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What is tactical dehydration, and can it improve your athletic performance?


If marketing is to be believed, dehydration is a performance killer. If you want to perform at your best dehydration should be prevented at all costs (or at least the cost of the sports drink being marketed to you). 

Yet this thinking doesn’t seem to exist at the elite level. A 2012 study on runners of the Dubai marathon found that the top athletes lost between 6.6 - 11.7% of their body water over the course of the race (The winner lost ~10%). Perhaps we don’t need to be worried about dehydration?

Turns out the science is there to back this up. Research shows that dehydration (at least mild dehydration of 0-2% body weight) doesn’t necessarily impact performance in real world settings and may even improve performance as you lose body weight .

Read more on what you lose in sweat and how to prevent it impacting your performance

John Brewer, professor of applied sport science at St Mary’s University, UK, says it’s a little-known fact that mild water loss can help rather than hinder performance. “Tactical dehydration” as he calls it, is a growing phenomenon amongst runners, triathletes and cyclists, at club level as well as the elite.

“Think about it,” Brewer says. “Each litre of fluid lost equates to approximately 1kg of body weight. Carrying around less weight has a positive impact on endurance performance, so people can train their bodies to cope with dehydration, rather than fighting to prevent it.”

What is tactical dehydration?


Tactical dehydration (TD) is the practice of purposefully training/competing in a mildly dehydrated state (we suggest between 1-2% body weight loss) so that your body gets used to it.

The aim is to find that sweet spot where your performance isn’t negatively impacted by the dehydration, but you benefit from being lighter. 

TD can benefit athletes in all sports, from running and cycling through to CrossFit and team sports like soccer.

How will tactical dehydration affect you?

How to use tactical dehydration to improve performance

Tactical dehydration (TD) is the rapidly growing trend of adapting your body to be able to perform when mildly, and safely dehydrated. 

There are two stages to executing tactical dehydration. 

  1. to condition the body to train in a state of mild dehydration. This takes about a week.  
  1. Learn to safely maintain a 1-2% dehydrated state when training or competing (as you won’t have a weigh scale with you). 

Disclaimer: The risk of tactical dehydration

Healthy athletes should not experience any major side effects from tactical dehydration

A quick word of caution before we continue. Severe dehydration can cause you a lot of harm, so please don’t try TD if you have any medical conditions that could impact your water balance/hydration status. Also, older athletes can be more susceptible to dehydration too. Please be careful, and if in doubt, seek medical clearance before trying it. 

Step 1. Training while mildly dehydrated

The first step to using TD is to spend some time (say a week) training while mildly dehydrated to both condition the body (if needed) and also get used the the “feel” of it. 

Here’s how to do it:

  1. Ensure you are in your “normal” fed and watered state to train like any other day, then measure your body weight (your baseline) 
  2. Calculate what you will weigh at if you lost 2% body weight (1-2% is the range you want to try to stay in). 
  3. Have a litre of your favourite hydration beverage on hand and ready (we suggest our Hydra+ product that we specifically designed for keeping you between 0-2% dehydrated)
  4. Start on a 60-90 min long, paced endurance training session (one that will get you sweaty). 
  5. At regular intervals, stop and check your body weight, using sips of your hydration drink if needed to stay between 1-2% weight loss (mildly dehydrated). Note how you feel, thirst levels etc. so you can replicate it via “feel” at a later date. Drinking only to thirst is a good place to start and usually keeps you within the desired range and is safe.  
  6. Replenish all liquid (and ideally carbs too), at the end of your training session
  7. Repeat this process ~5x in a row get you used to training in a dehydrated state, and know by feel how to sit in that sweet spot. We suggest logging each run intensity, temp, water intake body weight change. 

This “trial and error” process will cause your blood plazma volume to increase in just a few days, to ensure blood volume is maintained when training in a dehydrated state. 

Te result? You’ll be conditioned to train with a 1-2% lighter body (a weight of 1.85-3.7lb in your average person), which should make you feel lighter, and able to move faster. 

Step 2. Apply your learning to a race or training scenario, without a weigh-scale

With your body somewhat conditioned to mild dehydration, the next step before starting to use TD regularly to improve your training performance is to run a few test sessions. 

The goal is to be able to maintain mild levels of dehydration consistently without having to weigh yourself.

Here’s how to do it:

  1. Repeat the training session from part 1, but this time estimate your fluid intake requirement based on how you feel, rather than using the scale
  2. At the end of the session measure your body weight to see how accurate you have been (vs. your previous logged sessions)

It may take a few tries, but once you have this dialled, you’re ready to incorporate TD into your training and competition sessions, and will quickly start to see the benefits of being a little bit lighter. 

Use a Hydration mix to to help you achieve tactical dehydration

To ensure you stay between 1-2% dehydration you’ll benefit from having a hydration beverage on hand that contains a little salt and sugar. Sodium (in salt) and glucose (in sugar) move water quickly across the gut into the blood allowing you better control of your dehydration state.

We developed Hydra+ for athletes interested in trying TD who also prefer to keep their diet based on real whole foods. It provides glucose and sodium from fruit, coconut water and a little sea salt. The product comes with mixing guidelines that vary depending on the training you’re doing, so you can stay between 0-2% dehydrated. 

Blonyx Hydra+

Hydra+ provides the training body with electrolytes and carbs using real food ingredients like coconut water, mango, passionfruit and sea salt. It’s a versatile drink mix that can be used to replenish electrolytes and carbs in shorter, higher intensity training, or adjusted to maintain optimal hydration status on longer duration, sweaty training sessions. 

Hydra+ tastes like a light fruit juice, isn’t saturated with salt (as research shows it’s not needed) and is focused on ensuring you perform at your best by staying between 0-2% dehydrated.


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