ensure you are getting adequate fluids into your daily routine 

Show Notes


Outlining the current scientific thinking and research on hydration and exercise performance. Looking at study methodology and its limitations and how scientists are trying to overcome these difficulties. 

Moving on to consider “Involuntary Dehydration” and how easy an athlete could become overtly dehydrated over a short period of time.  


Giving you an understanding of normal fluid regulation within the body so you better understand how dehydration could occur so easily e.g. did you know that water is the most abundant molecule in the body making up between 45% and 70% body mass and is very tightly regulated. 


Discussing some of the health outcomes from severe dehydration whilst also pointing out some key symptoms to observe for which may suggest underhydration e.g. thirst, dark urine, dry lips, mouth, and eyes, and dizziness.


Delving into the impact of hydration status on exercise performance and introducing the condition called hypertonic hypovolemia ie intracellular dehydration. Moving on to discuss the physiological impact of dehydration including: reduced muscle function, increased cardiovascular strain and increase of core body temperature.  


Introducing a new debate in the Sports Nutrition world: drinking to thirst versus planned drinking, We give you our thoughts on this. 


Introducing the Female Factors

  1. There are no differences in effects of dehydration between men and women. 
  2. There no studies that I am aware of looking at women compared to men and the few female only studies carried out show similar results to men.
  3. In general, women have a lower body water percentage than men. This is thought to be due to the fact that women have more tissue than men. 
  4. The ideal water percentage for adult women will fluctuate between 45 and 60%, while the ideal percentage for adult men will be between 50 and 65% of the total body. 


Outlining some hints and tips to introduce to ensure you are appropriately hydrated on a daily basis AND for your running training. Some ideas include: Remembering to drink fluids before, during and after your run, use a camelback if you like to remain hands free, set a reminder on your phone to drink regularly. 


Key Takeaways:

1) Hydration is a limiting factor in exercise performance – so could make the difference between you winning or losing in reaching YOUR goals.

2) The current research on hydration status is conflicting regarding how dehydrated an individual needs to be for performance to be impaired

3) Our recommendation would be to remain EUHYDRATED – so appropriately hydrated on a day to day basis

4) Ensure you drink BEFORE, DURING and AFTER training so you do not go into your next training session already in a hypohydrated state.

5) Remember that although the degree of dehydration linked to performance effects is uncertain, it is known that more than 5% dehydration causes cognitive dysfunction and as much as 15% can lead to circulatory failure and death…..but this is extreme.

6) Be on the lookout for any symptoms that may suggest you are poorly hydrated including:

  • feeling thirsty.
  • dark yellow and strong-smelling urine.
  • feeling dizzy or lightheaded.
  • …………..But there are many others.

7) There are many factors that will determine how much fluid YOU require on a daily basis….a one size does not fit all.

8) Finally, PLAN your fluid intake for your training AND your everyday hydration using our tips as your guide to ensure that hydration does not become the limiting factor in your running performance.

Related Episodes:

Ep1 Sports Nutrition Foundations For Female Runners

Ep5 Hydration And Running Performance


The suggestions we make during this episode are for guidance and

advice only, and are not a substitute for medical advice or treatment.

If you have any concerns regarding your health, please contact

your healthcare professional for advice as soon as possible.

Aileen Smith and Karen Campbell met at as nutrition students (Institute for Optimum Nutrition, London) and became lifelong friends and nutritional buddies! Both have a love of running and a passion for nutrition, delicious food and healthy living.

Together they host RUNNERS HEALTH HUB. A place for like-minded runners who are looking for simple ways to support running performance, energy, endurance, and general great health.

We are excited to be able to share our expertise, experience and short cuts with you. We hope you'll join us again. If you'd like to know more about us and She Runs Eats Performs please check out our TRAILER.

If you're ready to make learn more about how you may introduce easy nutrition into your running and training plan join our Easy Nutrition For Healthy Runners Online Programme for short videos, recipes, downloads and LIVE training and Q&A.

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Happy Running!

Aileen and Karen 




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About the Podcast

She Runs Eats Performs
for mid-life female runners of all abilities
Are you confused about the science around nutrition for runners? Listen in to learn about the WHY, HOW, WHAT, and WHEN of eating to fuel your running performance.

We are here to help you translate sports nutritional science, into easy to apply tips and plans, helping you enjoy peak running performance. We focus on the FEMALE FACTORS every mid-life woman needs to know to be a healthy runner.

About your host

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Aileen Smith

Nutritionists, Educators, Podcasters, Runners and Friends

We have a love of running and a passion for nutrition, delicious food and healthy living. She Runs Eats Performs for female runners of all abilities who are looking for simple ways to improve their running performance and their health with nutrition and lifestyle.
We enjoy sharing our nutritional expertise, reviewing the latest sports science and most of all helping you to take easy action so you can enjoy your running life to the full.
We are here to help you achieve great health and good shape whilst staying injury-free with easy-to-understand sports nutritional concepts and easy-to-implement tips and plans.

Aileen and Karen are BANT and CNHC Registered Nutritional Therapists.