Weight Training: Does Hydration Affect How Strong You Are?


Weight Training: Does Hydration Affect How Strong You Are?

If there’s one substance that’s critical to health and to life, it’s water. In fact, our bodies are over 60% water. What might also surprise you is your muscles are 75% water. With muscles made up of such an abundance of water, you might wonder how it impacts how your muscles function and how it could affect your workout. Let’s take a closer look.

First, we know that dehydration can impact exercise performance. Studies show that even mild dehydration, as little as 1.5% percent, can negatively affect aerobic exercise performance. Why does this happen? As you lose fluid through sweating, the volume of your blood drops. To compensate for less blood and oxygen being pumped to your body with each beat, your heart rate goes up to compensate. So, your heart is working harder.

Your core body temperature also rises as you become more and more dehydrated. This places additional strain on your heart and on your entire body. Remember, your brain is largely composed of water too. Exercise feels more difficult and becomes harder to sustain, so your performance goes down. If you continue to lose water, you run the risk of more serious health consequences such as cramps, heat exhaustion, or heat stroke.

To make matters worse, as you lose more fluid and your blood volume continues to drop, less fluid reaches the surface of your skin. This means can’t release as much heat. So, your core body temperature continues to rise. If you’re in a hot or humid environment, the rise in core body temperature happens even faster. Plus, when you’re dehydrated and your core temperature rises, you use more muscle glycogen, causing glycogen to deplete more quickly. This doesn’t help the situation. Muscles need glycogen stores to perform at their best.

It’s obvious that hydration should be a priority when you’re doing any form of endurance exercise and that not staying hydrated affects your performance – but what about strength training? Does mild dehydration hurt your performance here too?

Hydration and Strength Training

Here’s the question – are you capable of lifting more when you’re well hydrated? A study carried out at Old Dominion University says “yes.” In this study, researchers tested the one-rep max of a group of healthy men when they were hydrated and also tested them when they were mildly dehydrated. As you know, one-rep max is a measure of how much weight you can lift a single time using good form. It’s a rough measure of how strong you are. The results? When the guys were dehydrated, their one-rep max scores dropped by almost 10%. The guys simply weren’t as strong when their fluid volume was low.

Another study carried out at the University of Connecticut found that dehydration affected performance on squats. Participants in a mildly dehydrated state could do fewer repetitions than those who were hydrated. Another study found that dehydration reduced power performance by 20%. This would impact performance for activities like plyometrics and kettlebell swings where you’re generating force quickly.

Long vs. Short-Duration Exercise

However, not all studies concur. Some research shows that mild dehydration doesn’t significantly affect exercise performance if that performance is less than 60 seconds in duration. This would include anaerobic exercise, like sprinting, as well as strength training sets. Of course, when you do a weight-training workout, you’re probably lifting for 30 minutes or more and you’ll eventually feel the effects of dehydration.

Does mild dehydration impact strength or not? A review of the literature in 2007 found that taking all previous studies into account, dehydration reduces power performance by 3%, strength by 2%, and high-intensity endurance exercise by 10%. While this isn’t an enormous difference, training FEELS easier when you’re well hydrated and you can give it your best. Plus, even mild dehydration affects brain function – and exercise performance is partially mental. It’s your brain that tells you to lift! Researchers put participants through a battery of tests when they were dehydrated and not dehydrated. What they found was participants when mildly dehydrated had problems concentrating and felt more fatigued. Some also experienced headaches and mood changes, particularly anxiety.

It’s easy to see how symptoms like this could disrupt your workout and reduce exercise performance, regardless of the type of training you’re doing. In this study, women developed more severe symptoms from dehydration than men. It’s worth mentioning that you can experience these symptoms any time you don’t drink enough water – at the office and when you’re going about your daily activities. It just happens faster when you’re exercising and losing water through sweat.

Tips for Staying Hydrated Every Time You Work Out

·       Drink 18-20 ounces of water 3-4 hours before a workout.

·       Drink another 6-8- ounces of fluid just before your workout.

·       Drink 15 ounces of water every 30 to 40 minutes during a workout.

·       Monitor your fluid status afterward.

If you want to know how dehydrated you were while training, check your urine afterward. If you were appropriately hydrated, your urine should be no darker than pale yellow. More color than that and you need to up your water intake beforehand, during, and afterward. Another approach is to weigh yourself before a workout and again afterward. For every pound you’re down, drink 16-20 ounces of fluid.

The Bottom Line

How hydrated are you when you enter into a weight-training session? Most research suggests that it matters not only for performance but for how you feel while you’re training. Now that you know the impact even mild dehydration can have on strength training performance, give yourself every advantage by drinking enough beforehand. If you don’t like plain water, infuse water with fruit to give it extra flavor. Place slices of fruit into a container of water and refrigerator for a few hours.

What about caffeinated drinks? Contrary to popular belief, drinking caffeinated beverages, like coffee and tea, don’t lead to net loss of fluid, so they really aren’t dehydrating. In fact, caffeine may improve your performance if you’re doing any kind of endurance activity.

Now you know why it’s so important to stay hydrated. Also, remember, a workout is more pleasant when you have enough fluid on board.



Journal of Athletic Training, 41(1)8-17.

Journal of Athletic Training, 35(2), 212-224.

FlexOnline.com “Immediate Strength Boost”

The Journal of Strength and Conditioning Research 15(1):102-8 · February 2001.

J Sports Sci Med. 2012 Jun; 11(2): 221–225.

Exercise Physiology: Nutrition, Energy, and Human Performance. McArdle, Katch, and Katch

Sports Med. 2007;37(10):907-21.

Psych Central. “Dehydration Influences Mood, Cognition”

ACE Fitness. “Healthy Hydration”


Related Articles By Cathe:

7 Ways to Get More Benefits Out of Every Workout

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

What Role Does Hydration Play in Boosting Muscle Hypertrophy?

6 Signs You’re Not Drinking Enough Water

How Hydration Affects Strength-Training Performance


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