How Hydration Affects Strength-Training Performance

How Hydration Affects Strength-Training Performance

Your organs and tissues are suspended in a dynamic sea of connective tissue and water. In fact, between 50 and 70% of your body is made up of water. No wonder! It serves a useful purpose. Water is the fluid that transports gasses and nutrients to tissues and helps eliminate waste products. It’s critical to health and to life. Yet, despite its importance and easy availability, most of us don’t drink enough fluid before, during, or after exercise.

How pervasive is the problem? A study carried out by Gatorade that measured urine concentration found that 4 out of 10 people were already dehydrated at the time they entered an exercise class. Staying hydrated is more challenging when you exercise. As your muscles move and your core body temperature rises, you lose fluid through your skin and your lungs – it’s how your body stays cool. Body temperature climbs quickly when you do high-intensity exercise or endurance exercise and your fluid requirements increase as well. Depending upon the type of exercise, your fluid demands can increase as much as 5 to 6 times.

Is there a hydration formula? The quantity of water you need to consume before, during, and after a workout depends on the temperature you’re exercising in, the relative humidity, and how hard you’re exercising. It’s obvious that you need more fluid when you run a marathon or do a hard, HiiT routine. Yet, even when you’re doing a strength workout, your body demands more water. Plus, it’s easy to forget to hydrate beforehand, especially when you’re not doing cardio. You might wonder how being underhydrated impacts a strength training workout? Can it reduce your strength and performance?

How Hydration Impacts Strength, Power, and Muscle Endurance

A small study published on Medscape.com found that underhydration had no measurable impact on maximal strength and power generation when participants performed a single, maximum rep. Where hydration did reduce performance was for resistance exercise with multiple reps and sets. In this study, participants performed less well in a dehydrated state when they did six sets of back squats. In fact, there were reductions in performance with mild degrees of dehydration, as little as 2.4%. The degradations in performance worsened as the degree of dehydration increased.

Where being less hydrated has the greatest impact is for resistance training volume. If you’re underhydrated, you may perform just as well on a one-rep max test. However, you will likely not achieve the same number of reps when you do a multi-rep resistance exercise. For example, you might do 8 reps when you squat with a load 80% of your one-rep max but only 6 or 7 when your body isn’t sufficiently hydrated.

That not drinking enough water hurts performance on multi-rep, multi-set resistance exercises isn’t surprising. Researchers believe that even mild dehydration reduces central drive, in other words, your brain tells you to stop. Another study came to a similar conclusion – improper hydration reduces performance on multi-rep resistance exercises and also makes exercise feel harder. So, a strength workout will likely feel more unpleasant when you don’t drink enough water beforehand.

Does Dehydration Impact Muscle Growth?

If dehydration reduces strength-training performance for multi-rep, multi-set exercises, could it not limit muscle growth and strength gains over time? One study showed that being poorly hydrated may have a short-term impact on muscle growth. When you aren’t sufficiently hydrated and you lift a heavy weight, you push water out of the muscle, rather than into the muscle. When muscle cells lose water, it can slow down the rate at which they synthesize new muscle proteins. This, in turn, can interfere with muscle recovery after a workout and, possibly, reduce gains in muscle size. Although this isn’t conclusively proven, it makes sense, based on the fact that your muscle cells need water to properly function.

Other Reasons Pre-Workout Hydration is Essential

Don’t forget that your joints need hydration as well. Adequate water intake helps keep your joints hydrated so that movement is smoother and the risk of injury is lower. In addition, being even mildly dehydrated can affect your mood and make you feel unmotivated. If you have a bad attitude toward training on a given day or you feel unusually tired, question whether you’re drinking enough water.

When you aren’t well hydrated, your body has to work harder. Since you have less fluid in your blood vessels, your heart has to speed up to push what’s remaining to your cells and tissues. So, your heart rate rises. Severe dehydration can put a substantial strain on your cardiovascular system.

Even Mild Dehydration is Problematic

Based on studies, physical performance suffers from even mild degrees of dehydration, around 2.4%, and the greatest fall-off in performance occurs with dehydration of 5% or greater. At this point, you’re just starting to feel thirsty. So, thirst isn’t a good indicator of how hydrated you are. Here are some general guidelines for hydrating before a workout:

·       Drink 14 to 20 ounces of water 2 hours before a workout

·       Drink another 5 to 10 ounces 30 minutes beforehand.

·       Drink 8 or so ounces every 15 to 20 minutes during exercise


These are general guidelines and you may need more if you’re working out in a hot or humid environment. If you exercise for more than 90 minutes, the risk of developing a low sodium level rises, so, it’s safest to drink an electrolyte-rich drink. This mainly applies to endurance exercise.

Another tip is to weigh yourself before and after your workout. For every pound of water you’re down, drink 16 to 20 ounces of fluid. If you forget to weigh, check the color of your urine. If it’s darker than pale yellow, you need more fluid.

The Bottom Line

As you can see, adequate hydration helps you get the most out of a strength-training workout and may, ultimately, help you make greater gains in strength and muscle size. Water is so basic to life well-being. Make sure you’re getting enough!



Med Sci Sports Exerc. 2007;39(10):1817-1824.
Nutr Rev (2014) 70 (suppl_2): S128-S131.
Appl Physiol Nutr Metab, 31(3), 320-7.
Bodybuilding.com. “Your Muscles Are Thirsty”
Exercise Physiology. Eight Edition. Wolters Kluwer. McArdle, Katch, and Katch


Related Articles By Cathe:

What Role Does Hydration Play in Boosting Muscle Hypertrophy?

Are Colder or Room Temperature Beverages Better for Exercise Hydration?

6 Signs You’re Not Drinking Enough Water

5 Ways to Make a Workout Feel Easier

Weight Training: Does Hydration Affect How Strong You Are?

Benefits of Drinking More Water and Tips for Making Sure You Do

Hydration and Exercise Performance: What Happens When You Don’t Drink Enough Water?


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