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  • Sean Jacobs MS, CSCS

Dehydration: Effects on Performance of Recreational Strength Training, Bodybuilding, and Other HIT.

Updated: Oct 12, 2019

Just the facts!


1. Humans can survive days, even sometimes weeks, without food, but can die after 3-5 days without water.


2. When you feel thirsty, you are likely already ~3% dehydrated.


3. Post-exercise recommendation for rehydration is 150% of the lost weight, to achieve normal hydration within 6 hours after the session. This equates to 20-24oz of water for every pound of body weight lost during training.


4. Up to 60% of the adult human body is water. The brain and heart are roughly 75% water. Skin, 64%. Bones, 31%. Muscles and kidneys, 79%.


5. Muscle cramps are a great indicator of dehydration and possible electrolyte imbalance, whether during/post exercise, or at night.



Much of the research to date on dehydration has been completed on athletes, specifically endurance athletes. This leaves many recreational gym-goers, HIT lovers, and novice body builders wondering how these findings fit into their training equation. A study conducted in two popular gyms in Chicago and L.A. found that regardless of location and respective climate differences, 46% of exercisers were likely to be dehydrated on the way into the gym.1️⃣ This is pretty scary considering that water accounts for approximately 73% of our lean body mass.


So, with this in mind, how can being even mildly dehydrated affect your workout?

All physiological systems in the human body are influenced by dehydration.2️⃣ Regarding exercise-specific effects on performance, the graphic below breaks it down using water loss as percent of body weight.



Dehydration has been found to impair sprint performance, negatively alter perception of recovery status before exercise, and increase ratings of perceived exertion as well as heart rate response.3️⃣ Furthermore, being dehydrated is likely to be associated with decrements in muscle endurance, strength, anaerobic power and capacity, and impaired resistance exercise performance.4️⃣5️⃣6️⃣ More specifically, an NSCA research review found that being dehydrated appears to decrease strength by approximately 2%, power by approximately 3%, and high-intensity endurance by approximately 10%.7️⃣ Also, for the HIT lovers, when raising the intensity of exercise, sodium and chloride losses increase by ~150%.8️⃣


It is necessary to point out that the impact of these factors associated with dehydration on non-bodyweight muscle performance is substantially mitigated in trained individuals.4️⃣ So if you’re just getting started, this has the potential to affect you more than someone who has been resistance training consistently for years.


If you’re dehydrated going into a training session, regardless of length, your performance will suffer. This could come in the form of an increased heart rate and length of time it takes to return your heart rate to normal, decreased strength in your reps, general increase in fatigue over time (lack of endurance) leading to the need to call it quits before you’d planned, and overall feelings of working harder than you actually are/should be.


A review by the NIH recommends an adequate water intake of 91 ounces (2.7 liters) per day for women and 125 ounces (3.7 liters) per day for men,9️⃣ however, it must be considered that these numbers are likely referring to the general population and not specifically to active individuals, therefore, if you're reading this article, depending on your activity level and the intensity of said activities, your daily intake will likely need to exceed these numbers.


To get the most out of your training sessions and your overall quality of life, the key is to take in plenty of fluids throughout the day. As we discussed, heading into a session dehydrated sets you back big time. Don’t wait until you are sweaty and thirsty to start drinking! Data suggests that a dehydrated state enhances the stress of a resistance exercise session and may interfere with training adaptations, so starting a training session well hydrated prepares you to get much more out of each rep and set, recover more quickly, and see much more progress in the long run.



References:

1. Stover, E. A., Petrie, H. J., Passe, D., Horswill, C. A., Murray, B., & Wildman, R. (2006). Urine specific gravity in exercisers prior to physical training. Applied Physiology, Nutrition, and Metabolism, 31(3), 320-327.


2. Casa, D.J., Armstrong, L.E., Hillman, S.K., Montain, S.J., Reiff, R.V., Rich, B.S.E., Roberts, W.O. & Stone, J.A. (2000b). National Athletic Trainers’ association Position Statement: Fluid Replacement for Athletes. Journal of Athletic Training, 35, 212-224.


3. Davis, J. K., Laurent, C. M., Allen, K. E., Green, J. M., Stolworthy, N. I., Welch, T. R., & Nevett, M. E. (2015). Influence of Dehydration on Intermittent Sprint Performance. Journal of Strength and Conditioning Research, 29(9), 2586-2593.


4. Savoie, F. A., Kenefick, R. W., Ely, B. R., Cheuvront, S. N., & Goulet, E. D. (2015). Effect of Hypohydration on Muscle Endurance, Strength, Anaerobic Power and Capacity and Vertical Jumping Ability: A Meta-Analysis. Sports Medicine, 45(8), 1207-1227.


5. Kraft, J. A., Green, J. M., Bishop, P. A., Richardson, M. T., Neggers, Y. H., & Leeper, J. D. (2010). Impact of dehydration on a full body resistance exercise protocol. European Journal of Applied Physiology, 109(2), 259-267.


6. Judelson, D. A., Maresh, C. M., Farrell, M. J., Yamamoto, L. M., Armstrong, L. E., Kraemer, W. J., ... & Anderson, J. M. (2007). Effect of hydration state on strength, power, and resistance exercise performance. Medicine and Science in Sports and Exercise, 39(10), 1817.


7. National Strength & Conditioning Association (U.S.)., Campbell, B. I., & Spano, M. A. (2011). NSCA's guide to sport and exercise nutrition. Champaign, IL: Human Kinetics.


8. Baker LB, De Chavez PJD, Ungaro CT, et al. Exercise intensity effects on total sweat electrolyte losses and regional vs. whole-body sweat [Na+], [Cl-], and [K+]. Eur J Appl Physiol. 2019;119(2):361–375. doi:10.1007/s00421-018-4048-z.


9. Popkin BM, D'Anci KE, Rosenberg IH. Water, hydration, and health. Nutr Rev. 2010;68(8):439–458. doi:10.1111/j.1753-4887.2010.00304.x

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