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dehydration affects lifting gains: Man taking a water break in the gym

Attention Lifters: Dehydration Is Likely Affecting Your Gains

One major component of planning nutrition for performance and/or physique optimization is a topic people don’t touch on nearly enough: hydration. Hydrating isn’t perceived as particularly sexy or fun, and therefore, we don’t hear much about water and how it can impact your performance. However, as everyone’s favorite waterboy, Bobby Boucher, would like you to know, water can have a major impact on all things exercise.

If you’re not already on top of how crucial hydration is for your gym performance and subsequent gains, it’s time for that to change. Grab yourself a glass of H2O and let’s get started.

Dehydration and Performance

While there’s no benefit to overhydrating (if anything, an overfull belly and constant bathroom runs take away from your training efforts), a huge stack of literature illuminates the negative effects of dehydration on physical performance and fitness progress.

First, it’s worth noting that studies have found that a reduction in as little as two percent of your body mass due to dehydration is enough to negatively affect performance. So, if you normally weigh 180 pounds, weighing in at anything under 177 before training means you’ll likely sacrifice some plates on the bar or miss out on some key reps.  

Read More: 7 Signs You’re Dehydrated

Now, as for the price you’ll pay: One review covering hydration and performance states that even mild dehydration consistently decreases muscle force production by two percent, power output by three percent, and endurance performance by 10 percent. Those numbers may not all sound huge, but if you are constantly dehydrated (which most people are), then you are consistently missing out on those precious few percentages every time you go to the gym, which adds up over time. They can also make or break you in a competitive setting.

And that’s not all. One study examined the effects of dehydration on hormone levels and found that dehydrated subjects had much higher cortisol levels following resistance training as opposed to hydrated subjects. This means that dehydrated individuals likely experience higher rates of protein breakdown and have to focus that much harder on diet to overcome this effect and make gains. 

This same study also found that dehydrated individuals had both higher insulin levels and higher blood glucose levels following exercise. The lowering in cell volume due to lack of water promotes cellular insulin resistance, which is a bad, bad thing if gains in size and strength are among your goals. Some consider insulin the most anabolic of hormones, so take advantage of that designation and make sure you’re always well-hydrated during and after exercising.

Are You Sweating Your Way to Dehydration?

You might be wondering how any drippiness during your training might tank dehydration and results.

Well, if it’s hot in the gym and you’re getting after it pretty hard, it’s reasonable to assume you’re sweating around 1.5 liters per hour, which equates to about three pounds of water weight lost per hour. This means that it takes just about an hour of sweating for the average gymgoer to lose two percent of their body weight, putting them square in that dehydration category. Even worse, if you’re exercising or practicing outside in the heat, it’s possible to sweat up to three liters an hour, which would be about six pounds of precious water weight per hour. 

Read More: How High-Sodium Electrolyte Supplements Help Heavy Sweaters

Another factor to consider is salt. A typical person sweats out about a gram of sodium per liter of sweat. Sodium is an incredibly important component of muscle contractions, especially in a fatigued state. Adequate sodium levels are also necessary for maintaining optimal fluid volume within a cell, so, typically, if you’re low on sodium, you’re also low on water and vice-versa. Sodium needs are way understated for athletes—that’s a big conversation for another time—but it’s worth mentioning that sodium intake is just as important as H2O intake around your workouts.

Keys to Hydration

So now that dehydration sounds terrifying, the good news is that taking in half a liter to one liter of water per hour of training is enough to stave it off during exercise. If you’re thrown off by metric measurements, that’s 16.5 fluid ounces (about the size of a medium single-use water bottle) to 33 fluid ounces (two bottles). A quick sip of water is usually about an ounce, give or take, so downing 16.5 to 33 ounces during a training session is easy if you consistently grab a swig between sets. Even if you’re not thirsty, it’s a good rule of thumb to hit the water fountain or take a quick gulp from your bottle between sets. 

Now, how can you prevent dehydration before training? One review states that ingesting 500 milliliters (16.9 fluid ounces) about two hours before exercise is a good place to start. If you haven’t been drinking consistently all day, simply set an alarm and start sipping water at least two hours before your workout. 

If you do these things and still find yourself lightheaded or nauseous during workouts, you might be experiencing symptoms of hyponatremia. This means that your sodium levels are running low. Most sports drinks and hydration supplements contain sodium, so it might be a good idea to sip on one during your workout if you think you have issues with sodium loss. I personally have found that a pre-workout with higher sodium content has made a huge difference in my workouts—particularly when it comes to endurance. Many intra-workout supplements also have solid electrolyte blends to help maintain sodium status during intense training.

If you work out in the morning, chug some water before going to bed at night. You’ll inevitably have to get up to pee in the middle of the night, but it’s still a good strategy for promoting proper hydration before your A.M. sweat. I usually work out first thing in the morning and try to drink about 20 to 30 ounces of water in the hour before I go to bed (in addition to my bedtime protein shake).


In summary, water is not at all exciting, but it may be one of the most important factors for your performance today and your gains over time. Luckily, it’s one of the easiest deficits to overcome. Just get yourself a cool water bottle and keep it at your side at all times. Heck, lug around a gallon jug if you feel the need. If you absolutely can’t stand plain water, don’t be afraid to toss some sort of flavoring into it to make it more palatable. Whatever you have to do to get those ounces in.

Known as ‘The Muscle Ph.D.,’ Dr. Jacob Wilson has a knack for transforming challenging, complex concepts into understandable lessons that can support your body composition and health goals. A skeletal muscle physiologist and sports nutrition expert, Wilson is a leader in muscle sports nutrition. As the CEO of The Applied Science & Performance Institute, he researches supplementation, nutrition, and their impact on muscle size, strength, and power.

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