Fluid loss, or dehydration due to activity happens daily in all of us and without replacing that loss – your entire body can be affected. The idea that dehydration can affect you physical and cognitive performance has been around for an age, but since then there has been a lot of research done to figure out how.
Since a study by et al in 1955 showed a decrease in VO2max with dehydration, a number of studies have been done to follow up on this and various other ways dehydration affects performance.
Dehydration can and often is induced by exercise, but there are a lot of other variables which come into play including:
- Type of exercise or physical activity
- Temperature and humidity
- Nutrition and hydration levels before activity
Given all the various studies that looked all the things that dehydration can impair, a recent study(1) has critically analysed the current literature and this is what they found:
- Dehydration caused a decrease in aerobic performance which can be generalised to all physical activity that lasts for more than 15 seconds
- Exercising with restricted hydration caused decreased performance, increased heart rate and increased core body temperature
- There were no changes in performance for exercise that lasted less than 15 seconds such as the vertical jump test. (this is because a different energy system is used for intense exercise less than 15 seconds that does not need water – the alactic component)
That, in a nutshell, is the current research on how hydration affects performance and the main thing to take from it is that, yes, it does affect performance (unless you are a 100m sprinter maybe) and you should do your best to be hydrated before exercise and during, while of course being careful not to over-hydrate as this can cause it’s own problems.
Check out this earlier post on how to keep an eye on your hydration and what you should aim for.