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The Importance of Hydration for Bodybuilders

Daniel Brady | January 18, 2013 in Nutrition

Hydration can be forgotten by bodybuilders, who may think that diet and exercise are the only things to think about. Hydration is important to your performance and results though, so read on to learn why.

A single day of moderate dehydration can drastically effect your strength, your hormones, and in turn, your muscle gains. By moderate dehydration, I mean a 2-5% decrease[1] in body weight due to forgetting to drink water or other suitable liquids. A 2-5% decrease is 1-4kg of water weight variance for most people. A signifier of dehydration is urine color[2]; if your urine is moderately dark, then you are not drinking enough water and hurting your performance and results. Following is a chart to check yourself against.

Urine Color Chart

Problem 1: Cortisol Increase

Dehydration increases cortisol production in the body.[1] Cortisol decreases amino acid uptake by the muscles and decreases protein synthesis.[3] This is detrimental to your muscle gains.

Problem 2: Testosterone Decrease

Usually exercising leads to an increase in testosterone levels but dehydration decreases this increase in testosterone.[1] Testosterone is very beneficial for muscle gains as seen in our article 6kg of Muscle in 10 Weeks, so limiting testosterone is not good.

Another journal found that the testosterone to cortisol ratio is lower (worse) with dehydration.[4] This leads directly to either lower muscle gains, or even muscle losses.

Problem 3: Premature Fatigue

Your energy levels (glycogen stores) run down far quicker when dehydrated, and central nervous system function is impaired.[5] This results in reduced motivation and effort exerted. Put into bodybuilding terms, you will run out of energy after fewer reps both physically and mentally. A more exact example is that 2% dehydration in a cycling experiment resulted in a 6.5% impairment of performance.[5] A time to exhaustion experiment with 2.5% dehydration found a 28.6% impairment of performance.

Problem 4: Increasing Severity While Exercising

People can sweat a lot while exercising, with some people losing up to 3 liters of sweat per hour.[5] If you’re an average person and working out moderately hard, you may sweat 1-2 liters in an hour. Do you drink 1-2 liters of water while in the gym? Most people don’t. Sweating more than you drink leads to increased dehydration and increased symptoms, making you particularly weak at the end of the session.


Being fully hydrated before the gym and at all times is optimal. Your urine will reflect your good hydration levels. At the gym, 600ml of water is probably insufficient. Go for a 1 liter or 1.5 liter bottle to get the most out of your body. Improving your hydration levels should improve your gym performance, comment here on your results.

Daniel has a strong interest in evidence supported fitness training, preparation and supplementation. His goal is to provide clear information that simply works. He's currently 16 kg of muscle above his starting weight (7kg in the past 12 months), and targeting a continued growth rate of 5kg+ per year.
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